Plant-Derived Mucilage: A Natural Antioxidant with Multi-Functional Applications in Food, Cosmetics, and Health ^†

Abstract

Mucilage, naturally occurring polysaccharides in various plant parts, possesses unique structural and multi-functional properties. These biopolymers consist primarily of com-plex polysaccharides associated with flavonoids, phenolics, and oxidized sugars. A systematic review of databases like PubMed, Scopus, and Web of Science evaluated 22 re-search papers on mucilage with antioxidant potential. The key finding highlights that Cydonia ob-longa, Abelmoschus esculentus, Zizyphus mauritiana, Coccinia indica, Hibiscus rosa-sinensis, Malva parviflora, Corchorus olitorius, and Dioscorea opposita contain antioxidants. Various analytical techniques include DPPH, ABTS, FRAP, hydroxyl radical, and superoxide radical assays for the evaluation of the antioxidant properties of mucilage. The findings aim to foster innovation in health benefits and applications in food and cosmetic products, leveraging the multi-functional potential of these biopolymers to enhance efficacy and safety.

1. Introduction

Antioxidants can delay or prevent the oxidation of cellular oxidizable substances. Synthetic antioxidants, such as butylated hydroxyanisole (BHA) and butylated hydroxy-toluene (BHT), have been commonly used for industrial processing to reduce damage to the human body and prolong the storage stability of food [1]. Naturally occurring antioxidants that have no adverse effects are drawing more attention. Mucilage, a gelatinous substance found in certain plants (such as dioscorea, flaxseeds, and okra), has been recognized for its antioxidant properties, which can contribute to various health benefits. Polysaccharides have a high molecular weight, consisting of sugar and uronic acid units that can be easily dissolved and dispersed in water [2]. Polysaccharides have traditionally been widely used as food stabilizers, thickeners, and emulsifiers to improve the stability and textural properties of many food products such as jellies, salad dressings, and desserts [3]. In addition, polysaccharides have also demonstrated significant physiological effects such as from dietary fiber [4]. In recent years, many studies have also investigated the health and functional benefits of polysaccharides as antioxidants. Mucilage is primarily composed of polysaccharides, which are known to interact with free radicals and reactive oxygen species (ROS). The structural complexity of these polysaccharides contributes to their ability to scavenge free radicals, thereby mitigating oxidative stress [5,6]. Antioxidants are useful in treating many human diseases, including cancer, cardiovascular diseases, and inflammatory diseases. A variety of polysaccharides from marine plants, microbes, and higher plants have been reported to demonstrate antioxidant properties [7]. In this review, we explore the consolidated knowledge on natural mucilage, its bioactive antioxidant compounds, the underlying mechanism of action, and its potential applications in the pharmaceutical, food, and cosmetic industries. This review not only synthesizes the existing literature but also identifies mucilage as a distinctive, multi-functional natural polymer with promising antioxidant potential, distinguishing it from prior reviews that addressed polysaccharides more generally.

2. Chemical Composition of Mucilage

Mucilage primarily consists of polysaccharides, which can include uronic acids and various sugars such as galactose, rhamnose, arabinose, and glucose. These components contribute to the mucilage’s ability to scavenge free radicals and reduce oxidative stress. Mucilage is often rich in minerals and proteins that may also play a role in enhancing its antioxidant capacity [8,9]. These compounds can donate hydrogen atoms or electrons to free radicals, thereby neutralizing them and preventing cellular damage [10]. The chemical composition of mucilage shown in Figure 1.

3. Phytochemical Analysis and Antioxidant Assay

3.1. Estimation of Total Phenolic Content

The determination of total phenolic content is a common analytical method employed in natural product research. A widely utilized approach is the Folin–Ciocalteu method [11], which involves combining the test solution with the Folin–Ciocalteu phenol reagent. Following a brief incubation period (typically 5 min), a sodium carbonate solution is added to the mixture. The reaction is then allowed to proceed for a longer incubation period, commonly 90 min, at room temperature. Finally, the absorbance of the developed blue chromophore is determined spectrophotometrically at 750 nm against a blank, using a UV–visible spectrophotometer. This absorbance value is then correlated with a standard curve (e.g., using gallic acid) to quantify the total phenolic content. Examples of this are given in

Table 1. Phenolic content of plant-derived mucilage.

Sr. No.	Plant Name	Plant Parts	Phenolic Content (mgGAE/g)	Ref.
1	Abelmoschus esculentus	Fruits	4.81	[12]
2	Talinum triangulare	Water leaf	5.44	[12]
3	Corchorus olitorius	Jews mallow	6.43	[12]
4	Opuntia ficus-indica	Cladodes	2 to 6	[13]
5	Abelmoschus esculentus	Pods	24.66 to 49.93	[14]

.

3.2. Methods for Antioxidant Activity

The antioxidant activities of natural polymers commonly utilize ABTS⁺ [9], reducing power [12], DPPH [15,16], hydroxyl [17], conjugated diene methods [18] and superoxide radical scavenging assays [19,20]. Absorbance was measured at respective wavelengths after incubation under specified conditions. The precise protocols for each assay have been outlined by various authors and researchers. The primary principle remains consistent: to demonstrate the potential of mucilage to neutralize free radicals and inhibit oxidative damage.

Table 2. Antioxidant activity of mucilage-containing plants evaluated by various assays.

Sr. No.	Plant Name	Model for Antioxidant Activity	Antioxidant Content	Ref.
1	Abelmoschus esculentus L.	DPPH	73.83 µg/mL	[8]
		FRA, DPPH	59.03%, 23.04%, and 40.40%	[12]
		DPPH	IC50 3.15 to 6.60 (mg/mL)	[14]
2	Corchorus olitorius L.	DPPH, ABTS•+	59.80, 31.20% for 1 mg/mL	[9]
		FRA, DPPH	73.60%, 10.29%, and 12.76%.	[12]
3	Malva parviflora L.	DPPH	IC50 value of 154.27 µg/mL	[10]
4	Talinum triangulare Willd.	FRA, DPPH	80.20%, 14.39%, and 16.71%	[12]
5	Opuntia ficus-indica Mill.	DPPH, FRA	IC50 25.78 ± 0.71, 153.86 ± 9.79, mg/mL	[13]
6	Cydonia oblonga Mill.	DPPH	% inhibition 30.64%	[15]
7	Dioscorea opposite L.	HRS and DPPH	90.03% and 68.57% (5.0 mg/mL)	[16]
8	Sinapis alba L.	DPPH and CDM	71% and 23%	[17]
9	Hibiscus rosa-sinensis L.	DPPH, NOS, SRS, HPS, and HRS	44.55 ± 0.05, 36.59 ± 0.87, 38.82 ± 0.43, 39.51 ± 0.72 (80 µg/mL), and 34.51 ± 0.12 (100 µg/mL)	[18]
10	Zizyphus mauritiana Lam.	ABTS•+, DPPH, HRS, and SRS	16,587.32 mmol Equ/g, 5.27 mg/g, 76.13%, and 85.12%	[19]
11	Coccinia indica L.	DPPH	71.85 ± 0.02% 300 mg/mL	[20]
12	Cordia myxa L.	DPPH	36.83%	[21]
13	Dioscorea opposite L.	HRS and SRS	187, 82, and 55 µg/mL and 241, 138, and 125 µg/mL	[22]

. Summarizes the antioxidant activities of the mucilage.

DPPH: 2,2-diphenyl-1-picrylhydrazyl free radical, ABTS: 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid), FRA: ferric reducing assay, HRS: hydroxyl radical scavenging, CDM: conjugated diene method, NOS: nitric oxide, SRS: superoxide anion, HPS: hydrogen peroxide scavenging, HRS: hydroxyl radical scavenging.

The antioxidant activity of different mucilage- and gum-containing plants varied widely depending on the assay used. Among all the plants studied, Dioscorea opposite showed the highest antioxidant potential, with very strong free radical scavenging in both the hydrogen radical scavenging (HRS) assay (90.03%) and the DPPH assay (68.57% at 5 mg/mL). It also displayed low IC₅₀ values in HRS and SRS assays, confirming its potency. Similarly, Zizyphus mauritiana demonstrated remarkable antioxidant effects, with exceptionally high ABTS•+ activity (16,587.32 mmol Equ/g) along with strong scavenging in HRS (76.13%) and SRS (85.12%). Talinum triangulare also showed strong ferric reducing activity and DPPH scavenging, reaching over 80% inhibition. Plants such as Abelmoschus esculentus and Hibiscus rosa-sinensis showed moderate activity, though their performance varied across assays. A. esculentus recorded inhibition values between 23% and 74% with IC₅₀ values of 3.15–6.60 mg/mL, while H. rosa-sinensis demonstrated consistent but moderate activity (36–45%) across several models including DPPH, NOS, SRS, and HRS. Malva parviflora showed similar 45%) across several models including DPPH, NOS, SRS, and HRS. Malva parviflora showed similar moderate activity, with a DPPH IC₅₀ value of 154.27 µg/mL respectively.

3.3. Mechanism of Antioxidants

Antioxidants exert their protective effects through various mechanisms, primarily by neutralizing reactive oxygen species (ROS) and reactive nitrogen species (RNS), thereby mitigating oxidative stress. Diverse in vitro assays have been developed to elucidate these mechanisms, broadly categorized into those based on radical scavenging ability and reducing potential. Lipid peroxidation involves the oxidation of polyunsaturated fatty acids into lipid hydroperoxides through free radical chain reactions [17]. Similarly, the Ferric Reducing Antioxidant Power (FRAP) assay is based on electron transfer, reducing Fe³⁺-TPTZ to the blue-colored Fe²⁺-TPTZ complex in acidic conditions (pH 3.6), enhancing redox activity and iron solubility [18]. Hydroxyl radicals (•OH), generated from hydrogen peroxide via metal-catalyzed reactions, are among the most reactive species and can degrade lipids, proteins, and nucleic acids. Antioxidants counteract ·OH either by donating hydrogen atoms (Hydrogen Atom Transfer, HAT) or by electron donation (electron transfer, ET), forming less reactive species [18,22]. Another widely used method is the ABTS assay, where ABTS is oxidized to its radical cation ABTS^•+ by potassium persulfate. Antioxidants reduce ABTS^•+ back to its colorless form, and the degree of decolorization reflects their scavenging potential [19]. Superoxide anion radicals (O₂^−•), produced during mitochondrial respiration, are detoxified through enzymatic action, which converts them to hydrogen peroxide and oxygen. Additionally, non-enzymatic antioxidants directly scavenge O₂^−• or enhance enzymatic pathways [19]. The DPPH assay employs the stable free radical DPPH·, characterized by a deep violet color. Antioxidants reduce radicals by donating a hydrogen atom, resulting in a color change, which is quantified spetrophotometrically [20,23]. Together, these assays provide comprehensive insights into the antioxidant efficacy of compounds. The Figure 2 show the diagrammatic mechanism of antioxidants.

4. Application of Mucilage

4.1. Pharmaceutical Applications

Mostly, mucilage is used as a pharmaceutical additive in different dosage formulations with a wide range of applications such as thickening, binding, disintegrating agents, suspending and emulsifying agents in biphasic liquid dosage forms, and stabilizing and gelling agents shown in

Table 3. Pharmaceutical application of plant-derived mucilages.

Sr. No.	Plant Name	Pharmaceutical Application	Ref.
1	Guazuma ulmifolia Lam.	Natural emulsifying and thickening agent	[24]
2	Linum usitatissimum L.	Sustained-release hydrogel	[25]
3	Salvia hispanica L.	Natural superdisintegrant	[26]
4	Hibiscus rosa-sinensis L.	Superdisintegrant	[27]
5	Trigonella foenum-graecum L.	Suspending agent	[28]
6	Pereskia aculeata Miller.	Emulsifier and fat replacement	[29]
7	Corchorus olitorius L.	Stabilized oil-in-water emulsions	[30]
8	Phoenix dactylifera L.	Nutraceutical potential	[31]
9	Abelmoschus esculentus L.	Nanocomposite bioactive agent	[32]

. Mucilage may also be used as an adjuvant in sustained and controlled release dosage forms.

4.2. Food Industry Applications

Mucilage derived from plants can enhance food’s storage limit and shelf life and also reduce the loss of moisture; therefore, it is used as an edible coating in food packaging industries. Examples of mucilage with their application in food industries summarized in

Table 4. Food industry uses of plant-derived mucilages.

Sr. No.	Plant Name	Application in the Food Industry	Ref.
1	Ocimum basilicum L.	Bionanocomposite—food packaging	[33]
2	Opuntia ficus-indica L.	Antioxidant—food packaging	[34]
3	Linum usitatissimum L.	Biodegradable and edible packaging	[35]
5	Pyrus communis L.	Food packaging	[36]
6	Colocasia esculenta L.	Polymeric nanocomposite food packaging film	[37]
7	Cydonia oblonga Mill.	Antioxidant, antimicrobial—film	[38]

.

4.3. Cosmeceutical Applications

Plant mucilages are valued in cosmetics for their natural hydrating and soothing properties, acting as a moisturizer and creating a protective skin film. It also functions as a stabilizer and thickening agent in various formulations like lotions, gels, and shampoos. Cosmeceutical applications of mucilage shown in

Table 5. Cosmetic application of plant-derived mucilages.

Sr. No.	Plant Name	Application in Cosmetics	Ref.
1	Linum usitatissimum L.	Probiotic and antioxidant	[39]
2	Salvia hispanica L.	Photostability and cytocompatibility of fibroblast cells	[40]
3	Colocasia esculenta L.	Emulsifying agent, physical–chemical stability	[41]

.

5. Conclusions

The growing concerns over the safety of synthetic antioxidants have driven significant interest in natural alternatives, particularly those derived from plant sources. Mucilage, a polysaccharide-rich plant hydrocolloid, demonstrates promising antioxidant potential through mechanisms such as free radical scavenging and the inhibition of oxidative chain reactions. Its inherent bioactive compounds, including phenolics and flavonoids, contribute not only to its antioxidant capabilities but also to a range of physiological benefits, including anti-inflammatory and anti-aging properties. Its application in food is as a natural stabilizer, thickener, and emulsifier. Moreover, its utility in the cosmetics, pharmaceuticals, and environmental sectors underscores its versatility and commercial value.