Superoxide Scavenging Activity of Rosmarinic Acid from Perilla frutescens Britton Var. acuta f. viridis

Rosmarinic acid (RoA) has been isolated in high yield (0.1%) from the leaves of Perilia frutescens Britton var. acuta f. viridis, one of the most common garnishes in Japan, as a superoxide scavenger in a xanthine/xanthine oxidase system. The scavenging activity of RoA was significantly higher than that of ascorbic acid (AA). The structure-activity relationships using RoA, caffeic acid (CaA), and its related compounds indicated that the presence of an ortho dihydroxyphenyl group is essential for the scavenging effect. In addition, the conjugated double bond in the C3 carbon chain is important for enhancing the effect. The activity of RoA was then shown to be due to the additive effect of both CaA and (3,4-dihydroxyphenyl)lactic acid units, both of which are hydrolyzed products of RoA. RoA significantly inhibited both intracellular superoxide and peroxide formation in differentiated HL-60 cells, suggesting that RoA effectively exhibited antioxidative activity in the biological systems through the scavenging of superoxide.