QUANTITATION OF BILOBALIDE AND GINKGOLIDE-A, GINKGOLIDE-B, GINKGOLIDE-C AND GINKGOLIDE-J BY MEANS OF NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

A quantitative H-1 NMR procedure for the determination of bilobalide and ginkgolides A, B, C and J in Ginkgo biloba leaves and in phytopharmaceuticals without prior chromatographic separation of the mixture has been developed. The method is based on the comparison of the integral of each H-12 proton of the five ginkgo terpene trilactones with that of the olefinic protons of the internal standard (maleic acid). These protons are all well separated at 200 MHz and occur in a less crowded region of the NMR spectrum (6.15-6.50 ppm). The selectivity, reproducibility and sensitivity are comparable with high pressure liquid chromatography (HPLC) with refractive index (RI) detection. The minimum amount that can be quantified within 30 min at 200 MHz is approximately 0.1 mg for all four ginkgolides and bilobalide. Advantages, in comparison with HPLC-RI, are that no reference substances are needed and that for the occasional analysis of a limited number of samples a very significant time-gain can be achieved.