Activity Of Secondary Metabolites Of Endophytic Fungi In Aloe Vera

The use of chemical pesticides reduces the damage of diseases and insect pests to crops and greatly improves agricultural output.However,due to the excessive use of chemical pesticides,the problems of pesticide residues,groundwater,and soil pollution are becoming more and more serious.Therefore,the research and development of environmentally friendly green pesticides is of great significance to ecological environmental protection and promoting the construction of green pesticide technology to develop agriculture.The purpose of this paper is to add seawater to the process of terrestrial plant-derived fungi culture and carry out high-salt stress,to obtain natural compounds with novel structure and excellent biological activity.The tracking technology separates and purifies its secondary metabolites,providing a theoretical and experimental basis for the design and development of new green pesticides.Four strains of fungi were isolated from abalone,aloe stalks,chondroid algae,and Ulva by tissue separation method.Using strain type,medium type,and culture time as variable factors,four different mediums were used to optimize the cultivation of 2W and4 W.The number of secondary metabolites and bacteriostatic activity was compared.By comparing the yield and antibacterial activity of secondary metabolites,it was found that after culturing in the RICE medium for 4 weeks,each strain could reach the maximum amount of secondary metabolites.O-02,U-04,A-01,C-03;secondary metabolites of RICE medium had broad-spectrum bacteriostasis to 6 indicator strains.The dominant strain with stronger productivity and antibacterial activity was finally determined to be the strain O-02 derived from aloe vera straw,in RICE medium(seawater stress),and the optimal culture time was 4 W.After molecular biology identification,O-02 strain is Aspergillus ochraceu.The strain O-02 was subjected to 30 L large-scale static fermentation for 4 W using the RICE medium to obtain about 400 g of ethyl acetate phase extract.It was subjected to VLC gradient elution to obtain 15 fractions of Fr.1-Fr.15.The activity screening test of animal and plant pathogenic bacteria,aquatic animals,aquatic plants,and plant pests was carried out with 6 indicator strains,Duckweed,Brine Artemia,and Aphididae as target organisms.The results found that the components Fr.4,Fr.8～Fr.13,and other biological activities are better.The above components were further separated and purified by various column chromatography methods such as preparative plate,silica gel column,and gel column to obtain 32 monomer substances.The monomers with larger mass were selected to screen for their anti-artemia and antibacterial activities.The results of the antibacterial activity screening showed that the compound AO-17 had a certain broad-spectrum antibacterial activity,and was effective against 5 other substances except for Bacillus thuringiensis.The indicator bacteria of the two strains have certain inhibitory activity,and the inhibitory effect on Bacillus subtilis and Pseudomonas aeruginosa is the strongest,and the diameter of the inhibition zone is22 mm and 20 mm respectively(the positive control is 30 mm and 32 mm,respectively);secondly,the compound AO-02,AO-09,AO-10,and AO-24 have high inhibitory activity against single indicator bacteria such as Staphylococcus aureus,Bacillus subtilis,and Xanthomonas campestris PV.Campestris(Pammel)Dowson,respectively,indicating that their antibacterial activity has a certain selectivity The screening results of anti-artemia activity found that each monomer showed a certain inhibitory activity against Artemia at high concentrations,among which compounds AO-18,AO-23,AO-24,AO-26,AO-27,AO-28 has the strongest activity,and the half-lethal concentrations are 0.134 mg/m L,0.111 mg/m L,0.108 mg/m L,0.112 mg/m L,0.121 mg/m L,0.111 mg/m L,respectively.It can be speculated that it has a strong Artemia lethal activity.According to the results of the above monomer activity screening test,it was found that AO-24 has strong antiartemia activity and strong selective bacteriostatic activity,which can be used as the focus of the follow-up in-depth study of the structure-activity relationship.