Thin layer chromatography of bilobalide and ginkgolides A, B, C and J on sodium acetate impregnated silica gel

A normal phase thin layer chromatographic procedure for the separation and detection of bilobalide and ginkgolides A, B, C and J has been developed. The method is based on the impregnation of commercially available silica gel F254 plates with sodium acetate. Silica gel thus impregnated gives a good separation of all major terpene trilactones in ginkgo leaves (0.06 ⩽ Δ R f 0.17) with the solvent systems ethyl acetate: hexane (9:1) (non‐saturated chamber) or 100% methyl acetate (saturated chamber). The sodium acetate has two functions: it greatly improves the separation of the ginkgolide pairs G‐A/G‐B and G‐J/G‐C, and it enhances the sensitivity of the acetic anhydride spray reagent. Quantities of less than 1 μg of all four ginkgolides and bilobalide can be detected.