Chemical composition, antibacterial and antioxidant activities of the essential oil from Vismia guianensis fruits

In recent decades, the essential oils of plants have drawn great interest as sources of natural products. Essential oil from the fruits of Vismia guianensis was tested for its chemical constituents and antimicrobial and antioxidant activities. Gas chromatography/mass spectrometry (GC-MS) analysis of the essential oil revealed the presence of 38 sesquiterpenoids. The major components were β-caryophyllene (25.8%), α-copaene (13.1%), and δ-cadinene (11.6%). Antimicrobial activities were measured against six species of Gram negative and seven species of Gram positive bacteria and showed antibacterial activity against the human pathogenic Gram-positive bacteria Staphylococcus lentus with minimum inhibitory concentration (MIC) values of 78 μg/ml. The antioxidant activity of the essential oil was evaluated using the beta carotene/linoleic acid assay and showed antioxidant activity.Key words: Vismia guianensis, chemical composition, antibacterial, antioxidant, fruits, essential oil

Synthesis of 2-hydroxy-3-(2-methyl-propenyl)-1,4-naphthoquinone and related oxime derivatives

<div class="WordSection1"><p><em>The condensation reaction</em><em> of commercial 2-hydroxy-1 ,4-naphthoquinone <strong>1 </strong>(lawsone) with isobutyraldehyde <strong>2</strong> furnishs norlapachol <strong>3 </strong>(2-hydroxy-3-(2-methyl-propenyl) -1,4-naphthoquinone) with yields ranging from 66 to 93% depending on the different conditions tested, and a reaction temperature factor determinant for the formation of the desired product. It was treated with hydroxylamine hydrochloride in alkaline (NaOH) to provide the oxime <strong>4</strong> from regioselective modification of the carbonyl C-1 with 91% yield.</em><strong> </strong><em>The</em><em> regioselectivity of the reaction can be explained by analyzing the </em><em></em><em></em><em>different</em><em> resonance structures which can be seen that the carbonyl C-4 is less electrophilic than C-1. In this work was also obtained the oxime <strong>5</strong>, <strong>6</strong> and <strong>7</strong> from lapachol, αlpha and β-lapachone, respectively, in yields of 64-85%. The oximes of αlpha and β-norlapachone, <strong>8</strong> and <strong>9</strong> are in obtention. </em><em>All the products were analyzed by IR and NMR, and were observed that oximes of lapachol and norlapachol are isolated as E/Z mixtures. Two-dimensional NOE-type experiments of the corresponding acylated derivative will be made to help identify the proportion of the mixture.</em></p></div