The Metabolites And Bioactivity Screening Of Four Kinds Of Marine Macroalgae Along Qingdao Coast

Marine organisms can produce various secondary metabolites. The novelstructures and unique biological activitis make them highly valued. Plant pathogenposes a serious threat for agricultural production; chemical pesticide residue, highdevelopment cost as well as marine bacterial fouling are also to be solved. So seekingfor environment-friendly pesticides and natural antifouling compunds is essential.Sagassum kjellmanianum, Sargassum thunbergii, Desmarestia viridis andAhnfehiopsis flabelliformi are four kinds of common algae along the coast of Qingdao,Shandong Province, China. In this paper, the four kinds of algae were researched ontheir chemical and biological screening, as to get environment-friendly pesticides andnatural antifouling materials.Chemical investigation of the four kinds of algae obtained crude extracts bycombination of column chromatography on silica gel and thin layer chromatography.The crude extracts were tested by HPLC and the antimicrobial activities were studied(5plant pathogen fungal strains and4marine bacteria strains). Sagassumkjellmanianum was found richer in compounds and better in antimicrobial activities.So we choose Sagassum kjellmanianum as our follow-up research object. The mainconclusions are as follows:1. The screening of four kinds of algae: Dry seaweed samples were ground intosmall pieces and extracted with95%ethanol and ultrasonic cleaner. The extracts wereevaporated under reduced pressure to a dark semisolid and dissolved in distilled water.The aqueous suspension was partitioned in ethyl acetate. The ethyl acetate extractswere evaporated to dryness in a rotary evaporator and the semisolid was separated bycolumn chromatography on silica gel. The crude extracts were tested by HPLC andscreened for their antimicrobial activities, and the result showed Sagassumkjellmanianum was richer in compounds than the other three algae; some of theextracts of Sagassum kjellmanianum had antimicrobial activities against the5plant pathogen fungi strains: Fr2showed the strongest activities against SphacralesGibberella zeae and Alternaria solani, reaching inhibition zones of11.4and11.3mm. Ofall the four algae, Sagassum kjellmanianum had the strongest antibacterial activities:Fr4reached an inhibition zone of17.5mm against Staphylococcus aureus, Fr2and Fr4reached inhibition zones of19.5and20.7mm against Bacillus thuringiensis.2. Chemical constituents of Sagassum kjellmanianum and the antimicrobialactivities: The separation was performed by column chromatography on silica gel and17crude extracts were obtained.5compounds were isolated by repeat columnchromatography on silica gel, Sephadex LH-20, pTLC and recrystallization, whichwere obtained as nature products for the first time. The structures of the isolatedcompounds were elucidated by spectroscopic analysis including1H-NMR,13C-NMRand DEPT.3compounds and their structures were identified. All of the17crudeextracts were tested for their antimicrobial activities and the resulting was determinedmainly the same as screening test. However,5compounds didn’t show any antifungalactivity. Compound V showed marked inhibition against Staphylococcus aureusmoderate inhibition against Staphylococcus aureu, reaching an inhibition zone of14.5mm.