| Duchesnea indica Andr. Focke was previously screened to have great larvicidal activity against mosquitos in Research & Development Center of Biopesticide Technology and Engineering, Northwest A&F University. Thus further extraction, separation and elucidation of its active-candidate compounds was carried out by bioassay-guided fractionation method. Mosquito-larvicidal bioassay of the isolated compounds was investigated. Results were as follows:1. At the concentrate of 800mg/L, the water suspension of 95 % methanol crude extracts of Duchesnea indica Andr. Focke was fractionated to obtain petroleum ether phase, acetic ester phase and n-butanol phase. The 3rd instar larvicidal activity against Aedes albopictus of these fractionated phases was investigated by WHO recommended method of immersion, resulting in 13.3%, 54.7%, 61.3% adjusted larvicidal rate, respectively. Acetic ester extraction phase and n-butanol extraction phase showed relative high mosquito-larvicidal activity with the LC50 values of 784.25 mg/L and 611.22 mg/L(resp.), and no significant difference was observed.2. Methanol crude extracts of Duchesnea indica Andr. Focke were separated by Bioassay-guided fractionation method, with Silica gel column chromatography, macroporous resin chromatography, semi preparative MCI medium, recrystallization technologies utilized. Five isolated organic compounds elucidated as phytyl aldehyde(C1), 2α, 3β-dihydroxyurs-12-en-28-oic acid(C2),sitosterol(C3), β-methyl-D-glucopyranoside(C4), and euscaphic acid(C5). Phytyl aldehyde was isolated for the first time from Duchesnea indica Andr. Focke.3. The 3rd instar larvicidal activity of 5 isolated compounds against Aedes albopictus was assayed. At the concentrate of 100mg/L, C2 showed best mosquito-larvicidal activity, with the adjusted larvicidal rate 53.3%(for 24h) and 71.7%(for 48 h).Further study showed that LC50 value of C2 against Aedes albopictus 3rd instar lavae for 24 h was 116.61 mg/L. |
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