SEASONAL VARIATION IN THE POLYPHENOLS AND FLAVONOIDS CONTENT IN SHOOTS OF HIGHBUSH BLUEBERRY CULTIVARS DURING VEGETATION STAGES

It is known that different groups of polyphenolic compounds that enter the human and animal body with food and/or herbal medicines have a significant impact on the course of metabolic processes, and hence the health of the body. During the last century, the species of Vaccinium corymbosum L. (highbush blueberry) (and its’ varieties) are widely used: berries as edible, other organs as a source of BAS. It is known that the accumulation of polyphenols by plants depends on many factors and their content in different organs and parts can vary. Objective. This study investigated polyphenols and flavonoids content of two varieties (Bluecrop and Blujay) of V. corymbosum shoot extracts harvested at four physiological stages. The aim was also to evaluate the effect of the solvents on the completeness of the extraction of polyphenols and flavonoids received from plant raw materials by maceration. Object and methods. Highbush blueberries (Vaccinium corymbosum L.) varieties Bluecrop and Blujay were grown in the field of Berry Partner Ltd. in Lviv region of Ukraine during 2018-2019. Shoots of Bluecrop and Blujay were harvested at four physiological stages (blooming (I), ripening of berries (II), after ripening (III), preparing to winter (IV), and extracted by ten solvents (water, 20, 30, 40, 50, 60, 70, 80, 95% ethanol). Results on total polyphenols content (TPC) are based on spectrophotometrically quantification following modified Folin-Ciocalteu method, the content of flavonoids (TFС) was evaluated spectrophotometrically. Data are means ± SDs (n=5). Results. Results expressed on dry matter basis revealed the shoots contain the following: it was found that the TPC varies in the range of 86.05-184.80 mg·g-1 DW in gallic acid equivalents in Bluejay and in the range of 84.32-176.72 mg·g-1 DW in gallic acid equivalents in Bluecrop. Good solvents for polyphenols were 30% ethanol and aqueous solutions of ethanol in higher concentrations, which extracted 33-68% more polyphenols compared to water in stage I, 34-79% in stage II, 75-134% in stage III, by 45-61% at stage IV in the variety Bludgey; by 34-63%, 64-86%, 75-106%, 103-136% in the Bluecrop variety, respectively. The maximum TFC in the Blujay was observed in the phase of flowering (99,2±7,67 mg·g-1 DW in quercetin equivalent), fruiting (93,46±4,33 mg·g-1 DW in quercetin equivalent) and 8-14% lower – in the phase of entering the winter period of physiological rest, and in the Bluecrop – the first two phases of development. Better solvents were different concentrations of aqueous ethanol compared to water: in phase I and III the best solvent was 70% and 80% ethanol, in II – 80%, in IV – 70%. Conclusion. Thus, the highbush blueberry polyphenols content depends on the seasons (and physiological phases of plant development) and may present variability through the leading to different final bioproducts with variable composition. Polyphenols content in highbush blueberry shoot extracts varied during extraction solvents. The obtained results allow estimating the optimal time of collection of plant material as a source of polyphenolic compounds. The results of the research allow considering the shoots of V. corymbosum varieties Bluecrop and Blujay a promising source of plant antioxidants of phenolic type for further investigation for the pharmaceutical industry and to be a raw material for nutraceutical products.