Chemical Constituents Of Ascidia Longistriata. And Alternanthera Philoxeroides. And Their Antifoulants Activities

Marine fouling organisms are harmful for aquaculture. The physical cleaning method needs more manpower, and many antifouling chemical substances containing heavy metals have led to environmental pollution of many seas. Therefore, this study focuses on the finding of natural antifouling resources, and the screening of antifouling natural compounds with safety, non-toxic to other marine lives. Based on chemical defence theory of fouling organisms, this thesis selected Ascidia longistriata, a major species among fouling ascidians in China Seas, and Alternanthera philoxeroides with antibacterial and molluscicidal effect as the research resources. Natural products and antifouling investigations were carried out on these two aquatic organisms, including isolation/identification of various chemical constituents, and their bioassay of antifouling or some other pharmaceutical activities.By classic column chromatography including chromatography on silica gel, reverse-phased silica gel, Sepadex LH-20, MCI gel and macroporus resin, and semi-preparative HPLC,16compounds were obtained, and15of them have been identified on the basis of spectroscopic analyses (including El MS, ESI MS,’H-NMR,13C-NMR,’H-’H COSY, HSQC and HMBC), and comparison with the literatures. From Ascidia longistriata,8compounds were identified as (3-carboline (1),1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (2), y-carboline (3), cholestane-3β,5α.6β-triol (4), cholest-5-ene-3β-ol (5), acanthacerebroside B (6) and two glycerol derivatives with long fatty chains. This is the first report of carboline alkaloids1-3and cerebroside6from the geus Ascidia.. eight compounds were isolated from the plant A Iternanthera philoxeroides, of which7compounds have been identified as syringin (9), coniferin (10), Benzyl6-O-α-L-fucopyranosyl-D-galactoside (11), oleanolic acid3-0-[(3-D-glucuronopyranosyl]-28-O-β-D-glucopyranoside (12), oleanolic acid3-0-[β-D-(6-methyl)-glucuronopyranosyl]-28-O-β-D-glucopyranoside (13),3-O-[β-D-glucuronopyranosyl]-30-dien-12,20(29)-nor-oleanic acid-28-O-p-D-glucopyranoside (1.4), oleanolic acid3-O-β-D-glucuronopyranoside (15). Four known compounds9—11and13were isolated from this plant for the first time. The major constituents of ascidian A. longistriata were inactive in bioassay against several microorganisms of fouling or pathogenic origins. While p-carboline (1) showed weak cytotoxicity against K562cell line with IC50of11.7ng/mL. Saponins12,14, and15from the plant Alternanthera philoxeroides showed moderate activity against3fouling microorganisms, and Saponins14showed moderate molluscicidal effect agaist the wild barnacles at the dose close to that of positive control CUSO4. Some other saponins mixtures were also observed toxic to barnacles in the same test.