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.

-The objective of this work was to screen plants with insecticide activity, in order to isolate, identify and assess the bioactivity of insecticide compounds present in these plants, against Coleoptera pests of stored products: Oryzaephilus surinamensis L. (Silvanidae), Rhyzopertha dominica F. (Bostrichidae) and Sitophilus zeamais Mots. (Curculionidae). The plant species used were: basil (Ocimum selloi Benth.), rue (Ruta graveolens L.), lion's ear (Leonotis nepetifolia (L.) R.Br.), jimson weed (Datura stramonium L.), baleeira herb (Cordia verbenacea L.), mint (Mentha piperita L.), wild balsam apple (Mormodica charantia L.), and billy goat weed or mentrasto (Ageratum conyzoides L.). The insecticide activity of hexane and ethanol extracts from those plants on R. dominica was evaluated. Among them, only hexane extract of A. conyzoides showed insecticide activity; the hexane extract of this species was successively fractionated by silica gel column chromatography, for isolation and purification of the active compounds. Compounds 5,6,7,8,3',4', 5,6,7,8,3'-pentamethoxy-4',5'-methilenedioxyflavone and coumarin were identified. However, only coumarin showed insecticide activity against three insect pests (LD 50 from 2.72 to 39.71 mg g -1 a.i.). The increasing order of insects susceptibility to coumarin was R. dominica, S. zeamais and O. surinamensis.Index terms: natural insecticide, pest management, alternative control, secondary metabolites. Compostos de plantas com atividade inseticida a coleópteros-praga de produtos armazenadosResumo -O objetivo deste trabalho foi selecionar plantas com atividade inseticida, para isolar, identificar e avaliar a bioatividade de compostos inseticidas presentes nessas plantas, contra as seguintes pragas de produtos armazenados da ordem Coleoptera: Sitophilus zeamais Mots. (Curculionidae), Rhyzopertha dominica F. (Bostrichidae) e Oryzaephilus surinamensis L. (Silvanidae). As espécies de plantas usadas foram: anis (Ocimum selloi Benth), arruda (Ruta graveolens L.), cordão-de-frade (Leonotis nepetifolia L.), datura (Datura stramonium L.), erva baleeira (Cordia verbenacea L.), hortelã (Mentha piperita L.), melão-de-são-caetano (Mormodica charantia L.) e mentrasto (Ageratum conyzoides L.). Avaliou-se a toxicidade dos extratos hexânico e etanólico dessas plantas sobre R. dominica. Somente o extrato hexânico de A. conyzoides apresentou atividade inseticida. O extrato hexânico desta planta foi fracionado, sucessivamente, por cromatografia de coluna de sílica gel, para isolamento e purificação dos compostos ativos. Os compostos 5,6,7,8,3',4', 5,6,7,8,5'-metilenodioxiflavona e cumarina foram identificados. Entretanto, somente a cumarina apresentou atividade inseticida às três espécies de insetos (DL 50 de 2,72 a 39,71 mg g -1 de i.a.). A ordem crescente de suscetibilidade à cumarina foi R. dominica, S. zeamais e O. surinamensis.Termos para indexação: inseticida natural, manejo de pragas, controle alternativo, metabolito secundário.

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 mg 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.

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.

Colleters are secretory structures that occur in vegetative or reproductive shoot apices of many botanical families. However, in the order Myrtales, reports of colleters have considered only external morphology. We therefore evaluated apical meristems of 52 species belonging to 17 genera from seven tribes of subfamily Myrtoideae (Myrtaceae), so as to analyse the incidence and morphological types of colleters. The samples were fixed for light and scanning electron microscopy. Histochemical tests were carried out on fresh and methacrylate-embedded material. Proteins of the colleter secretions were analysed by SDS-PAGE. We have classified and described the following three new colleter types: petaloid, conic and euryform. None of the species contained all three colleter types. The petaloid colleters were present in three tribes (Syzygieae, Melaleuceae and Lophostemoneae). The conic colleters were observed in three tribes (Leptospermeae, Myrteae and Melaleuceae) and the euryform type occurred in five tribes (Leptospermeae, Syncarpieae, Myrteae, Syzygieae and Melaleuceae). In the tribe Eucalypteae, we found no evidence of colleters. The presence of mucilaginous secretion that defines colleters was confirmed by histochemical tests, and no proteins were found in the secretion. The colleters in Myrtoideae may help clarify the phylogenetic relationships of the Myrtaceae family.

The catalytic oxidation of 2alpha,4alpha-dimethyl-8-oxabicyclo[3.2. 1]oct-6-en-3-one with osmium tetraoxide and excess hydrogen peroxide resulted in the formation of 2alpha,4alpha-dimethyl-6, 7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan-3-one (2), with 91% yield. Addition of aryllithium reagents to this compound resulted in the formation of the aromatic alcohols (6a-h) with 48-76% yield. These alcohols were treated with thionyl chloride in pyridine, and the corresponding alkenes (7a-h) were obtained with 46-80% yield. The effect of compounds 6a-h and 7a-h on the root growth of Sorghum bicolor was evaluated at a concentration of 6.6 microg g(-)(1). The alcohols 6a-h caused an inhibitory effect (8-100%) on the S. bicolor radicle growth. The three most active compounds were 6e (aryl = p-methylphenyl), 6g (aryl = p-chlorophenyl), and 6h (aryl = p-fluorophenyl) and caused 100% inhibition. The effect of alkenes 7a-h was less pronounced and varied from 15% to 46% inhibition. Another experiment was carried out in a greenhouse to evaluate the effect of alcohols 6e, 6g, and 6h, at a 6.6 microg g(-)(1) dose, against Cucumis sativus, S. bicolor and the weeds Bidens pilosa, Desmodiumtortuosum, and Pennisetum setosum. All three compounds showed an inhibitory effect on the development of the aerial parts (26-73%) and roots (13-79%) of the weeds and crops.

RESUMO. O efeito de estresse hídrico sobre o teor, a composição química do óleo essencial e o crescimento de Melaleuca alternifolia Cheel (Myrtaceae) foi estudado. Cada tratamento constituiu-se de um regime hídrico: 1-irrigação em dias alternados com 0,5 L de água por vaso; 2-irrigação diária com 1 L de água por vaso; 3-lâmina de 1 cm de água (1 L) e 4-lâmina de 10 cm de água (12 L). A deficiência hídrica severa diminuiu o crescimento, a produção de biomassa fresca e seca das plantas e o teor de óleo essencial. Os principais constituintes do óleo essencial de M. alternifolia não diferiram significativamente entre os tratamentos, com 1,77 a 3,22% para o p-cimeno, 1,86 a 3,54% para o 1,8-cineol, 9,05 a 10,25% para o α-terpineol, 19,10 a 20,80% para o γ-terpineno e 37,89 a 39,37% para terpinen-4-ol.Palavras chave: Myrtaceae, terpenos, 1,8-cineol, efeitos ambientais, α-terpineol, tea tree.ABSTRACT. Effect of the water stress on the growth and the essential oil production of the Melaleuca alternifolia Cheel. The effect of water stress on the production, chemical composition of the essential oil and on the growth of Melaleuca alternifolia Cheel (Myrtaceae) was investigated. Each treatment consisted of a water regime (1-irrigation with 0,5 L of water per pot every two days; 2-irrigation with 1L of water per pot every day; 3-the pots were kept in a container with 1 cm of water (1L); 4-the pots were kept in a container with 10 cm of water (12L). The severe water deficiency resulted in a reduction in the plant growth, production of fresh and dry biomass and in the essential oil. The major constituents of the essential oil of M. alternifolia did not differ significantly among the treatments, with 1.77 to 3.22% for p-cymene, 1.86 to 3.54% for 1,8-cineol, 9.05 to 10.25% for α-terpineol, 19.10 to 20.80% to γ-terpinene and 37.89 to 39.37% for terpinen-4-ol.Key-words: Myrtaceae, terpenes, 1,8-cineol, environmental effects, α-terpineol, tea tree. IntroduçãoA adaptabilidade das plantas em condições de estresse é influenciada pela duração e magnitude do estresse, além da variabilidade genética. A concentração de princípios ativos nas plantas depende do controle genético e também das interações genótipo e ambiente, que podem ser desencadeadas em condições de estresse, ou seja, excesso ou deficiência de algum fator do meio ambiente, como água, luz, temperatura, nutrientes, dentre outros (Andrade e Casali, 1999).A água é essencial à vida e ao metabolismo das plantas, portanto, seria esperado que em ambientes mais úmidos a produção de princípios ativos fosse maior. No entanto, para algumas plantas medicinais a maior disponibilidade de água pode diminuir a produção de óleo essencial. Alguns estudos têm verificado que plantas com deficiência hídrica são mais vulneráveis a pragas e doenças, porém a resposta quanto as defesas químicas de muitas espécies ainda não está bem esclarecida (Andrade e Casali, 1999). Em condições de baixa disponibilidade de água no solo, vários processos metabólicos nas plantas podem ser influenciados, como o fec...

The sesquiterpene lactone glaucolide B (1), isolated from Vernonia fruticulosa (Asteraceae), was transformed into six lactones (2Ð7). The structures of the products were elucidated by spectroscopic analysis. A series of solutions of compounds 1Ð7, at 200 µm, were tested on the germination and on the root and shoot growth of the dicotyledons Physalis ixocarpa and Trifolium alexandrinum and of the monocotyledons Lolium multiflorum and Amaranthus hypochondriacus. Lactone 5 exhibited clear selectivity towards dicotyledonous species at 200 µm, with an average inhibition of 90% on the germination of P. ixocarpa. Lactones 1, 3 and 4 had a greater effect on root length of monocotyledonous species, inhibiting around 70% at 200 µm in L. multiflorum. It seems that the diol function is required in lactones 4Ð6 to increase the activity, the polarity in the molecule might be required to reach its target.