EFFECT OF HERBAL MIXTURE STUDENT-RASAYANA ON LIPOXYGENASE ACTIVITY AND LIPID-PEROXIDATION

Brain cellular functions are affected by free radicals. Arachidonic ac id and its 12-lipoxygenase metabolites have been proposed as important in enhancing long-term potentiation associated with learning. It has been reported that Student Rasayana (SR), an herbal mixture, improves brain functions. In this study we evaluated the antioxidant capacity o f SR and its effect on lipoxygenase activity. Both alcoholic and aqueo us extracts of SR inhibited enzymatic- and nonenzymatic-induced micros omal lipid peroxidation in a concentration-dependent manner. The agent concentrations (mu g/mL) that produced 50% inhibition (IC50) of enzym atic- and nonenzymatic-induced microsomal lipid peroxidation, respecti vely, were 99.1 +/- 3.9 and 1999.0 +/- 122.7 for the aqueous extract, and 17.7 +/- 0.9 and 646.7 +/- 79.7 for the alcoholic extract. The aqu eous extract inhibited soyabean lipoxygenase (SLP)-induced LDL oxidati on in a concentration-dependent manner (IC50: 515.5 +/- 11.5), whereas the alcoholic extract enhanced SLP-induced LDL oxidation. Simultaneou s addition of aqueous and alcoholic extracts inhibited SLP-induced LDL oxidation. The alcoholic extract (but not the aqueous extract) enhanc ed the ability of SLP to induce oxidation of linoleic acid. Rats fed 2 % (w:w) SR showed inhibition of toluene-induced brain microsomal lipid peroxidation. These results suggest SR improves brain functions throu gh scavenging free radicals as well as increasing the second messenger for long-term potentiation.