João Carlos da Costa Assunção

Larvicidal and Nematicidal Activities of the Leaf Essential Oil of Croton regelianus

The chemical composition of the leaf essential oil of Croton regelianus collected from wild plants growing in two different sites at Ceará State (Brazil) was analyzed by GC/MS and GC‐FID. Twenty monoterpenoids, representing more than 96% of the chemical composition of the oils, were identified and quantified. The oils showed similar chemical composition but considerable variation in the levels of each constituent. Ascaridole (33.9–17.0%), p‐cymene (22.3–21.6%), and camphor (13.0–3.1%) were the predominant constituents. The monoterpene ascaridole was isolated and characterized by spectroscopic data. The essential oils and the isolated compounds were tested against Aedes aegypti and Artemia sp. larvae, and the root knot nematode Meloidogyne incognita. The bioassay results show that the essential oil of C. regelianus and ascaridole were moderately active against the M. incognita, but strongly effective against both A. aegypti and Artemia sp. larvae.

Constituintes químicos de Lippia sidoides (Cham.) Verbenaceae

Thirteen compounds, 3-O-acetyloleanolic acid (1), methyl 3,4-dihydroxy benzoate (2), lapachenol (3), tecomaquinone (4), tectoquinone (5), tectol (6), acetilated tectol (7), quercetin (8), luteolin (9), glucoluteolin (10), lippisidoquinone (11), taxifolin (12) and isolariciresinol (13), were isolated from ethanol extract of Lippia sidoides. Their structures were assigned unambiguously by a combination of 1D and 2D NMR, IR and EIMS spectral data analysis and comparison with the published data for structurally related compounds. In brazilian traditional medicine the aerial parts of this specie are used as anti-infective agent, particularly as antiseptic.

Lens culinaris: A New Biocatalyst for Reducing Carbonyl and Nitro Groups

A series of aliphatic and aromatic aldehydes and ketones, as well as some nitrocompounds were reduced using whole plant cells from Lens culinaris seeds. In addition, we also investigated the possibility of enzymatic ester hydrolysis to explore the potential of these seeds. The reduced ketones products were obtained in yields of 8 ∼ 82% and enantiomeric excess of 39 ∼ 75%. Aldehydes were more reactive than ketones with high chemical yield (95→99%), whereas the aromatic nitrocompounds showed low (2%) to high (> 99%) conversion depending upon the nature and position of the aromatic ring substituents. Ester hydrolysis by the Lens culinaris was quite effective with the ester p-nitrophenyl acetate (> 99% conversion).

Bioacetylation of alcohols catalysed by Saccharum officinarum

Lipase-catalysed esterifications of alcohols using immobilized enzyme system from sugar cane (Saccharum officinarum) as biocatalyst afforded the corresponding esters in considerable yields (68-93%). Under optimized conditions, the material was utilized for reactions of acetylation with several advantage. It also investigated the possibility of reuse of immobilized enzymes of S. officinarum as biocatalyst under optimal reaction conditions.

Asymmetric reduction of acetophenone derivatives by Lens culinaris

Abstract The enzymatic reduction of acetophenone derivatives has been evaluated using whole cells from the edible plant lentil (Lens culinaris) as biocatalyst to afford chiral (R) and (S)-alcohols in enantiomeric excess 68–99%. Acetophenone was selected as the model substrate for enantioselective bioreduction. The reaction was performed under a range of conditions in order to optimize the bioreduction procedure with respect to reaction time, media and optimal mass of lentil. With substituted (fluorine, chlorine, bromine, methyl, hydroxyl, methoxy, amino and nitro groups) acetophenones, electronic and steric influences on the course of the reaction were observed.

Seasonal variation, larvicidal and nematicidal activities of the lef essential oil of Ruta graveolens L.

This study investigated the seasonal variation (October 2009 to September 2010) in the chemical composition of the leaf essential oil of Ruta graveolens L. and evaluated its activity against third-instar larvae of Aedes aegypti and juvenile nematodes (J2) of Meloidogyne incognita. The essential oil was obtained by hydrodistillation and analyzed by gas chromatography/flame ionization detection (GC/FID) and GC/mass spectrometry (GC/MS). Nine compounds were identified in the oil samples obtained during a year. The major components were 2-undecanone (37.0±2.0% to 58.2±5.1%) and 2-nonanone (17.6±1.3% to 53.1±3.9%). The essential oil showed lc50 and lc90 values of 39.55 and 64.17 ppm for A. aegypti respectively, and 267.20 and 482.03 ppm for M. incognita, respectively.

Essential oil of Alpinia zerumbet (Pers.) B.L. Burtt. & R.M. Sm. (Zingiberaceae): chemical composition and modulation of the activity of aminoglycoside antibiotics

Essential oils are new natural medicines, which have been studied extensively in recent years. In this paper, the chemical composition of the essential oil from Alpinia zerumbet leaves and its ability to modulate the activity of aminoglycoside antibiotics is reported. The essential oil was extracted by hydrodistillation and analyzed by gas chromatography (GC) and GC–mass spectrometry (GC/MS). The antibacterial activity of the essential oil alone or in association with aminoglycosides was determined by a microdilution test against twelve strains (standards and multi-resistant clinical isolates obtained from sputum and wounds), seven Gram negative and five Gram positive. The major components identified by GC/MS were 4-terpineol (32.9 ± 4.0%), 1,8-cineole (21.4 ± 1.2%), γ-terpinolene (10.0 ± 1.8%) and sabinene (7.1 ± 4.6%), with a strong predominance of monoterpenes. The results indicated that the multi-resistant clinical isolates Staphylococcus aureus 358 and Escherichia coli 27 were more sensitive to the essential oil, exhibiting minimum inhibitory concentrations (MICs) of 32 and 128 μg/mL, respectively. The essential oil was capable of enhancing the antimicrobial activity of aminoglycosides against all strains tested, except for S. aureus 358. Very significant reductions in the MICs of the antibiotics were found, with a 94% decrease in MIC of neomycin against Klebsiella pneumoniae ATCC 10031. The results obtained indicate that the A. zerumbet essential oil has a significant synergistic antibiotic effect when combined with aminoglycosides, demonstrating that its constituents may act as potentiators of the antibiotic activity of aminoglycosides.

New volatile constituents from leaves of Stemodia trifoliata (Link.) Reichb. (Schrophulariaceae).

The leaf essential oils of Stemodia trifoliata (Scrophulariaceae), collected at the same month of two different years (August 2005 and 2006), were analized by GC-MS and GC-FID. A total of 22 volatile components represented by sesquiterpenes and diterpenes was identified. β-Caryophyllene (9.4-15.4%) and caryophyllene oxide (6.2-9.0%) were the major compounds identified in the sesquiterpene fraction, while the diterpenoids 6α-acetoxymanoyl oxide (13.9-23.2%) and 6α-hydroxymanoyl oxide (25.1-29.7%) were the main constituents of the diterpene fraction. The two novel manoyl oxide derivatives had their structures established by means of spectroscopic methods, particularly 1D and 2D NMR. This work describes for the first time the chemical investigation on the volatile composition of S. trifoliata.