A phytochemical investigation on Lagotis brevituba led to the isolation and characterisation of 11 phenolic compounds: p-hydroxy-benzoic acid 1, methyl 3,4-dihydroxybenzoate 2, vanillic acid 3, protocatechuic acid 4, caffeic acid 5, glucose ester of (E)-ferulic acid 6, p-coumaric acid 7, vanillin 8, diosmetin-7-O-β-d-glucoside 9, chrysoeriol 10 and luteolin 11. Their structures were elucidated using spectroscopic methods and by comparison with data in the literature. Compounds 1-6 were first obtained from the genus Lagotis, and compounds 1-9 were isolated from L. brevituba for the first time. Compound 4 and 11 displayed remarkable antioxidant activities against DPPH radical (IC50 = 5.60 ± 0.09, 27.5 ± 0.06 mg/L, respectively), which were superior to positive control rutin. And compound 11 was also superior to rutin in ABTS assay (IC50 = 2.04 ± 0.13 mg/L).
Keywords: Lagotis brevituba; phenolics; spectroscopic methods.