Characterizations of the hydrolyzed products of ginkgolide A and ginkgolide B by liquid chromatography coupled with mass spectrometry

Abstract

Ginkgolides are diterpenoid trilactones responsible for the neuromodulatory properties of Ginkgo biloba extracts. They are to be hydrolyzed in aqueous solutions as mixed carboxylate forms potentially including three monocarboxylates, three dicarboxylates and one tricarboxylate. Characterizations of the hydrolyzed products are challenging because there is no way to prepare them individually. In this work, the major hydrolyzed products of ginkgolide A (GA) and ginkgolide B (GB) including all three monocarboxyaltes have been produced in buffers and subjected to liquid chromatography coupled with triple quadrupole MS and LTQ Orbitrap MS analysis. With the comparative analysis of the trilactone of GA and GB, it was highlighted a unique charge-driven fragmentation pathway of twice neutral losses of CO on the lactone-C. The monocarboxylates were accordingly identified based on the construction of their fragmentation pathways cross-linked with those of the trilactone. In brief, the lactone-C hydrolyzed product is characteristic of the absence of product ions between [M−H]− and [M−H−C2H2O3]− (m/z 351 for GA and m/z 367 for GB). The featured fragmentation pathway of the lactone-F hydrolyzed product is the cleavage of ring-A, yielding a fragment (m/z 295 for GA and m/z 309 for GB) followed with twice (GA) or triple (GB) neutral losses of CO. The most characteristic fragment of the lactone-E hydrolyzed product is [M−H−H2O−CO2−2CO]− (m/z 307 for GA and m/z 323 for GB) in contrast to the other two monocarboxylates. The knowledge gained in this work was of special uses to investigate the biological fates and the corresponding pharmacological mechanisms of ginkgolides.