Abstract: The volatile oil from Premna microphylla leaves was extracted by water-steam distillation and analyzed by GC-MS.The antioxidant activity of volatile oil was examined using various antioxidant assays,such as reducing power,1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate (ABTS) free radical scavenging assays.The volatile oil was also evaluated for antimicrobial activity by paper disc diffusion method.The results showed that twenty-six compounds representing 98.10% of the total constituents were identified.The major constituents of the volatile oil were propanoic acid ethyl ester (33.70%),2,2′-methylenebis(6-tert-butyl-4-methylphenol) (9.38%),phytol (7.91%),α-eudesmol (3.75%),squalene (3.39%),and palmitic acid (3.34%). The volatile oil exhibited strong antioxidant capacities such as reducing power,DPPH and ABTS free radical scavenging abilities.When the scavenging rate against DPPH and ABTS free radicals was 50%,the concentrations of volatile oil were 3.396 mg/mL and 0.761 mg/mL,respectively.The volatile oil also had the inhibition effects on E.coli,S.aureus,B.subtilis and P.aeruginosa in a dose-dependent manner.Its minimum inhibitory concentration (MIC) against four common bacterial strains was 1.125 mg/mL.In conclusion,the volatile oil from P.microphylla leaves showed remarkable antioxidant and antimicrobial activities,and this research provided theoretical basis for the further study and application of volatile oil in food and medicine products.

Key words: Premna microphylla leaves, volatile oil, chemical constituents, antioxidant, antimicrobial