In our promising project toward discovery of secondary metabolites with potential anticancer activity against human cervical cancer, seven marine organisms were screened for their cytotoxic activity against HeLa cancer cell line using MTT colorimetric assay. The crude extract of the outer shell of Diadema setosum showed promising activity with 88.02% inhibition at a concentration 250 µg/ml. Chromatographic investigation of the Ethyl acetate fraction, which is the main contributor to the activity (IC50= 43.1 ± 5.94 µg/ml), led to isolation of five compounds. Structures of the isolates (1-5) were elucidated by 1 D and 2 D NMR spectroscopy and HR-ESI-MS analysis. 5α,8α-epidioxycholest-6-en-3β ol (2) and 5α,8α-epidioxycholest-6,9(11)-en-3β ol (3) showed the highest cytotoxic activity with IC50 values 12.1 ± 2.74 µg/ml and 21.8 ± 6.32 µg/ml, respectively. Epidioxy steroids with cholestane nucleus could be a prospective candidate for the development of drugs for treatment of human cervical cancer.
Keywords: diadema; Epidioxy steroids; HeLa; cytotoxicity; sea urchin.