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Article

Phytochemical and Nutritional Profile of Apricot, Plum-Apricot, and Plum Stones

by
Dasha Mihaylova
1,
Galia Gentscheva
2,
Nadezhda Petkova-Ognyanova
3,
Anton Slavov
3 and
Aneta Popova
4,*
1
Department of Microbiology and Biotechnology, University of Food Technologies, 4002 Plovdiv, Bulgaria
2
Department of Chemistry and Biochemistry, Medical University-Pleven, 5800 Pleven, Bulgaria
3
Department of Organic and Inorganic Chemistry, University of Food Technologies, 4002 Plovdiv, Bulgaria
4
Department of Biochemistry and Nutrition, University of Food Technologies, 4002 Plovdiv, Bulgaria
*
Author to whom correspondence should be addressed.
Separations 2025, 12(8), 216; https://doi.org/10.3390/separations12080216
Submission received: 8 July 2025 / Revised: 26 July 2025 / Accepted: 14 August 2025 / Published: 15 August 2025
(This article belongs to the Special Issue Green Extraction Processes to Recover Natural Bioactive Compounds from Food By-Products)
Browse Figure
Versions Notes

Abstract

Fruit stones constitute a significant portion of solid waste generated from the consumption and processing of fruits. This study demonstrated the potential of fruit stones as viable sources of nutritional compounds. The stones from three types of fruits—the “Modesto” apricot, the “Stendesto” plum-apricot, and the “Stanley” plum—were assessed for their protein, carbohydrate, lipid, and mineral content. Additionally, their total phenolic content, total flavonoid content, and total anthocyanin content were also analyzed. The antioxidant activity, evaluated through four contemporary assays (DPPH, ABTS, FRAP, and CUPRAC), revealed the biological potential of these stones. Notably, the results pertaining to the hybrid plum-apricot variety “Stendesto” are absent from the existing literature, rendering them novel. The findings indicate that the stone of this hybrid has the lowest caloric value in kcal/100 g, including its fat content, when compared to the other studied stones. Therefore, fruit stones can be effectively utilized as innovative food ingredients, aligning with the need for proper waste management and their potential application across various industries.

1. Introduction

Recently, the idea of zero waste, particularly regarding the recovery of food waste, has emerged as a significant field of research with many contributions. In this context, fruit stones present a substantial opportunity, as they account for a considerable percentage of the total fruit weight, ranging from 10% to 27% [1], and are often regarded as waste by-products [2,3]. Moreover, 8% of total food waste is generated from the fruit processing industry [4]. Furthermore, natural sources including plants, fruits, vegetables, and flowers, both collectively and in their individual components—such as pulp, peels, stones/kernels, and seeds—represent an endless resource that captivates scientists, particularly in light of contemporary trends advocating for the replacement and even banning of synthetic colorants, preservatives, and functional ingredients [5]. In recent years, functional foods have attracted interest due to their possible health advantages that extend beyond fundamental nutrition, acting as abundant sources of proteins, carbohydrates, vitamins, and dietary fiber [6]. The contemporary period, marked by a steadfast commitment to achieving optimal health and well-being, places nutrition at the forefront of public interest [6]. In light of this increasing awareness, functional foods are surfacing as key drivers of a transformative shift in societal perceptions and interactions with food choices. Numerous studies conducted in recent years have highlighted the connection between food intake and the presence of bioactive compounds. Among these, phenolic compounds have been extensively researched, not only for their impact on the color and flavor of food items but also for the additional health advantages they offer to consumers [7]. The role of nutrition in promoting well-being and preventing diseases has been a prominent discussion for over a decade [7]. A closer examination of the composition of functional foods uncovers a wide variety of bioactive compounds that differentiate them from conventional foods [6]. From this viewpoint, waste materials like fruit pits may be regarded as a potential source of nutritional and biologically active compounds, which are often undervalued, insufficiently researched, and not fully utilized.
The fruit stone or pit signifies the firm interior of the fruit that houses the seed. While they are consumable, they are seldom part of the everyday diet. The apricot kernel, along with the cherry kernel, is utilized in the making of the Italian liqueur known as “Amaretto”, which is rich in phenolic compounds, specifically hydroxycinnamic acids, hydroxybenzoic acids, and flavanols [8].
Fruit pits have also been regarded as a valuable aggregate in concrete, adding fiber strength [9]. The possible uses of fruit by-products have been assessed in numerous recent research studies as value-added components for food applications [5,10,11,12,13]. Apricot and plum stones are regarded as a significant by-product for future investigation [14]. This indicates a distinct interest in recent years in utilizing these by-products to enhance sustainability and minimize food waste, which is the focus of the current scientific inquiry into the potential of plum, apricot, and plum stones.
The objective of the present study was to uncover the potential of fruit stones from the “Modesto” apricot, the “Stendesto” plum-apricot, and the “Stanley” plum as sources of nutrients (protein, carbohydrate, lipid, and mineral content) and bioactive compounds (total phenolic content, total flavonoid content, and total anthocyanin content, as well as antioxidant activity). Serving as a preliminary study on this topic, it can establish a foundation for future comparisons and encourage the improved use of food waste.

2. Materials and Methods

2.1. Stone Samples

Stone samples were collected in the 2024 season from the “Modesto” apricot, the “Stendesto” plum-apricot, and the “Stanley” plum (Figure 1).
The trees are part of the experimental fields of the Fruit Growing Institute (Plovdiv, Bulgaria). A total of sixty collected stones were washed and left to air-dry. Then, the stones with kernels were grinded separately, and kept in air-tight containers (ambient conditions) prior to extraction and analysis.

2.2. Protein Analysis

Total nitrogen content was determined using the Kjeldahl method according to ISO 1871 [15]. The protein content was calculated by multiplying the nitrogen content by 6.25 nitrogen-to-protein conversion factor.

2.3. Lipid Analysis

Total lipids content was evaluated by continuous extraction in a Soxhlet apparatus. Every sample (approximately 4 to 5 g) was packed in a pre-weighed, oven-dried thimble. The thimbles were stapled and placed in a Soxhlet apparatus, and extracted for a duration of six hours with n-hexane. The extracts were evaporated using a rotary vacuum evaporator (RV 10, Ika, Staufen, Germany) and the residues were weighed. The results are expressed as g/100 g.

2.4. Carbohydrate Analysis

2.4.1. Sugars

The concentrations of sugars and sorbitol were analyzed using a Shimadzu HPLC system, which included an LC-20 AD pump and a Shimadzu RID-10A refractive index detector (RID), as outlined by Mihaylova et al. [16]. The separation process was carried out on a Shodex® Sugar SP0810 column (300 mm × 8.0 mm i.d.) with Pb2+ and a Shodex SPG guard column (5 μm, 6 mm × 50 mm) (Shodex Co., Tokyo, Japan) at a temperature of 85 °C. The mobile phase utilized was ultra-purified water, sourced from an Adrona B30 Integrity + HPLC water purification system in Riga, Latvia, with a flow rate set at 0.5 mL/min. An injection volume of 20 μL was employed [17].
The total carbohydrate content of the samples was calculated by:
Total carbohydrates, % = 100 − (moisture, %) − (ash, %) − (protein, %) − (lipids, %)

2.4.2. Fibers

The total dietary fibers were determined using a K-TDFR-100A (Megazyme, Ireland), according to the AOAC method 991.43 [18] “Total, soluble and insoluble dietary fibers in foods” (First action 1991) and the American association of cereal chemistry (AACC) method 32-07.01 “determination of soluble, insoluble and total dietary fibers in foods and food products” (final approval 10-16-91). The results are presented as percentages.

2.5. Mineral Composition

Trace elements were determined by atomic absorption spectrometry according to EN 14082:2003 [19]. The content of potassium, calcium, and magnesium is determined by atomic absorption spectrometry according to EVS-EN 1134:2000 [20].

2.6. Nutritional Data

The nutritional data were established based on the calculation method. The energy equivalent of each macronutrient (proteins, carbohydrates, lipids) was used to calculate the energy value in 100 g of product. Protein, carbohydrate, and lipid content is presented as g/100 g, while the energy value as kcal/100 g.

2.7. Total Phenolic Content (TPC), Total Flavonoid Content (TFC), Total Monomeric Anthocyanins (TMAs)

The procedure commenced with a threefold extraction of free phenolic compounds, wherein 0.5 g of the sample was combined with 10 mL of 80% (80:16, v/v) ethanol. This mixture was subjected to extraction at 70 °C for 30 min under ultrasound (UST 5.7150 Siel, Gabrovo, Bulgaria) and, subsequently, centrifuged at 10,000× g for 20 min. The resulting phenolic extracts were filtered using filter paper (Whatman No. 1) and evaporated to dryness (RV 10, Ika, Staufen, Germany). The final volume of the extracts was adjusted by the addition of 10 mL of 80% methanol (80:20, v/v) and stored at −20 °C until further analysis. In the second phase, the bound phenolic compounds were extracted utilizing two protocols: the alkaline hydrolysis method and the acid hydrolysis method, respectively. The alkaline extraction procedure was performed in accordance with the method outlined by Ding et al. [21], with modifications, while the acid extraction procedure was executed as previously documented by Mihaylova et al. [22]. Both dried bound extracts were reconstituted in 10 mL of 80% HPLC grade methanol (80:20, v/v) and stored in the dark at −20 °C until analysis. The total phenolic content (TPC), expressed as mg gallic acid equivalents (GAEs)/g stone, was assessed using the Folin–Ciocâlteu reagent [23]. The evaluation of the total flavonoid content (TFC), expressed as mg quercetin equivalents (QEs)/g stone with quercetin as a standard, adhered to the method established by Kivrak et al. [24]. The total monomeric anthocyanins (TMAs) content, expressed as μg cyanidin-3-glucoside (C3GE)/g stone, was determined using the pH differential method [25].

2.8. Antioxidant Activity

Extracts of free and bound phenolic samples were subjected to the determination of the in vitro antioxidant activity based on the (1,1-diphenyl-2-picrylhydrazyl (DPPH•) radical scavenging assay, 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS•+) radical cation decolorization, ferric reducing/antioxidants power (FRAP), and cupric ion reducing capacity in the presence of neocuproine (CUPRAC)) following the method description of Mihaylova et al. [22]. The antioxidant potential was expressed as Trolox equivalent antioxidant capacity (TEAC)/g stone dry weight.

2.9. Statistical Analysis

Results presented as mean value ± SD (triplicated) using MS Office 365 were statistically analyzed using one-way ANOVA and a Tukey–Kramer post hoc test (α = 0.05) via the online application of the Texas A&M University, USA as described by Assaad et al. [26].

3. Results and Discussion

3.1. Biological Value of Studied Samples

The potential of fruit stones (apricot, plum, and plum-apricot) as viable sources of nutritional compounds has been investigated using three types of extracts. Table 1 displays the findings regarding the total phenolic content, total flavonoid content, and total monomeric anthocyanins content in both free phenolic and bound phenolic fractions, which also include alkaline and acidic extracts from plum-apricot, plum, and apricot stones for the bound fractions.
Phenolic acids represent a significant category of phenolic compounds and are typically found in various conjugated forms instead of the free form. In general, free phenolics are located within the vacuoles of plant cells. Bound phenolics in plants are primarily found in protective tissues, such as the seed coat, pericarp, and hull, and are also present in nutritional tissues, including the germ, epicotyl, hypocotyl radicle, and endosperm, among others [27].
Information regarding the stones is currently unavailable, rendering the results obtained as preliminary for future research and comparisons. Data are only accessible for apricot kernels, where the authors have identified the impact of genotype on both the antioxidant capacity and the total phenolic content of apricot kernels [28]. The total phenolic content (TPC) varied from 92.2 to 162.1 mg GAE/100 g.
Similar to the other two varieties, the findings related to the stones of “Stendesto” are novel, and thus, no comparisons can be drawn. Among the three types of stones examined, it can also be inferred that there existed a greater resemblance between the hybrid stone and that of the plum. Acid hydrolysis seems to be a more effective extraction technique for bound phenolic fractions.
Flavonoids constitute a group of over 4000 phenolic compounds. The total flavonoid content was generally most abundant in the plum stone, while the apricot stone did not carry any flavonoids (Table 1). The hybrid stone had inherited the presence of flavonoids from the plum. Total monomeric anthocyanins were not detected in any of the samples. Anthocyanins are an important natural pigment and are usually identified in fruit and vegetables [29].
To evaluate the influence of the extracted compounds by the applied extraction procedures, the in vitro antioxidant potential was investigated. The antioxidant capacity of plant extracts containing free phenolic compounds exhibits higher values for all examined raw materials when compared to the extracts of bound phenols (Table 2).
The acid extraction method for bound phenols yielded the highest results. However, the values recorded for the hybrid were the lowest in comparison to the other two. Notably, the antioxidant potential of plum stones was the highest among them (Table 2). These findings provide new information that will serve not only as a reference for comparison but also as a foundation for the utilization of stones that are typically regarded as waste. Other researchers have indicated that the activity of apricot kernels in capturing free radicals, measured in terms of inhibitory concentration (IC(50)), ranged from 43.8 to 123.4 mg/mL, while the iron-reducing antioxidant potential (FRAP) varied from 154.1 to 243.6 μg/mL FeSO4 · 7H2O. A variation of 1–1.7 times in total phenolic content, 1–2.8 times in IC(50) as determined by the DPPH assay, and 1–1.6 times in antioxidant potential for iron reduction among the analyzed stones underscored the significant influence of genetic background on the phenolic content and antioxidant potential of apricot kernels [28]. Other authors also affirm the potential of apricot by-products as significant carriers of biological compounds [30,31,32].
As can be seen from Table 2, the values varied between the samples evaluated by the four in vitro techniques. However, a notable superiority in terms of antioxidant potential was observed for the sample containing bound phenols obtained by acid hydrolysis of plum stones. A similar trend was observed for the extract by acid hydrolysis of apricot stones. This revealed the presence of potent bound phenolic compounds that were efficiently extracted by the aforementioned approach. This aligns with earlier reports that determine that acid hydrolysis can effectively break glycosidic bonds and liberate phenolic compounds from the matrix [33].
Taking into account the results of Table 1 regarding the presence of total polyphenols, total flavonoids, and total monomeric anthocyanins, it can be assumed that different phenolic compounds and groups contribute to the established antioxidant activity. As for plum stones, the extract of bound phenolic compounds obtained by acid extraction consisted of both polyphenolic compounds and flavonoids, suggesting their contribution to the antioxidant activity observed. This aligns well with earlier research that posited stone fruits have elevated concentrations of phenols, which are the primary contributors to their antioxidant capabilities and associated health advantages [34]. However, the extract of apricot stones did not contain flavonoids, at least not in detectable amounts, which excludes their contribution to the antioxidant potential of the “Modesto” cultivar.
The existing literature regarding the antioxidant activity of the plum from the “Stanley” cultivar includes authors providing data on juices, peels, and fruits. However, no information was found concerning extracts of free and bound phenolic compounds, nor was there an evaluation using more than one method to assess antioxidant potential of not only traditional samples like fruit, but also stones. The current results offer new comprehensive data that will enhance the existing literature up to this point.

3.2. Nutritional Value of Studied Samples

Mineral elements play a crucial role in the metabolism of plants. They can be categorized into macro- and microelements based on their functions. Table 3 presents the information regarding the mineral composition of the stones from the three studied varieties.
Potassium, calcium, magnesium, sodium, iron, copper, zinc, manganese, cobalt, nickel, and chromium were the identified elements. The stones of all three varieties exhibit higher magnesium, calcium, and potassium values. Among these, the hybrid stone had the lowest magnesium values when compared to the plum and apricot. Copper absorption primarily occurs in the small intestine through both saturated mediated and unsaturated non-mediated mechanisms, with a daily recommended dose of 1700 μg/day [35]. This suggests that the studied stones can serve as a moderately sufficient source of copper in the daily diet. The recommended daily intake of iron is 0.35 mg/kg [36]. Consequently, all varieties examined could contribute a small portion to the daily intake of Fe, as Fe and Zn, which are essential trace elements, are unevenly distributed among the different varieties. Zinc is the most prevalent element found in apricot stones. It acts as a coenzyme for over 200 enzymes that are involved in immunity, new cell growth, acid-base regulation, and other functions [37].
The concentration of chromium in all varieties remained below the maximum permissible limit value of 2.3 mg/kg [38]. Among the macronutrients, potassium is clearly the most dominant in all varieties studied. Its intake is positively correlated with bone metabolism, lower blood pressure, and decreased morbidity and mortality from cardiovascular diseases [39]. Potassium serves as a major intracellular cation in the body, with a recommended daily intake ranging from 0.4 to 5.1 g/day. All varieties examined can significantly contribute to the daily intake of K. Potassium positively influences human health by lowering blood pressure, reducing mortality from cardiovascular diseases, and preventing the progression of kidney diseases [40]. The variety “Modesto” exhibited the highest potassium content. Alongside calcium and magnesium, potassium plays a role in the synthesis of amino acids.
Table 4 displays the information regarding the content of protein, lipids, and carbohydrates. The total carbohydrate content varied between 75.17 ± 0.30 and 85.52 ± 0.15 g/100 g dw. In general, the total lipid content ranged from 2.96 ± 0.18 to 8.03 ± 0.07 g/100 g dw. Additionally, the total protein content did not show significant variation among the hybrid and apricot stone, while the examined plum stones differed in protein content. This suggests the potential of waste products like stones, which are rich in macronutrients.
All stones are primarily rich in carbohydrates; however, the amount of sugars constitutes a minor fraction of their composition. The hybrid stone exhibited the highest sugar content, whereas the apricot stone contained the least. Glucose was the most prevalent sugar, with fructose following closely behind. There was a predominance of complex sugars, which may be advantageous for human nutrition by promoting stable glucose levels and a reduced glycemic index.
Dietary fiber is a bioactive compound, primarily consisting of a blend of complex organic soluble and insoluble polysaccharides that are indigestible and exhibit lower hydrophobicity [41]. Dietary fiber is recognized as a nutritional supplement that has been shown to positively affect human health. Furthermore, the acceptable daily intake of dietary fiber offers additional health advantages, including the adsorption of bile salts, polyphenols, and minerals. Moreover, it influences the physiology of the gastrointestinal tract by possessing a high water-holding capacity and viscosity, which contributes to a sense of satiety, alters the activity of digestive enzymes, enhances gastric emptying, and promotes a healthy microbial biomass in the colon [42]. The values obtained for total dietary fiber ranged from 78.83 ± 1.63% for “Stendesto” to 81.65 ± 1.05% for “Modesto” (Table 5).
The lowest percentage value was recorded for the stone of the plum-apricot hybrid. In the comprehensive analysis of soluble and insoluble dietary fibers, it was determined that insoluble fibers were predominant. There is a scarcity of information regarding the dietary fiber content in stones in the existing literature, rendering the presented data novel. Other researchers have indicated a broad range of total dietary fiber (TDF) values for prune fruits, specifically between 58% and 82% [43]. Incorporating plant materials into various food products enables their functionalization, as it is established that, according to European Union regulations, food systems containing over 3 weight percent can be classified as a “source of dietary fiber” [44,45].
The energy value of the studied stones was also calculated using the energy equivalents of the macronutrients where their nutritional value (kcal) was determined (Table 6).
The findings regarding the energy value indicated that apricot stones possessed the highest energy content, recorded at 449.71 kcal/100 g. The predominant portion of the energy is attributed to the carbohydrates present in the analyzed stones, as carbohydrates serve as the primary energy sources for living organisms. In relation to the data acquired for the stones, their values align with those of non-traditional flours available in the market, including apricot kernel flour. All stones are primarily rich in carbohydrates; however, the amount of sugars constitutes a minor fraction of their composition.

4. Conclusions

This research highlighted the potential of apricot, plum-apricot, and plum fruit stones as promising sources of nutritional compounds. The existing literature lacks information regarding the composition of fruit stones; therefore, these findings will contribute new insights that will not only serve as a reference for comparison but also establish a basis for the use of stones that are often considered waste. The “Stanley” stone exhibited the highest levels of total phenolics and total flavonoids. The acid extraction method for bound phenols produced the most significant results in terms of antioxidant capacity for all studied samples. The stones from all three varieties showed elevated levels of magnesium, calcium, and potassium. In the analysis of soluble and insoluble dietary fibers, it was found that insoluble fibers were the most prevalent. Although apricot kernels are still often undervalued due to concerns about potential toxicity due to their amygdalin content, it should be noted that this does not make them inedible, quite the opposite. In this regard, the present study pointed out that fruit stones can be effectively utilized as innovative food ingredients, which aligns with the need for proper waste management and their potential applications in various industries. However, any health concerns should be subject to discussion and research.

Author Contributions

Conceptualization, A.P. and D.M.; methodology, D.M., N.P.-O., G.G. and A.S.; software, D.M., N.P.-O., G.G. and A.S.; validation, D.M., N.P.-O., G.G. and A.S.; formal analysis, D.M., N.P.-O., G.G. and A.S.; investigation, D.M., N.P.-O., G.G., A.P. and A.S.; resources, A.P.; data curation, D.M., N.P.-O., G.G., A.P. and A.S.; writing—original draft preparation, A.P. and D.M.; writing—review and editing, D.M., N.P.-O., G.G., A.P. and A.S.; visualization, A.P.; supervision, A.P.; project administration, A.P.; funding acquisition, A.P. All authors have read and agreed to the published version of this manuscript.

Funding

This research was funded by the Bulgarian National Science Fund, grant number KП-06-H67/2.

Data Availability Statement

The data presented in this study are available on request from the corresponding authors.

Acknowledgments

The authors would like to acknowledge Argir Zhivondov for actively working on expanding plumcot varieties in Bulgaria, and registering the “Stendesto”.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of this study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

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Separations 12 00216 g001
Figure 1. Stone samples from the “Modesto” apricot (A); “Stendesto” plum-apricot (B); and “Stanley” plum (C).
Figure 1. Stone samples from the “Modesto” apricot (A); “Stendesto” plum-apricot (B); and “Stanley” plum (C).
Separations 12 00216 g001
Table 1. Total phenolic content (TPC, mg GAE/g dw), total flavonoid content (TFC, μg QE/g dw), and total monomeric anthocyanins (TMAs, µg cyanidin-3-glucoside (C3GE)/g dw) of free and bound (insoluble) phenolics fractions of plum-apricot, plum, and apricot stones.
Table 1. Total phenolic content (TPC, mg GAE/g dw), total flavonoid content (TFC, μg QE/g dw), and total monomeric anthocyanins (TMAs, µg cyanidin-3-glucoside (C3GE)/g dw) of free and bound (insoluble) phenolics fractions of plum-apricot, plum, and apricot stones.
Samples/AnalysesTPCTFCTMAs
“Stendesto”
Free phenolics2.15 ± 0.07 c71.0 ± 6.1 bN.D.
Alkaline hydrolysis (bound phenolics)0.99 ± 0.01 e16.7 ± 3.8 dN.D.
Acid hydrolysis (bound phenolics)1.16 ± 0.02 e46.9 ± 4.3 cN.D.
“Stanley”
Free phenolics2.17 ± 0.02 c76.09 ± 3.82 bN.D.
Alkaline hydrolysis (bound phenolics)0.94 ± 0.03 e14.80 ± 0.87 dN.D.
Acid hydrolysis (bound phenolics)18.25 ± 0.22 a274.27 ± 6.31 aN.D.
“Modesto”
Free phenolics2.14 ± 0.12 c0N.D.
Alkaline hydrolysis (bound phenolics)1.56 ± 0.13 d0N.D.
Acid hydrolysis (bound phenolics)9.64 ± 0.21 b0N.D.
N.D.—not detected; Different letters in the same column show statistically significant differences (p < 0.05), as established by ANOVA and the Tukey test.
Table 2. In vitro antioxidant activity of free and bound phenolics (DPPH, ABTS, FRAP, CUPRAC, µM TE/g dw) of free and bound (insoluble) phenolics fractions of plum-apricot, plum, and apricot stones.
Table 2. In vitro antioxidant activity of free and bound phenolics (DPPH, ABTS, FRAP, CUPRAC, µM TE/g dw) of free and bound (insoluble) phenolics fractions of plum-apricot, plum, and apricot stones.
Samples/AnalysesDPPHABTSFRAPCUPRAC
“Stendesto”
Free phenolics3.13 ± 0.10 d27.70 ± 0.53 cd13.09 ± 0.61 d13.23 ± 0.52 f
Alkaline hydrolysis (bound phenolics)1.76 ± 0.01 f20.60 ± 1.56 de8.48 ± 0.12 e9.49 ± 0.05 g
Acid hydrolysis (bound phenolics)2.51 ± 0.02 e26.80 ± 0.49 cd4.23 ± 0.04 f14.97 ± 0.12 ef
“Stanley”
Free phenolics5.56 ± 0.04 c31.77 ± 0.91 c15.68 ± 0.46 c16.94 ± 0.17 e
Alkaline hydrolysis (bound phenolics)1.54 ± 0.03 f18.11 ± 1.11 e7.88 ± 0.25 e8.24 ± 0.05 g
Acid hydrolysis (bound phenolics)44.70 ± 0.39 a318.98 ± 7.91 a174.24 ± 1.05 a190.50 ± 3.02 a
“Modesto”
Free phenolics5.12 ± 0.04 c34.75 ± 0.84 c15.49 ± 0.32 cd20.76 ± 0.53 d
Alkaline hydrolysis (bound phenolics)3.27 ± 0.19 d29.71 ± 0.63 c17.71 ± 0.53 c28.83 ± 0.57 c
Acid hydrolysis (bound phenolics)26.86 ± 0.14 b234.76 ± 2.57 b131.66 ± 2.20 b108.13 ± 1.54 b
Different letters in the same column show statistically significant differences (p < 0.05), as established by ANOVA and the Tukey test.
Table 3. Mineral content of plum-apricot, plum, and apricot stones, mg/kg.
Table 3. Mineral content of plum-apricot, plum, and apricot stones, mg/kg.
SamplesKCaMgNaFeCuZnMnCoNiCr
“Stendesto”3197 ± 195 b1013 ± 75 a575 ± 30 c47.7 ± 3.8 a5.4 ± 0.35 b5.28 ± 0.31 c8.74 ± 0.43 c4.97 ± 0.15 c0.65 ± 0.03 b4.1 ± 0.3 a0.63 ± 0.05 ab
“Stanley”3175 ± 214 b1003 ± 72 a701 ± 50 b39.7 ± 2.5 a3.33 ± 0.25 c6.15 ± 0.29 b12.5 ± 0.82 b12.8 ± 0.53 a0.53 ± 0.03 c2.19 ± 0.14 c0.55 ± 0.05 b
“Modesto”6450 ± 370 a776 ± 47 b997 ± 54 a43.5 ± 3.0 a6.56 ± 0.5 a7.04 ± 0.35 a17.1 ± 1.1 a5.99 ± 0.18 b0.96 ± 0.05 a2.92 ± 0.2 b0.74 ± 0.04 a
Different letters in the same column show statistically significant differences (p < 0.05), as established by ANOVA and the Tukey test.
Table 4. Carbohydrates (g/100 g dw), total lipids (g/100 g dw), and total proteins (g/100 g dw) content of plum-apricot (“Stendesto”), plum (“Stanley”), and apricot (“Modesto”) stones.
Table 4. Carbohydrates (g/100 g dw), total lipids (g/100 g dw), and total proteins (g/100 g dw) content of plum-apricot (“Stendesto”), plum (“Stanley”), and apricot (“Modesto”) stones.
Parameter/Samples“Stendesto”“Stanley”“Modesto”
Sucrose0.15 ± 0.08 a0.07 ± 0.02 a0.14 ± 0.01 a
Glucose1.12 ± 0.01 a0.65 ± 0.05 b0.47 ± 0.02 c
Fructose0.52 ± 0.03 a0.30 ± 0.02 b0.21 ± 0.01 c
SorbitolN.D.0.40 ± 0.04 a0.02 ± 0.01 b
Total sugars1.79 ± 0.07 a1.02 ± 0.03 b0.82 ± 0.02 c
Total carbohydrates75.17 ± 0.30 c81.11 ± 1.20 b85.52 ± 0.15 a
Total lipids2.96 ± 0.18 c4.84 ± 0.05 b8.03 ± 0.07 a
Total protein8.41 ± 0.21 a5.50 ± 0.35 b8.84 ± 0.04 a
N.D.—not determined; Different letters in the same row show statistically significant differences (p < 0.05), as established by ANOVA and the Tukey test.
Table 5. Dietary fiber content in the studied plum-apricot (“Stendesto”), plum (“Stanley”), and apricot (“Modesto”) stones.
Table 5. Dietary fiber content in the studied plum-apricot (“Stendesto”), plum (“Stanley”), and apricot (“Modesto”) stones.
Sample/ParameterTotal Dietary Fibers, %Insoluble Dietary Fibers, %Soluble Dietary Fibers, %
“Stendesto”78.83 ± 1.63 a76.86 ± 1.44 a1.97 ± 1.38 a
“Stanley”81.51 ± 1.36 a79.97 ± 1.84 a1.54 ± 1.08 a
“Modesto”81.61 ± 1.05 a80.21 ± 1.69 a1.40 ± 1.10 a
Different letters in the same column show statistically significant differences (p < 0.05), as established by ANOVA and the Tukey test.
Table 6. Energy and nutritional value in the studied plum-apricot (“Stendesto”), plum (“Stanley”), and apricot (“Modesto”) stones.
Table 6. Energy and nutritional value in the studied plum-apricot (“Stendesto”), plum (“Stanley”), and apricot (“Modesto”) stones.
Sample“Stendesto”“Stanley”“Modesto”
Energy value, kcal/100 g360.96390.00449.71
Proteins, g/100 g8.41 ± 0.215.50 ± 0.358.84 ± 0.04
Fats, g/100 g2.96 ± 0.184.84 ± 0.058.03 ± 0.07
Carbohydrates, g/100 g75.17 ± 0.3081.11 ± 1.2085.52 ± 0.15
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Mihaylova, D.; Gentscheva, G.; Petkova-Ognyanova, N.; Slavov, A.; Popova, A. Phytochemical and Nutritional Profile of Apricot, Plum-Apricot, and Plum Stones. Separations 2025, 12, 216. https://doi.org/10.3390/separations12080216

AMA Style

Mihaylova D, Gentscheva G, Petkova-Ognyanova N, Slavov A, Popova A. Phytochemical and Nutritional Profile of Apricot, Plum-Apricot, and Plum Stones. Separations. 2025; 12(8):216. https://doi.org/10.3390/separations12080216

Chicago/Turabian Style

Mihaylova, Dasha, Galia Gentscheva, Nadezhda Petkova-Ognyanova, Anton Slavov, and Aneta Popova. 2025. "Phytochemical and Nutritional Profile of Apricot, Plum-Apricot, and Plum Stones" Separations 12, no. 8: 216. https://doi.org/10.3390/separations12080216

APA Style

Mihaylova, D., Gentscheva, G., Petkova-Ognyanova, N., Slavov, A., & Popova, A. (2025). Phytochemical and Nutritional Profile of Apricot, Plum-Apricot, and Plum Stones. Separations, 12(8), 216. https://doi.org/10.3390/separations12080216

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