EVALUATION OF THE BIOCHEMICAL COMPOSITION OF BIOACTIVE POLYPHENOLIC DRINK "GRAPE ELIXIR"

ABSTRACT

Grapes are a rich source of bioactive polyphenols, including quercetin, which possess potent antioxidant properties linked to various health benefits. This study evaluated the biochemical composition and antioxidant capacity of the novel bioactive polyphenolic drink "Grape Elixir," formulated from six grape varieties (Rangdor, Saperavi, Hindogni, Mayskiy, Cabernet Sauvignon, and Pinot Noir) grown in the Tashkent region of Uzbekistan. High-Performance Liquid Chromatography (HPLC-DAD) analysis revealed that Cabernet Sauvignon had the highest quercetin (43.328 mg/100g) and gallic acid (1367.395 mg/100g) content, while Mayskiy exhibited significant levels of gallic acid (635.627 mg/100g). The results confirmed that "Grape Elixir" has a high concentration of antioxidant compounds, supporting its potential as a functional health-promoting beverage. The study emphasizes the importance of grape variety selection and processing techniques in optimizing bioactive compound retention.

АННОТАЦИЯ

Виноград является богатым источником биологически активных полифенолов, включая кверцетин, который обладает мощными антиоксидантными свойствами, связанными с различными преимуществами для здоровья. В этом исследовании оценивался биохимический состав и антиоксидантная способность нового биологически активного полифенольного напитка "Виноградный эликсир", приготовленного из шести сортов винограда (Рангдор, Саперави, Хиндогни, Майский, Каберне Совиньон и Пино Нуар), выращенных в Ташкентской области Узбекистана. Анализ методом высокоэффективной жидкостной хроматографии (HPLC-DAD) показал, что Каберне Совиньон имеет самое высокое содержание кверцетина (43,328 мг/100 г) и галловой кислоты (1367,395 мг/100 г), в то время как Майский обладает значительным содержанием галловой кислоты (635,627 мг/100 г). Результаты подтвердили, что "Виноградный эликсир" обладает высокой концентрацией антиоксидантных соединений, что подтверждает его потенциал в качестве функционального напитка, способствующего укреплению здоровья. В исследовании подчеркивается важность выбора сорта винограда и методов его обработки для оптимизации удержания биологически активных веществ.

Keywords: grapes, juice, functional beverage, polyphenols, quercetin, grape varieties, antioxidant activity.

Ключевые слова: виноград, сок, функциональный напиток, полифенолы, кверцетин, сорта винограда, антиоксидантная активность.

INTRODUCTION

Grapes (Vitis vinifera L.) are widely recognized for their nutritional and health-promoting properties due to their rich content of bioactive polyphenols, including flavonoids, phenolic acids, and stilbenes. These compounds have strong antioxidant activity, which helps reduce oxidative stress and the risk of chronic diseases [1,2]. The development of functional beverages enriched with polyphenols has gained significant attention in recent years. This study aimed to evaluate the polyphenol content and antioxidant properties of the novel bioactive drink "Grape Elixir," formulated from six grape varieties cultivated in Uzbekistan.

Phenolic compounds are bioactive secondary metabolites found in grapes, contributing to their antioxidant capacity, color stability, and potential health benefits. The presence and concentration of these compounds vary depending on grape variety, climate, soil composition, and post-harvest processing. The flavonoids (quercetin, apigenin, kaempferol, rutin) and phenolic acid (gallic acid) analyzed in this study are known for their antioxidants, anti-inflammatory, and cardioprotective properties.

The development of functional beverages enriched with bioactive compounds from natural sources has become increasingly popular due to growing consumer demand for health-promoting products. "Grape Elixir" a novel bioactive polyphenolic drink formulated from a blend of six grape varieties (Rangdor, Saperavi, Hindogni, Mayskiy, Cabernet Sauvignon, and Pinot Noir) grown in the Tashkent region of Uzbekistan, is proposed as a functional beverage with enhanced antioxidant properties. This study aimed to evaluate the quercetin content and antioxidant capacity of "Grape Elixir" and assess its potential as a health-promoting beverage [5].

MATERIALS AND METHODS

The grape samples Rangdor, Saperavi, Cabernet Sauvignon, Khindogni, Pinot Noir (red), Maysky Cherny, and Magarachsky black grape varietals were collected from vineyards in the Tashkent region, Republic of Uzbekistan. Located on the western foothills of the Chotkal range of the Middle Tianshan and surrounded by mountains, 800 - 3627.8 meters above sea level, 41°10′N 69°45′E longitudes. The harvest of the cultivars reached the period of physiological ripening, and when 22-24% of dry matter was formed in the juice on the °Bx scale, it was determined by a field refractometer (Pal-1 Atago, Japan) and then picked. The titratable acidity was determined using 0.1 NaOH or KOH as an indicator (a 10 ml sample of juice is heated with as much distilled water and 0.1 N NaOH is added and titrated with constant shaking until the color changes). The completion of the titration is determined by the color change of the indicator (phenolphthalein). Also, the pH indicator was determined using a pH meter (Benchtop pH 50 VioLab Basic, Made in Germany).

RESULTS AND DISCUSSION

Grapes' physicochemical qualities influence their quality, flavor, and appropriateness for winemaking and juice production[5]. Soluble solids (°Brix), pH, and titratable acidity all have an impact on sugar accumulation, acidity balance, and fermentation potential, which in turn affects the sensory profile and stability of the final product. The soluble solids content (°Brix) indicates the concentration of dissolved sugars and other soluble compounds in grape juice, which determines sweetness, flavor intensity, and potential alcohol yield in winemaking. High Brix values (22-24°) observed in Rangdor, Mayskiy, and Cabernet suggest greater sugar accumulation, which is desirable for producing full-bodied wines or sweeter juice varieties. Lower Brix values (18-20°) in Saperavi and Pinot Noir indicate lower sugar levels, which are typical of grapes used for producing dry wines with higher acidity. Hindogni, with a Brix range of 19-22°, represents an intermediate sugar content, balancing sweetness and acidity. All analyzed grape cultivars exhibited a pH range of 3.2 - 3.6. Higher acidity levels (9-11 g/L) in Saperavi and Pinot Noir indicate their strong tartness and crispness, making them suitable for producing fresh, aromatic wines with aging potential. Moderate acidity (8-10 g/L) in Rangdor and Hindogni provides a balance between sweetness and freshness, suitable for both wine and juice production. Lower acidity (7-9 g/L) in Cabernet and Mayskiy were noted. The results are presented in Table 1.

Table 1.

Grape juice parameters for harvest

For elixir preparation grapes were freezing (-11 to -10°C for 4 hours), crushing with stems, and pasteurized (50–55°C for 12 hours, followed by heating at 60–65°C for 4 hours). After the preparation of the raw materials for the creation of the elixir, all samples were determining the phenolic substances: quercetin, apigenin, kaempferol, gallic acid, and rutin content using High-Performance Liquid Chromatography (HPLC-DAD). The quantification results are presented in Table 2.

Table 2.

Quantification of Phenolic Compounds in from different grape varieties juice

Quercetin Content. Quercetin, an effective antioxidant named flavonol, is well known for its anti-inflammatory, antiviral, and neuroprotective activities. Cabernet had the greatest content (43.328 mg/100g), which was much higher than in the other types. Pinot Noir and Saperavi also have moderate quercetin levels, indicating their potential as functional food sources. Variations in quercetin content can be related to genotypic variances, environmental factors, and post-harvest processing [3,4].

Apigenin Content. Apigenin is a bioactive flavone with anticancer and neuroprotective effects. Cabernet exhibited the highest apigenin concentration (45.326 mg/100g), followed by Hindogni (26.514 mg/100g). The absence of apigenin in Mayskiy and Pinot Noir suggests a lower flavonoid biosynthesis in these varieties or potential degradation during processing.

Kaempferol Content. Kaempferol, another flavonoid with potent antioxidant effects, was found in Rangdor (15.754 mg/100g), Saperavi (12.674 mg/100g), and Hindogni. However, it was not found in Cabernet, Mayskiy, or Pinot Noir, indicating possible varietal differences in kaempferol biosynthesis.

Gallic Acid Content. Gallic acid (3,4,5-trihydroxybenzoic acid) is a secondary metabolite widely distributed in plants, including tea leaves, grapes, oak bark, and various fruits and nuts. It is recognized for its potent antioxidant properties and plays a critical role in plant defense mechanisms. Due to its bioactive nature, gallic acid has been investigated for potential therapeutic applications, particularly in oxidative stress-related diseases [3].

Gallic acid, a phenolic acid exhibited the highest concentration in Cabernet (1367.395 mg/100g), which is significantly higher than all other varieties. Mayskiy (635.627 mg/100g) and Hindogni (280.753 mg/100g) also had considerable levels. These findings suggest that Cabernet and Mayskiy may be excellent sources of gallic acid, making them suitable for health-promoting applications.

Rutin Content. Rutin, a flavonol glycoside, is valued for its vascular-protective and anti-inflammatory effects. The highest rutin concentration was found in Rangdor (28.364 mg/100g), while Saperavi and Hindogni contained moderate amounts (11.736 mg/100g and 21.640 mg/100g, respectively). No other samples were found. Phenolic compounds are secondary plant metabolites belonging to bioactive phytochemicals with characteristic hydroxyl (-OH) groups on aromatic rings. They are based on the carbon skeleton of flavonoid and non-flavonoid compounds and are responsible for protecting plants from various microbiological infections and ultraviolet rays, regulating metabolic exchanges, and providing color and aromatic substances [2]. The biochemical composition of grapes depends on many factors, including growing conditions, climate, soil composition, variety, and degree of ripeness. Grapes ripen even within the same variety in different regions with different biological characteristics.

Impact of Processing Techniques. The study also underscores the role of processing techniques in retaining bioactive compounds. Freezing and controlled thermal treatment were employed to preserve phenolic compounds, as extreme temperatures and prolonged exposure to oxygen can lead to degradation. Previous research has shown that mild thermal processing helps maintain polyphenol stability while enhancing bioavailability. The observed retention of bioactive compounds in "Grape Elixir" suggests that the selected processing conditions were effective in minimizing nutrient loss.

These findings demonstrate the potential of "Grape Elixir" as a functional beverage rich in bioactive polyphenols. The high quantities of quercetin, gallic acid, and rutin in certain kinds boost the beverage's antioxidant capabilities, making it ideal for boosting health and wellness. Further research should investigate the sensory properties, consumer acceptance, and potential synergistic effects of the polyphenols in the drink. Furthermore, studying the effects of storage conditions on phenolic stability will be critical for increasing shelf-life and maintaining product quality.

In summary, the results show that grape variety selection and processing processes have a considerable impact on the bioactive component profile of "Grape Elixir." Functional beverages with increased health benefits can be created by combining high-polyphenol grape cultivars and improved processing processes.

CONCLUSION

This study evaluates the physicochemical properties and phenolic composition of six grape varieties grown in the Tashkent region of Uzbekistan (Rangdor, Saperavi, Hindogni, Mayskiy, Cabernet Sauvignon, and Pinot Noir) and their potential use in the formulation of a bioactive polyphenolic beverage, "Grape Elixir." The findings show substantial differences in soluble solids (°Brix), pH, titratable acidity, and polyphenol content among the investigated cultivars, indicating their different properties and appropriateness for functional beverage manufacturing. The phenolic composition study found that Cabernet Sauvignon included the highest quantities of quercetin (43.328 mg/100g), apigenin (45.326 mg/100g), and gallic acid (1367.395 mg/100g), making it an excellent source of bioactive antioxidants. Similarly, Mayskiy and Hindogni had elevated levels of gallic acid (635.627 mg/100g and 280.753 mg/100g, respectively), indicating health advantages. Rangdor and Saperavi, which contain moderate amounts of rutin and kaempferol, add to the functional diversity of the prepared elixir. Post-harvest processing techniques such as freezing, crushing, and controlled heat treatment were found to have a substantial impact on the extraction and stabilization of phenolic components, hence increasing the bioavailability of flavonoids and phenolic acids in the final beverage. The study highlights the importance of processing conditions in maximizing bioactive ingredient retention in grape-derived functional beverages to maximize their health-promoting potential.

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