Quantitative Analysis of Bilobalide and Ginkgolides from Ginkgo biloba Leaves and Ginkgo Products Using ¹H-NMR

Abstract

¹H-NMR spectrometry was applied to the quantitative analysis of the bilobalide, ginkgolides A, B, and C in Ginkgo biloba leaves and six kinds of commercial Ginkgo products without any chromatographic purification. The experiment was performed by the analysis of each singlet H-12, which were well separated in the range of δ 6.0—7.0 in the ¹H-NMR spectrum. However, the H-12 protons of bilobalide and ginkgolides may have overlapped with H-6 or H-8 protons of the Ginkgo flavonoids. Therefore, the optimum ¹H-NMR solvent for the analysis of the compound was selected through the evaluation of solvent effects on the resolution of these signals from the compounds. Acetone-d₆–benzene-d₆ (50 : 50) was found to be the best one among the solvents evaluated. The quantity of the compounds was calculated by the relative ratio of the intensity of each compound to the known amount of internal standard (25 μg/ml), phloroglucinol. This method allows rapid and simple quantitation of underivatized bilobalide and ginkgolides in 5 min without any pre-purification steps.