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色谱 2008
Investigation on the convertion between ginkgolide B and its derivative
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Abstract:
A derivative decomposed from ginkgolide B (GB) was isolated by semi-preparative chromatography. The results of the high performance liquid chromatography (HPLC) showed that the retention time of the derivative was approximately three times of that of GB with ultraviolet detection (UV), and the derivative can not exist independently without the presence of GB. The UV spectrum showed that the lamdamax of the derivative was 212.1 nm and the epsilonmax was 2.29 x 10(4), which were approximately 100 times higher than those of GB. This means a new conjugation bond has been formed and that means that the conjugation bond's pii-pi* electron jump occured in the derivative. Liquid chromatography-mass spectrometry showed the molecular ion peaks of the derivative in the positive mode and negative mode were m/z 429.1 (M + Na)+ and m/z 405.2 (M-H)-, respectively. The relative molecular mass of the derivative is 406.2. The derivative showed the same mode of fragment ion as GB in the mass spectrum, which might be due to the loss of a H2O from GB. Thermal stability of GB was greater than that of the derivative. They were both easily to be dissolved in dilute alkali. When the pH gradually increases, the ring-opening speed of the derivative is higher than that of GB. The derivative was obviously affected by solvent and higher temperatures. When GB was dissolved in PEG, the peak of the derivative disappeared at 50 degrees C for 15 h or at 120 degrees C for 4 h. Besides the main peak of GB, there appeared a small peak with a retention time of 1.2-3.0 min after heating 4 h at 120 degrees C. The result showed that the derivative was in a high energy state, and GB had a better stabilization. They coexisted and converted to each other. Under some specific conditions, the derivative could all convert to GB.
