Free Radical Scavengers and Antioxidants from Tagetes mendocina

Abstract

Tagetes mendocina (Asteraceae) is a medicinal plant widely used in the Andean provincesof Argentina. Preliminary assays showed free radical scavenging activity in the methanolextract of the aerial parts, measured by the decoloration of a methanolic solution of the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and scavenging of the superoxide anion. Assayguidedisolation led to 4-hydroxyacetophenone (1), protocatechuic acid (2), syringic acid(3), patuletin (4), quercetagetin 7-O--d-glucoside (5), patuletin 7-O--d-glucoside (6) andaxillarin 7-O--d-glucoside (7) as the free radical scavengers and antioxidant compoundsfrom Tagetes mendocina. On the basis of dry startingmaterial, the total phenolic content ofthe crude drugwas 3.00% with 0.372% of flavonoids. The content of compounds 1Ð7 in thecrude drugwas 0.008, 0.015, 0.010, 0.029, 0.238, 0.058 and 0.017%, respectively. Quercetagetin7-O--d-glucoside proved to be the main free radical scavenger of the extracts measured bythe DPPH decoloration test as well as for quenchingthe superoxide anion and inhibition oflipoperoxidation in erythrocytes. In the lipid peroxidation assay the percentual inhibition wasrelated with the number of methoxy groups in the molecule, ranging from 86% for thequercetagetin glucoside to 67% for the monomethoxylated and 31% for the dimethoxylatedderivative. The compounds showed low cytotoxicity towards human lungfibroblasts withIC50 > 1mm for compounds 1Ð3 and 0.24 to 0.52 mm for the flavonoids 4Ð7.