Screening of anticandidal activity of Vaccinium corymbosum shoots’ extracts and content of polyphenolic compounds during seasonal variation

Abstract

Background. A comprehensive analysis of polyphenols (flavonoids and proanthocyanidins) content of aqueous and hydroethanolic shoots’ extracts of Vaccinium corymbosum L. (highbush blueberry) (HB) cv. Elliott was performed. Materials and Methods. In this study, water and various concentrations of aqueous-ethanol (AE) were used as extragents, and plant material – the shoots of V. corymbosum harvested at stages of flowering (I), fruiting (II), after fruiting (III), and at the beginning of winter dormancy (IV). The anticandidal activity of aqueous (A) and AE extracts was studied with five strains of fungi: Candida pseudotropicalis (Kluyveromyces marxianus ATCC 4922=VKM Y-922), C. curvata (Cutaneotrichosporon curvatus ATCC 10567=VKM Y-2230), C. kefyr (Kluyveromyces marxianus VKM Y-459), C. parapsilosis ATCC 22019=UKM Y-73т=VKM Y-58 and C. tenuis ATCC 10573=UKM Y-1525т (Yamadazyma tenuis ATCC 10573=VKM Y-70). These strains were treated with extracts to investigate their effect on the growth of these microorganisms in vitro and compare with commercially available herbal medicinal extracts and antiseptic drugs. Anticandidal activity has been compared with the content of total phenolic compounds (flavonoids and proanthocyanidins). Results. Our results reveal that phenolic compounds concentration of V. corymbosum shoots’ extracts were significantly dependent on extragents and the stage of growth. The total content of phenolic compounds in aqueous-ethanol extracts was generally higher than aqueous and depended on the concentration of aqueous-ethanol. The highest extraction yield of total phenolic compounds was obtained using 40–80%-AE at all investigated stages. The highest content of flavonoids (105–123 mg·g-1 DW in quercetin equivalent) was observed at the stage of winter dormancy (IV). The content of proanthocyanidins was the highest at stages II and IV, and with 40–96% AEs as solvents; their contents varied within 178–239 mg·g-1 DW in catechin equivalent. Extracts prepared with 40–80% AE have pronounced inhibitory activities against all investigated Candida spp., but the maximum inhibition zone of a single strain may vary. High correlations indicate the determining effect of proanthocyanidins on the anticandidal activity of the extract. Conclusions. The study results indicate that V. corymbosum shoots may have promising properties in supporting therapy as anticandidal drugs.