Antioxidant activities of uyaku (lindera strychnifolia) leaf extract: a natural extract used in traditional medicine.

Uyaku (Lindera strychnifolia, Sieb. et Zucc.) is used in traditional Asian medicine to treat stomach and renal diseases, neuralgia, rheumatism, and aging. In this study, the effects of lyophilized extracts on hydroxyl ((.)OH) and superoxide (O(2) (.-)) radicals were examined using an electron spin resonance (ESR) spectrometer with the spin trap, 5,5'-dimethyl-1-pyrroline-N-oxide. Inhibitory effects were assessed using the following reagents: for nitric oxide (NO(.)), the Griess reagent; for (Fe(2+) + H(2)O(2))-induced lipid peroxidation, 2-thiobarbituric acid; for (Fe(2+) + H(2)O(2))-induced protein carbonyl, 2,4-dinitrophenylhydrazine. Analysis of ESR data of the extracts indicated the direct (.)OH and O(2) (.-) scavenging. The extracts scavenged NO(.) in a dose-dependent manner, inhibited lipid peroxidation of linolenic acid, and protein carbonyl formation in bovine serum albumin. In conclusion, the Uyaku leaf hot-water extract has potent scavenging activity against reactive oxygen species and reactive nitrogen species, and effectively inhibited lipid peroxidation. These results might contribute to understanding age-associated or free radical-related diseases induced by excess reactive oxygen and also nitrogen species.