Isolation, Identification Of Endophytic Fungi From Six Kinds Of Chinese Herbal Medicine And Their Bioactivities

Endophytic fungi have attracted more attention from researchers, due to its diversity and potential function of synthesizing various bioactive compounds. In this study, 6 kinds of Chinese herbal medicine(Humata tyermanni Moore,Tetrastigma hemsleyanum Diels et Gilg, Zingiber kawagoii Hayata, Alisma plantago-aquatica Linn., Common Vladimiria Root, Smilax china L.) were selected as research objects. The endophytic fungi were isolated, purified by the tissue separation method, streak plate method, and identified by fungal morphological identification method including the colony morphology, microscopic morphology and physiological and biochemical characteristics. Fermented liquids and mycelia of 40 endophytic fungi were extracted with ethyl acetate and ethanol, respectively.And Antibacterial activity, antioxidant activity and α-glucosidase inhibition activity of the extracts were investigated. On this basis, the antimicrobial mechanism of B06 e against Escherichia coli and Staphylococcus aureus was studied according to the changes of the bacterial cell membrane permeability and bacteria cell membrane integrity, as well as, gel retardation assay of the binding between B06 e and bacterial DNA. The results are shown as follows:(1) 137 endophytic fungi were isolated from 6 kinds of Chinese herbal medicine, and identified to Aspergillus, Rhizopus, Penicillium, Fusarium,Cephalosporium, Gliocladium, respectively.(2) Antibacterial activity assay showed that the B06 e have stronger inhibitory activity among the samples against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Streptococcus pneumoniae, with the inhibition zones beyond 17 mm and minimum inhibitory concentration(MIC) was less than 50μg/m L. The results of antioxidant activity showed that the ethyl acetate extract of Z05 secondary metabolites have the strongest total reducing power(1.354±0.051), with half maximal effective concentration(EC50) of 0.5664 mg/m L.The crude extracts from fermented liquid of S24 showed a great hydroxyl radicals scavenging activity with IC50(0.2405 mg/m L) lower than Vc(0.2648 mg/m L).DPPH radical scavenging assay indicated that ethanol extracts from mycelia of S05 have a strong DPPH radical scavenging activity with IC50(0.0554mg/ m L)lower than that of Vc(0.0845mg/m L). However, all samples owe an unsatisfactory superoxide radical scavenging potential. The results of α-glucosidase inhibition activity assay was that 37 sample have the potential to inhibit α-glucosidase withthe inhibition rate higher than 70%. Especially, ethanol extracts from mycelia of Z003 have a high inhibition rate(96.11%±0.57 %) and low IC50(0.1928 mg/m L).(3) Study on the antibacterial mechanism of B06 e against Escherichia coli and Staphylococcus aureus manifested that B06 e make a change of bacterial cell membrane permeability, inducing leakage of nucleic acid and protein, and B06 e can enter into bacterial cells and interaction with nucleic acid, thereby, inhibit the growth of bacteria.