Studies On Chemical Constituents And Bioactivities Of Endophytic Xylaria Cf.XC-16

Natural products are a huge repository of drug lead compounds.Endophytic fungi are potential sources of natural products,and their secondary metabolites are widely used agriculture production.But the rise in resistance to disease becomes a major threat to agriculture.Thus there is an uegent need to discover new bioactive compounds with specific active units.In this paper,the bioactive metabolites of Xylaria cf.XC-16 were studied using OSMAC,and the results are showed as follows:Twenty fermentation conditions were screened for Xylaria cf.XC-16,including 11 liquid cultures and 9 solid cultures.By TLC and HPLC analysis,two optimal culture conditions were determined for mass fermentation.Fifteen compounds were isolated via various chromatographic methods（Sephadex LH-20,LC-MS,HPLC,silica and RP-silica column）and elucidated with advanced spectroscopic analysis means（1D,2D NMR,IR,UV,HRMS）,which including two new diterpenes:Hydroxyldecandrin G（1）,Hydroxyldecandrin H（2）,and three cytochalasins:Epoxyrosellichalasin（3）,Epoxycytochalasin Z8（4）and Epoxycytochalasin Z17（5）.The absolute configuration of compound 1 is confirmed by biogenetics,ECD,Mo₂（OAc）₄ chemical reactions and chiral analysis.The allelochemical activity results showed that compounds 1,2,3,4,7,8,9,11,12,13 and 15 showed moderate inhibitory activity on root growth of monocotyledonous plants(IC₅₀ values ranged from 16.51-77.27μM).Among them,compound 8 showed Extremely inhibitory activity against wheat root growth with an IC₅₀ value of 22.84μM,which was comparable to that of the herbicide glyphosate(IC₅₀=22.50μM).Compounds 6 and 9 are more inhibitory active than herbicide glyphosate with IC₅₀ values of 16.51μM and 19.98μM.Moreover,compounds 6 and 9 showed moderate inhibitory activity on dicotyledon radish seed root growth with IC₅₀ values of 93.97μM and 37.50μM,respectively,which were comparable to herbicide glyphosate(The IC₅₀ value is 81.28μM).Compound 8 showed extremely strong inhibitory activity against radish seed root growth with an IC₅₀ value of 1.64μM.The activity results of the anti-phytopathogenic showed that the inhibitory rates of compounds 3,5 and 6 against Botrytis cinerea were 60.39%,52.08% and 55.15% at 100μM,respectively,which were higher than other compounds.