Microwave assisted Soxhlet extraction of essential oil from Vietnamese Star anise fruits (Illicium verum Hook.f.) and their chemical composition

The influence of microwave power (W), irradiation time (h) and particle size (P) on the yield of extraction and composition of essential oil from Illicium verum Hook.f has been assessed by means of a new experimental design. The combined effects of three factors above on the yield of extraction of essential oil Y% (r.m) have been determined using Doehlert matrices in the range of 100 - 400 W for microwave power, 10 - 40 mins for irradiation time and 0.4 - 2.0 mm for particle size. In these conditions, second order polynomial relationship between Y% (r.m) and these factors have been established with regression coefficients close to 0.93. The major effect of microwave power and particle size on the yield of extraction of essential oil has been highlighted. In the conditions of 325 W microwave power, 20 min irradiation time and 0.4 mm particle sizes, the highest essential oil yield by microwave assisted Soxhlet extraction was 8.3%. The main compound of Illicium verum Hook.f was the (E)-anethole (92 %). The composition of α-pinene, ß-mycrene, α-phellandren were absent from the essential oil extracted from Illicium verum Hook. f. by use of MASE.