Antibacterial and Cytotoxic Potential of Two Steroids from the Indonesian Soft Coral Sinularia polydactila

Soft corals of the genus Sinularia are well recognized as a rich source of steroidal compounds. These constituents have been reported as possessing antitumor, antimicrobial, and antiviral activities.

This study was designed to isolate and elucidate antibacterial and cytotoxic compounds from the soft coral Sinularia polydactila.

Structure elucidation of steroids was determined based on spectroscopic data through 1D and 2D NMR analyses and mass spectrometry, with the results compared to data in the literature. Antibacterial activity was determined using four human bacterial pathogens, namely B. subtilis (ATCC 6633), P. aeruginosa (ATCC 27853), S. aureus (ATCC 25923), and E. coli (ATCC 25922). Cytotoxic activity was evaluated using the human colon cancer cell HCT 116 and brine shrimp lethality assay (BSLA).

Two steroids (Compounds 1 - 2) were isolated from the Indonesian soft coral Sinularia polydactila. (22R,23R,24R)-22,23-methylene-24-methylcholest-6-en-5α,8α-epidioxy-3β-ol (1) and 5α,8α-Epidioxy-24(R)-methylcholesta-6,22-dien-3α-ol (2) showed moderate activity against colon carcinoma cancer HCT 116 at the concentrations of 24.8 and 27.3 μg/mL, respectively. Furthermore, compounds 1 and 2 showed cytotoxic activity using the brine shrimp lethality assay with the concentrations of 57.1 and 121.3 3 μg/mL, respectively. Compound 2 showed moderate activity against S. aureus and B. subtilis at the 250 μg/mL concentration.

Two steroids isolated from soft coral Sinularia polydactila were found to possess moderate cytotoxic and antibacterial activities.