Abstract: Effects of drying methods on total triterpenoids content and molluscicidal activity of ethanol extracts from Eucalyptus urophylla × Eucalyptus grandis bark and its mechanism were studied.The results showed that when the volume fraction of ethanol was 60%,the total triterpenoids contents of hot air-dried and freeze-dried ethanol extracts of E. urophylla × E. grandis bark were the highest,with the total triterpenoids contents of 10.81% and 13.90%,respectively.The ethanol extracts of E. urophylla × E. grandis bark obtained by two drying methods possessed strong molluscicidal activity against P.canaliculata,with mortalities of 93.1% and 100.00% after 72 h,respectively,at a concentration of 50 mg/L.The extract of Eucalyptus bark also significantly inhibited climbing by P.canaliculatathe,and the inhibitory effect was better than that of tea saponin at the same concentration (P < 0.05).Compared to the control group,after treatment with the hot air-dried ethanol extracts of E. urophylla × E. grandis bark,the protein content in cephalopodium and liver of snails was no significant difference between them (P > 0.05).After treatment with the freeze-dried ethanol extracts of E. urophylla × E. grandis bark,significantly decreased the protein content in cephalopodium of snails compared with the control group (P < 0.05),while the protein content in the liver did not significantly change (P > 0.05).Both hot air dried and freeze-dried extracts of E. urophylla × E. grandis bark significantly decreased enzyme activities of LDH,AKP and AST/GOT in cephalopodium (P < 0.05) and ALT/GPT and AST/GOT in liver of the snails (P < 0.05).Higher triterpenoids content and molluscicidal activity were found in freeze-dried extracts of E. urophylla × E. grandis bark when compared to hot air-dried extracts.

Key words: Eucalyptus urophylla ×, Eucalyptus grandis;bark;drying;triterpenoids content;Pomacea canaliculata;molluscicidal activity