The Phenolic constituents and free radical scavenging activities of Gynura formosana Kiamnra

Gynura formosana Kiamnra (Compositae) is a herbal folk medicine that is a popular vegetable in Taiwan. The free-radical scavenging activities of a 70% aqueous acetone extract from the herb G formosana were evaluated. Bioassay-guided fractionation, column separation on Diaion, Toyopearl HW 40(C), Sephadex LH-20 and MCI CHP20P, and high-performance liquid chromatography (HPLC) were used to isolate for the first time in G formosana four potent phenolics [caffeic acid (I), quercetin 3-O-rutinoside (II), kaempferol 3-O-rutinoside (III) and kaempferol 3-O-robinobioside (IV)]. The IC50 values of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity for compounds I–IV were 6.7, 7.7, 300.3 and 286.7 µM, respectively, and, for superoxide radical scavenging activity, they were 187.3, 25.8, 55.3 and 87.4 µM, respectively. Using a spin trapping electron spin resonance (ESR) method, caffeic acid (I) and quercetin 3-O-rutinoside (II) exhibited good hydroxyl radical activity. The free radical scavenging activity of G formosana phenolics may improve the economic value of this herb and assist in its development as a health food. Copyright © 2004 Society of Chemical Industry