Naturally ocurring polyphenols as antioxidants – conclusion

Natural substances have traditionally provided lead compounds for drug development. The current review discusses the medicinal properties of naturally occurring polyphenols highlighting the structure activity relationships and mechanisms that explain their mode of action. Polyphenols are widely distributed in plants occurring in roots, leaves, roots, berries and seeds of various higher plants. Their notable activity is their antioxidant capability but some groups possess other activities as antimicrobial and neuroprotective effects. The antioxidant activity is influenced by aspects such as hydroxylation of the A and B rings, o-methylation in ring B, and carbohydrate substituents in the A and B rings. Antimicrobial activity is influenced by prenyl substituents at position 6, hydroxyl groups on the phenyl rings and cyclization between OH and prenyl groups. Mechanisms of action of polyphenols are wide ranging including direct scavenging of reactive species, inhibition of oxidation by chelating metal cations, inhibition of fatty acid synthase, and inhibition of topo IV activity in bacteria. Structural similarities with estrogen also help isoflavones to bind estrogen receptors thus establishing their effect in hormonal replacement therapy. A possible negative effect is the prooxidant effect noted in some polyphenols in in vivo assays.

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