ANTIFUNGAL ACTIVITY OF QUINHYDRONE AGAINST Saccharomyces cerevisiae

Quinhydrone (QH) is a redox active charge transfer complex commonly used as a redox standard. Information on quinhydrone generation in plants is scarce and its physiological role is still unclear. Recently we have showed that excess zinc may induce oxidative stress through QH accumulation in the cell wall and stabilization of phenoxyl radicals [1]. The aim of our research was to investigate the antifungal activity of quinhydrone against yeast Saccharomyces cerevisiae (112, Hefebank Weihenstephan). Saccharomyces cerevisiae was grown on the Sabouraud maltose broth (HiMedia, Mumbai, India) in the presence of different concentrations of QH ranging from 75 mu M to 500 mu M. Concentrations of QH greater than 300 mu M had complete inhibitory effect on yeast growth, while lower concentrations (up to 200 mu M) did not affect the growth. QH had a significant impact on antioxidative defense enzymatic systems, indicated by the changes in the activity in catalase (CAT) and superoxide dismutase (SOD). CAT activities increased by 43% (150 mu M QH) and SOD activities by 122% and 60% at 150 mu M and 220 mu M QH respectively. However, abrupt inhibition of both enzymes was observed at concentrations higher than 220 mu M QH (>= 70%), to be almost completely diminished at 280 mu M QH. High molecular weight genomic DNA without any laddering or smearing was detected in both control and QH treated yeast cells, indicating the absence of apoptosis.