Isolation and purification of four flavone C-glycosides from antioxidant of bamboo leaves by macroporous resin column chromatography and preparative high-performance liquid chromatography

The present study investigated a robust method for the preparation of four flavone C-glycosides, i.e. orientin, homoorientin, vitexin and isovitexin, which were prepared from an ethanol aqueous extract, i.e. antioxidant of bamboo leaves (AOB), by AB-8 resin-based column chromatography and preparative high-performance liquid chromatography (HPLC) using a mobile phase consisting of 10% and 15% (v/v) of acetonitrile and 1% acetic acid. These flavone C-glycosides were further purified by the drowning-out crystallization method using methanol and water as drowning-out anti-solvents and salting-out agents, respectively. The purity was assessed by analytical HPLC and the confirmation of chemical structures was performed by IR, MS, NMR and UV spectroscopy. Orientin (49 mg), homoorientin (142 mg), vitexin (15 mg) and isovitexin (62 mg) were prepared from 6.5 g of crude column chromatography fraction obtained from 5 L of AOB concentrated solution. The present method is robust and suitable for preparing available quantities of pure flavone C-glycosides and the quantification of orientin, homoorientin, vitexin and isovitexin in bamboo leaves.