the medical importance of Ae. albopictus is due to its ability to transmit many human pathogens and parasites e.g. yellow fever, dengue fever, West Nile, Japanese encephalitis, St. Louis encephalitis, chikungunya viruses, filarial nematodes. The control of adult mosquitoes commonly relies on the use of synthetic insecticides and repellents, but treatments with such chemicals are expensive, show scarce efficacy and have a strong environmental impact associated to relevant human health risks 6, 7. For these reasons, alternative natural insecticides and repellents are now very appreciated by consumers. Essential oils of aromatic plants are con-Abstract: The chemical composition and larvicidal activity of essential oils from the leaves and rhizomes of Zingiber collinsii Mood & Theilade (Zingiberaceae) were reported. The main compounds in the leaf oil were α-pinene (25.6%), β-caryophyllene (16.8%), β-pinene (16.1%) and bicyclogermacrene (6.9%) while the rhizome oil consist mainly of camphene (22.5%), β-pinene (16.3%), α-pinene (9.0%) and humulene oxide II (9.0%). The rhizome oil demonstrated larvicidal effects towards fourth instant larvae of mosquito vectors. The highest mortality (100%) was observed at 24 h exposure against Aedes albopictus (concentration 100 μg/mL) and 48 h (concentration of 50 and 100 μg/mL), while the highest mortality (100%) was observed for Culex quinquefasciatus at 24 h and 48 h at concentration of 100 μg/mL. The 24 h mosquito larvicidal activity of the rhizome oil against Ae. albopictus were LC 50 = 25.51 μg/mL; LC 90 = 40.22 μg/mL and towards Cx. quinquefasciatus with LC 50 = 50.11 μg/mL and LC 90 = 71.53 μg/mL). However, the 48 h larvicidal activity were LC 50 = 20.03 μg/mL and LC 90 = 24.51 μg/mL (Ae. albopictus), as well as LC 50 = 36.18 μg/mL and LC 90 = 55.11 μg/mL (Cx. quinquefasciatus). On the other hand, no appreciable mortality and larvicidal activity was observed for the leaf oil. The larvicidal activity of the essential oils of Z. collinsii was being reported for the first time.

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In the present study, the chemical investigation of the leaves of Annona reticulata has resulted in the identification of nine compounds, including annonaretin A, (1), a new triterpenoid. The purified compounds were subjected to the examination of their effects on NO inhibition in LPS-activated mouse peritoneal macrophages and most of them exhibited significant NO inhibition, with IC50 values in the range of 48.6 ± 1.2 and 99.8 ± 0.4 μM.

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The chemical constituents of essential oils from the leaf, stem bark and resins of Canarium parvum Leen., and Canarium tramdenanum Dai et Yakovl. (Burseracea) grown in Vietnam are being reported. The hydrodistilled oils were analysed for their chemical constituents by means of gas chromatography-flame ionisation detector and gas chromatography coupled with mass spectrometry. The main compounds of C. parvum were β-caryophyllene (18.7%), (E)-β-ocimene (12.9%), (Z)-β-ocimene (11.9%), germacrene D (8.8%) and α-humulene (8.4%) in the leaf; β-caryophyllene (30.4%), α-copaene (20.5%) and (E)-β-ocimene (7.7%) in the stem. However, germacrene D (23.2%), α-amorphene (14.9%), α-copaene (9.8%) and β-elemene (8.6%) were present in the resin. The leaf of C. tramdenanum comprises β-caryophyllene (16.8%), α-phellandrene (15.9%), γ-elemene (13.1%) and limonene (11.8%), while limonene (25.7%), α-phellandrene (21.7%), α-pinene (12.3%) and β-caryophyllene (10.9%) were present in the stem. However, δ-elemene (14.6%) and bulnesol (16.0%) are the main constituents in the resin.