Studies On Isolation And Activities Of Bioactive Compounds From Eichhornia Crassipes

Water hyacinth is a perennial floating herbaceous weed which is one of the top tennoxious weeds in the world and one of the important invasive plants in our country. Annuallycontrol of water hyacinth has spent huge human, financial and material resources. If it can betaken as a resource and recycled, it can not only serve the human but also play an importantrole in the management of water hyacinth. This paper focused on the insecticidal activities ofthis weed species:Ethanol, chloroform and acetone were used as solvents, and the bioactivities of eachextract were bioassayed on larvae of different instars of T. molitor so as to choose a bestsolvent for further study. The crude extract from the chosen solvent was isolated by petroleumether, chloroform, ethyl acetate and n-butanol, which with different polarity, and each extractwas also bioassayed on T. molitor in order to find out which solvent can be applied for theisolation of the effective substances.(1) Extracts from ethanol, chloroform and acetone were diluted with ethanol, and foursolutions with different concentration were prepared. The third instar larvae of T. molitorwere bioassayed for the activities of these solutions by topical application. And resultsshowed all these extracts had the effects of contact poisoning, growth inhibition, and moltingretarding, and the relative importance was: ethanol extract> chloroform extract> acetoneextract,96h LC50were:9.91mg/ml,25.40mg/ml and521.11mg/ml; no significant effects onmolting inhibition were observed with acetone extracts. Bioassay on the last instar larvaewith the three extracts indicated that only ethanol extracts showed contact poisoning effects,the96h LC50107.20mg/ml; all these results indicated that ethanol would be the best solventfor further extraction and isolation.(2) Isolation of ethanol extract by petroleum ether, chloroform, ethyl acetate and n-butanol,and each isolated part was tested for their bioactivities on larvae of T. molitor. Also, foursolutions with different concentration were prepared and topical application method was used.Results showed that: The96h LC50of the extracts from petroleum ether and n-butanol were45.52mg/ml and19.62mg/ml, respectively. Growth inhibition effect was: petroleum etheringredients> ethyl acetate extract ingredients> chloroform extract ingredients> n-butanolextract ingredients; Molting retardation was: petroleum ether extract> chloroform extract>ethyl acetate extract. Among the four isolated extracts, only n-butanol showed contact toxicityon the last instar larvae with the96h LC5041.23mg/ml.