The Studies On Isolation And Identification Of Chemical Constituents And Antifungal Activities Of Xanthium Sibiricum

In preliminary studies, cangersu has been confirmed to have antifungal activities, which is extracted from Xanthium sibiricum. It has a strong antifungal effective on Rhizoctonia solani, Fusarium oxysporium Schl., Botrytis cinerea Pers., etc. On this study, purification and identification of acetone extraction of Xanthium sibiricum were studied, eleven compounds were obtained and identified, respectively. After that, the compounds were tested for their antifungal activity by mycelium growth rate, and we had screened out the compounds with the highest antifungal activity among those isolated compounds. Moreover, the preliminary structure-activity relationship research was made, it provided conditions for the following biomimetic synthesis. The results were as following:1. The acrial part of Xanthium sibiricum was as raw material and acetone was the extractive solvent, eleven compounds were isolated by repeated silica gel column chromatography (CC), Sephadex LH-20CC, and MCI CC, includes eight sesquiterpenes, one triterpene and two steroids. Their structures were identified as xanthnon(1), xanthatin(2),3-cycloheptene-1-acetic acid(3), inusoniolide(4), xanthinosin(5),5-azuleneacetic acid(6),2-deacetyl-13-dihydroxy xanthinin(7),2-hydroxy xanthinosin(8),β-sitosterol (9),6β-hydroxystigmast-4-en-3-one(10), taraxerol(11), respectively, on the basis of their spectroscopic data. Compound1xanthnon is a new compound, compounds3-cycloheptene-1-acetic acid,5-azuleneacetic acid,2-deacetyl-13-dihydroxy xanthinin and2-hydroxy xanthinosin are isolateded from this plant for the first time, and compound inusoniolide is obtained from the genus of Xanthium for the first time.2. Rhizoctonia solani and Botrytis cinerea Pers., etc as the test fungis, antifungal activity of some of the isolated compounds which had a large quantity were tested, as a result, compound2xanthatin displayed a strong antifungal effective on Rhizoctonia solani. and Botrytis cinerea Pers., their EC50were11.18ug/ml and7.31ug/ml, respectively. But for Fusarium oxysporium Schl. and Alternaric solani (Ellis et Martin) Jones et Grout, the activities displayed relatively weak. Among those compounds, xanthatin accounts for0.1%of the acrial part of Xanthium sibiricum, so it has the potential to be exploited as a novel fungicide.3. The preliminary structure-activity relationship research showed α, β-unsaturated γ-lactone was an important antibacterial functional group, the side chain for hydrophilic or oleophilic properties may affect the compounds through the permeability of fungal cell wall or cell membrane and their activity may be influented as well.