Abstract: A DPPH microplate assay was made to determine the free radical scavenging activity of80% methanol extracts from leaves of some subtropical essential oil trees.Results revealed that all extracts from trees have different free radical scavenging capacities.Their free radical scavenging capacities increased with the raising of concentration and incubation time at 37℃.Of all trees, Pistasia chinensis Bunge, Liquidambar formosana Hance, Myrica rubra (Lour.) Sieb.et Zucc., Rosa banksiae Ait. and R.cymosa Tratt. have the strongest free radical scavenging capacity with a DPPH decreasing rate of 90.6%, 85.7%, 79.1%, 62.5% and 61.3%, respectively at a concentration of 0.5 mg/mL after incubated for 20 min. Phoebe sheareri (Hemsl.) Gamble, Pinus elliottii Engelm., Lindera praecox Bl., L.erythrocarpa Makino, R.chinensis Jacq., Juniperus formosana Hayata and Litsea coreana Levl.var. sinensis (Allen) Yang et P.H.Huang have also moderate free radical decreasing ratio under the same conditions.

Key words: essential oil, extracts of fresh leaves, free radical scavenging activity, 1-diphenyl-2-picrylhydrazine(DPPH) free radical