Application of growth tests employing a Δsod1 mutant of Saccharomyces cerevisiae to study the antioxidant activity of berry fruit extracts

The aim of the study was to evaluate the content of major bioactive compounds (BACs) and the antioxidant properties of aqueous berry extracts using ABTS
- + and DPPH
- biochemical assays and a novel bioassay based on the growth of a Δsod1 mutant of Saccharomyces cerevisiae on osmotic shock plates (OSPs). The extracts were prepared from raspberry ('Cascada Delight', 'Glen Fyne' and 'Octavia') cultivars, blackberry ('Navaho') cultivar, and wild blackberry, as well as a raspberry-blackberry hybrid. Concentrations of phenolic compounds, anthocyanins and ascorbic acid differed significantly in the fruit extracts, but were highest in the raspberry-blackberry hybrid. The antioxidant activity against DPPH
- and ABTS
- + among the berry cultivars and hybrid was highly dependent on the anthocyanin content. The Δsod1 yeast mutant growth test confirmed the antioxidant properties of all the extracts, with the variant based on counting of single colonies proving more sensitive than the spot test.