The essential oils of eight samples of Piper aduncum L., collected at dierent localities of the Amazon region, were analysed by GC±MS. The major component identi®ed in all samples was dillapiole (31.5± 97.3%). Sample A, collected at Serra do Navio (AP), showed a yield of oil and dillapiole content of 3.3% and 31.5%, respectively; sample B, collected at MelgacË o (PA), 1.8% and 50.8%; sample C, collected at Ben®ca (PA), 1.6% and 56.3%; samples D and E, collected at Bele m (PA), 1.2% and 82.2%; 1.5% and 86.9%, respectively; sample F, collected at Manaus (AM), 3.4% and 91.1%; sample G, collected at Road Manaus-Caracaraõ , km 30 (AM), 3.0% and 97.3%; sample H, collected at Cruzeiro do Sul (AC), 3.2% and 88.1%. The yield of oil and dillapiole content of samples of P. aduncum occurring in Malaysia and Fiji showed 1.3% and 64.5%; and 0.5% and 58.0%, respectively. By comparison, the plants growing wild in Amazonas State had the highest oil yield and dillapiole content. #

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The leaves and fine stems, bark, and trunk wood oils of Aniba canelilla showed yields ranging from 0.2 to 1.3%. The main volatile constituent identified in the oils was 1-nitro -2-phenylethane (70.2-92.1%), as expected. The mean of DPPH radical scavenging activity (EC 50) of the oils (198.17 +/- 1.95 microg mL(-1)) was low in comparison with that of wood methanol extracts (4.41 +/- 0.12 microg mL(-1)), the value of which was equivalent to that of Trolox (4.67 +/- 0.35 microg mL(-1)), used as antioxidant standard. The mean amount of total phenolics (TP) (710.53 +/- 23.16 mg of GAE/g) and this value calculated as Trolox equivalent antioxidant capacity (TEAC) (899.50 +/- 6.50 mg of TE/g) of the wood methanol extracts confirmed the high antioxidant activity of the species. On the other hand, in the brine shrimp bioassay the values of lethal concentration (LC50) for the oils (21.61 +/- 1.21 microg mL(-1)) and 1-nitro-2-phenylethane (20.37 +/- 0.99 microg mL(-1)) were lower than that of the wood methanol extracts (91.38 +/- 7.20 microg mL(-1)), showing significant biological activities.

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