ABSTRACT
Rosmarinic acid (Figure 2.1), a plant secondary metabolite belonging to the class of hydroxycinnamic esters, is a constituent of the members of Lamiaceae, Boraginaceae and Apiaceae families (De-Eknamkul and Ellis, 1987). Its chemical structure was identified in rosemary extracts (Scarpati and Oriente, 1958). A promising bioactive substance, rosmarinic acid has applications as a food preservative and a part of medication due to its functional properties as an antioxidant and a antimicrobial (Deighton et al., 1993; Frankel et al., 1996; Shetty et al., 1997). It was reported that in bulk corn oil, rosemary extract containing carnosic acid and rosmarinic acid showed significantly more antioxidant activity than carnosol (Frankel et al., 1996). In addition, recent studies show that rosmarinic acid can also
inhibit inflammatory reactions in vivo (Engleberger et al., 1988; Peake et al., 1991). Zou et al. (1993) reported on the antithrombotic effect of rosmarinic acid, which might be associated with its inhibition of platelet aggregation and promotion of fibrinolytic activity. This plant metabolite also accounts for the antioxidant activity of sage (Baricevic, 2000; Deans and Simpson, 2000). When measuring the radical scavenger effect on 1,1diphenyl-2-picrylhydrazyl (DPPH) free radical, the antioxidative effect of rosmarinic acid (EC50 = 2.7 pg/ml) was comparable to that of ascorbic acid (Lamaison et al., 1991). Rosmarinic acid, as also its methyl ester isolated from EtOAc fraction of the methanolic extract of Salvia miltiorrhiza, were proved to have strong inhibitory effects on adenylate cyclase (AC) in both rat brain and in rat erythrocytes (Kohda et al., 1989).
