Isolation and Identification of Chemical Constituents and In Vitro Antioxidant Activity of Ethyl Acetate Extracts from Psidium guajava Linn Leaves
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Abstract:
The in vitro antioxidant activity and the material basis for its antioxidant activity of the ethyl acetate extracts from Psidium guajava leaves were investigated in this study. The antioxidant ability of ethyl acetate extracts was first analyzed in vitro after 95% ethanol percolating, n-hexane and ethyl acetate extraction from Psidium guajava leaves, and then the chemical compounds were isolated and identified by combing column chromatography (such as silica gel column chromatography, Sephadex LH-20) and spectrometry (such as mass spectrometry, nuclear magnetic resonance spectroscopy). The results showed that the ethyl acetate extracts had strong antioxidant activity in vitro to scavenge DPPH radicals, superoxide anion free radicals, and hydroxyl radicals in a dose-dependent manner, and when the concentration was 1 mg/mL, the scavenging abilities for 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, superoxide radicals and hydroxyl radical were 94.15%, 87.88%, 67.3%, respectively, which were close to or better than those of Vc. Five compounds were isolated and purified from the ethyl acetate extracts of Psidium guajava leaves by silica gel column chromatography and Sephadex LH-20 column chromatography, four of which were identified as demethoxymatteucinol (1), cryptostrobin (2), quercetin (3), and isoquercitri (4), respectively, by comparison of their mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopic data with those in literatures. Furthermore, compound 2 was the first flavanone isolated from the genus Psidium Linn.
