Abstract

The chemical composition of hydro-distilled oil from the ground aerial parts of Wedelia trilobata (L.) Hitchc. was analysed by gas chromatography/gas chromatography–mass spectrometry (GC/GC–MS). 18 compounds representing all the oils were identified. The main components were demonstrated to be α-phellandrene (28.84%), germacrene D (15.79%), D-limonene (14.22%), 1,5,5-trimethyl-6-methylene- cyclohexene (10.11%) and caryophyllene (9.08%). In addition, some pharmaceutical components such as β-pinene, D-limonene, germacrene D and phytol were discovered. Orthogonal methodology L₉(3⁴) were applied to optimize extraction technology and evaluate the extraction yield, and the effects of soaking time, extraction time and solid to liquid ratio on oil extraction efficiency were studied.Experimental results showed that extraction time had significant effect on the yield ofoil, the influence order of different factors: extraction time > soaking time > solid to liquid ratio. The optimum operating parameters were determined as follows: soaking time, extraction time of 3 h and solid to liquid ratio of 1:10. Under the optimized conditions, the maximal yield of oil was enhanced to 0.1778%. Antioxidant activity of the oil was also assessed by the free radical scavenging, 2,2'-diphenyl-b-picrylhydrazyl (DPPH). The study offers theoretic basis for utilization of the medicinal herb W. trilobata.

Key words: Wedelia trilobata, essential oil, chemical composition, orthogonal methodology, extraction yield.