Study On The Secondary Metabolites From Two Marine Actinomycetes And Their Activities Against Fruit Pathogens

Banana blight caused by Fusarium oxysporum f.sp.Cubense(FOC)and mango anthracnose caused by Colletotrichum gloeosporioides are two serious agricultural diseases in hot regions of China,which seriously affect the economy of our country.Of the numerous methods for preventing banana blight,the chemical method is the most direct,effective,and convenient.However,it has not been screened so far to obtain chemical agents that are very effective to control agricultural diseases.Natural products have the characteristics of low toxicity and high selectivity,and are the main source of drug leading structure.Microorganisms are an important source of natural antibiotics,and marine actinomycetes,as a group of it,have great potential in the development of antibiotics and are considered to have unprecedented potential in producing clinically useful antibiotics.In this study,6 strains have anti-activity against F.cubense and 1 strain against C.gloeosporioides were obtained from 120 marine actinomycetes by the experiments of flat plate confrontation.Combining with chemical diversity and biological activity,HNWSW-3 and HNWSW-49 were selected as the research objects,and their activities against agricultural pathogens were studied.The secondary metabolites were separated by decompression/pressurization silica gel column chromatography,Sephadex LH-20 column chromatography and preparative HPLC.The structures of the compounds were identified by spectroscopic data and physicochemical constants.Four compounds were isolated and identified from the fermentation products of the strain HNWSW-3,which were 4'-N-demethyl-ST(1),staurosporine(2),RK-1409(3),Tjipana-zole G1(4),and 7 compounds were isolated and identified from the strain HNWSW-49,which were ascyclo-(Phe-Ala)(5),cyclo-(Leu-Gly)(6),cyclo-(Phe-Val)(7),cyclo-4-OH-Pro-Phe(8),N-(2-phenylethyl)acetamide(9),?-Adenosine(10),and 2-Piperidone(11).The antibacterial activity test was carried out by gradient dilution method,and the results showed that compounds 1?3 have good activity against C.gloeosporioides(MIC of 3.13 ?g/mL,6.25?g/mL and 25.00 ?g/mL,respectively),at the same time,compound 1 had the activity against F.cubense(MIC was 12.50 ?g/mL).The action mechanism of compound 1 against FOC and C.gloeosporioides was studied by cell biological method.It was found that the mechanism of compound 1 on FOC was to inhibit the germination of spores and the synthesis of squalene to block the formation of cell membrane,while on C.gloeosporioides was to destroy the structure of cell membrane.