Study On Allelopathy And Allelochemicals In The Invasive Plant Ambrosia Trifida

Alien species invasion has always been a serious economic and environmental problem in the world.Allelopathy is closely related to the invasiveness of exotic plants.The isolation and identification of allelochemicals from invasive plants is the basis to study their allelopathy,and can better explain the invasiveness of exotic plants.Ambrosia Trifida L.is a malignant invasive weed in many countries in the world.It was first discovered in Tieling,Liaoning Province,northeast China,and is now widely distributed in 20 provinces and municipalities.The invader has strong allelopathic effects,and can affect maize fruiting when invading corn field or next to the field.However,the reason is not clear until now.We hypothesized that the allelopathy of its pollens may at least be one of the important reasons for that phenonemon.In this study,the chemical components in the leaves of A.Trifida were separated and purified using phytochemistry methods,and the structures of the components were identified by analyzing their physical and chemical properties,and the characteristics of their chromatography and spectroscopy.On this basis,the effects of pollen extracts of the invader on the activities of maize pollen and stigma were further studied,and the possible active compounds were discussed.A total of 13 compounds were isolated,purified and identified from leaves of A.Trifida.Among them,1)four terpenoids,including compound 2(P2): 9-epi-blumenol B,compound 3(P3): 3-hydroxy-8-cyclo-hrmogeruniol,compound 4(P8):(3R,6R,7E)-3-hydroxy-4,7-megastigmadien-9-one and compound 7(P12):3-hydroxy-5α,6α-epoxy-β-ionone;2)one flavonoid,i.e.,compound 8(P14):nevadensin(5,7-dihydroxy-6,8,4’-trimethoxyflavone);3)six phenylpropanoids,including compound 1(P1): caffeic acid methyl ester,compound 5(P10): umbelliferone,compound 10(P20): 4-methoxycinnamic acid,compound 11(P21):(+)-pinoresino,compound 12(P22):(+)-syringaresinol and compound 13(P24):2,3-dicarboxy-6,7-hydroxy-l-(3’,4’-dihydroxy)-phenyl-1,2-dihydronaphthalene-10-methyl ester;4)two others,compound 6(P11): indole-3-carboxaldehyde and compound 9(P16):2-hydroxy-benzaldehyde.Compound 5 was isolated for the first time from the invader;and compounds 1,2,3,4,6,7,8,9,10,11,12 and 13 were isolated for the first time from the generus Ambrosia.The ethanol crude extract of the pollens of the invader was further separated using petroleum ether and ethyl acetate,and the biological activities of the extracts were measured.The results of the bioassays showed that the extracts could inhibit the activitis of maize pollen and stigma,and the inhibition effects increased with the increase of the concentration of the extracts.The above studies have further enriched the allelopathy study of A.Trifida,and provided a possible explanation for its inhibition of maize fruiting,and laid a foundation for further study on its invasion mechanism.