Studies On Secondary Metabolites And Antibacterial And Antifungal Activity Of Two Endophytic Fungi In The Euphorbia Plants

Endophytic fungi have become a treasure trove of novel active compounds due to their interactions and co-evolution with host plants and other microorganisms in the microenvironment.In the past 20 years,a large number of compounds with novel structures and extensive biological activities have been discovered from plant endophytic fungi,especially some compounds with good antibacterial activity.This indicates that endophytic fungi in plants have a good potential to produce novel antibiotic precursors.There are various types of secondary metabolites produced by endophytic fungi of Euphorbia,including polyphenols,flavonoids,enols,glycosides,and glutamate derivatives.These substances have anti pathogen,antibacterial,anti cancer,anti aging,and immunomodulatory effects.In this paper,the goal is to search for antibacterial lead compounds,and screening for antibacterial activity of endophytic fungal metabolites isolated from medicinal plants of the Euphorbia sp.by the research group in the early stage.The endophytic fungus Myrothecium verrucaria LZUC-Dl₄ in the stem of Euphorbia humifusa Willd and the soil symbiotic fungus Alternaria alternata LZUC-S₃ in the root of Euphorbia pekinensis Rupr were selected as the research objects.The active components in the fermentation products of the two fungi were separated by combining activity tracking with modern separation and analysis technology（thin layer chromatography,column chromatography,gel chromatography,high performance liquid chromatography,etc.）,and the isolated compounds were identified by various spectral methods（NMR,ESIMS,ECD,IR,UV,X-ray,etc.）.37compounds were isolated from the strain Myrothecium verrucaria LZUC-Dl₄,including 22 trichothecenes compounds（3 new compounds）,10 benzopyran derivatives（6 new compounds）,3 benzofuran derivatives（1 new compound）,and 2 polyketone compounds（1 new polyketolactone）.25 compounds were isolated from the strain Alternaria alternata LZUC-S₃,including 24 altenuenes compounds and a new sweet myrrhane type sesquiterpene.The inhibitory activity of trichothecenes against the growth of 5 Fusarium species（F.oxysporum,F.solani,F.chlamydosporum,F.trictum,F.equiseti）was tested,and the compounds Dl₄-6 and Dl₄-8 showed excellent antifungal activity,with IC₅₀ values are 14—64μg/m L.The anti methicillin resistant staphylococcus aureus（MRSA）activity of altenuenes compounds was tested.Among them,compounds S₃-1,S₃-2,and S₃-3 showed excellent anti MRSA activity,especially compound S₃-3,which had the best activity with a MIC value of 20μg/m L。In addition,this article reviews the structure,plausible biogenetic pathway,biological activities,chemical synthesis,and biosynthesis of trichothecenes compounds derived from fungi since 2000.This paper not only provides a new research idea for the functional development of Euphorbia medicinal plants and their endophytic fungi,but also provides a material basis and reference template for the discovery of new antibacterial lead compound.