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Abstract

tDifferent solvent extracts of Dichotomaria obtusata (J. Ellis & Solander) Lamark, Galaxauraceae, a redalgae collected from the coast of Bushehr in the Persain Gulf, was investigated for its cytotoxic prop-erties and chemical constituents. The fresh alga, after extraction with methanol and dichloromethanewere combined and partitioned between water, dichloromethane and ethyl acetate. The above fractionswere then tested against MOLT-4 (human lymphoblastic leukemia) cancer cell line. The IC50values ofthe dichloromethane and ethyl acetate layers of the crude extract were 29.8 ± 3.1 and 30.6 ± 7.9 g/mlagainst MOLT-4 cells, respectively, while the water layer showed a week activity with IC50> 50 g/ml.After fractionation of the active extracts using open column chromatography over silica gel and prepar-ative thin layer chromatography purification, two terpenoid derived compounds, trans-phytol palmitateand -tocopherol were isolated from the dichloromethane and ethyl acetate extracts. The structures ofthe compounds were elucidated using different spectral data including1H NMR,13C NMR, HSQC, HMBCand EI-MS. The IC50values of compounds trans-phytol palmitate, -tocopherol and an undetermined mix-ture of compounds (F-13-14) were determined as 43.4 ± 1.6, – and 20.3 ± 6.2 g/ml against LS180 (humancolon adenocarcinoma); 53.2 ± 9.3, >100 and 27.6 ± 6.9 g/ml against MCF-7 (human breast adenocarci-noma) and 40.0 ± 4.1, 48.8 ± 1.8 and 15.9 ± 0.3 g/ml against MOLT-4 cell lines, respectively, which werecomparable to the IC50values of standard anticancer agent, cisplatin against the same cell lines. The redalgae collected from the Persian Gulf contained substances that could inhibit the growth of human cancercell lines and may represent a natural source for the discovery of novel anticancer agents.