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The South China Sea is a rich resource of acquiring secondary metabolites of unique structure with various bioactivities such as anti–tubercular, anti-tumor, anti-virus,antibiosis, ,anti-inflammatory, anti-allergy, treatments for neurological disorders and osteoporosis, and immunomodulation.According to the methodology of chemical ecology combining with modern technology of marine natural products, in this paper, study of the chemical constituents of the sponge Haliclona cymaeformis and Topsentia sp. which was collected from the South China Sea, was carried out. The compounds were isolated and purified by column chromatography on silica gel, reversed-phase silica gel (ODS) and Sephadex LH-20, and their structures were elucidated on the basis of physicochemical and sp.tral analysis. As a result, Fifteen compounds were isolated from the ethanol extract of H. cymaeformis, and their structures were identified as 9-(4’-carbonypentan-2’(R)-yl)purine-6-hydroxy(1), 7- (4’-carbonypentan-2’-yl)purine -2-hydroxy(2), 7-(5’-carbonylpentan-3’-yl)purine-2-hydroxy (3), 7- (4’- carbonylpentan-2’-yl)purine-2-hydroxy (4),24-methylene-cholesta-3β-ol (5), 5α,8β-epidioxy-cholesta-6-en-3-ol (6), cholesta-7-en-3β,5α,6β,9α-tetraol (7), cholesterol (8), 1H-indole-3-carboxylic acid (9), uracil (10), thymine (11), uridine (12), thymidine (13), 2’-deoxyuridine (14), and 2’-deoxythymidine (15), resp.tively. Compounds 1– 4 were new purine alkaloids, Compounds 5– 15 were obtained from the sponge H. cymaeformis for the first time. Moreover, twenty-two compounds were isolated from the ethanol extract of Topsentia sp., and twenty of their structures were identified as Topsentiasterol (F-J) (16-20) (22E)-24-Isopropyl-22-dehydrocholesterol (21), cholesterol (22), Hydroxy-(4-hydroxyphenyl)-acetic acid ethyl ester (23), diethyl 2,2’-(4,4’-oxybis(4,1-phenylene)) bis(2-hydroxyacetate) (24),4-Hydroxybenzoic acid (25), 4-Methylbenzoic acid (26), 2-Methylbenzoic acid (27), 1H-indole-3-carboxylic acid (28), 1-(O-5,9,13-trimethyltetradecanoyl)-glycerol (29), Octadecanoic acid (30), 1-O-cis-9-octadecenylglycerol (31), batyl alcohol (32), 7(Z),10(Z)-Hexadecadienoic acid (33), stearic acid (34),β-D-Fucoside-O-ethylene glycol (35)。Compounds 16– 20 and 24 were new compounds, compounds 23, 29, 35 were new natural products.The cytotoxic activities was tested by MTT assay, Compounds 7 showed significant inhibitory activities towards chronic myelogenous leukemia (K562) and human hepatoma (SMMC-7721) cell lines. Compounds 16 showed significant inhibitory activities towards chronic myelogenous leukemia (K562) and human gastric carcinoma (SGC-7901) cell lines. Compounds 17 showed significant inhibitory activities towards chronic myelogenous leukemia (K562) cell lines. The antimicrobial activities against Staphylococcus aureus, and Methicillin-resitant Staphylococcus aureus (MRSA), were measured using paper disco diffusion method. Consequently, only compound 30 showed weak inhibitory activity against both S. aureus and MRSA. The antimicrobial activities against Phytophthora capsiciPythium aphanidermatum, Pythium vexans,and Fusarium oxysporum f.sp. cubense were also tested, unfurturaly, no activity was found
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