| Algae, one of the important marine organism, are rich of secondary metabolites owning novel structure and unique bioactive because of their special living environment. In order to search for new bioactive compounds from algae distributed in Chinese sea, three red algae were investigated. Also the Rhodomela confervoides which is widely distributed along coast of Qingdao, Shandong Province, was screened for its anti-diabetes activity in vivo.26 compounds were isolated from EtOAc-soluble portion of red alga Gymnogongrus flabelliformis by chromatography including normal phase silica gel, Sephadex LH-20 gel and HPLC, as well as recrystallization. Structures were elucidated by spectroscopic methods including IR, MS and NMR. They are (3R,6R,7E)-(+)-3-O-phenylacetyl-4,7-megastigmadiene-9-one(1),(3R,7E)-(?)-3-O- phenylacetyl-5,7-megastigmadiene-9-one(2),(3S,6R,7E)-(+)-3-hydroxyl-4,7-mega- stigmadien-9-one(3),(3S,5R,6S,7E)-(-)-3-hydroxy-5,6-epoxy-7-megastigmene-9- one ( 4 ), (3S,5S,6R,7E)-(+)-3-hydroxy-5,6-epoxy-7-megastigmene-9-one ( 5 ),Dehydrovomifoliol(6),(3R)-(?)-4-[(2R,4S)-4-acetoxy-2-hydroxy-2,6,6-trimethyl- cyclohexylidene]-3-buten-2-one ( 7 ), 2,3,3′-tribromo-4,4′,5,5′-tetrahydroxy-1′- ethyloxymethyldiphenyl methane (8),2,2′,3,3′-tetrabromo-4,4′,5,5′-tetrahydroxy- diphenyl methane(9),3-bromo-4,5-dihydroxybenzaldehyde(10),2,3-dibromo-4,5- dihydroxybenzylmethyl ether(11),2,3-dibromo-4,5-dihydroxybenzyl alcohol(12),N, N-Dimethyltyramine(13),ethyl 4-hydroxybenzoate(14),ethyl 4-hydroxyphen- methylethe(r15),4-hydroxyphenethyl acetate(16),methyl 4-hydroxybenzeneacetate(17),4-hydroxybenzaldehyde(18),stigmast-4-en-3-one(19),cholest-4-en-3-one (20), cholesterol (21),uracil (22),uridine (23),adenosine (24), succinic acid (25),5-Hydroxy-4-methyl-5-pentyl-2,5-dihydro-furan-2-on(26). All of these compounds were obtained from this species for the first time including two new compounds 1, 2 and new natural product 3.Cytotoxicity of compounds was screened by MTT method on human cancer cell lines including HCT-8, Bel-7402, BGC-823, A549 and A2780. Compounds 8, 9, 10 and 12 were active against all the cancer cell lines screened. Compounds 11 was active against A549, Bel7402 and HCT-8. Compounds 8,9,11,13,17,23,24,25 showed significantly inhibition against secretion of murine peritoneal emacrophage TNF-αduring anti-inflammation assay.From the red alga Corallina pilulifera 14 compounds were isolated and identified, including a new natural product 2α-hydroxycholest-4-en-3-one(31)and other known compounds 2α-ethoxycarbonyl-2β-hydroxy-A-nor-cholest-5-ene-4-one ( 27 ),cholest-4-en-3-one ( 28 ), cholesterol ( 29 ), 3β-hydroxy-24(28)-methylene- 5-choleste-7-one(30),6α-hydroxy-cholest-4-en-3-one(32),3β-hydroxycholest-5- en-7-one(33),(E)-phytol epoxide(34),Phytenal(35),3,7,11,15-tetramethyl- hexadec-2-en-1-oll(Phytol)(36),Loloilide(37),(3S,5R,6S,7E)- (-)-3-hydroxy- 5,6-epoxy-7-megastigmene-9-one(38),Dehydrovomifoliol(39),4-hydroxybenzal- dehyde(40). These compounds were all obtained from this species for the first time. Cytotoxicity of the compounds was screened by using the standard MTT method. Compounds 27 and 32 were active against all the cancer cell lines screened with compounds 27 showed middle inhibition against BGC823, HCT-8, and A2780. Compounds 28, 31 and 33 showed selective activity against cell lines Bel 7402, HCT-8 and A2780.Chemical constituents investigation into EtOAc-soluble portion of red alga Polysiphonia sp. led to the isolation of 6 compounds and 5 of them were characterized as cholesterol(41),3,7,11,15-tetramethyl-hexadec-2-en-1-ol(42),indolyl-3- carbaldehyde(43),4-hydroxybenzaldehyde(44),4-hydroxybenzoic acid (45).STZ-DM on rat was employed to investigate the anti-diabetes activity of the ethanolic extraction of a red alga Rhodomela confervoides. The results proved that ethanolic extraction of R. confervoides could significantly decrease the level of blood glucose and improve metabolic disturbance partly, as well as increase the surviving rate of diabetes rat.
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