Marine Bioactive Steryl Esters from the Red Sea Black Coral Antipathes dichotoma

Two new marine steryl hexadecanoates, 3β‐hexadecanoylcholest‐5‐en‐7‐one (1) and 3β‐hexadecanoylcholest‐5‐en‐7β‐ol (2), along with seven known compounds, cholest‐5‐en‐3β‐yl‐formate (3), thymidine (4), indole‐3‐carboxaldehyde (5), 3β‐hydroxycholest‐5‐en‐7‐one (6), cholesterol (7), 22‐dehydrocholestrol (8), and 24‐methylenecholesterol (9), were isolated from the anthozoan black coral, Antipathes dichotoma. The structures of all isolated compounds were determined by interpretation of their spectral data 1D (1H, 13C and DEPT) and 2D (COSY, HSQC and HMBC) NMR, UV, IR, and MS. Compounds 1–5 were evaluated for their anticancer activities, employing four cancer panels; HepG2, WI 38, VERO, and MCF‐7. All tested compounds, except 4, showed moderate activities. Compound 4 exhibited significant anticancer activity against VERO and MCF‐7, with IC50 20.5 and 20.2 µg/mL, respectively. Antipathes dichotoma is a source of several secondary metabolites; most of them were already isolated from, e.g., sponges, octocorallia, and macro‐algae. The spreading of these metabolites in the macro‐organisms (marine invertebrates) strongly indicates that dietary or symbiotic micro‐organisms are involved in the production of these isolates.