Evaluation of the Ability of Polyphenol Extracts of Cocoa and Red Grape to Promote the Antioxidant Response in Yeast Using a Rapid Multiwell Assay.

Saccharomyces cerevisiae has been used as a model organism to study the capacity of cocoa and red grape extracts to trigger an antioxidant response. A methodology adapted to microtiter plates has been developed to monitor yeast growth after culture preincubation with food ingredients and exposure to oxidative stress by hydrogen peroxide and menadione. This methodology proved effective in measuring the ability of cocoa and red grape extracts to promote an antioxidant response in yeast, and also the prospect of conducting dose-response studies. Additionally, the method has proven useful to perform studies with mutant strains lacking genes that may be related to the mechanism of action underlying the antioxidant properties. Thus, in a single assay, it is possible to elucidate the sensitivity of strains to oxidative stress, the ability of an ingredient to promote an antioxidant response, and the possible implication of certain genes. Results of assays using strain hst3Δ showed that the antioxidant protection provided by exposure to cocoa and red grape extracts was not present in the strain lacking gene HST3 when H O and menadione were used as oxidizing agents. This effect was previously reported for cocoa extract only, with H O as stressor. Moreover, the results showed that the mutant strain hst3Δ is more resistant to menadione and H O in the absence of preincubation with cocoa and red grape extract, hinting at the possible implication of sirtuin Hst3 in the antioxidant cellular response.