Transforming By-Products into Functional Resources: The Potential of Cucurbitaceae Family Seeds in Cosmetics

Abstract

Seeds of Cucurbitaceae crops represent a promising yet underexplored source of bioactive compounds with potential applications beyond nutrition, particularly in the cosmetics industry. This review examines the seeds of Citrullus lanatus (watermelon), Cucumis melo (melon), and Cucurbita pepo (pumpkin), focusing on their biochemical composition and evaluating their functional value in natural cosmetic development. Although these fruits are widely consumed, industrial processing generates substantial seed by-products that are often discarded. These seeds are rich in polyunsaturated fatty acids, proteins, carbohydrates, and phytochemicals, positioning them as sustainable raw materials for value-added applications. The incorporation of seed-derived extracts into cosmetic formulations offers multiple skin and hair benefits, including antioxidant activity, hydration, and support in managing conditions such as hyperpigmentation, acne, and psoriasis. They also contribute to hair care by improving oil balance, reducing frizz, and enhancing strand nourishment. However, challenges such as environmental instability and low dermal permeability of seed oils have prompted interest in nanoencapsulation technologies to improve delivery, stability, and efficacy. This review summarizes current scientific findings and highlights the potential of Cucurbitaceae seeds as innovative and sustainable ingredients for cosmetic and personal care applications.

1. Introduction

Fruits of the Cucurbitaceae family, including watermelon (Citrullus lanatus), melon (Cucumis melo), and pumpkin (Cucurbita pepo), are widely cultivated and consumed worldwide due to their rich nutritional profile and health-promoting properties. The industrial processing of these fruits yields a wide variety of products such as pulps, juices, and salads. However, it also generates substantial quantities of by-products, which are often relegated to low-value uses such as animal feed, soil erosion prevention, or biofuel production [1,2,3]. These residues, which contain high levels of moisture and microbial loads, have been identified in recent years as a major problem contributing to the global environmental burden [1].

In alignment with the waste hierarchy and the European Union’s circular economy directives, there is a growing emphasis on waste prevention, improved separate collection systems, and a reduction in landfilling. As climate change intensifies and non-renewable resources continue to deplete, the valorization of agro-industrial food waste has become an urgent priority. This issue has garnered increasing attention from governments, environmental organizations, industries, and the scientific community. In this context, Cucurbitaceae by-products, especially seeds, have gained recognition for their potential as renewable sources of bioactive compounds with applications in the food, pharmaceutical, and cosmetic industries [4].

The use of seeds from the Cucurbitaceae family, such as those of watermelon (Citrullus lanatus), melon (Cucumis melo), and pumpkin (Cucurbita pepo), holds significant promise for the cosmetics sector, especially in the context of sustainability and the circular economy. These seeds are often underutilized by-products of fruit processing, but contain valuable compounds, such as fatty acids, phenolics, vitamins, and antioxidants that can contribute to skin health and protection [5,6]. Incorporating such bioactives into cosmetic products not only adds value to agricultural waste but also reduces environmental impact [7]. This approach responds to both ecological concerns and increasing consumer demand for natural, plant-based ingredients in skincare formulations [2,3]. Economically, valorizing these seeds can offer new income sources for producers and lower raw material costs for cosmetic manufacturers. Additionally, modern extraction technologies, such as ultrasound-assisted methods, allow for the efficient recovery of active ingredients without the use of harmful solvents, making the process both effective and environmentally friendly [7]. Overall, using Cucurbitaceae seeds in cosmetics represents a practical and responsible way to merge innovation with sustainability.

Cucurbitaceae seeds are particularly promising for cosmetic applications due to their richness in bioactive compounds, including vitamins, minerals, dietary fiber, oils, carotenoids, and polyphenols [5,6]. Regarding polyphenols, several families of compounds attained from plant seeds with potential for cosmetic application are alkaloids, saponins, flavonoids, and phenolic acids. Figure 1 presents the general structures of the main groups of secondary metabolites described in the watermelon, melon, and pumpkin seeds.

From a sustainability perspective, these seeds represent an underutilized yet valuable resource that aligns well with circular bioeconomy and green innovation principles [4].

Among the various functional properties of these seeds, their antioxidant and moisturizing effects are of particular relevance for cosmetic formulations. The high lipid and protein content enhances their utility in developing natural, non-toxic skincare products, especially those aimed at hydration and anti-aging [4]. Seed oils from Cucurbitaceae fruits are rich in essential fatty acids, phytosterols, carotenoids, and squalene—compounds with proven skin benefits [7]. For example, C. lanatus seed oil, known since ancient Egyptian times, is lightweight and functions as an effective emollient. Its high essential fatty acid content contributes to skin nourishment and elasticity, and it has been traditionally used in soap-making and for treating dermatological conditions [8]. In Europe, C. lanatus seed oil is increasingly incorporated into formulations aimed at skin hydration and rejuvenation [9,10]. Similarly, C. melo polysaccharide extracts have demonstrated significant short-term skin hydration efficacy [11], while phenolic compounds and carotenoids in melon and pumpkin seeds exhibit antioxidant properties that help neutralize free radicals and promote skin health [12].

Consumer preference is shifting toward natural and organic cosmetic products, particularly in Western markets such as Europe and North America [8]. The “green beauty” movement has accelerated demand for clean-label formulations based on plant-derived ingredients with minimal side effects [13,14]. In this context, agro-industrial by-products represent a sustainable and ethical alternative to synthetic chemicals used in personal care products [15]. Their incorporation not only supports global sustainability goals but also aligns with consumer expectations for environmentally friendly and responsibly sourced raw materials [14].

There are several methodologies for extracting compounds with potential application in cosmetics from Cucurbitaceae seeds. Within conventional methods, Soxhlet extraction and cold press extraction stand out, while in advanced methodologies, ultrasound-assisted extraction, active motion-encouraged extraction, microwave-assisted extraction, aqueous enzymatic extraction, among others, can be used. Extraction methods affect process yield, quality, nutritional value, physicochemical properties, and the oxidative stability of seed oils [16,17]. In general, advanced methods are environmentally friendly, allow higher yield, faster extraction, energy saving, higher purity and quality of the product, and lower susceptibility to thermal degradation but are more expensive and need more technical skills and expertise [18].

Despite these promising attributes, the seeds of C. lanatus, C. melo, and C. pepo remain underexplored in cosmetic research and product development. A more comprehensive evaluation of their bioactivity, safety, and efficacy is essential to unlock their full potential. Therefore, this study aims to investigate the cosmetic applications of Cucurbitaceae seeds, focusing on their moisturizing and antioxidant properties, with the goal of contributing to sustainable innovation in the cosmetics industry.

2. Chemical Composition of Cucurbitaceae Seeds and Their Application in Cosmetics

Several seed-derived oils have found widespread application in the cosmetic industry due to their beneficial effects on skin and hair. Notable examples include oils from chia (Salvia hispanica) [19], jojoba (Simmondsia chinensis) [20,21], sesame (Sesamum indicum) [22], and hazelnut (Corylus avellana) [23]. These oils are used to address skin conditions such as acne, psoriasis, and minor wounds. They are incorporated into various cosmetic products, including moisturizers, lipsticks, eye shadows, and hair care formulations—particularly those targeting hair growth and scalp health, such as shampoos and shaving products. Cocoa (Theobroma cacao) and cupuaçu (Theobroma grandiflorum) seeds are also valued for their skin-beneficial lipids, while walnut oil is increasingly employed for encapsulation and targeted delivery of active ingredients [23].

In this context, Cucurbitaceae seeds exhibit promising characteristics that justify their inclusion in cosmetic applications. These seeds typically contain high levels of both water and lipids, including essential fatty acids, which confer significant moisturizing and emollient properties. Oils extracted from Cucurbitaceae seeds are particularly rich in unsaturated fatty acids, primarily linoleic and oleic acids [10,16]. These fatty acids are crucial structural components of cell membranes and play an essential role in maintaining skin integrity and hydration.

The light texture and quick absorption of these oils make them suitable for all skin types. Once applied, they form a protective barrier that helps reduce transepidermal water loss. The dual action of moisturizing and emollient effects supports the balance between the skin’s surface lipids and water content in the stratum corneum—an essential factor for maintaining healthy, supple skin [24,25,26].

In addition to their moisturizing properties, Cucurbitaceae seeds exhibit notable antioxidant activity, primarily due to their content of phenolic compounds [27], vitamins C and E [28], and specific amino acids [29]. The Cucurbitaceae family includes cardiac glycosides (e.g., amygdalin), ∆⁷ sterols (avenasterol and spinasterol), and ∆⁵ sterol (sitosterol and stigmasterol). Likewise, triterpenoids, sesquiterpenoids, squalene, phenolic glycosides, lignans, and tocopherols (mainly α-tocopherol) are common in this botanical family [28]. These bioactive molecules help neutralize free radicals generated by ultraviolet radiation and environmental pollutants, thereby preventing oxidative damage and premature skin aging. Beyond antioxidant effects, phenolic compounds also possess anti-inflammatory and antimicrobial properties, further enhancing their value in cosmetic formulations [27].

Vitamins A, D, C, and E, all present in varying concentrations in Cucurbitaceae seeds, play critical roles in skin care, offering protection against environmental stressors and aiding in the treatment of conditions such as acne and psoriasis [28]. Also, thiamine, riboflavin, niacin, pyridoxine, and pantothenic acid are described. Additionally, amino acids contribute to skin hydration and help maintain pH homeostasis, both of which are essential for a healthy epidermal barrier [29].

The mineral content of these seeds also enhances their cosmetic potential. Certain minerals function as active components in natural clays, imparting bactericidal, antiseptic, and regenerative properties [30]. These properties make them particularly relevant in formulations aimed at acne treatment and anti-dandruff shampoos [31].

Taken together, the rich biochemical composition of Cucurbitaceae seeds underscores their significant potential as multifunctional ingredients in cosmetic products, offering hydration, antioxidative protection, anti-inflammatory action, and support for skin and scalp health.

2.1. Phenolic Compounds

Phenolic compounds are key bioactive constituents in many cosmetic formulations due to their broad-spectrum biological activities. These include antioxidant, anti-inflammatory, antimicrobial, and photoprotective effects, which support their use in a variety of skincare and dermatological products, such as anti-aging creams, sunscreens, after-sun formulations, hair masks, and treatments for specific skin conditions [32,33].

One of the most significant roles of phenolic compounds in cosmetics lies in skin protection against oxidative stress and environmental aggressors. Phenolic acids act as potent antioxidants by neutralizing free radicals and reactive oxygen species (ROS), which are responsible for premature aging and cellular damage. These compounds help stabilize skin cells under UV radiation exposure by reducing oxidative stress, minimizing mitochondrial dysfunction, and modulating inflammatory mediators such as IL-1β and TNF-α. Moreover, they support collagen synthesis—especially type III collagen—and improve cell viability, which enhances skin resilience and contributes to anti-aging and wound-healing effects [34,35].

Beyond their antioxidant properties, phenolic acids, such as gallic and caffeic acid, exert depigmenting effects by inhibiting tyrosinase, a key enzyme in melanogenesis. This mechanism reduces melanin synthesis, making these compounds promising candidates for the development of skin-lightening and tone-correcting products [36]. Their ability to chelate copper ions, which are essential cofactors for tyrosinase activity, further enhances this effect, positioning them as effective natural alternatives for managing hyperpigmentation in multifunctional skincare formulations [37,38]. Moreover, phenolic acids also possess antimicrobial and anti-inflammatory properties. These effects support their use in the treatment of inflammatory skin conditions such as acne, seborrheic dermatitis, and atopic skin by modulating inflammatory pathways and inhibiting the proliferation of pathogenic microorganisms.

Flavonoids, another important group of phenolic compounds, are also widely used in cosmetics. They are recognized for their ability to protect the skin from oxidative and UV-induced damage, stimulate collagen production, improve microcirculation, and support skin elasticity. Additionally, their soothing and anti-inflammatory effects are particularly beneficial in managing conditions such as psoriasis and dermatitis, contributing to their growing use in both therapeutic and daily skincare formulations [39,40,41].

Table 1. Predominant phenolic compounds in Cucurbitaceae seeds and seed oils and their functional properties relevant to cosmetic applications.

Group	Compound	C. lanatus	C. melo	C. pepo	Properties/Applications
Alkaloids		28.33–95.8 mg/g [1,42]	2.54–304.12 mg/g [1,42]	41.47 mg/g [43]	Anticellulitis and anti-aging products; tonics, creams, lotions, face masks; hair masks and discoloration [33]
Saponins		11.62–16.87 mg/g [1,42]	13.25 mg/g [42]	33.05 mg/g [43]	Skin, hair and oral care products; emulsifiers; antioxidants; surface-active activities [44]
Flavonoids	Naringenin-7-O-glycoside	Not found	4.30 mg/100 g [45]	Not found	Anti-inflammatory effects in cells exposed to ultraviolet B (UVB) radiation [46]
	Luteolin	7.19 mg/mL [47]	2.10 mg/100 g [45]	Detected; not quantified [48]	Anti-inflammatory, signs of skin diseases (psoriasis and dermatitis) attenuation, wound healing; photoprotection and anti-aging [46]
	Apigenin	Detected; not quantified [49,50]	0.50 mg/100 g [45]	Not found	Symptoms of skin inflammatory diseases attenuation, psoriasis combat, and pruritus alleviation [40]
	Amentoflavone	Not found	1.78 mg/100 g [45]	Not found	Anti-wrinkle [51]; anti-inflammatory; improvement of psoriasis-like lesions [52]
	Hydroxytyrosol	Not found	1.28 mg/100 g [45]	Not found	Antioxidant; antimicrobial; anti-inflammatory; anti-aging; photoprotector; depigmenting [53]
	Oleuropein	Not found	3.03 mg/100 g [45]	Not found	Antioxidant; antimicrobial; anti-inflammatory; anti-aging; hydration effect [54]
	Resveratrol	Not found	2.92 mg/100 g [45]	Not found	Antioxidant; antimicrobial; anti-inflammatory; anti-aging; photoprotector [55]; hair growth promotion [56]
	Quercetin-3-rutinoside	0.46 mg/mL [47]	3.91 mg/100 g [57]	Detected; not quantified [58]	Antioxidant, anti-inflammatory, photoprotector [59]
	Catechin	Not found	4.33–7.4 mg/100 g [57,60] 0.90–1.77 μg/mL [61]	9.7 mg/100 g [60]	Component of soaps, sunscreens, creams; antioxidant; antibacterial; anti-inflammatory; anti-acne; anti-aging; photoprotector [62]
Phenolic acids	Gallic acid	3.765 μg/100 g [47] 2.37 mg/mL [44]	4.24–8.4 mg/100 g [45]	945–5.4 × 103 μg/100 g [60,63]	Antioxidant; anti-inflammatory; anti-skin aging; atopic dermatitis and hyperpigmentation combat; wound-healing improvement [64,65]
	Protocatechuic acid	Not found	0.93–4.9 mg/100 g [45,60]	158–5.2 × 103 μg/100 g [1,60]	Antioxidant; anti-inflammatory; environmental damage protection; anti-wrinkle and anti-aging effects [66,67]
	Chlorogenic acid	Not found	1.25–5.3 mg/100 g [45,60]	79–1490 μg/100 g [63]	Antioxidant; anti-inflammatory; anti-aging effects [35]
	p-hydroxybenzoic acid	52.84 μg/100 g [68]	3.28 mg/100 g [45]	2.70 × 10−3–364 μg/100 g [1,69]	Antimicrobial; cosmetic preservative [70]
	Vanillic acid	28.42 μg/100 g [68]	3.87 mg/100 g [45] 0.58–1.02 μg/mL [61]	224–835 μg/100 g [63]	Anti-aging; photoprotector [71]
	Rosmarinic acid	Not found	1.87 mg/100 g [45]	Not found	Atopic dermatitis symptoms combat [72]; skin hydration, elasticity, and firmness [36]
	Phenylacetic acid	Not found	1.35 mg/100 g [45]	Not found	Applied in cosmetics due to its honey-like scent characteristic [73]
	Sinapic acid	138.41 μg/100 g [68]	Not found	62–155 μg/100 g [63]	Skin whitening; anti-aging [74]
	Caffeic acid	26.33–133 μg/100 g [1,68] 0.45 mg/mL [47]	1.9–66.0 mg/100 g [57,60]	32–184 μg/100 g [63]	Antimicrobial; antioxidant; anti-inflammatory; anti-skin aging; photoprotector [75]; anti-wrinkle [76]
	Syringic acid	15.11 μg/100 g [68]	1.5 mg/100 g [60]	47–1.0 × 103 μg/100 g [60,63]	Antioxidant; photoprotector; wound-healing improvement [34]
	p-coumaric acid	28.52 μg/100 g [68] 2.29 mg/mL [47]	1.2 mg/100 g [60]	123–504 μg/100 g [1,63]	Antioxidant; antimelanogenic; UV-induced erythema attenuation [37]
	Ellagic acid	Not found	6.52 mg/100 g [57] 0.06–0.07 μg/mL [61]	7.191 mg/100 g [66]	Skin whitening agent; UV photoprotector and anti-photoaging [38]
	Ferulic acid	74.12 μg/100 g [68]	13.483 mg/100 g [77]	44–132 μg/100 g [63]	Antioxidant; skin photoaging protection; collagen and elastin fibers synthesis stimulation; anti-wrinkle creams, sunscreens, body scrubs, skin moisturizing, anti-seborrheic, and anti-acne preparations [36]

summarizes the most abundant phenolic compounds found in Cucurbitaceae seeds, including alkaloids, saponins, flavonoids, and phenolic acids. Among these, alkaloids and saponins are present in significantly higher concentrations compared to flavonoids and phenolic acids. Melon seeds are especially rich in flavonoids such as catechin and naringenin-7-O-glycoside. Regarding phenolic acids, C. melo, C. lanatus, and C. pepo seeds all contain notable amounts of gallic, p-hydroxybenzoic, vanillic, sinapic, caffeic, syringic, p-coumaric, and ferulic acids, with melon seeds again demonstrating the highest overall content.

2.2. Fatty Acids, Tocopherols, and Phytosterols

Fatty acids, their salts and derivatives (including fatty alcohols, fatty acid esters, anionic and nonionic surfactants, fatty amines, and quaternary ammonium compounds) are widely used in cosmetic, hair care, and personal care products. They are found in soaps, alcohol-based sticks, bars, pressed powders, gels, suspensions, emulsions, and aerosols [78].

Tocopherols, commonly used as antioxidants and skin-conditioning agents, are generally recognized as safe. These lipophilic compounds are prone to oxidation when exposed to air or light, although their susceptibility varies among the four analogs—α-, β-, γ-, and δ-tocopherol—due to differences in oxidation potential and reactivity with oxygen [79]. Mixtures of these analogs, in varying ratios, are frequently used in cosmetic formulations [30]. Tocopherols not only provide anti-aging benefits but also help stabilize other ingredients in the formulation [80].

Among over a hundred known phytosterols, sitosterol, stigmasterol, and campesterol are the most abundant in plants [81]. These compounds are of particular interest in the cosmetic industry for their ability to delay the UV-induced decline in collagen synthesis or even stimulate its production, making them valuable in anti-aging formulations [82]. β-sitosterol, in particular, stimulates hyaluronic acid synthase expression in fibroblasts, thereby increasing hyaluronic acid production and improving the expression of key functional skin barrier proteins, which supports moisture retention [83]. As a result, phytosterols are often incorporated into products such as creams and lipsticks [81].

The fatty acid, tocopherol, and phytosterol profiles of seed oils derived from C. lanatus, C. melo, and C. pepo highlight their potential for cosmetic applications (

Table 2. Predominant fatty acids, tocopherols, and phytosterols (expressed in %) in Cucurbitaceae seed oils and their application in cosmetics.

Compound	C. lanatus	C. melo	C. pepo	Properties/Applications
Palmitic acid	14.84–16.58 [10]	7.19–9.74 [87]	9.8–15.3 [88]	Lotions and cleansers; essential for skin barrier health [89]
Stearic acid	13.83–14.58 [10]	4.57–5.86 [87]	6.9–9.1 [88]	Lotions and cleansers; essential for skin barrier health [89]
Oleic acid	10.51–17.73 [10]	15.23–33.96 [87]	37.9–45.5 [88]	Cleansing agent [90]; effective penetration enhancer in topical application [85]; used in nanoparticle-mediated delivery systems [86]
Linoleic acid	52.57–56.94 [10]	50.69–69.22 [87]	32.6–35.4 [88]	Repair of the skin barrier; skin whitening; photoprotection; stimulation of hair growth [84]
α-Tocopherol	6.22 × 10−3–9.23 × 10−3 [10]	3.74 × 10−3–7.47 × 10−3 [87]	1.01 × 10−3–1.15 × 10−3 [91]	Lipsticks, sunscreens, hair and nail cosmetics, body lotions, and anti-wrinkle creams [30]; antioxidants and skin-conditioning agents [79]
β-Tocopherol	0.73 × 10−3–0.78 × 10−3 [10]	1.15 × 10−3–2.13 × 10−3 [87]	1.35 × 10−3 [92]
γ-Tocopherol	16.33 × 10−3–59.99 × 10−3 [10]	9.99 × 10−3–45.67 × 10−3 [87]	25.10 × 10−3–96.4 × 10−3 [91,92]
δ-Tocopherol	4.28 × 10−3–4.54 × 10−3 [10]	0.93 × 10−3–2.72 × 10−3 [87]	2.2 × 10−4–1.99 × 10−3 [91,92]
Stigmasterol/β -Sitosterol	28.30 × 10−3–58.05 × 10−3 [10]	1.29 × 10−3–324.84 × 10−3 [93]	147.7 × 10−3–208.2 × 10−3 [16]	Creams and lipstick [94]; anti-aging products, promote collagen and hyaluronic acid biosynthesis; retain moisture within skin [83]

). Linoleic acid emerges as the most abundant fatty acid across all three species, particularly in C. melo, where it can reach up to 69%. Linoleic acid is valued for its skin-repairing and whitening properties, as well as its roles in photoprotection and promoting hair growth [84]. Oleic acid, more prevalent in C. pepo, functions as a skin penetration enhancer and is often employed in nanoparticle-based delivery systems [85,86].

Regarding tocopherol composition, γ-tocopherol is predominant across the three species. This form is widely incorporated into lipsticks, sunscreens, and anti-wrinkle products for its antioxidant and skin-conditioning effects [30,79]. Among phytosterols, stigmasterol and β-sitosterol are notably concentrated in C. pepo, suggesting strong potential for this species in anti-aging cosmetic formulations [83].

2.3. Aminoacids

Amino acids and their salts play a fundamental role in maintaining skin and hair health, primarily through their involvement in hydration, pH regulation, and structural support. Consequently, they are widely incorporated into cosmetic formulations, particularly those aimed at skin moisturization and hair conditioning. Due to their biocompatibility and low irritation potential, amino acids are deemed safe for use in products applied around sensitive areas, including the eyes, mucous membranes, and infant skin. Among the most commonly used amino acids in cosmetic and personal care products are arginine and glycine [29,95]. Members of the L-aspartate family—such as L-threonine, L-lysine, L-methionine, and L-isoleucine—also find diverse applications in cosmetic formulations.

The topical use of amino acids in cosmetics is considered highly safe. Toxicological assessments report no evidence of carcinogenicity, genotoxicity, or oral toxicity and generally indicate minimal risk of dermal or ocular irritation. While animal studies involving rats, guinea pigs, and mice have revealed no adverse effects from topical application of amino acids like arginine, cysteine, or glycine, mild ocular irritation has been reported for serine and arginine. In rare cases, glutamate has been associated with allergic contact dermatitis [95,96,97].

Beyond their general cosmetic safety, it is important to highlight that Cucurbitaceae seeds, namely C. pepo, C. lanatus, and C. melo, exhibit a distinctive amino acid composition that reinforces their dermocosmetic potential. These seeds are particularly rich in arginine, glutamate, and branched-chain amino acids such as leucine and valine, compounds known for their roles in collagen synthesis, antioxidant defense, and hair follicle maintenance [95,98,99,100,101,102,103]. Compared to more commonly used sources such as soy or chia, Cucurbitaceae seeds present a composition especially suitable for multifunctional cosmetic formulations targeting hydration, tissue repair, and anti-aging effects [102,104,105,106].

As shown in Table 3, glutamate and arginine are the most abundant amino acids across the analyzed Cucurbitacea seeds. C. lanatus seeds are notably rich in aspartate, phenylalanine, alanine, valine, serine, proline, and leucine. In C. melo, elevated levels of tryptophan, aspartate, and leucine are observed, while C. pepo seeds predominantly contain phenylalanine, leucine, and aspartate.

Arginine is of particular interest due to its role in enhancing collagen deposition and promoting type I collagen secretion, which supports wound healing and tissue regeneration in keratoconus-derived constructs [98,107]. In murine models, both oral and topical administration of L-arginine has been shown to promote wound healing. Oral administration of this amino acid stimulates TGF-β signal transduction and modulates NO production, triggering a Th1-driven immune response and collagen deposition at injury sites, while topical application reduces IL-8 and CCR1 expression, mitigating the inflammatory response [108]. Furthermore, formulations combining arginine, glutamine, and β-hydroxy-β-methylbutyrate have demonstrated synergistic effects on collagen synthesis [98].

Although glutamate promotes keratinocyte proliferation, its limited solubility presents challenges for topical applications. However, when formulated as an arginine-glutamate ion pair, it significantly enhances skin elasticity and reduces damage by stimulating fibroblast-mediated collagen synthesis, showing superior efficacy compared to either amino acid alone [109].

In addition to arginine and glutamine, glycine and proline also contribute to enhanced collagen production through their metabolic pathways [110]. Furthermore, many amino acids found in these seeds support skin health through anti-aging effects related to antioxidant activity and increased collagen production/deposition [29,111]. They also promote hair health by strengthening the strands, improving their condition, and helping prevent split ends [112,113]. Amino acid deficiencies, particularly in histidine, leucine, valine, alanine, and cysteine, have been implicated in various forms of alopecia, underscoring their importance in hair follicle biology [114].

Table 3. Amino acids (expressed as g/100 g of protein) in Cucurbitaceae seeds and their application in cosmetics.

Amino Acid	C. lanatus	C. melo	C. pepo	Properties/Applications
Alanine	3.786–5.05 [99,100]	4.028–4.45 [45,101]	3.7–4.210 [102,103]	Used in conditioners to improve hair surface hydrophobicity of bleach-damaged hair [115]
Arginine	4.977–15.21 [99,100]	13.044–13.4 [45,101]	3.182–16.4 [102,103]	Antioxidant, supports collagen production [29], increasing collagen deposition [116]
Aspartate	6.09–10.39 [99]	7.318–8.98 [45,101]	9.0 [102]	Antioxidant, collagen production-promoting effect [116]
Cysteine	0.043–6.09 [99]	5.32 [101]	1.1 [102]	Used in hair waving and straightening formulations; fragrance ingredients [97]
Glutamate	4.462–16.75 [99,100]	19.7–20.523 [45,101]	17.9 [102]	Conditioning, cleansing, and emulsifying properties [96]; wrinkle formation and skin roughness reduction [111]
Glycine	1.20–5.04 [99]	1.983–4.94 [45,101]	4.2–5.912 [102,103]	Improvement in moisture retention and collagen production and strengthens the skin; skin repair and regeneration [29]
Histidine	2.15–2.887 [99,100]	1.58 [101]	2.312–2.4 [102,103]	Improve hair tensile strength [115]
Isoleucine	3.48–5.21 [99]	4.631–5.01 [45,101]	2.141–3.9 [102,103]	Repair and/or prevention of split ends in hair (in combination with lysine) [113]
Leucine	1.723–7.19 [99,100]	7.36–9.640 [45,101]	6.9–8.512 [102,103]	Minimize muscular flaccidity and decreased muscle tone; improving intramuscular protein synthesis, potentiating the increase in tonus and the contractile response of the muscle during daily living activities [117]
Lysine	0.315–3.05 [99,100]	2.81–3.369 [45,101]	3.012–3.8 [102,103]	Repair and/or prevention of split ends in hair (in combination with isoleucine) [113]
Methionine	0.88–2.17 [99]	0.82–2.205 [45,101]	2.1–7.217 [102,103]	Skin-conditioning agent, softener, and conditioner [118]
Phenylalanine	4.35–5.83 [99]	4.74–6.335 [45,101]	5.5–7.217 [102,103]	Production of the pigment melanin; treatment of vitiligo [119]; improvement in hair tensile strength [115]
Proline	3.05–4.142 [99,100]	3.86 [101]	3.4–4.126 [102,103]	Collagen biosynthesis [116]
Serine	3.91–4.96 [99]	2.381–4.86 [45,101]	2.013–5.2 [102,103]	Ultraviolet damage reduction [111]
Threonine	2.61–4.249 [99,100]	3.58–4.741 [45,101]	3.1–1.963 [102,103]	Makes up collagen and elastin; skin-conditioning agent; hair styling and care, hair conditioner, hair waving or straightening [120]
Tryptophan	1.037–1.17 [99,100]	12.991 [45]	0.517–2.7 [102,103]	Improve the strength and condition of the hair [112]
Tyrosine	3.298–3.96 [99,100]	2.40–4.06 [45,101]	3.012–3.9 [102,103]	Anti-melanogenic effect [121]
Valine	3.48–4.572 [99,100]	1.430–4.34 [45,101]	4.021–4.7 [102,103]	Make-up (eyeliners or brow-coloring products); flavoring [122]

Table 3. Amino acids (expressed as g/100 g of protein) in Cucurbitaceae seeds and their application in cosmetics.

Amino Acid	C. lanatus	C. melo	C. pepo	Properties/Applications
Alanine	3.786–5.05 [99,100]	4.028–4.45 [45,101]	3.7–4.210 [102,103]	Used in conditioners to improve hair surface hydrophobicity of bleach-damaged hair [115]
Arginine	4.977–15.21 [99,100]	13.044–13.4 [45,101]	3.182–16.4 [102,103]	Antioxidant, supports collagen production [29], increasing collagen deposition [116]
Aspartate	6.09–10.39 [99]	7.318–8.98 [45,101]	9.0 [102]	Antioxidant, collagen production-promoting effect [116]
Cysteine	0.043–6.09 [99]	5.32 [101]	1.1 [102]	Used in hair waving and straightening formulations; fragrance ingredients [97]
Glutamate	4.462–16.75 [99,100]	19.7–20.523 [45,101]	17.9 [102]	Conditioning, cleansing, and emulsifying properties [96]; wrinkle formation and skin roughness reduction [111]
Glycine	1.20–5.04 [99]	1.983–4.94 [45,101]	4.2–5.912 [102,103]	Improvement in moisture retention and collagen production and strengthens the skin; skin repair and regeneration [29]
Histidine	2.15–2.887 [99,100]	1.58 [101]	2.312–2.4 [102,103]	Improve hair tensile strength [115]
Isoleucine	3.48–5.21 [99]	4.631–5.01 [45,101]	2.141–3.9 [102,103]	Repair and/or prevention of split ends in hair (in combination with lysine) [113]
Leucine	1.723–7.19 [99,100]	7.36–9.640 [45,101]	6.9–8.512 [102,103]	Minimize muscular flaccidity and decreased muscle tone; improving intramuscular protein synthesis, potentiating the increase in tonus and the contractile response of the muscle during daily living activities [117]
Lysine	0.315–3.05 [99,100]	2.81–3.369 [45,101]	3.012–3.8 [102,103]	Repair and/or prevention of split ends in hair (in combination with isoleucine) [113]
Methionine	0.88–2.17 [99]	0.82–2.205 [45,101]	2.1–7.217 [102,103]	Skin-conditioning agent, softener, and conditioner [118]
Phenylalanine	4.35–5.83 [99]	4.74–6.335 [45,101]	5.5–7.217 [102,103]	Production of the pigment melanin; treatment of vitiligo [119]; improvement in hair tensile strength [115]
Proline	3.05–4.142 [99,100]	3.86 [101]	3.4–4.126 [102,103]	Collagen biosynthesis [116]
Serine	3.91–4.96 [99]	2.381–4.86 [45,101]	2.013–5.2 [102,103]	Ultraviolet damage reduction [111]
Threonine	2.61–4.249 [99,100]	3.58–4.741 [45,101]	3.1–1.963 [102,103]	Makes up collagen and elastin; skin-conditioning agent; hair styling and care, hair conditioner, hair waving or straightening [120]
Tryptophan	1.037–1.17 [99,100]	12.991 [45]	0.517–2.7 [102,103]	Improve the strength and condition of the hair [112]
Tyrosine	3.298–3.96 [99,100]	2.40–4.06 [45,101]	3.012–3.9 [102,103]	Anti-melanogenic effect [121]
Valine	3.48–4.572 [99,100]	1.430–4.34 [45,101]	4.021–4.7 [102,103]	Make-up (eyeliners or brow-coloring products); flavoring [122]

2.4. Vitamins

Vitamins are biologically active, readily absorbed compounds that confer a range of dermatological benefits, including the treatment of acne, hyperpigmentation, and atopic dermatitis, as well as exhibiting anti-aging properties and protecting the skin from environmental stressors. Their incorporation into skincare formulations is increasingly common, with particular emphasis on the antioxidant properties of vitamins C and E [28].

Vitamin E is a lipid-soluble antioxidant that plays a central role in dermal protection by preventing lipid peroxidation and mitigating reactive oxygen species (ROS)-induced damage. Vitamin C (ascorbic acid), a water-soluble compound, is widely used in topical applications due to its ability to stimulate collagen synthesis and protect against ultraviolet (UV)-induced skin damage [123].

The B-complex vitamins, known for their broad dermatological benefits, are commonly found in cosmetic products. However, their limited chemical stability often compromises product shelf-life and efficacy [124]. Vitamin A, another lipophilic antioxidant, is extensively used to prevent skin aging, particularly photoaging, due to its capacity to promote cell turnover and mitigate oxidative stress [123].

Vitamin D, particularly in the form of D₃ (cholecalciferol), exhibits multiple skin benefits. In keratinocytes, it regulates cellular proliferation and promotes differentiation, contributing to skin homeostasis and collagen production. Additionally, vitamin D has demonstrated anti-inflammatory and antioxidant properties, inhibited UV-induced DNA damage, and enhanced DNA repair mechanisms [125]. Topical formulations containing vitamin D₃ have shown efficacy in reducing inflammation and irritation, improving skin hydration and texture, and minimizing the appearance of fine lines and wrinkles [126].

Vitamin K has also gained attention in dermatology, particularly for its role in managing periorbital hyperpigmentation. Topical application of 1% vitamin K in hydrogel formulations has been shown to enhance dermal penetration and distribution, thereby improving its anti-pigmentation efficacy [127]. Vitamin K oxide-based gels have demonstrated effectiveness in reducing laser-induced purpura and resolving bruising associated with cosmetic procedures, such as soft tissue filler injections [128]. Furthermore, vitamin K has shown potential in promoting wound healing through mechanisms involving increased wound contraction, accelerated epithelialization, and enhanced fibroblast and collagen fiber formation, likely due to its antioxidant activity [129].

The seeds analyzed in this study contain measurable amounts of both water- and fat-soluble vitamins, though their concentrations are generally modest compared to those found in many fruits and vegetables. As detailed in Table 4, C. lanatus seeds exhibit the highest concentrations of vitamins A and C. C. melo seed oil is notably rich in vitamin E, with reported concentrations often exceeding 400 mg/kg, placing it among the most potent natural sources of this antioxidant [87]. Similarly, C. pepo seeds and their derived oils consistently show high levels of vitamin E isoforms, particularly γ- and δ-tocopherol [130]. The observed variability in vitamin content is largely influenced by cultivar, environmental conditions, and differences in analytical methodologies used in the studies summarized in Table 4.

Table 4. Most abundant vitamins (expressed in mg/kg) in Cucurbitaceae seeds and their applications in cosmetics.

Vitamin	C. lanatus	C. melo	C. pepo	Properties/Applications
Vitamin A	701 [131]	1.513 [132]	0.048–0.19 [133,134]	Promote a normal keratinization cycle; control sebum production in acne; reverse and treat damage from sun exposure, striae, and cellulite [28]
Vitamin B1	0.2–2.14 [130,131]	0.013 [132]	0.34–2.72 [133,134]	Antipruritic action, rosacea, and seborrheic diseases treatment [124]
Vitamin B2	0.796–2.54 [110,131]	Not found	0.52–1.5 [133,134]	Anti-inflammatory action, rosacea, and seborrheic disease treatment [124]
Vitamin B3	0.81–33.2 [130,131]	Not found	2.86–48 [133,134]	Antimicrobial; anti-inflammatory; antipruritic; vasoactive; lightening; photoprotective; sebostatic effects, acne, atopic dermatitis, skin aging, melasma, light damage of the skin, hyperpigmentation treatment [124]
Vitamin B6	0.053–125.50 [110,131]	Not found	0.37–1.4 [133,134]	Increase skin barrier’s integrity and function; atopic dermatitis treatment [124]
Vitamin B9	1.843 [110]	0.0043 [132]	0.09–0.58 [133,134]	Cell replication, gene regulation, skin renewal, photodamaged treatment, anti-aging [124]
Vitamin B12	1.07–1.092 [110,131]	Not found	Not found	Pro-inflammatory cytokine production suppression; cell proliferation; lymphocyte activity enhancement; atopic dermatitis and childhood eczema treatment [124]
Vitamin C	19.450–372.90 [110,131]	1.636 [132]	2.72–3 [133,134]	Antioxidant; regulation of collagen synthesis; formation of a hydrolipidic mantle in the stratum corneum; vitamin E regeneration; photoprotection (when combined with vitamin E) [28]
Vitamin D	8.760–13.98 [110,131]	Not found	Not found	Control of cutaneous immune system and epithelial proliferation stimulates differentiation [28]; photoprotection and prevention of skin aging [125]; atopic dermatitis, vitiligo, acne, and rosacea treatment [126]
Vitamin E	3.533–8.86 [110,131]	1.5 × 102 [132]	2.22–351 [133,135]	Antioxidant, protection of the integrity of cell membranes against oxidative damage; photoprotection (when combined with vitamin C) [28]
Vitamin K	1.437 [110]	Not found	0.071 [134]	Treatment of under-eye circles, anti-aging, anti-wrinkle [136]

Table 4. Most abundant vitamins (expressed in mg/kg) in Cucurbitaceae seeds and their applications in cosmetics.

Vitamin	C. lanatus	C. melo	C. pepo	Properties/Applications
Vitamin A	701 [131]	1.513 [132]	0.048–0.19 [133,134]	Promote a normal keratinization cycle; control sebum production in acne; reverse and treat damage from sun exposure, striae, and cellulite [28]
Vitamin B1	0.2–2.14 [130,131]	0.013 [132]	0.34–2.72 [133,134]	Antipruritic action, rosacea, and seborrheic diseases treatment [124]
Vitamin B2	0.796–2.54 [110,131]	Not found	0.52–1.5 [133,134]	Anti-inflammatory action, rosacea, and seborrheic disease treatment [124]
Vitamin B3	0.81–33.2 [130,131]	Not found	2.86–48 [133,134]	Antimicrobial; anti-inflammatory; antipruritic; vasoactive; lightening; photoprotective; sebostatic effects, acne, atopic dermatitis, skin aging, melasma, light damage of the skin, hyperpigmentation treatment [124]
Vitamin B6	0.053–125.50 [110,131]	Not found	0.37–1.4 [133,134]	Increase skin barrier’s integrity and function; atopic dermatitis treatment [124]
Vitamin B9	1.843 [110]	0.0043 [132]	0.09–0.58 [133,134]	Cell replication, gene regulation, skin renewal, photodamaged treatment, anti-aging [124]
Vitamin B12	1.07–1.092 [110,131]	Not found	Not found	Pro-inflammatory cytokine production suppression; cell proliferation; lymphocyte activity enhancement; atopic dermatitis and childhood eczema treatment [124]
Vitamin C	19.450–372.90 [110,131]	1.636 [132]	2.72–3 [133,134]	Antioxidant; regulation of collagen synthesis; formation of a hydrolipidic mantle in the stratum corneum; vitamin E regeneration; photoprotection (when combined with vitamin E) [28]
Vitamin D	8.760–13.98 [110,131]	Not found	Not found	Control of cutaneous immune system and epithelial proliferation stimulates differentiation [28]; photoprotection and prevention of skin aging [125]; atopic dermatitis, vitiligo, acne, and rosacea treatment [126]
Vitamin E	3.533–8.86 [110,131]	1.5 × 102 [132]	2.22–351 [133,135]	Antioxidant, protection of the integrity of cell membranes against oxidative damage; photoprotection (when combined with vitamin C) [28]
Vitamin K	1.437 [110]	Not found	0.071 [134]	Treatment of under-eye circles, anti-aging, anti-wrinkle [136]

2.5. Minerals

Cucurbitaceae seeds are a rich source of bioactive minerals, including calcium (Ca), potassium (K), magnesium (Mg), zinc (Zn), and iron (Fe), with concentrations varying across species such as C. lanatus, C. melo, and C. pepo (Table 5). These minerals have well-documented applications in cosmetics due to their diverse dermatological benefits and their role in promoting environmentally responsible formulations.

Ca, found in high levels in C. melo (up to 806.4 mg/100 g), functions as a skin protectant and bulking agent in products such as sunscreens, deodorants, and cleansers. Its similarity to synthetic agents makes it an increasingly sustainable alternative in cosmetic formulations [137].

Mg and K, particularly abundant in C. melo and C. pepo, contribute to detoxification and hydration when incorporated into white clay-based facial masks and exfoliants. These clays—rich in Ca, K, Mg, aluminum (Al), and silicium (Si)—exhibit antibacterial, antiseptic, and regenerating properties and are effective in treating acne and inflammatory skin conditions [30].

Zn, present at levels up to 24.6 mg/100 g in C. melo, is a key mineral in dermatological care due to its antimicrobial, anti-inflammatory, and photoprotective properties. It is frequently used in sunscreens, anti-dandruff shampoos, and acne treatments because of its effectiveness and low systemic toxicity [31,138]. In the form of zinc pyrithione, it is also utilized to treat seborrheic dermatitis [139]. Furthermore, when combined with iron oxides, zinc oxide enhances protection against UV and high-energy visible (blue) light, offering a safe and sustainable alternative for skin photoprotection [140].

Fe, reaching up to 144.70 mg/100 g in C. lanatus, is widely used as a natural pigment in mineral makeup, including foundations and lipsticks. Additional trace elements like copper (Cu, up to 89.84 mg/100 g in C. pepo), Al, and manganese (Mn) support skin regeneration and collagen production, while also contributing to anti-aging and anti-inflammatory effects.

Together, these mineral constituents highlight the multifunctionality and sustainability of Cucurbitaceae seeds as cosmetic ingredients.

Table 5. Most abundant minerals (mg/100 g) in Cucurbitaceae seeds and their applications in cosmetics.

Mineral	C. lanatus	C. melo	C. pepo	Properties/Applications
Al	0.0015 [100]	Not found	0.921 [102]	Skin care products, such as creams; inflammatory skin condition ulcers, pimples, and other types of skin rash treatments; active base in face masks [30]
Ca	0.10–30.8 [141,142]	8.34–806.4 [143]	3.76–141.00 [103,144]	Texture enhancer, bulking agent, and opacifying agent; oral care (whitening agents, bleaching agents, abrasives); skin care (sunscreens, pigments, foundations, sebum adsorbers, delivery of nutrients, cleansers); hair care (dyes and solid hair products); deodorants (antibacterials, antiperspirants, odor control) [137]
Cr	0.0683 [100]	Not found	0.284 [102]	Eyeshadow, face paint, lipstick, make-up powder, skin cream and emulsion, soap [145]
Cu	0.243–2.53 [100,141]	0.53–15.9 [143]	0.21–89.84 [103,144]	Collagen maturation stimulation and skin elasticity improvement [123]
Fe	1.5190–144.70 [100,141]	2.69–81.17 [143]	3.75–33.14 [144]	Colorants in skin, hair, and nail cosmetic products [146]; eyeshadow, blusher, powder, lipstick, and mineral make-up [147]
K	1.8189–236.7 [100,141]	309.1–9548.33 [142,143]	103.12–4300.00 [144]	White clays [30]
Mg	1.0637–25.0 [140]	101.71–3299.27 [143]	4.20–2385.00 [103,144]	White clays [30]
Mn	0.0301–22.73 [100,141]	1.25–15.20 [143]	0.06–8.90 [144]	Lipstick, lip gloss/lip balm, face powder, eyeliner, eyeshadow/pencil, blush, mascara [145]
Na	0.21–98.6 [140,141]	41.22–386.13 [143]	0.69–189.81 [102,144]	White clays [30]
Zn	0.0905–21.05 [100,141]	2.34–24.6 [142,143]	1.24–14.14 [144]	UV irradiation skin protection [123]; acne and seborrheic dermatitis treatment [138]

Table 5. Most abundant minerals (mg/100 g) in Cucurbitaceae seeds and their applications in cosmetics.

Mineral	C. lanatus	C. melo	C. pepo	Properties/Applications
Al	0.0015 [100]	Not found	0.921 [102]	Skin care products, such as creams; inflammatory skin condition ulcers, pimples, and other types of skin rash treatments; active base in face masks [30]
Ca	0.10–30.8 [141,142]	8.34–806.4 [143]	3.76–141.00 [103,144]	Texture enhancer, bulking agent, and opacifying agent; oral care (whitening agents, bleaching agents, abrasives); skin care (sunscreens, pigments, foundations, sebum adsorbers, delivery of nutrients, cleansers); hair care (dyes and solid hair products); deodorants (antibacterials, antiperspirants, odor control) [137]
Cr	0.0683 [100]	Not found	0.284 [102]	Eyeshadow, face paint, lipstick, make-up powder, skin cream and emulsion, soap [145]
Cu	0.243–2.53 [100,141]	0.53–15.9 [143]	0.21–89.84 [103,144]	Collagen maturation stimulation and skin elasticity improvement [123]
Fe	1.5190–144.70 [100,141]	2.69–81.17 [143]	3.75–33.14 [144]	Colorants in skin, hair, and nail cosmetic products [146]; eyeshadow, blusher, powder, lipstick, and mineral make-up [147]
K	1.8189–236.7 [100,141]	309.1–9548.33 [142,143]	103.12–4300.00 [144]	White clays [30]
Mg	1.0637–25.0 [140]	101.71–3299.27 [143]	4.20–2385.00 [103,144]	White clays [30]
Mn	0.0301–22.73 [100,141]	1.25–15.20 [143]	0.06–8.90 [144]	Lipstick, lip gloss/lip balm, face powder, eyeliner, eyeshadow/pencil, blush, mascara [145]
Na	0.21–98.6 [140,141]	41.22–386.13 [143]	0.69–189.81 [102,144]	White clays [30]
Zn	0.0905–21.05 [100,141]	2.34–24.6 [142,143]	1.24–14.14 [144]	UV irradiation skin protection [123]; acne and seborrheic dermatitis treatment [138]

Figure 2 summarizes the composition of Cucurbitaceae seeds, as well as their potential applications in cosmetics.

3. Nanoencapsulation Techniques for Seed Oils in Cosmetic Applications

Building on previous discussions regarding the potential of seed oils in skincare formulations, this section focuses on advanced nanoencapsulation strategies designed to optimize their functional performance. Seed oils, known for their richness in polyunsaturated fatty acids, tocopherols, phytosterols, and phenolic compounds, exhibit moisturizing, antioxidant, anti-inflammatory, and regenerative effects that are highly desirable in cosmetic applications. These attributes support their use in products targeting hydration, anti-aging, sun protection, and skin barrier enhancement. However, their inherent instability—marked by susceptibility to oxidation, photodegradation, low water solubility, and limited skin permeability—poses significant formulation challenges [148].

To address these limitations, nanoencapsulation has gained prominence as a versatile and efficient delivery strategy. By incorporating seed oils into nanoscale carriers such as lipid-based nanoparticles, polymeric nanocapsules, liposomes, and nanoemulsions, researchers have been able to improve the oils’ physicochemical stability, enhance dermal absorption, and increase bioavailability. Moreover, these nanocarriers enable controlled and sustained release, extending the bioactive effects while minimizing the frequency of application [149,150,151]. Enhanced sensory attributes, such as reduced greasiness and improved spreadability, further contribute to the commercial appeal of nanoformulated products [150].

Typically ranging from 20 to 500 nm in diameter, nanocarriers can be engineered to suit specific formulation objectives and the distinct physicochemical characteristics of each seed oil. Encapsulation techniques—such as nanoemulsification, electrospinning, nanoprecipitation, and ionic gelation—offer diverse advantages regarding encapsulation efficiency, formulation stability, scalability, and compatibility with cosmetic matrices [152,153]. For instance, nanoemulsions are prized for their straightforward fabrication and lightweight texture, while solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) offer superior oxidative protection and enhanced skin occlusion [154]. Selecting an appropriate encapsulation method thus requires careful consideration of both technical feasibility and desired functional outcomes.

Table 6. Nanoencapsulation strategies for seed oils in cosmetic applications.

Technique/Delivery System	Encapsulating Material	Particle Size	Encapsulation Efficiency	Stability	Description	Cosmetic Application	Seed Oil	References
Nanoemulsification	Tween 80, lecithin, PEG-40 hydrogenated castor oil	20–200 nm	80–95%	Stable for up to 3 months (RT)	Oil-in-water or water-in-oil systems stabilized by surfactants. Enhance dispersion of hydrophobic oils. Increase bioavailability and stability of lipophilic compounds.	Provides light and non-greasy texture. Increased skin absorption. Used in moisturizers, sunscreens, and anti-aging creams.	Caesalpinia decapetala, Melaleuca alternifolia, Nigella sativa. Cucurbita pepo, Cucurbita maxima, Cucurbita moschata	[149,150,155,156,157,158]
Electrospinning	Chitosan and polyvinyl alcohol (PVA)	~200–700 nm (fiber diameter)	Moderate (~60%)	Stable in dry conditions; moisture-sensitive	High-voltage technique producing nanofibers embedding oils.	Applied in dermal masks, wound dressings, and anti-inflammatory pads. Biodegradable and high-surface release systems.	Nigella sativa, Cucurbita pepo	[159,160]
Nanoprecipitation	Propolis–phosphatidylcholine complex and Eudragit	100–250 nm	80–90%	Stable for >30 days at RT or 4 °C	Solvent displacement process creating polymer nanoparticles. Improves oxidative stability and dispersibility of seed oils. Rapid and energy-efficient process.	Incorporated in antioxidant gels and anti-aging emulsions. Employed in cosmetic formulations containing heat-sensitive lipophilic bioactives.	Camellia sinensis, Salvia hispanica	[152,161,162]
Ionic gelation	Chitosan and sodium tripolyphosphate (TPP)	~50–800 nm	~70–85%	Stable in acidic pH; sensitive to multivalent ions	Nanoparticles formed by ionic crosslinking of oppositely charged biopolymers. Carried out under mild conditions without organic solvents. Suitable for encapsulating heat- and pH-sensitive seed oils.	Used in moisturizing gels, anti-inflammatory creams, and sensitive skin formulations. For controlled release of antioxidants and enhanced dermal delivery.	Citrus sinensis, Linalool oil	[163,164,165,166]
Liposomes	Phosphatidylcholine and cholesterol	50–300 nm	Moderate to high (60–85%)	Physically unstable over time (risk of fusion/leakage); improved with ethosomes or gel-thickened systems	Spherical vesicles with phospholipid bilayers encapsulating aqueous and lipophilic phases. Mimic skin lipid structure, enhancing bioavailability and hydration. Flexible formulations include ethosomes, niosomes, transfersomes, and gelosomes.	Used in anti-aging serums, eye creams, and skin-repair gels. Enhance skin penetration, reduce irritation, and provide deep moisturization.	Ribes nigrum, Cucurbita pepo, Cucumis melo; Punica granatum	[148,151,167,168]
Colloidosomes	Silica nanoparticles, chitosan, polymeric shells	200 nm–2 μm	Moderate (~60–75%)	Stable under controlled pH and ionic conditions; tunable release via shell permeability	Microcapsules formed by self-assembly of colloidal particles at oil–water interfaces. Can be designed to respond to pH or temperature for controlled release. Limited commercial application but promising for targeted delivery.	Potential use in serums or targeted release patches. Offers protection of sensitive compounds and gradual release of antioxidants or fragrances.	Punica granatum, Linum usitatissimum	[169,170,171]
Nanostructured lipid carriers (NLCs)	Mixture of solid (e.g., glyceryl behenate) and liquid lipids (e.g., oleic acid), stabilized with surfactants	80–200 nm	High (70–95%)	Good physical and chemical stability; resistant to lipid polymorphism if optimized	Lipid matrix combining solid and liquid lipids forms imperfect crystalline structure. Enables high loading and controlled release of bioactives. Suitable for hydrophobic seed oils needing enhanced penetration and shelf-life.	Widely used in anti-aging creams, UV-protective lotions, and intensive moisturizers. Improves skin retention, hydration, and antioxidant protection.	Opuntia ficus-indica, Punica granatum, Cucurbita pepo, Ribes nigrum, Morus nigra, Rubus idaeus, Fragaria × ananassa, Prunus domestica	[148,154,172,173,174,175,176]
Solid lipid nanoparticles (SLNs)	Solid lipids (e.g., stearic acid, glyceryl stearate) and surfactants	50–300 nm	Moderate to high (60–85%)	High oxidative and photostability; crystallization may lead to bioactive expulsion over time	Nanoparticles composed entirely of solid lipids forming a crystalline matrix. Protects oils from oxidation and light degradation.	Used in skin barrier-repair creams, antioxidant serums, and wound-healing ointments. Improves bioactive stability, prolongs skin contact and moisturizing effect.	Cucurbita pepo, Vitis vinifera	[177]

provides a comparative summary of the most relevant nanoencapsulation approaches currently employed for seed oils in cosmetic applications, highlighting key parameters such as encapsulating materials, particle size, entrapment efficiency, formulation stability, and targeted cosmetic outcomes. This overview serves as a practical reference for the formulation of next-generation dermocosmetic products.

Nanoencapsulation of Cucurbitaceae Seed Oils: Applications and Advancements in Cosmetics

As with other botanical seed oils, the incorporation of Cucurbitaceae seed oils into nanocarrier systems has led to significant advancements in their stability, bioavailability, and cosmetic efficacy. For example, Klopcevska et al. [178] demonstrated that nanoemulsions containing C. pepo (pumpkin) seed oil significantly improved antioxidant activity and skin hydration, supporting their application in moisturizers and anti-aging products. Similarly, Al-Bayati et al. [179] reported that encapsulating pumpkin seed oil via ionic gelation into chitosan-based nanoparticles enhanced skin penetration and enabled the controlled release of active compounds, rendering it particularly suitable for wound-healing and skin-repair applications.

Nanostructured lipid carriers (NLCs) formulated with C. pepo oil have exhibited photoprotective effects, allowing for the stable integration of UV filters and improved protection against ultraviolet radiation [175]. Electrospun nanofiber scaffolds incorporating pumpkin seed oil have also shown potential in regenerative applications, offering a moist, protective matrix conducive to dermal repair and sustained bioactive release [160].

Other studies have explored the incorporation of watermelon seed oil and melon seed oil into nanocarriers to maximize their cosmeceutical potential. Petchsomrit et al. [26] reported that nanoemulsions containing watermelon seed oil improved skin hydration and antioxidant activity, suggesting their relevance for moisturizing creams and sunscreens. Likewise, Akhter et al. [180] developed nanoemulsions of melon seed oil that enhanced skin permeability and antifungal activity, broadening their application to topical treatments. Teeranachaideekul et al. [181] also formulated niosomes with pumpkin seed oil, achieving enhanced skin permeation and anti-hair loss effects.

In addition to these application-oriented findings, Cucurbitaceae seed oils exhibit compositional and functional traits that differentiate them from other botanical sources. Oils from Cucurbita pepo, Citrullus lanatus, and Cucumis melo are particularly rich in linoleic and oleic acids, γ-tocopherol, and phytosterols such as β-sitosterol and stigmasterol, a profile that underpins their antioxidant, anti-inflammatory, skin-conditioning, and barrier-repair effects [26,79,80,81,180,181]. Notably, C. melo oil is particularly rich in linoleic acid, a key component in skin barrier repair and photoprotection, while C. pepo shows higher levels of oleic acid, known to enhance the dermal penetration of active compounds [84], while C. pepo presents higher levels of oleic acid, which facilitates the dermal penetration of encapsulated actives [16,43,86]. Compared to other oils like Nigella sativa (rich in thymoquinone) or Salvia hispanica (rich in α-linolenic acid), Cucurbitaceae oils display a more balanced lipid composition suitable for a wide range of cosmetic functions [152,162,166,167].

These compositional advantages translate into strong performance in nanoencapsulation systems. Due to their balanced polarity and relatively low viscosity, Cucurbitaceae oils are highly compatible with various nanocarriers, showing excellent encapsulation efficiency, formulation stability, and scalability under mild processing conditions [160,175,178,179,180]. The encapsulation of their bioactives enhances dermal absorption and protects labile compounds from oxidation and photodegradation, thereby maximizing their efficacy in anti-aging, skin regeneration, and photoprotective products [151,161].

Furthermore, the use of Cucurbitaceae seed oils aligns with circular bioeconomy principles and sustainability goals. As abundant, low-cost by-products of the food industry, these seeds offer an ethical and environmentally responsible alternative to synthetic ingredients [4,5,6,7,14,15,93,99,182]. Their valorization into high-performance cosmetic formulations supports waste reduction and adds economic value to agro-industrial chains, reinforcing the ecological and innovative character of this research.

These findings illustrate how nanoencapsulation strategies not only stabilize Cucurbitaceae seed oils but also expand their functional versatility in cosmetic products.

Table 7. Cosmetic applications of nanoencapsulated Cucurbitaceae seed oils.

Seed Oil	Encapsulation System	Cosmetic Application	Observed Benefits	Reference
C. pepo	NLCs	Sunscreens; photoprotective lotions	UV protection and photostability increasement	[175]
	Niosomes	Topical anti-inflammatory creams; anti-hair loss therapy	Enhanced skin permeation; inhibition of 5α-reductase; hair loss reduction of 44.42% in vivo	[181]
	Chitosan/PVA-based electrospun nanofiber	Wound dressing; dermal regeneration	Promotes skin regeneration; provides sustained release; protective moist environment for wound healing	[160]
	Nanoemulsion	Moisturizing creams; anti-aging products	Enhanced skin hydration; improved antioxidant stability; formation of stable O/W emulsions	[178]
	Chitosan nanoparticles (phytosome via ionic gelation)	Wound-healing gels; skin care formulations	Improved skin penetration; controlled release of bioactives; accelerated wound healing in vivo	[179]
C. melo	Nanoemulsion	Topical delivery with antifungal activity	Improved skin permeability; enhanced antifungal activity (vs. Candida albicans and Trichophyton rubrum)	[180]
C. lanatus	Nanoemulsion	Cosmeceutical formulations; moisturizing creams	Enhanced antioxidant activity; improved skin hydration; high PUFA content contributes to barrier repair	[26]

summarizes selected examples from the literature, detailing the encapsulation systems employed, their cosmetic applications, and the observed benefits.

4. Perspectives and Current Limitations in the Cosmetic Use of Cucurbitaceae Seed Oils

Despite the increasing interest in Cucurbitaceae seed oils as functional ingredients in cosmetics, several challenges remain that may limit their broader commercial applications. A key issue is the high variability in their phytochemical composition, influenced by factors such as species, cultivar, geographic origin, agricultural conditions, and extraction methods [183]. This lack of standardization complicates quality control and batch-to-batch consistency, both essential in the development of safe and effective dermocosmetic products.

Another critical limitation is their chemical instability. Rich in polyunsaturated fatty acids, Cucurbitaceae oils are highly susceptible to oxidation during processing and storage, especially when exposed to light, heat, and air [184]. Although nanoencapsulation can significantly improve oxidative stability and prolong shelf life, further formulation strategies are needed to fully overcome these degradation risks. In addition, certain sensory properties, such as greasiness or strong odor, may affect consumer acceptability unless properly refined or masked through formulation [148].

From a biological standpoint, skin penetration and bioavailability of bioactives remain complex. Even with advanced carriers, delivering lipophilic compounds to deeper skin layers in effective concentrations is a known challenge. Moreover, as with any natural extract, there is potential for skin irritation or sensitization in sensitive individuals, reinforcing the need for thorough safety testing and dermatological assessments [185].

Another limitation lies in the still-limited number of well-controlled clinical trials. Most available data on Cucurbitaceae oils derive from in vitro or preclinical studies, which, although promising, do not fully validate their efficacy and safety in human skin applications [186]. Stronger clinical evidence is needed to support specific cosmetic claims and guide regulatory approval.

Looking ahead, several strategies can strengthen the role of Cucurbitaceae oils in cosmetic science. Advancing nanoencapsulation technologies, including stimuli-responsive and multifunctional systems, may enhance both efficacy and formulation stability while allowing reduced active concentrations. Integrating these oils into synergistic formulations with other botanicals or bioactives could offer enhanced, multi-targeted skin benefits. Simultaneously, embracing omics technologies (e.g., metabolomics and lipidomics) can provide deeper insights into the bioactive profiles of different Cucurbitaceae species, leading to the discovery of novel compounds with dermatological potential [187,188].

In addition, adopting integrated biorefinery approaches and sustainable sourcing protocols will be crucial to maximizing value from these agro-industrial by-products, reinforcing their relevance in the clean beauty and circular bioeconomy movements [4,14,189].

By addressing these current limitations and focusing on innovation and standardization, Cucurbitaceae seed oils have the potential to become highly valued, eco-conscious ingredients in next-generation cosmetic formulations.

5. Conclusions

This review underscores the untapped potential of Cucurbitaceae seeds—particularly from watermelon (Citrullus lanatus), melon (Cucumis melo), and pumpkin (Cucurbita pepo)—as multifunctional ingredients in the cosmetic industry. Rich in polyunsaturated fatty acids, tocopherols, phytosterols, phenolic compounds, vitamins, amino acids, and minerals, these seeds offer a wide range of cosmetic benefits. Their bioactive profiles support deep skin hydration, antioxidant protection, anti-inflammatory action, sebum regulation, collagen synthesis, and the treatment of skin disorders such as acne, hyperpigmentation, and psoriasis. Additionally, in hair care, their lipid and amino acid contents contribute to strengthening strands, reducing frizz, and promoting scalp health.

Among the seeds studied, C. pepo (pumpkin) stands out as particularly promising for future cosmetic applications. Its oil exhibits a favorable fatty acid composition (notably high in oleic and linoleic acids), robust antioxidant and anti-inflammatory effects, and a rich content of γ-tocopherol, β-sitosterol, and phenolic acids. These attributes make it highly suitable for incorporation into anti-aging, moisturizing, and regenerative formulations. Moreover, its demonstrated compatibility with nanoencapsulation techniques—such as nanoemulsions, liposomes, and nanostructured lipid carriers—enhances its bioavailability, stability, and dermal absorption, further expanding its application potential.

C. melo and C. lanatus also show strong cosmetic promise, especially due to their high flavonoid and vitamin contents, as well as their skin-brightening, moisturizing, and photoprotective effects. Notably, C. melo seeds are rich in catechins and resveratrol, while C. lanatus seeds provide significant amounts of vitamins A and C—both crucial for skin health and anti-aging.

The valorization of these seeds not only supports the development of innovative, high-performance, and eco-conscious cosmetic products but also aligns with circular economy and sustainability goals by repurposing agricultural by-products. Future research should prioritize the comprehensive evaluation of their safety, efficacy, and optimal delivery systems to facilitate their widespread adoption in next-generation cosmetic formulations.

While Cucurbitaceae seeds exhibit promising bioactive properties for cosmetic applications, several challenges must be considered for their broader industrial adoption. One significant limitation involves the cost and complexity of extracting and purifying the active compounds from natural sources, which can be higher than those associated with synthetic ingredients. Furthermore, incorporating these bioactives into stable and effective formulations, particularly through advanced delivery systems such as nanoencapsulation, often requires specialized technology and increased production costs. Compared to synthetic alternatives, which are typically more cost-efficient and easier to scale, natural seed-based ingredients may face barriers in terms of economic feasibility. Nevertheless, the increasing consumer preference for natural, sustainable, and plant-derived cosmetic products is helping to drive innovation and investment in overcoming these limitations. These factors highlight the need for continued research into optimizing processing methods and improving cost-effectiveness while maintaining the functional benefits of Cucurbitaceae-derived compounds.