Potential allelochemicals from an invasive weed Mikania micrantha H.B.K.
Phytotoxicity-directed extraction and fractionation of the aerial parts of Mikania micrantha H.B.K. led to the isolation and identification of three sesquiterpenoids: dihydromikanolide, deoxymikanolide, and 2,3-epoxy-1-hydroxy-4,9-germacradiene-12,8:15,6-diolide. These sesquiterpenoids inhibited both germination and seedling growth of tested species with deoxymikanolide possessing the strongest phytotoxicity. In a bioassay against lettuce (Lectuca sativa L.), deoxymikanolide reduced radicle elongation at low concentration (IC50 = 47 microg/ml); dihydromikanolide showed a weaker effect (IC50 = 96 microg/ml), and 2,3-epoxy-1-hydroxy-4,9-germacradiene-12,8:15,6-diolide exhibited the least effect (IC50 = 242 microg/ml). Deoxymikanolide caused yellowish lesions at the root tips of lettuce at a concentration of 50 microg/ml, and a 250 microg/ml solution killed lettuce seedlings. A bioassay against the monocot ryegrass (Lolium multiforum) revealed similar results on radicle elongation, which implied that the growth inhibition by these compounds was not selective. To evaluate their phytotoxicity to plants in natural habitats, three common companion tree species in south China, Acacia mangium, Eucalyptus robusta, and Pinus massoniana, were also tested and similar results were obtained. This is the first report on the isolation of 2,3-epoxy-1-hydroxy-4,9-germacradiene-12,8:15,6-diolide as a naturally occurring product.
Shao
Hua
H
South China Institute of Botany, Chinese Academy of Sciences, Guangzhou, Guangdong, China.
Peng
Shaolin
S
Wei
Xiaoyi
X
Zhang
Deqing
D
Zhang
Chi
C
D000818:Animals; D018545:Lactuca / Q000187:drug effects / Q000502:physiology*; D035742:Mikania / Q000378:metabolism*; D035261:Plant Components, Aerial; D010936:Plant Extracts / Q000494:pharmacology*; D018517:Plant Roots / Q000187:drug effects / Q000502:physiology; D006109:Poaceae / Q000187:drug effects / Q000502:physiology*; D036226:Seedlings / Q000187:drug effects / Q000502:physiology; D012717:Sesquiterpenes / Q000494:pharmacology
D010936:Plant Extracts; D012717:Sesquiterpenes