A New Natural Herbicide Based On Secondary Metabolites Of Endophytic Fungi From Polygonatum

In the process of crop growth,the control effect of weeds is always the key to to increasing its yield.Through the screening of strains by the research team in the early stage,a Polygonatum endophytic fungus Phomopsis sp.By254 is finally used as the experimental material to explore its secondary metabolites under fermentation conditions and its potential for use as natural herbicides.At the same time,some of the isolated crude extract and some monomer compounds are tested for antioxidant activity.On the bases of the separation,purification and activity screening of the ethyl acetate extract phase of the ethanol extract,the following conclusions are drawn:（1）A total of 5 compounds are identified.The structures of five compounds are identified by mass spectrometry and nuclear magnetic resonance(¹H-NMR,¹³C-NMR)spectra and literature comparison.They belong to cytochalasin H,tetradec-7-enoic acid,teretonins A,phenolic compound（（+）-Scytalone）,and alkaloid compound（trichodermamide A）.Teretonins A and tetradec-7-enoic acid are isolated from the fermentation product of Phomopsis sp.By254 for the first time.（2）In order to explore its biological activity and tap its development potential as a natural herbicide,ryegrass,wheat,radish,purple leaf lettuce,and Chinese cabbage are selected as allelopathy experiment objects,which can reflect the effects of the ethyl acetate phase extracts were numbered A1,A2,A4 components and the compound teretonins A on seed germination and plant growth.Its results show that compared with the negative control group,A1,A2,and A4 all have inhibitory effects on ryegrass seed germination,and the A4 component inhibited ryegrass seed germination by 90%,which is higher than 83.7%of the positive control.Both A1 and A4 can promote the germination of radish seeds.The treated seeds with compound 1cannot germinate normally;however,after transplanting the seedlings into pots,the treated radish seeds begin to germinate after six days,while the rest do not yet germinate.Therefore,it is speculated that the A4 component has become the active ingredient of the new natural product pesticide.In the following experiment,the activity tracing method will be used to concentrate on the separation and purification.The antioxidant activity test results of the crude ethyl acetate phase and monomer compounds show that the crude product has a strong free radical scavenging effect,and the components numbered A1 and A2 have the strongest antioxidant capacity.Compared with the positive control ascorbic acid,the free radical scavenging rate only differs by 3%.In conclusion,the study on the secondary metabolites of the endophytic fungus Phomopsis sp.By254 and the activity test results of its chemical components reveal its potential as a natural herbicide.At the same time,the study also expands the research direction of natural products of endophytic fungi,and provides a valuable reference for future research.