Screening and identification of the endophytic fungi antagonistic strain of Cassia tora Linn. and the analysis of antibacterial substances of Penicillium citrinum ZH-11

Abstract:

[Background] Considering the emergence of "super bacteria" due to the abuse of antibiotics, the search for new antibacterial drugs is necessary for effectively conquering the problem of bacterial resistance. Since most antibacterial drugs are found from microorganisms, the research on endophytic fungi in medicinal plants can expand the medicinal resources, so it has a promising future for application. [Objective] To isolate the endomycete from the Cassia tora Linn. collected from Lushan Botanical Garden of Jiujiang, Jiangxi Province; screen out the antagonistic strains; isolate the secondary metabolites of such strains and analyze the physical and chemical properties of their antibacterial substances to prepare for the research of new antibacterial substances. [Methods] The antagonistic strains were screened by the cup-plate method and then identified based on morphological characteristics and molecular biology. Their secondary metabolites were isolated by silica gel, Sephadex LH20 and RP-C18 column chromatography, and the molecular weight and molecular formula of antibacterial substances were analyzed by liquid chromatography-mass spectrometry (GCMS) and EDS spectrometer. [Results] Penicillium citrinum ZH-11, a broad-spectrum antagonistic strain was screened out. As shown by the cup-plate method, it had a good bacteriostatic effect on eight indicator bacteria such as Escherichia coli, Staphylococcus aureus, Bacillus thuringiensis, Xanthomonas oryzae, Bacillus subtilis, Bacillus licheniformis, Candida albicans and Bacillus cereus etc. Active pure compound Y3 was isolated from the secondary metabolite of endomycete Penicillium citrinum ZH-11 with a molecular weight of 410.169 1 and a formula of C₂₄H₂₆O₆. When the concentration of Y3 was 10 µg/mL, the diameter of the inhibition zone against Escherichia coli and Bacillus thuringiensis was 16.23 mm and 17.27 mm, respectively. [Conclusion] This active substance is different from the known antibacterial active substances derived from Penicillium citrinum. The results laid a foundation for further exploration of the active products of Penicillium citrinum, and expanded our recognition of the endophytic fungi in Cassia tora Linn.