Interaction of flavonoids with 1,1-diphenyl-2-picrylhydrazyl free radical, liposomal membranes and soybean lipoxygenase-1.

The interaction of the antiperoxidative flavonoids namely, quercetin, quercetrin, rutin, myricetin, phloretin, phloridzin, catechin, morin and taxifolin with the 1,1,-diphenyl-2-picrylhydrazyl (DPPH) free radical was demonstrated. Flavonoid-DPPH interaction was looked at in the absence and presence of liposomes so as to reveal some information on bilayers. Perturbations in the lipid bilayers were monitored with the fluorescent probe, dansylhexadecylamine (DSHA). It was observed that the interaction of the flavonoids on the lipid bilayer occurred in the polar zone of the lipid bilayers. The flavonoids were able to scavenge free radicals and could do so in biomembranes. It is suggested that the DPPH free radical abstracts the phenolic hydrogen of the flavonoid molecule and that this could be the general mechanism of the scavenging action of the antiperoxidative flavonoids. The effects of the flavonoids on soybean lipoxygenase-1 were investigated both in buffer and also in liposomal suspension. All the flavonoids studied showed inhibition of the enzyme in both systems but the inhibition was greater in the liposomal suspension. Quercetin was the most potent and it inhibited the lipoxygenase in the liposomal suspension by about 42% while the other flavonoids inhibited the enzyme by about 14-23%. We observed that the effect of myricetin and quercetin on the enzyme was pH dependent.