RESUMO
Objective: To isolate, purify, and analyze the anti-oxidants from the leaves of Lantana trifolia. Methods: The anti-oxidative activities of the crude extracts from liquid-liquid extraction of L. trifolia leaves were assayed by 1,1-diphenyl-2-picrylhydrazyl (DPPH) method to assess their radical scavenging and reducing abilities. The total flavonoids and phenol contents in the ethyl acetate fraction were determined by colorimetric and Folin-Ciocalteu methods, respectively. Chemical constituents were isolated from the ethyl acetate fraction and repeatedly purified using silica gel, Sephadex LH-20 column chromatography, and HPLC, respectively. The chemical structures isolated were identified by spectral analysis and chemical evidence. Results: Ethyl acetate partition from liquid-liquid extraction exhibited the highest anti-oxidative activity with an IC50 value of 4.94 μg/mL, close to that of the standard (vitamin C, VC, 4.23 μg/mL). The extract was proved to contain total flavonoids and phenol contents with values of (39.0 ± 1.6) and (29.27 ± 1.46) mg/g, respectively. Six compounds were isolated and identified as kaempferol-3,7-dimethyl ether (1), verbascoside (2), apigenin (3), umuhengerin (4), ladanetin (5), and scutellarein-7-O-β-D-apiofuranoside (6). Conclusion: The ethyl acetate extract from the leaves of L. trifolia possesses the potent anti-oxidative and free radical scavenging activities which are directly proportional to the concentration of phenolic contents. The anti-oxidative activity of the extract from the leaves of L. trifolia is due to its proton donating ability that converts free radicals to more stable products and terminates chain reactions. Compound 1 is isolated from the plants of Lantana Linn. for the first time. The mechanisms may be related to the therapeutic benefits of the certain traditional claims of wild L. trifolia. © 2014 Tianjin Press of Chinese Herbal Medicines.