The Extraction, Chemical Constituents And Insecticidal Activity Of Essential Oil From Hydrocotyle Wilfordi Maxim.

Hydrocotyle wilfordi Maxim. (Umbelliferae) is an annual plant and widely distributed in China. This paper dealed with the analysis of base chemical constituent, the insecticidal activity and mode of different extracts by steam distillation and systemic solvent extraction, the optimum of extracting essential oil by supercritical CO₂extraction technology with single factor test and orthogonal test, the comparison of chemical constituents and insecticidal activity of essential oil by steam distillation, solvent extraction and supercritical CO₂extraction technology, the toxicity of main constitutent Cedrol against Brevicoryne brassicae L.and Odontotermes Formosans and the tese of synergistic action of crude tea saponin on Cedrol.The results of insecticidal activity of different extracts from Hydrocotyle wilfordi Maxim. showed that the essential oil was best effect on insecticidal activity. Its insecticidal mode was contact toxicity against Brevicoryne brassicae L.and fumigation toxicity against Odontotermes Formosans.The optimum of extracting essential oil from Hydrocotyle wilfordi Maxim. was conducted by supercritical CO₂extraction technology with single factor test and orthogonal test. The results showed that optimized conditions were sample size 60-80 mesh, extraction pressure 35 MPa, extraction temperature 50℃, separation pressure 5 MPa, separation temperature 40℃, extraction time 75min, CO₂flow 34-36 L·h-1. Extraction rate of essential oil was up to 5.32% by supercritical CO₂extraction technology.The chemical components of the essential oil were analyzed by GC-MS. 32 components were identified for the essential oil extracted by steam distillation, embrasing terpenes and enols. The major components of essential oil are Cedrol (45.669%), Bicychlo [4,1,0] hept- 3-ene,3,7,7-trime-, trimethyl-,[1S] (19.344%), Caryophyllene oxide(10.702%). 38 components were identified for the essential oil extracted by solvent extraction, embrasing long-chain alkylations, phenols, enols and esters. The major components of essential oil are Phenol, 2,4-bis(1,1-dimethylethyl)-(29.644%),Cedrol(14.512%), 1,2- Benzenedicarboylic acid, bis(2-methylpropyl) ester ( 12.061%), Caryophyllene oxide(5.665%), 2-Ethylhexyl ester of butanoic acid(4.943%). 19 components were identified for the essential oil extracted by supercritical CO₂extraction technology, embrasing nonvolatilizable metabolites, long-chain alkylations, enols and esters. The major components were Bis (2-ethylhexyl) phthalate (64.302%), 2,2'-methylenebis[6-(1,1- dimethylethyl)-4-methyl](7.783%), 2-Pentene, 2,3,4- trimethy(2.304%).The mortality rate of Brevicoryne brassicae L.and Odontotermes Formosans was increased with the increase of concentration of the essential oil. By comparing three extraction methods, the essential oil extracted by steam distillation was best effect on insecticidal activity. In contact toxicity test against Brevicoryne brassicae, Toxic regression equation was Y=6.1640+3.1967x (r =0.8456), and LC₅₀ was 0.4324 mg·mL^-1 for 24 h;In fumigation toxicity test against Odontotermes Formosans, Toxic regression equation was Y=4.2316+2.7161x (r =0.9838) and LC₅₀ was 1.9183 mg·mL^-1 for 24 h.In contact toxicity test of Cedrol against Brevicoryne brassicae, LC₅₀ was 10.9107 mg·mL^-1 for 24 h. After added crude tea saponin at concentrations of 5 and 10 mg·mL^-1 into Cedrol, LC₅₀ was reduced to 3.0933 mg·mL^-1and 1.8332 mg·mL^-1 respectively. Results showed that crude tea saponin had certain synergistic action on Cedrol.This research have great significance in the academic aspect for the development and utilization of Hydrocotyle sibthorpoioides Lam..