Luiz C. A. Barbosa

Seasonal variation in the composition of volatile oils from Schinus terebinthifolius raddi

-1 concentrations. The three samples tested were more active in inhibiting the radicle growth for L. sativa (88.6-92.4%) than for C. sativus (50.5-84.5%) at 10,000 μg mL -1 concentration.

Synthesis and insecticidal activity of new amide derivatives of piperine.

The natural lipophilic amides piperine and piperiline were isolated from Piper nigrum L (Piperaceae). Piperine was hydrolysed into piperic acid (85% yield) which was converted into 16 amides (28–89% yield). The contact toxicity of all synthetic amides, and also that of piperine and piperiline, at the dose 10 µg per insect, was evaluated for the Brazilian economically important insects Ascia monuste orseis Latr, Acanthoscelides obtectus Say, Brevicoryne brassicae L, Protopolybia exigua DeSaus and Cornitermes cumulans Kollar. The results demontrated that the insects have different sensivities to the various amides, with mortality ranging from 0 to 97.5% according to the compound and insect species. © 2000 Society of Chemical Industry

Evaluation of the chemical composition of Brazilian commercial Cymbopogon citratus (D.C.) stapf samples.

The concentration and the chemical composition of the essential oils obtained from different samples of Cymbopogon citratus were evaluated. Among the 12 samples investigated (11 dried leaf samples and fresh plant leaves), seven presented essential oil concentrations within the threshold established by the Brazilian legislation. The moisture content was also determined and the majority of the samples presented humidity contents near 12%. The GC and GC/MS analyses of the essential oils led to identification of 22 compounds, with neral and geranial as the two major components. The total percentage of these two compounds varied within the investigated sample oils from 40.7% to 75.4%. In addition, a considerable variation in the chemical composition of the analyzed samples was observed. The process of grinding the leaves significantly decreased (by up to 68%) the essential oil content, as well as the percentage of myrcene in the oils.

Chemical composition and antibacterial activities from the essential oils of myrtaceae species planted in Brazil

The essential oils of seven Myrtaceae species were investigated for its chemical composition and antibacterial activity. The volatile oils were characterized by a high content of monoterpenoids of which 1,8-cineole (88.0, 65.0 and 77.0% for Melaleuca hypericifolia, Callistemon viminalis and Callistemon citrinus respectively), terpinen-4-ol (47.0 and 49.8% for Melaleuca thymifolia and Callistemon polandii respectively) and α-pinene (54.5% for Kunzea ericoides) were the major components. The oil from M. linariifolia was characterized by a high concentration of methyleugenol (87.2%). The oil from Melaleuca thymifolia was the most active, exhibiting high antimicrobial activity against all tested bacteria.

TEOR E COMPOSIÇÃO DO ÓLEO ESSENCIAL DE CINCO ACESSOS DE MENTRASTO

This study aimed to analyse the content and the composition of the essential oil of five accesses of mentrasto (Ageratum conyzoides). Five accesses of mentrasto with three repetitions were used. The accesses were obtained in Mariana-MG (AMA), Piranga-MG (API), Visconde do Rio Branco (ARB) and Vicosa-MG (AVB and AVP). The essential oil was obtained by hydrodistillation and the identification of the oil components by CG and GC/MS. The ARB access presented the higher essential oil content, that is 0.70% (P < 0.05). Eleven chemical compounds were identified. The precocene I was the main constituent in the access API, and the precocene II was the main constituent in the accesses AMA, ARB, AVB and AVP.

Recent mechanistic developments and next generation catalysts for the Sonogashira coupling reaction

The Pd-catalyzed Sonogashira reaction is a powerful method for the formation of Csp2–Csp bonds and has found application in a wide variety of areas including medicinal chemistry, agrochemistry, materials and electronics. Development of competent catalysts for the Sonogashira reaction is a particular scientific challenge since it is traditionally a di-metallic-mediated homogeneous catalytic process including some major drawbacks. This review provides a concise overview of the mechanistic aspects of the Cu co-catalyzed, Cu-free and Au-catalyzed Sonogashira coupling processes. More recent developments and next generation catalysts for the Sonogashira reaction are also presented. These include non transition-metal catalysts, metal free couplings and photo-induced protocols. Finally, the application of metal nanoparticles in Sonogashira reactions is presented. These include Pd nanoparticles, Pd bi- and tri-metallic nanoparticles, magnetically separable Pd/Fe3O4 nanoparticles, Ru nanoparticles and Au nanoparticles.

Seasonal Variation in the Chemical Composition and Antimicrobial Activity of Volatile Oils of Three Species of Leptospermum (Myrtaceae) Grown in Brazil

This study investigates the seasonal variation of three species of Leptospermum (Myrtaceae) grown in Brazil. The chemical composition of the volatile oils of L. flavescens and L. petersonii did not show any significant seasonal variation in the major components, while for Leptospermum madidum subsp. sativum the levels of major constituents of the volatile oils varied with the harvest season. Major fluctuations in the composition of L. madidum subsp. sativum oil included α-pinene (0–15.2%), β-pinene (0.3–18.5%), α-humulene (0.8–30%), 1,8-cineole (0.4–7.1%) and E-caryophyllene (0.4–11.9%). Levels of β-pinene (0.3–5.6%), terpinen-4-ol (4.7–7.2%) and nerolidol (55.1–67.6%) fluctuated seasonally in the L. flavescens oil. In L. petersonii, changes were noted for geranial (29.8–32.8%), citronellal (26.5–33.9%) and neral (22.7–23.5%). The activity of the volatile oils against the tested bacteria differed, depending on season the oils were obtained. In general, the volatile oils were more active against Gram-positive bacteria.

Variação química do óleo essencial de Hyptis suaveolens (L.) Poit., sob condições de cultivo

This study was performed to establish the correlation between the growth conditions and essential oil composition of Hyptis suaveolens from Alfenas (MG), Brazil. The plants were grown in a greenhouse, four treatments were used and they were harvested at two different periods of time (60 and 135-day-old plants). The essential oil composition was determined by GC-MS analysis. The terpenes spathulenol, globulol, dehydroabietol, a-cadinol and b-phellandrene were the major constituents found in the essential oil. Oxygenated sesquiterpenes represented the main group of constituents in most of the treatments. The major changes in the essential oil composition were found in 135-day-old plants grown under NPK deficiency. We also identified three groups of volatile components that have not been previously described in H suaveolens.

Basil conservation affected by cropping season, harvest time and storage period

O manjericao (Ocimum basilicum L.) e empregado tanto na industria culinaria quanto fitoterapica e na medicina tradicional, devido ao teor e composicao de seu oleo essencial. No entanto, o manjericao nao pode ser conservado por longo periodo apos a colheita e sua qualidade pode ser prejudicada. O objetivo deste trabalho foi verificar a influencia da epoca e do horario de colheita sobre a conservacao de manjericao armazenado por diferentes periodos. O manjericao foi colhido as 8h e as 16h em agosto/1999 e em janeiro/2000. Os ramos foram acondicionados em filmes de PVC e armazenados por 3, 6 e 9 dias. Durante o armazenamento, o teor de clorofila, e o teor e a composicao do oleo essencial foram determinados e foram conduzidas analises microbiologicas. A epoca de colheita e os dias de armazenamento influenciaram o teor final de oleo essencial. Houve decrescimo linear dos teores de oleo essencial e de clorofila e do numero de colonias de fungos e bacterias ao longo do armazenamento. Nao houve efeito da epoca de colheita ou do horario de colheita sobre a composicao do oleo essencial, mas os teores de eugenol e linalol aumentaram durante o armazenamento. O numero de coliformes ficou abaixo de 0,3 NMP g-1 e o numero de Staphylococcus aureus, abaixo de 1,0x102 UFC g-1.

Essential oil in the taxonomy of Ocimum selloi benth

Chemical composition analysis of the essential oil from the leaves and flowers of two accessions of Ocimum selloi Benth, cultivated at the Federal University of Vicosa was carried out. For accession A the major component was identified as estragole and represented 94,95% and 92,54% of the oil from the leaves and flowers respectively. For accession B, the oil from the leaves and flowers was constituted by 65,49% and 66,18% of methyleugenol, respectively. For both accessions several minor constituents were also identified. The phenotypic and chemical differences observed between these two accessions suggest the existence of two chemicaly distinct varieties for Ocimum selloi Benth.