Purification of quercetin in Anoectochilu roxburghii (wall) Lindl using UMAE by high-speed counter-current chromatography and subsequent structure identification

Quercetin is a major phenolic compound in the Chinese medicinal herb. It has been proved to have many important pharmacological active compounds. To the best of our knowledge, this is the first paper to report that quertin exists in Anoectochilu roxburghii (wall) Lindl. The high-speed counter-current chromatography (HSCCC) was successfully applied to purify quercetin from the extracts of A. roxburghii (wall) Lindl after ultrasound-microwave assisted extraction. The two-phase solvent system used in HSCCC was n-hexane-ethyl acetate-methanol-water (4:6:3:3, v/v/v/v). The purity of the obtained quercetin was over 96.8%, i.e. 30.8 mg quercetin was obtained from 6.02 g of the crude extract. Its chemical structure was identified by using UV spectra, FT-IR, electrospray ionization mass spectrometry (ESI-MS) and H-1 NMR. The results showed that ultrasound-microwave assisted extraction was a promising method for extracting quercetin, and HSCCC was a feasible method to be used in the purification of quercetin from the herb. This separation method was more effective than some conventional techniques. (C) 2008 Elsevier B.V. All rights reserved.