Isolation And Identification Of Antibacterial Substances From Chinese Cabbage Under The Stress Of Rhizopus

The clubroot disease e is a kind of earth-borne disease in the world,which is caused by the infection of the Chinese cabbage and other cruciferous plants by plasmodiophora brassicae.Phytoanticipins are low molecular weight secondary metabolites of plants in plants before they are attacked by microorganism.At present,the research on the prevention and control of root disease is concentrated on the molecular level,and there are few reports on the phytoanticipins in the root of Chinese cabbage under the stress of plasmodiophora brassicae.In this study,the chemical constituents of Chinese cabbage root induced by plasmodiophora brassicae were identified by various chromatographic separation techniques and the modern spectroscopy method,and the activity of the main phytoanticipins was identified according to the antibacterial activity and plant toxicity test.The main findings are as follows:1.12 chemical constituents were isolated from the roots of Chinese cabbage infected by plasmodiophora brassicae,including 5 indoles(indole-3-propionic acid,indole-3-carboxylic acid,indole-3-acetonitrile,indole-3-carboxaldehyde,Arvelexin),3amphetamines(p-hydroxyphe nylpropionic acid,N-(2-Phenylethyl)acetamid,phenylpropionic acid),4 fatty acid methyl esters(eicosapentaenoic acid methyl ester,octatrienoic acid methyl ester,eicosatetraenoic acid methyl ester,methyl octadecadienoate).2.Screening of antibacterial activity of 3 kinds of fungi(Fusarium graminearum,Curvularia lunata(Walker)Boedijn and Monilia albican)and 1 kind of bacteria(Staphylococcus aureus)were found that there was no obvious inhibitory effect of amphetamine compounds on microorganisms.The chemical constituents of fatty acid methyl ester only had weaker inhibitory effect on the Fusarium,and the indole chemical constituents inhibited both fungi and bacteria.Among them,the highest inhibitory rate of indole-carboxylic acid on maize corn leaf fungus 79%,and the highest inhibitory rate of Candida albicans under indole-3-acetonitrile was 66%,so it was concluded that the main phytoanticipins in the root of Chinese cabbage under the stress of indole.3.By analyzing the disease resistant variety ‘222'and 4 susceptible varieties(3-2,CN-1,CN-2,ECD05)The content of indole phytoanticipins in the root of Chinese cabbage found that resistant and susceptible genotypes were different in the content of phytoanticipins after being infected by plasmodiophora brassicae.The content of indole-3-acetonitrile,indole-3-carboxylic acid,indole-3-propionate acid in the late stage of infection(5 weeks and 6 weeks)of the root-infected species was significantly elevated.Arvelexin had high concentrations in the early stage(1 weeks and 2 weeks)of disease-resistant variety ‘222' by root-infection.The concentrations of CN-1 in the 3 week of four susceptible cultivars were significantly elevated.The responses of phytoanticipins to root infection were not detected in the other susceptible varieties.4.In order to further identify the activity of these phytoanticipins,the effects of three kinds of main indole phytoanticipins(indole-3-acetonitrile,indole-3-carboxylic acid,indole-3-propionate acid)on seed germination and seedling biomass of Chinese cabbage were determined.The results showed that the three kinds of indole phytoanticipins could inhibit the germination and seedling growth of Chinese cabbage.It is concluded from this study that indoles are the main phytoanticipins in Chinese cabbage plants,which have inhibitory effects on microbes and also have a certain influence on the growth of plant itself.