Comparative Analyses of Biologically Active Substances and Antioxidant Activity in Fresh and Stored Fruits of Apple Varieties from the Republic of Tajikistan

Abstract

Our purpose was to carry out a comparative phytochemical analysis of fruits (both fresh and stored for 1 month) of two local apple varieties of the Republic of Tajikistan. Assays were carried out to quantify total phenolic compounds, flavonols, catechins, tannins, phenolcarboxylic acids, pectins, and protopectins by UV spectrometry and ascorbic acid by titration. The profile and levels of phenolic compounds were investigated by high-performance liquid chromatography. Antiradical activity was quantitated by means of free radical DPPH (2,2-diphenyl-1-picrylhydrazyl). In fresh fruits, total levels of tannins (19 mg/g) and phenolcarboxylic acids (15 mg/g) (including chlorogenic acid: 451 μg/g) and of a flavonol (quercetin: 26 μg/g) and two catechins [epigallocatechin (173 μg/g) and L-epicatechin (50 µg/g)] were shown to be higher in the Surkhseb apple variety than in the Kosimsarkori variety. The antioxidant activity of water–ethanol extracts from Surkhseb apples (20 mg/mL) was also higher in comparison with Kosimsarkori apples. In the latter, concentrations of other detected biologically active substances, such as flavonols (0.78 mg/g), ascorbic acid (65 mg/100 g), and pectins (37 mg/g), were found to be higher, suggesting that the fruits of this apple variety have biological effects other than antioxidant, potentially anti-inflammatory, or antidiabetic. Further phytochemical and pharmacological studies on Kosimsarkori fruits may identify these other potential biological effects that may be useful in the prevention of disease. Fruits of the analyzed apple varieties should preferably be consumed fresh because after the apples were stored in the refrigerator for 1 month, indicators of antioxidant activity (22 mg/g in Surkhseb apples) and levels of almost all biologically active substances (tota) levels of tannins (14 mg/g), phenolcarboxylic acids (9 mg/g) (including chlorogenic acid: 250 μg/g) and catechin L-epicatechin (30 µg/g) in Surkhseb apples decreased. This study highlights the importance of conserving local, unique varieties of major worldwide crop plants because they may unearth novel combinations of compounds beneficial to humanity.