Abstract: To study the effects of two extraction methods on the chemical compositions and antioxidant activity of volatile oils from the leaves of Moringa oleifera.Volatile oils from the leaves of three species of Moringa oleifera were extracted by the methods of soxhlet extraction and ultrasonic extraction,the chemical constituents and mass fractions of volatile oils were analyzed by gas chromatography-mass spectrometry (GC-MS),to analysis the chemical composition data of volatile oils by principal component analysis,the antioxidant activities of volatile oils were studied by using DPPH free radical scavenging capacity.The results showed that the volatile oils obtained by soxhlet extraction from the leaves of Moringa oleifera in African species,Myanmar species and Indian species were analyzed and identified as 72,74 and 62 chemical constituents,the mass fractions were 79.63％,93.69％and 95.97％.The volatile oils from the leaves of Moringa oleifera obtained by ultrasound extraction,were analyzed and identified as 63,63 and 57 chemical constituents,the mass fractions were 97.20％,95.17％ and 98.28％,five principal components were extracted by principal component analysis from chemical constituents of volatile oils from leaves of Moringa oleifera,the eigenvalues were 18.000,6.733,3.981,3.182 and 1.104,the contribution rates were 54.55%,20.40%,12.06%,9.64% and 3.35%.The volatile oils obtained by the two methods from the leaves of Moringa oleifera had certain antioxidant activity,and DPPH free radical scavenging rate enhanced with the increase of volatile oils mass concentration.The IC₅₀ values of DPPH radical scavenging rate of volatile oils extracted by soxhlet extraction were 0.35 mg/mL (African species),0.26 mg/mL (Myanmar species) and 0.20 mg/mL (Indian species)；The IC₅₀ values of DPPH radical scavenging rate of volatile oils extracted by ultrasonic method were 0.50 mg/mL (African species),0.30 mg/mL (Myanmar species) and 0.30 mg/mL (Indian species).The results provided a scientific basis for identifying the different qualities,further research,development and utilization of volatile oils from the leaves of Moringa oleifera.

Key words: volatile oils of Moringa oleifera leaves, soxhlet extraction;ultrasound extraction；content analysis；antioxidant activity