Study On Antimicrobial Secondary Metabolites From Two Symbiotic Fungi

Pesticide is an important means to control agricultural pest.Due to the unreasonable use of pesticides,problems such as the increasing resistance of target organisms,the destruction of ecosystem balance and environmental pollution are increasingly prominent.Therefore,it is a very important work to develop new green pesticides with high activity,low toxicity and low residue.Natural products play an important role in the exploration and development of new pesticides because of their unique and novel structure and good biological activity.Microorganisms are widely distributed in nature,and in the process of interacting with the environment,they can produce some metabolites with novel chemical structures and unique biological activities,and these products are also important sources of pesticide lead compounds.In this paper,we studied the structure and activity of secondary metabolites from two symbiotic fungi Fusarium sp.JDJR1 and Talaromyces sp.ZL10-2,which were derived from plants and animals,respectively.Among them,the plant symbiotic fungus Fusarium sp.JDJR1 was fermented by solid fermentation method,and the insect symbiotic fungus Talaromyces sp.ZL10-2 was fermented by liquid fermentation method.The secondary metabolites were extracted with organic solvents,and 23 monomer compounds were isolated and purified by various column chromatography methods.The structures of these monomer compounds were analyzed by NMR,MS and X-Ray spectroscopic techniques,and the biological activities of these monomer compounds,such as antimicrobial and herbicidal activities,were tested.The details as follows:Nineteen compounds were isolated from the plant symbiotic fungus JDJR1.The main structural types included sterols（1）,benzene derivatives（2、3、5-9、17、18）,alkaloids（4,14）,pyrone（10-12,16）,polyketone（13）,sesquiterpenoids（15）and fatty acid（19）.The results of bioactivity tests showed that compound 14（Equisetin）had a broad spectrum of anti-plant pathogens.The EC₅₀ values against Botrytis cinerea,Fusarium graminearum,Sclerotinia sclerotiorum and Rhizoctonia solani were 10.7,12.6,17.1,21.0μg/m L,respectively.The MIC values against Xanthomonas oryzae pv.oryzicola,Xanthomonas oryzae pv.oryzae and Pseudomonas solanacearum were 4,16,and 16μg/m L,respectively,which were better than positive control streptomycin sulfate.In vivo protection experiments,the protective effect of compound 14 against S.sclerotiorum on rape leaves and against B.cinerea on tomato fruits at 200μg/m L reached 35.9 and 72.9%,respectively.In the herbicidal activity test,compound 14 had a good inhibitory effect on the growth of weed roots.At the concentration of 100μg/m L,the inhibition rates of Echinochloa crusgalli root and Eclipta prostrata root were 98.8 and 94.4%,respectively.Six compounds were isolated from the insect symbiotic fungus ZL10-2.The main structural types included benzene derivatives（20,22,23）and nonadride（21）.The results of bioactivity tests showed that these compounds had weak inhibitory activity against plant pathogenic fungi and bacteria.At a concentration of 50μg/m L,the inhibitory rates of compound 23 against F.graminearum and S.sclerotiorum reached 54.2 and 42.0%,respectively.In the herbicidal activity test,the inhibitory rate of compound 21 on the roots and shoots of E.crusgalli at a concentration of 100μg/m L reached 62.3 and 30.5%,in addition the inhibition rates on the roots and shoots of E.prostrata at the same concentration were 89.1 and 33.8%.,respectively.