Role of Herba Pyrolae Essential Oil in Skin Aging and Their Inhibition of Free Radicals

Essential oil of Herba pyrolae, a Chinese herbal medicine, has been suggested to exhibit anti-aging effects. To understand underlying mechanism, we have examined its effect on inhibition of two free radicals (2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) and tyrosinase. The half maximal inhibitory concentration (IC₅₀) of the essential oil was 0.1045 mg/mL for DPPH, while that for ABTS was 0.3961 mg/mL. In addition, the essential oil inhibited both monophenolase and diphenolase activities of tyrosinase. Further examination of the tyrosinase inhibition mechanism and kinetics showed that the diphenolase activity inhibition by H. pyrolae essential oil was a non-competitive reversible process. These data suggest possible mechanism(s) underlying anti-aging effects of H. pyrolae essential oil.