Comparative Influence of Flavonoids on the Toxicity of Copper to Alternaria alternata

Three ~avonols\ morin\ rutin and quercetin\ and a ~a! vonone\ naringenin\ were in vitro tested for their in~uence on the toxicity of copper to Alternaria alternata[ Copper sulphate "CuSO3# displayed dose!dependent inhibition of fungal growth\ resulting in a reduction in growth by one! half at 9[96mM[ The addition of quercetin and morin conferred substantial protection against the inhibition of fungal growth by copper\ whereas naringenin and rutin o}ered protection less e}ectively[ Higher concentrations of copper could overcome the ~avonoid e}ect\ but the reduction of copper toxicity was more apparent in the presence of quercetin than morin[ The metal chelating ability of quercetin was highly speci_c for copper among toxic metals such as Co\ Ni\ Zn\ and Cd[ The results show that the protection e}ect of the ~avonoids against copper toxicity is highly dependent on the keto function and hydroxyl group substitution of the ~avonoid skeleton