Phenolic inhibitors of chemical and enzymatic oxidation in the leaves of Myrica rubra.

Potent inhibitory activity of the leaves of Myrica rubra against both chemical and enzymatic (tyrosinase and lipoxygenase) oxidation was found in our project to develop utility of unused and rarely used plant resources in the local area. A constituent analysis of the most active ethyl acetate-soluble part of a methanol extract of the leaves clarified the structures of eight major compounds. The tyrosinase and lipoxygenase inhibitory activities and DPPH radical scavenging activity of the isolated compounds were measured as indicators of the inhibitory capacity against the enzymatic and chemical oxidation of food. The obtained data indicate that the chemical and enzymatic (lipoxygenase and tyrosinase) antioxidant activities of the leaves mainly depended on the galloyl flavonoid derivatives.