Isolation of kaempferol from the leaves of Ginkgo biloba and establishing a quantitative evaluation procedure of Kaempferol in preperations containing Ginkgo biloba extracts

Abstract

   The aim of this research is to develope a procedure to isolate kaempferol from Ginkgo leaves extract, and then use the isolated kaempferol to validate the quantification method. Flavonoids in ginkgo leaves were extracted using 96 % ethanol. These flavonol glycosides, which are hydrolysed in the presence of hydrocloric acid, convert to aglycones. Flavonol aglycones were then extracted from the hydrolysing solution with ethyl acetate. The solvent was evaporated under reduced pressure to produce crude flavonol aglycones named C2. Kaempferol was then purified from C2 by traditional column chromatography twice. The first mobile phase required mixing petrol ether and ethyl acetate, acquiring PDD1. PDD1 was then repeatedly crystalized in acetone, to achieve PDD2, supposedly composed of kaempferol, quercetin and isorhamnetin. Kaempferol in this fraction was then purified by traditional column chromatography with a mobile phase composed of chlorform and methanol. After that, The isolated kaempferol was characterized in terms of purity (Thin layer chromatography and High Performance Liquid Chromatography-HPLC) and structures (IR, MS, 1H-NMR and 13C-NMR). Kaempferol was eventually used as a standard to establish and validate the qualification method applied for Tanakan® by replacing phase HPLC with PDA detector. After being validated, the procedure meets the requirements of specificity, repeatability,intra-day and inter-day precision, linearity, and exactitude.