Abstract: 【Abstract】 Objective To investigate the molluscicidal activities of the ginkgolic acid(GA) monomers isolated and purified from GAs. Methods Five monomers of GAs from the sarcotesta of Ginkgo biloba. were extracted by petrol ether, separated by silica gel column chromatography, purified by semi-prepared reversed-phased HPLC, and identified by LC-MS analysis. The molluscicidal activities of GAs and their monomers against Oncomelania hupensis were determined as referring to the WHO guidelines for laboratory molluscicidal test. Results The five purified ginkgolic acid monomers were GA_13︰0, GA _15︰0, GA _15︰1 , GA _17︰1 and GA _17︰2 , with a side chain of 13, 15, 17 alkyl or ethylenic radicals respectively on their benzene loop. The five monomer proportions to the total GAs were 17.6%, 3.2%, 52.3%, 23.3% and 3.6% respectively. The order of molluscicidal activities for the five monomers was as follows: GA _13︰0>GA _15︰1>GA _15︰0>GA _17︰1>GA _17︰2 , and their LC50 for snails was 20.79 mg/L, 22.28 mg/L, 33.76 mg/L, 51.89 mg/L, and 59.10 mg/L respectively after immersion for 24 hours. Two monomers, GA _13︰0 and GA15︰1 inhibited the snails' climbing up significantly. Conclusion The molluscicidal activities of GAs may be dependent on the monomer's structure with different number of carbon molecules and double-bonds on the side carbon-chain. The two monomers, GA _13︰0 and GA _15︰1 , are mainly responsible for the molluscicidal activities of GAs and both effectively inhibit snails' climbing up as well. GA _15︰0 also shows certain molluscicidal activity.

Key words: Ginkgolic acid, Molluscicide, Oncomelania hupensis, Monomer