Isolation and Purification of Galloyl, Caffeoyl, and Hexahydroxydiphenoyl Esters of Glucoses from Balanophora simaoensis by High-Speed Countercurrent Chromatography and Their Antioxidant Activities In Vitro

5 High-speed counter-current chromatography was used to separate and purify galloyl, caffeoyl, and hexahydroxydiphenoyl esters of glucoses from the aerial parts of the parasitic plant Balanophora simaoensis for the first time using n-hexane-ethyl acetate-methanol-water (1:2:1:2, v/v) as the optimum solvent system. Accordingly, 1-O-(E)-caffeoyl-3-O-galloyl-beta-D-glucopyranose (I, 12.5 mg), 1-O-(E)-caffeoyl-3-O-galloyl-4,6-(S)-hexahydroxydiphenoyl-beta-D-glucopyranose (II, 27.2 mg), and 1-O-(E)-caffeoyl-4,6-(S)-hexahydroxydiphenoyl-beta-D-glucopyranose (III, 52.8 mg) with 98.0%, 98.5%, and 98.7% purities, respectively, were purified from 210 mg crude extract of B. simaoensis in a one-step separation. The structures of the glucose esters were identified by electrospray ionization mass spectrometry (ESI-MS) and nuclear magnetic resonance spectra (NMR). Their antioxidant activities were evaluated by measuring their inhibition activity on liver microsomal lipid peroxidation induced by the Fe2+-Cys system in vitro. Compounds I-III showed significant antioxidant activities with IC50 values ranging from 2.51 to 6.68 mu m, respectively.