| Ginkgolic acids and ginkgols are alkylphenol compounds extensively exist in leave, nut and sarcotesta of Ginkgo biloba L. Because of the thermolability of the carboxylic group, ginkgolic acids could be converted into ginkgols(3-alkylphenols) by decarboxylation when they were heated. Ginkgols also exhibited excellent anticancer activity and thermostability. In this paper, the microwave decomposition of ginkgolic acids was researched. The six ginkgol monomers were separated and identified, and antitumor activity of them was assayed. The methods of simultaneous analysis of ginkgolic acids and ginkgols had been established. The main work of this thesis was as follows:(1) The impact of microwave treatment on the decomposition of ginkgolic acids has been studied. The effect of alkali catalyst in the microwave decomposition of ginkgolic acids was compared with the group without alkali. The mixture of ginkgolic acids and Ca(OH)2 or KOH solid was treated by microwave with the power 700 W and production of reaction was detected by HPLC-MS. The results showed that ginkgolic acids without alkali was not decomposed observably with the microwave treatment for 30 min, while the group with Ca(OH)2 was decomposed within 25 min, and the group with KOH was decomposed only within 10 min. The degradation products were ginkgols, and ginkgol dimer was also produced during the process.(2) The separation conditions of ginkgol monomers from ginkgol homologues by preparative chromatography have been studied. The optimum conditions were as follows: 200 mg of the sample was added on Welch Ultimate AQ-C18 HPLC column and eluted by Me OH-H2O(86:14, v/v) with the flow rate at 24.0 m L/ min, the ginkgol monomers were monitored at 280 nm. Under the above conditions, six ginkgol monomers were obtained with two isomers of ginkgol C17:1 separated for the first time. The structures of the ginkgol monomers were identified by UV, IR, 1H-NMR, 13C-NMR spectroscopy and GC-MS, they were identified as 3-tridecyl phenol, 3-[(8Z)-pentadecenyl] phenol, 3-[(9Z, 12Z)-heptadecadieny] phenol, 3-pentadecyl phenol, 3-[(10Z)-heptadecenyl] phenol and 3-[(12Z)-heptadecenyl] phenol.(3) Antitumor activities of the six ginkgol monomers were compared by MTT assay. The results showed that all of the ginkgol monomers exhibited cytotoxicity against Hep G2 and HGC cells. Among which, ginkgol monomers with unsaturated side chains performed stronger inhibitory effects than those with saturated side chains. In the four ginkgol monomers with unsaturated side chains(C15:1-Δ8, C17:2-Δ9, 12, C17:1-Δ10 and C17:1-Δ12), ginkgol C15:1-Δ8 showed the strongest cytotoxicity. As for the two ginkgol C17:1 isomers, double bond at Δ10 performed higher antitumor activities than that at Δ12. Besides, ginkgol C17:2 showed similar antitumor activities with ginkgol C17:1. The antitumor activities of the six ginkgol monomers were in order: C15:1-Δ8 > C17:1-Δ10 > C17:2-Δ9, 12 > C17:1-Δ12 > C15:0 > C13:0.(4) The HPLC-DAD-FLD method for simultaneous analysis of ginkgolic acids and ginkgols was established. The detection conditions of DAD and FLD were as follows: the UV detector wavelength for ginkgolic acids was 310 nm; the excitation wavelength of fluorescence was 275 nm, emission wavelength was 600 nm. The linear correlation of the method was good. RSD values of precision, repeatability and recovery of ginkgolic acids and ginkgols were: 1.4% and 1.7%, 1.9% and 2.1%, 1.9% and 1.6%, respectively. The method was applied to determinate the content of ginkgolic acids and ginkgols in the Ginkgo biloba extracts, and satisfactory results were achieved. |
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