A method of gas chromatography-mass spectrometry(GC-MS) with steam distillation(SD) and supercritical CO2 extraction(SC-CO2) was developed for the analysis of components of essential oil in leaves of Zanthoxylum piperitum ‘Odorum’.The samples were extracted by SD and SC-CO2

respectively

then analyzed by GC-MS. The quality of extracts was distinguished by determining the scavenging ability and reducibility for free radical DPPH·.A total of 34 components

extracted by both SD and SC-CO2

were mainly lipids and alkenes.However

the types of components obtained by the two methods were significantly different.The SD extracted components

contained relatively high contents of ethyl benzene(43.15%)

methyl cinnamate (30.33%)

α-caryophyllene(1.81%) and α-myrcene(8.41%).In contrast

the SC-CO2 method mainly yielded methyl cinnamate (73.91%)

limonene(11.13%) and α-caryophyllene(4.12%).As the scavenging ability for DPPH· was concerned

the essential oils extracted by SC-CO2 reached the butylated hydroxytoluene(BHT) inhibition rate of 97.27% at the concentration of 8 mg/mL

with an IC50 of 3.173 3.At 20 mg/mL

their reducibility reached to 34.86% of that of vitamin C(Vc).In contrast

the SD extracted essential oils only had a BHT inhibition rate of 14.27% at 20 mg/mL

and 5.98% of Vc reducibility.Therefore

the differential components between the two extraction methods were mainly those reductive and antioxidative substances such as phenols and terpenes.In conclusion

the essential oils extracted from leaves of Zanthoxylum piperitum by SC-CO2 contained more insect repelling and antimicrobial agents

and its extraction effects were superior to those of SD method.