Repellent,larvicidal and adulticidal activities of essential oil from Dai medicinal plant Zingiber cassumunar against Aedes albopictus

Zingiber cassumunar is an important plant used in traditional medicine and as a natural mosquito re-pellent.However,the compounds responsible for the repellent activity of the plant are still unknown.The aim of the study is to identify the components of Z.cassumunar essential oil that show repellent activity against Aedes albopictus.We also evaluated the larvicidal and adulticidal activities of Z.cassumunar essential oil against Ae.albopictus.In-cage mosquito repellent experiments showed that Z.cassumunar essential oil possessed moderate repellent activity with a minimum effective dose(MED)of 0.16±0.01 mg/cm^(20,compared to reference standard N,N-diethyl-3-methylbenzamide(DEET,0.03±0.01 mg/cm^(20).Bioassay-guided fractionation identified the major active compound of Z.cassumunar essential oil as(-)-terpinen-4-ol(1)(MED:0.19±0 mg/cm^(20).We also found that Z.cassumunar essential oil showed moderate larvicidal activity against first instar larvae of Ae.albopictus with a LC50(50%lethal concentration)of 44.9 mg/L after 24 h.Fumigation bioassays showed that Z.cassumunar essential oil exhibits moderate adulticidal activity against Ae.albopictus with a LC50 of 5.44%,while(-)-terpinen-4-ol showed significant adulticidal activity with a LC50 of 2.10%after 24 h.This study verifies that the Z.cassumunar essential oil has mosquito repellent activity,and that(-)-terpinen-4-ol is mainly responsible for this activity.Furthermore,this study provides scientific support for the folk usage of Z.cassumunar essential oil as mosquito repellent and indicates that Z.cassumunar essential oil and(-)-terpinen-4-ol can be used as plant-derived repellents and insecticides for mosquito control.

Three New C_(21) Steroidal Glycosides from Roots of Cynanchum otophyllum

Objective To investigate the chemical structures of glycosides in the roots of Cynanchum otophyllum（Asclepiadaceae） and to find new glycosides. Methods The total glycosides in the roots of C. olophyllum were separated by silica gel column chromatography. The structures of the resulting compounds were determined by NMR and FAB-MS spectra. Results Three C21 steroidal glycosides were separated. Their structures were determined as caudatin 3-O-（4-O-methyl-β-D-cymaropyranosyl）-（1→4）-ɑ-D-oleandropyranosyl-（1→4）-β-D-glucopyranosyl-（1→4）-ɑ-L-rhamnopyranoside（1）, caudatin 3-O-β-D-digitoxopyranosyl-（1→4）-ɑ-D-oleandropyranosyl-（1→4）-β-Ddiginopyranosyl-（1→4）-β-D-glucopyranoside（2）, and caudatin 3-O-β-D-diginopyranosyl-（1→4）-ɑ-D-oleandropyranosyl-（1→4）-ɑ-D-oleandropyranosyl-（1→4）-β-Dglucopyranoside（3）, respectively. Conclusion Glycosides 1-3 are new compounds.

C_(21) Steroidal Saponins from Cynanchum otophyllum

Objective To study the chemical structures of saponins in the rhizome of Cynanchum otophyllum（Asclepiadaceae）, and to find new compounds. Methods The total saponins of the rhizome were separated by silica gel column chromatography. The chemical structures of obtained compounds were determined by NMR and FAB-MS spectra. Results Three C21 steroidal saponins were separated. Their structures were determined as caudatin 3- O-β-D-glucopyranosyl-（1 →4）-β- D-digitoxopyranosyl-（1 → 4）-β-D-digino- pyranosyl-（1 -4）-α-D-oleandropyranoside （1）, caudatin 3-O-β-D-oleandropyranosyl- （1→4）-α-D-oleandropyranosyl-（1→4）-α-D-oleandropyranoside （2）, and caudatin 3-O- β-D-glucopyranosyl-（1 →4）-α-D-oleandropyranosyl-（1 -4）-β-D-diginopyranosyl-（1→4）- α-D-oleandropyranoside （3）, respectively. Conclusion Saponins 1-3 are new compounds.