Structure Elucidation and Bioactivity of Marine Natural Products from the Red Sea Sponge

A new neviotine-type triterpene, neviotine-C (137), along with four known triterpenes; sipholenol-A (52), sipholenone-A (60), neviotine-A (68), and sipholenol-L (138) were isolated from CH2Cl2-MeOH extract of the Red Sea sponge Siphonochalina siphonella. All compounds except (138), were tested towards human breast cancer cells (MCF-7). The anti-cancer effect of 5-fluorouracil on human breast cancer cells was found to be enhanced by the addition of the isolated neviotine-C triterpene to the treatment. Cellular proliferation was observed to be significantly inhibited in cells exposed to 5- fluorouracil plus neviotine-C triterpene, compared with the proliferation in cells exposed only to 5-fluorouracil. This may indicate that 5-fluorouracil (IC50 (μM) = 10) may acts synergistically with isolated triterpenes (IC50 (μM) :18, 23, 23, and 28 for 52, 68, 138, and 60 respectively) in inhibiting MCF-7. Two new polyacetylenes, Callyspongenol D (139) and Callyspongendiol E (140) and two known Dehydrosiphonochalynol (84) polyacetylene and sipholenol A (52) triterpenoid derivative were isolated from CH2Cl2-MeOH extract of the Red Sea sponge Siphonochalina sp. The impact of the three isolated acetylinic compounds (84, 139 and 140) on the human mammary carcinoma cell line (MCF-7) was evaluated. Cytotoxicity effect was measured by lactate dehydrogenase (LDH) assay. Compound 140 proved to retain the best cytotoxic activity against breast cancer cell line (MCF-7) as manifested by LDH and the viability over a 48 h period. The structures of all compounds were determined by interpretation of their spectroscopic data 1D and 2D-NMR, IR and MS, as well as comparison with literature.