Antioxidative and free radical scavenging activities of some plants used in Thai folk medicine

Ten methanol extracts from various parts of seven medicinal plants, Angiopteris evecta Hoffm., (Marattiaceae) Citrus hystrix DC., (Rutaceae) Laurentia longiflora (L.)Peterm., (Campanulaceae) Nelumbo nucifera Gaertn., (Nelumbonaceae), Piper sarmentosum Roxb., (Piperaceae), Portulaca oleracea Linn., (Portulacaceae) and Stachytarphera indica (L.)Vahl (Verbenaceae), commonly used in Thai traditional medicine, were evaluated for their antioxidative and free radical scavenging activities. Among them, only that prepared from sacred lotus (N. nucifera) leaves exhibited a pronounced activity in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay with an IC 50 of 90 mu g/ml, compared with an IC50 of 30 mu g/ml for the butylated hydroxytoluene (BHT) control. The same extract was also found to be the most potent in removing the superoxide anion (O-2(-)) radical and in inhibiting the 2,2'-azo-bis-(2-amidinopropane) dihydrochloride (AAPH)-induced erythrocyte hemolysis and lipid peroxidation in a rat brain homogenate. The extract from leaves and peels of the Kaffir lime (C. hystrix ) exerted the strongest effect on production of the hydroxyl radical (OH center dot). They conferred a twice greater protection of deoxyribose from OH center dot than did tannin. However, none of the extracts examined in this study showed a significant pro-oxidant action in the bleomycin-dependent DNA oxidation system.