Studies Of The Anti-glioma Consitituents Of Fatsia Japonica,Anthopleura Midori And Holothuria Moebii

Gliomas are one of the most common and malignant brain tumors. Despite recent advances in standard therapy including surgical resection followed by radiation and chemotherapy, the efficacy of current drugs is limited due to serious side effect, poor drug delivery, and chemo-resistance. There is therefore a need to develop novel anti-glioma agents for treating malignant gliomas. Natural products especially marine natural products are highly significant sources of novel drug leads. In this thesis, the anti-glioma constituents of Fatsia japonica, Anthopleura midori and Holothuria moebii were investigated. By using column chromatography combined with High Performance Liquid Chromatography (HPLC), a total of 27 natural compounds and two hydrolytic products including six novel compounds, two new natural products and one new artificial compound were obtained from the three organisms. The structures of these compounds were determined by means of extensive 1D and 2D NMR. HRESIMS. and CD spectral analyses as well as chemical degradation. All 29 compounds obtained were assayed for their activity inhibiting the proliferation of glioma cells. Several new compounds were found to significantly suppress the proliferation of tested glioma cells, to induce apoptosis and necrosis and block cell cycle in glioma cells, and to selectively reduce the expression level of several glioma metabolic enzymes.From the fruits of Fatsia japonica,11 triterpenoidal saponins were isolated and identified. They are fatsioside A (Fl), hederoside I (F2). staunoside A (F3), cauloside G (F4), cauloside D (F5), akebia saponin D (F6), hederagenin3-O-α-L-arabinopyranosyl-28-O-α-L-rhamnopyranosyl-(1→4)-O-6-O-acetyl-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl ester (F7), ciwujianoside A1 (F8). acanthopanaxoside B (F9), ciwujianoside C3 (F10) and pulsatilla saponin B (F11). Fatsioside A is a rare novel baccharane-type saponin. F. japonica is the third baccharane glycoside-contained species reported to date in the plant kingdom. Fatsioside A was found to inhibit the proliferation of rat glioma C6 cells and human glioma U251 cells, induce apoptosis in glioma cells and arrest the cell cycle at the G0/G1 phase.From sea anemone A. midori,11 sterols including six rare polyoxygenated 24,28-epoxyergosterols (A1-A6) and one carotenoid were isolated and identified. A1 and A2 were found to be new natural products and A3-A6 are new compounds. The 24(R) and 24(S) configurations of this type of epoxyergosterols could be assigned based on their HPLC retention times and CD Cotton effect at 250-300 nm. Bioactive assay showed that this type of epoxyergosterols had activity inhibiting the proliferation of glioma cells and inducing apoptosis in glioma cells.Four sulfated saponins (M1-M4) were isolated from sea cucumber H. moebii. A desulfated saponin (M3B) with an unusual modified xylose was also obtained from the alkaline hydrolysate of saponin M3, the major component in the crude saponins. Moebioside A (M2) is a new triterpenoid glycoside (saponin) and M3B is a new artificial compound. Sulfated saponins (M1-M4) had potent activity suppressing the proliferation of four different glioma cells with IC50 values ranging from 0.99 to 8.64μM, while the activity of desulfated prosapogenin M3B and the modified sapogenin M3A was significantly decreased. These results suggested that the sulfate group at C-4 of xylose might be important for the activity of this type of triterpenoid saponins. New saponin M2 remarkably induced apoptosis in human glioblastoma cells. Western blot analysis showed M2 did not regulate the expression levels of pro-apoptotic genes (BAD and BAX), anti-apoptotic genes (BCL-2 and BCL-XL) and survivin gene, suggesting that the apoptosis induced by M2 in U87-MG cells might not relate to these analytic genes. Further investigation revealed that M2 reduced the expression levels of several glioma metabolic enzymes of glycolysis and glutaminolysis, but it had no effects on these enzymes in normal human astrocytes. Also, M2 did not regulate the enzymes of ACO2, ATPB, PDHB, CytoC, which are important regulators in the processes of tricarboxylic acid cycle and oxidative phosphorylation. Taken together, the results indicated that by selectively targeting multiple glioma metabolic regulators of glycolysis and glutaminolysis might be one of the anti-glioma mechanisms of new saponin M2.