In vitro Cytotoxic, Antibacterial and Antiviral Activities of Triterpenes from the Red Sea Sponge, Siphonochalina siphonella

Purpose: To study the phytochemical composition of Siphonochalina siphonella sponge from the western coast of the Red Sea and to evaluate the isolates for possible in vitro cytotoxic, antibacterial and antiviral activities. Methods: The compounds obtained were isolated and purified by different chromatographic means. Their structures were established by means of spectral analysis including 1D H and C and 2D correlation nuclear magnetic resonance (NMR) and high resolution mass spectroscopy (HR-MS). Crystal violet staining method (CVS) was used for the assessment of the cytotoxic activity against HepG-2 and MCF-7 human cell lines, while agar-well diffusion method was employed to measure antimicrobial activity against two Gram-positive and two Gram-negative bacteria. The antiviral activity was determined by the inhibition of cytopathic effect (CPE) in susceptible mammalian cells. Results: Four triterpenes, possessing two different skeletons, were isolated and identified as sipholenone A, sipholenol A, neviotine A and sipholenol L. All four compounds were significantly cytotoxic to MCF-7 and HepG-2 cancer cell lines (p < 0.05) in a concentration-dependent manner with IC50 (the inhibitory concentration required to reduce cell survival by 50 %) in range 2.8 19.2 μg/mL. The highest antibacterial activity was observed for neviotine A (Compound 3) against Bacillis subtilis (17.2 ± 0.58). On the other hand, all the compounds showed moderate to weak anti-viral activity. Conclusion: The findings reveal the strong cytotoxic activity of all the isolated triterpenes from the Red Sea Sponge, S. siphonella. Sipholenone A (Compound 1) displayed significant cytotoxic activity towards MCF-7 and HepG-2 cancer cell lines with IC50 = 3.0 and 2.8 μM, respectively.