Antibacterial Activity Secondary Metabolite Research From Diaporthe Sp. AHNC6

Pesticides occupy an important position in agricultural production and are an important means of chemical control of agricultural diseases and insect pests.In recent years,with the increase in the use of pesticides,many problems have arisen.The long-term and large-scale use of pesticides have gradually increased the resistance of target organisms,and have caused serious damage to non-target organisms.Residual pesticides on the ground will enter the river with rain to pollute the environment,thereby endangering human health.Therefore,the development of new pesticides with low toxicity,low residue and high efficiency is an important task.Natural products have various advantages such as a variety of structures and a wide range of biological activities,and are an important basis for the development of new pesticides.Among them,endophytic fungi are widely present in nature,and because of their diversity of hosts and growth environments,they can produce natural products with diverse types,novel structures and unique activities,are important sources of pesticide lead compounds.Diaporthe sp.is a common pathogenic fungus with a wide range of host plants.The secondary metabolites of Diaporthe sp.are rich in ketones,alkaloids and terpenes.In this paper,an endophytic fungus,AHNC6,was isolated from the branches and leaves of American pecan.This endophytic fungus was subjected to large-scale fermentation,crude extracts were separated by column chromatography,and the structure of the compounds was identified by spectroscopy methods such as nuclear magnetic resonance,mass spectrometry,and ECD.Finally,these compounds were subjected to antibacterial activity In the measurement,we hope to find compounds with novel structure and excellent activity.The specific experiments are as follows:（1）By isolating and purifying endophytic fungi from plants collected in Guizhou,a total of 40 endophytic fungi were obtained,including seven common bacteria,were obtained:Pseudomonas syringae pv.Lachrymans,Ralstonia solanacearum,Bacillus subtilis,anthomonas oryzae pv.Oryzicola,Xanthomonas oryzae pv.Oryzae,Lavibacter michiganense and Erwinia were used as test strains.The crude extract of the fungi was tested.Combined with the nuclear magnetic resonance and mass spectrometry analysis of the crude extract,the strain AHNC6 was finally selected as the target strain.The morphology and molecular biology were used to determine that the endophytic fungus was Diaporthe sp.This endophytic fungus was subjected to large-scale fermentation,extraction with ethyl acetate,and the crude extract was separated and purified by methods such as column chromatography,HPLC,X-Ray,and other popular science methods to identify the structure,a total of 25 compounds were identified,2 of which were new compounds alternariol methyl ether-12-O-α-D-arabinoside and（R）-5-（1-hydroxybutyl）-3-methoxy-4methyl-2H-pyran-2-one.（2）The inhibition experiment of plant pathogenic fungi was carried out by mycelia growth rate method,Compound 2 had a good inhibitory activity on Sclerotinia sclerotiorum and Fusarium graminearum at 50 μg/mL,and the mycelium inhibition rates were 55.1%and 45.4%,respectively.It has a poor inhibitory effect on Botrytis cinerea,Fusarium moniliforme and Rhizoctonia solani,with inhibition rates of 38.7%,34.5%and 16.7%,respectively.Compound 2 has no inhibitory effect on Phytophthora capsici.In the bacterial inhibitory activity test,Compound 1 has a certain inhibitory effect on xoo and xoc,and its MIC value is 16 μg/mL.Compound 2 has effects on xoc,xoo and B.subtilis.The inhibitory effect is obvious,and the MIC value measured by MTT method is 16,8 and 32μg/mL.The inhibitory effect of Compound 3 on B.subtilis is obvious,and its MIC value reaches 16 μg/mL At a concentration of 100μg/mL,1 and 2 inhibited gibberella spores of wheat at 53.2%and 65.1%.In a live-protection test,the protective effect of Compound 1 on Botrytis cinerea disease reached 35.9%,which was equivalent to the positive control boscalid.In addition selecting the intestine and barnyard grass as the test objects,the herbicidal activity test was carried out on the compound,and the results showed that the inhibitory rate of new compound 4 on yarrow intestine reached 18.7%at 12.5μg/mL,and the resistance to yarrow washes at 125 μg/mL.The inhibitory rate was 20.3%,poor inhibitory activity and no growth regulating activity.