| Plant endophytic fungi live in the tissues and organs of plant for their entire life or part of their life and don't cause obvious symptoms of plant disease.Plant endophytic fungi can not only produce metabolites with the same or similar activity as the host plant,but also produce active compounds with novel structure,which are the main source of new natural compounds and new pollution-free pesticides.Sophora tonkinensis,the dried root and rhizome of Sophora tonkinensis Gagnep.,whose main chemical compositions are alkaloids,flavonoids and polysaccharides,has lots of medicinal functions,such as antibacterial activity,anti-inflammatory activity,antineoplastic activity and so on.At home and abroad,there are few reports on the metabolites of endophytic fungi from Sophora tonkinensis.The main pathogens that cause diseases of Panax notoginseng during cultivation are Colletotriehum gloeosporioides,Fusarium solani and Alternaria panax Whetz.,which seriously damage the quality of Panax notoginseng.In early study,part of endophytic fungi in Sophora tonkinensis Gagnep.had inhibitory effect on three types of pathogens about Panax notoginseng.Therefore,in this paper,three kinds of pathogensabout Panax notoginseng were used as the target bacteria to test the antibacterial activity of endophytic fungal and their metobolites,firstly.Then,part of endophytic fungal were preliminary analyzed by morphological identification.Finally,the antibacterial secondary metabolites of the strongest antibacterial strain TRXY-46 were researched.The main results were as flollws:(1)23 active strains of endophytic fungi from Sophora tonkinensis Gagnep.were selected for the activity screening against three kinds of pathogens about Panax notoginseng.A total of 5 strains had an inhibition rate of more than 50 %,which were potential antibacterial active strains and deserved further study.(2)The metabolites of 5 potential active strains were selected for testing the antibacterial effect on the mycelium growth of three kinds of pathogens about Panax notoginseng.At the concentration of 2 mg/m L,the metabolites of 2strains had the inhibition rate of more than 90 %,which were TRXY-46 and TRPH-87.Besides,the inhibition rate of TRXY-46 was 100 %,which was worthy of in-depth study.(3)According to the morphological identification of endophytic fungi,it was preliminarily concluded that TRXY-46 strain and TRPH-87 strain were both Rhexocercosporidium sp..(4)After a large amount of fermentation of chosen strains TRXY-46,a total of 15 monomer compounds were isolated from their solid fermentation product.According to the physical and chemical properties,the spectral characteristics and the relevant literatures,the structure of 15 compounds hadbeen identified finally.There were not new structural compounds found from 15 compounds,but all of 15 compounds were isolated from the endophytic fungus of Rhexocercosporidium for the first time.15 compounds were listed as follow:isomyristic acid(1),herbimin A(2),herbimin B(3),herbimin F(4),2'-O-demethylherbicidine F(5),cyclo-(L-Tyr-L-Pro)(6),genistein(7),daidzein(8),6,4'-dihydroxy-7-methoxyisoflavone(9),4-hydroxyphenylacetic acid(10),4-methoxyphenylacetic acid(11),Carotenoids(12),succinic acid(13),2-hydroxybenzoic acid(14),dimethylisopyrazine(15).(5)15 monomer compounds isolated from TRXY-46 were tested in vitro for the inhibition of three kinds of pathogens about Panax notoginseng.A total of 6 compounds showed a certain antibacterial activity.They were Compound 2,Compound 3,Compound 4,Compound 5,Compound 10 and Compound 11.The MIC value of antimicrobial activity was between 512 and 32 ?g/m L.The highest antibacterial activity against Fusarium solani and Alternaria panax Whetz.was 4-hydroxyphenylacetic acid(10),whose MIC values were 64 and 32?g/m L.The highest antibacterial activity against the Colletotriehum gloeosporioides was 4-methoxyphenylacetic acid(11),whose MIC value was32 ?g/m L.Compared with the inhibitory effect of the positive control carbendazim,these compounds didn't have strong antibacterial activity,and didn't have the value of development and utilization.Besides,other compounds didn't show antibacterial activity. |
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