In vitro anti-proliferative activities of the sterols and fatty acids isolated from the Persian Gulf sponge; Axinella sinoxea.

Objective: Marine sponges are rich sources of anticancer metabolites. Axinella sinoxea is a less studied sponge, found in the Larak Island's waters, of the Persian Gulf. In the present study, we have explored the cytotoxic properties and chemical constituents of A. sinoxea.

Methods: Repeated silica gel flash column chromatography of methanol extract of the Axinella sinoxea sponge, yielded fatty acid and sterol fractions. These fractions were analyzed by GC-MS and their anti-proliferative activities were evaluated by MTT assay against three human cancer cell lines including MOLT-4, MCF-7 and HT-29 as well as NIH/3 T3 fibroblast cells. The sterol-rich fractions were pooled and purified by HPLC and its sub fractions' cytotoxic activities were evaluated by MTT assay against MOLT-4 and NIH/3 T3 cells.

Results: The GC-MS spectral analysis of a fraction eluted with hexane: diethyl ether (90: 10), resulted in the identification of twelve fatty acids, including five linear chain saturated fatty acids; tetrdecanoic acid (1), pentadecanoic acid (3), hexadecanoic acid (5), heptadecanoic acid (7), and octadecanoic acid (10); one branched chain isoprenoid fatty acid, 4,8,12-trimethyltridecanoic acid (2); four monoenoic fatty acids; 9-hexadecenoic acid (4), 7-methyl-6-hexadecanoic acid (6), 9-octadecenoic acid (8) and 11-octadecenoic acid (9) and two polyunsaturated fatty acids; 5,8,11,14-eicosatetraenoic acid (11) and 4,7,10,13,16,19-docosahexaenoic acid (12). Spectral analysis of a non-polar fraction eluted with hexane: diethyl ether (85: 15), resulted in the identification of eight steroids including: cholesta-5,22-dien-3β-ol (13), cholest-5-en-3β-ol (14), ergosta-5,22-dien-3β-ol (15), ergost-5-en-3β-ol (16), stigmasta-5,22-dien-3β-ol (17), γ-sitosterol (18), 33-norgorgosta-5,24(28)-dien-3β-ol (19) and stigmasta-5,24(28)-dien-3β-ol (20). Fatty acids-containing fraction was active against HT-29 cell line with IC50 26.52 ± 8.19 μg/mL, while the steroids-rich fraction was active against the three above mentioned cell lines with IC50 values of 1.20 ± 0.24, 4.12 ± 0.40 and 2.47 ± 0.31 μg/mL, respectively. All of the above-mentioned fractions and sub-fractions were inactive (IC50s > 50 μg/mL) when assayed against normal fibroblast cells.

Conclusions: The present study suggests A. sinoxea as a potential natural source of cancer chemotherapeutics. Graphical abstract Cytotxic constituents of Axinella sinoxea.