Abstract: In this study,we firstly reported that the volatile oil from Ormosia hosiei Hemsl.Et Wils.leaves was extracted by water-steam distillation and then analyzed by gas chromatography-mass spectrometry (GC-MS).The antioxidant activity of the volatile oil was determined by free radical scavenging assays against 1,1-diphenyl-2-picrylhydrazine (DPPH) and 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS).And its antimicrobial activity was also examined by inhibition zone.The results showed that thirty-six compounds,which represented 90.50% of the total constituents,were identified from the volatile oil.The major compounds of the volatile oil were 1,4-eicosadiene (25.72%),1,19-eicosadiene (10.85%),2,6-di-tert-butyl-4-methylphenol (10.14%),butyl isobutyl phthalate (9.75%),(Z,Z)-6,9-eicosadiene (7.60%),(E,E)-α-farnesene (7.51%),leaf alcohol (4.74%) and 2-isopropenyl-5-methyl-6-hepten-1-ol (4.04%).The volatile oil exhibited significant antioxidant activities against DPPH and ABTS free radicals in a concentration-dependent fashion,with the median effective dose ED₅₀ values of the antioxidant activities against DPPH and ABTS free radicals were 0.27 mg/mL and 0.14 mg/mL,respectively.When the concentration of the volatile oil was 7.1 mg/mL,the inhibition zone of Bacillus subtilis,Staphylococcus aureus,Escherichia coli,and Pseudomonas aeruginosa was 11.29,9.88,10.85,and 11.03 mm,respectively.These results provide theoretical basis for the comprehensive development and utilization of the natural resources of O.hosiei Hemsl.Et Wils..

Key words: Ormosia hosiei Hemsl.Et Wils., volatile oil, chemical constituents, antioxidant activity, antibacterial activity