Research On Allelopathy And Active Components Of Xanthium Spinosum L.

Xanthium spinosum L.is a 1-year-old herbaceous plant of the genus Xanthium of the family Asteraceae,native to South America.In 1932,the wild naturalized species of Xanthium spinosum L.was found in China.In this thesis,Xanthium spinosum L.in the TuKai desert of YiNing,Xinjiang,was used as the object.Through bioassay methods,explored allelopathic effect of the different growing stages（seedling stage,blooming stage,maturity stage）、different parts（leaves,stems,fruits）and its fruit extracts（petroleum ether,chloroform,n-butanol）.On the basis of this,separation and purification the leaves and stems of Xanthium spinosum L.by biological activity as the guide.A total of 8 compounds with herbicidal activity were isolated.Research indicates:1)The allelopathic effect of the seedling stage was more stronger than other growthing stages.In the seedling growthing stage,the aqueous extract of the whole plant completely inhibited growth of 4 receiver plants at concentration of 5 mg·mL^-1,10 mg·mL^-1;At a concentration of 2.5 mg·mL^-1,the inhibition rates of root lengths of 4 plants were between 52.96%and 65.67%.However,in the early blooming stage,the aqueous extract of the whole plant completely inhibited growth of 4 receiver plants at concentration of 10 mg·mL^-1.In the maturity stage,the aqueous extract of the whole plant showed obvious“low-enhanced and high-inhibited”effects on the four tested plants,and root and shoot length of four plants were inhibited by 39.25%-69.43%and 13.17%-58.02%,respectively.2)The allelopathic effect of the leaf extract(concentration of 0.05 g·mL^-1)was more stronger than other parts of Xanthiumspinosum L,and the allelopathic effect of the ethanol extract was more stronger than aqueousextract.Among the aqueous extracts,leaf extract inhibited the root length of Setaria glauca,Lolium multiflorum,Lactuca sativa,Brassica chinensis by 62.7%,68.4%,26.8%and 34.7%,respectively.The ethanol extract of leaves inhibited root length of Setaria glauca,Lolium multiflorum,Lactuca sativa,Brassica chinensis by 92.5%,89.3%,36.7%,and48.4%,respectively.In addition,the ethanol extracts of roots and fruits showed a certain inhibitory effect.The inhibition rates were 21.2%-46.4%（except for Brassica chinensis）and 48.0%-54.8%（except for Lolium multiflorum）.3)The allelopathic effect of the chloroform extraction(concentration of 1mg·mL^-1)was more stronger than other extraction.and the sensitivity of the four tested plants to the same extraction was different.The extract of chloroform showed significant allelopathic inhibitory effects on the growth of root length and shoot height of three plants of Brassica chinensis,Lactuca sativa and Lolium multiflorum.The order of their strength was Lactuca sativa>Brassica chinensis>Lolium multiflorum.The extract of petroleum ether showed significant allelopathic enhanced effects on the growth of root length and shoot height of three plants of Brassica chinensis,Lactuca sativa and Setaria glauca.The promotion effect is as follows:Brassica chinensis>Lactuca sativa>Setaria glauca.4)The eight compounds isolated from the stems and leaves of Xanthium spinosum L.were:xanthatin（1）,1α,5α-epoxyxanthatin（2）,4-epiisoxanthanol（3）,4-epixanthanol（4）,Loliolide（5）,dehydrovomifoliol（6）,coniferoldehyde（7）,isoxanthanol（8）.The IC50 values of compounds 1-4,8 for root length growth of amaranth were 28.03μg·mL^-1,60.06μg·mL^-1,133.13μg·mL^-1,82.53μg·mL^-1,223.7μg·mL^-1,respectively;The IC₅₀ of root growth of bluegrass were 124.60μg·mL^-1,200.20μg·mL^-1,56.75μg·mL^-1,106.10μg·mL^-1,16.1μg·mL^-1,respectively.The compound xanthatin（1）had the strongest inhibitory effect on the growth of amaranth,and the compound coniferoldehyde（8）had the strongest inhibitory effect on the growth of bluegrass.