Rea����es de 1,2-dicloro-4,5-dinitrobenzeno com aminas: monossubstitui����o de nitro e dissubstitui����o de cloro e nitro

1,2-dichloro-4,5-dinitrobenzene (DCDNB) reacts with primary and secondary amines, in acetonitrile, at room temperature, to give a monosubstituted nitro product with a yield of 85 to 95%. The chloro-nitro-disubstituted product is formed with excess amine under reflux. Piperidine, pyrroline, dimethylamine and methylamine were the most reactive reagents in both mono- and disubstitution.

Gas collisions and pressure quenching of the photoluminescence of silicon nanopowder grown by plasma-enhanced chemical vapor deposition

The quenching of the photoluminescence of Si nanopowder grown by plasma-enhanced chemical vapor deposition due to pressure was measured for various gases ( H2, O2, N2, He, Ne, Ar, and Kr) and at different temperatures. The characteristic pressure, P0, of the general dependence I(P)=I0exp(-P/P0) is gas and temperature dependent. However, when the number of gas collisions is taken as the variable instead of pressure, then the quenching is the same within a gas family (mono- or diatomic) and it is temperature independent. So it is concluded that the effect depends on the number of gas collisions irrespective of the nature of the gas or its temperature

Essential oils from leaves of cryptocarya spp from the atlantic rain forest

The essential oils from leaves of four Cryptocarya spp endemic in the Brazilian Atlantic rain forest were obtained by hydrodistillation and shown by GC-MS analysis to contain mono and sesquiterpenes. The major components of the oil of Cryptocarya moschata were linalool (34.3%), a-terpinene (17.0%), g-terpinene (10.4%), 1,8-cineole (5.8%) and trans-ocimene (4.8%), whilst those of C. botelhensis were a-pinene (22.7%), b-pinene (9.2%), trans-verbenol (8.4%), trans-pinocarveol (5.5%) and myrtenal (5.4%). The principal compounds of C. mandioccana oil were b-caryophyllene (13.8%), spathulenol (10.2%), caryophyllene oxide (7.8%), d-cadinene (6.9%) and bicyclogermacrene (6.4%), whilst those of C. saligna were germacrene D (15.5%), bicyclogermacrene (13.8%), spathulenol (11.8%) and germacrene B (5.7%).

HPLC-ESI-MS/MS analysis of oxidized di-caffeoylquinic acids generated by metalloporphyrin-catalyzed reactions

This paper reports an HPLC-ESI-MS/MS investigation on the oxidation of 3,5- and 4,5- dicaffeoylquinic acid using iron(III) tetraphenylporphyrin chloride as catalyst. Two major mono-oxidised products of the quinic acid moiety have been identified for both compounds. However, only the 4,5-derivative afforded two different tri-oxo products. Thus, it seems that the oxidation pattern depends on the number and positions of the caffeic acid moieties present in caffeoylquinic acid molecules.

Variabilidade sazonal e bioss��ntese de terpen��ides presentes no ��leo essencial de Lippia alba (Mill.) N. E. Brown (Verbenaceae)

The essential oil of the leaves of Lippia alba chemotype linalool-1,8-cineol was extracted by hidrodistillation at different seasons and analyzed by GC/MS. Qualitative and quantitative variations in regard to the period of harvesting have been performed and the results were correlated with meteorological data. The essential oil yield varied from 0.33 to 0.67%. The chemical diversity of the constituents increased throughout the year, being 1,8-cineol and linalool the major components. Possible biosynthetic routes of mono and sesquiterpenoids present in the essential oil are discussed.

Terpenos em cupins do g��nero Nasutitermes (Isoptera, Termitidae, Nasutitermitinae)

The chemical composition of the front gland of termites has been studied for over 40 years. The genus Nasutitermes, considered the most evolved of the Termitidae family, has a peculiarity that sets it apart from the others: a caste of soldiers that carry a terpenic mixture used in defense. This secretion is formed by mono, sesqui and diterpenes from trinervitane, kempane and rippertane skeletons, only found in termites. This article sought to review the scientific literature and contribute to the knowledge on the chemical composition of the secretion of the Nasutitermes soldiers from the interesting aspects of its behavior.

Epoxida����o do β-cariofileno com lipases imobilizadas em gel de ��gar

The immobilization of enzymes and microorganisms on solid supports has been developed in recent years. These biocatalysts may be used in organic media allowing their storage and reuse, thus reducing costs of the process. Herein, lipases from various sources were immobilized in agar gel and used as catalysts in the chemo-enzymatic epoxidation of β-caryophyllene. Several experimental parameters, such as the use of different organic solvents including ionic liquids, time, temperature, and agitation rate were evaluated. The mono-epoxide was obtained as a single product. The best result was achieved using immobilized F-AP15 lipase, forming the corresponding β-caryophyllene epoxide at a conversion of 96% in an 8h reaction at 35 ��C.

HS-SPME-GC-MS ANALYSIS OF VOLATILE AND SEMI-VOLATILE COMPOUNDS FROM DRIED LEAVES OF Mikania glomerata Sprengel

This paper reports on the identification of volatile and semi-volatile compounds and a comparison of the chromatographic profiles obtained by Headspace Solid-Phase Microextraction/Gas Chromatography with Mass Spectrometry detection (HS-SPME-GC-MS) of dried leaves of Mikania glomerata Sprengel (Asteraceae), also known as 'guaco.' Three different types of commercial SPME fibers were tested: polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB) and polyacrylate (PA). Fifty-nine compounds were fully identified by HS-SPME-HRGC-MS, including coumarin, a marker for the quality control of guaco-based phytomedicines; most of the other identified compounds were mono- and sesquiterpenes. PA fibers performed better in the analysis of coumarin, while PDMS-DVB proved to be the best choice for a general and non-selective analysis of volatile and semi-volatile guaco-based compounds. The SPME method is faster and requires a smaller sample than conventional hydrodistillation of essential oils, providing a general overview of the volatile and semi-volatile compounds of M. glomerata.

APROVEITAMENTO DE RES��DUO DE BIODIESEL PARA PREPARA����O DE CARV��ES ��CIDOS COM ELEVADA ATIVIDADE CATAL��TICA NA REA����O DE ETERIFICA����O DO GLICEROL

Environmentally friendly acid carbon (CG) catalysts, containing a high amount of sulfonated and oxygenated groups, were prepared from glycerin, a biodiesel waste. CGs were produced by glycerin carbonization in the presence of H2SO4 at 1:3 m:m ratio in a closed autoclave at 180ºC for different times: 0.25; 1; 3 and 6 hours (CG-0.25h; CG-1h; CG-3h and CG-6h, respectively). The catalyst properties for all carbons were evaluated in the glycerol etherification reaction with tert-butyl alcohol (TBA). The yield for mono-tert-butyl glycerol (MTBG), di-tert-butyl glycerol (DTBG) and tri-tert-butyl-glycerol (TTBG) was high and very similar for all CGs, of about 43% and 20% for the MTBG and DTBG + TTBG, respectively. Furthermore, the activity of these catalysts were close to those obtained using a commercial resin, Amberlyst-15, of about 50% and 27% for MTBG and DTBG + TTBG, respectively.

SYNTHESIS AND ANTIFUNGAL ACTIVITY OF PALMITIC ACID-BASED NEOGLYCOLIPIDS RELATED TO PAPULACANDIN D

A series of six new palmitic acid-based neoglycolipids related to Papulacandin D were synthesized in five steps, resulting in good yields, and they were evaluated against Candida spp. All twelve synthetic intermediates were also evaluated. The synthesis involved the initial glycosylation of two phenols (4-hydroxy-3-methoxybenzaldehyde and 3-hydroxybenzaldehyde) via their reaction with peracetylated glucosyl bromide. This was followed by deacetylation with potassium methoxide/metanol solution and the protection of two hydroxyls (C4 and C6 positions) of the saccharide unit as benzilidene acetals (10-11). The next step involved the acylation of the acetal derivatives with palmitic acid, thereby affording a mixture of two isomers mono-acylated at the C2 and C3 positions and a di-acylated product (12-17). After being isolated, each compound was subjected to the removal of the acetal protecting group to yield the papulacandin D analogues 18-23. Three compounds showed low antifungal activity against two species: C. albicans (compounds 7 and 23) and C. tropicalis (compound 17) at 200 ��g mL−1.

Biologia molecular do processo de infec����o por Agrobacterium spp.

Agrobacterium tumefaciens �� o agente causal da galha-da-coroa, doen��a que afeta a maioria das plantas dicotiledôneas e caracteriza-se pelo crescimento de tumores na jun����o entre o caule e a raiz (coroa). A forma����o desses tumores �� o resultado de um processo natural de transfer��ncia de genes de Agrobacterium spp. para o genoma da planta infetada. Esses genes est��o contidos em um plasm��dio de alto peso molecular (120 a 250 kb), denominado Ti ("tumor inducing"), presente em todas as linhagens patog��nicas de Agrobacterium spp. Duas regi��es do plasm��dio Ti est��o diretamente envolvidas na indu����o do tumor: a regi��o-T, que corresponde ao segmento de DNA transferido para a c��lula vegetal, e a regi��o de virul��ncia (regi��o vir), que cont��m genes envolvidos na s��ntese de prote��nas respons��veis pelo processo de transfer��ncia da regi��o-T. Esta regi��o, uma vez transferida e integrada no genoma da c��lula vegetal, passa a ser denominada de T-DNA ("transferred DNA"). Os genes presentes no T-DNA codificam enzimas envolvidas na via de bioss��ntese de reguladores de crescimento, auxinas e citocininas. A s��ntese desses reguladores pelas c��lulas transformadas causa um desbalan��o hormonal, levando �� forma����o do tumor no local da infec����o. Outro grupo de genes presentes no T-DNA codifica enzimas respons��veis pela s��ntese de opinas, que s��o catabolisadas especificamente pela bact��ria colonizadora, como fonte de nutrientes. O conhecimento preliminar das bases moleculares envolvidas no processo de infec����o de uma planta hospedeira por Agrobacterium spp., permitiu a utiliza����o desta bact��ria como vetor natural de transforma����o gen��tica de plantas.

Development of virus resistant transgenic papayas expressing the coat protein gene from a Brazilian isolate of Papaya ringspot virus

Translatable and nontranslatable versions of the coat protein (cp) gene of a Papaya ringspot virus (PRSV) isolate collected in the state of Bahia, Brazil, were engineered for expression in Sunrise and Sunset Solo varieties of papaya (Carica papaya). The biolistic system was used to transform secondary somatic embryo cultures derived from immature zygotic embryos. Fifty-four transgenic lines, 26 translatable and 28 nontranslatable gene versions, were regenerated, with a transformation efficiency of 2.7%. Inoculation of cloned R0 plants with PRSV BR, PRSV HA or PRSV TH, Brazilian, Hawaiian and Thai isolates, respectively, revealed lines with mono-, double-, and triple-resistance. After molecular analysis and a preliminary agronomic evaluation, 13 R1 and R2 populations were incorporated into the papaya-breeding program at Embrapa Cassava and Tropical Fruits, in Cruz das Almas, Bahia, Brazil.

Silicon and rice disease management

The element silicon (Si) is not considered an essential nutrient for plant function. Nevertheless, Si is absorbed from soil in large amounts that are several fold higher than those of other essential macronutrients in certain plant species. Its beneficial effects have been reported in various situations, especially under biotic and abiotic stress conditions. The most significant effect of Si on plants, besides improving their fitness in nature and increasing agricultural productivity, is the restriction of parasitism. There has been a considerable amount of research showing the positive effect of Si in controlling diseases in important crops. Rice (Oryza sativa), in particular, is affected by the presence of Si, with diseases such as blast, brown spot and sheath blight becoming more severe on rice plants grown in Si-depleted soils. The hypothesis underlying the control of some diseases in both mono- and di-cots by Si has been confined to that of a mechanical barrier resulting from its polymerization in planta. However, some studies show that Si-mediated resistance against pathogens is associated with the accumulation of phenolics and phytoalexins as well as with the activation of some PR-genes. These findings strongly suggest that Si plays an active role in the resistance of some plants to diseases rather than forming a physical barrier that impedes penetration by fungal pathogens.

Potencial do uso da restri����o h��drica em testes de sanidade de sementes de algodoeiro

Nos testes de sanidade, realizados por meio dos m��todos de incuba����o em papel de filtro e em meio agarizado, a germina����o r��pida das sementes dificulta a identifica����o dos fungos e pode comprometer a validade desses m��todos. Para impedir ou reduzir a germina����o de sementes de esp��cies dicotiledôneas, o uso de 2,4-D (sal de s��dio) tem sido a alternativa dispon��vel havendo, no entanto, questionamentos sobre este composto por in��meras raz��es, inclusive o aspecto toxicol��gico. Neste trabalho, o objetivo foi estudar a viabilidade do uso da restri����o h��drica como recurso para reduzir a germina����o das sementes em substitui����o ao 2,4-D. Foram utilizados os restritores h��dricos manitol e Cloreto de s��dio, nos potenciais -0,6, -0,8, -1,0 e -1,2 MPa, sendo avaliados seus efeitos sobre a germina����o das sementes, comprimento de pl��ntulas e crescimento micelial in vitro dos principais fungos associados a sementes de algodoeiro e seu desenvolvimento sobre as sementes no teste de incuba����o em papel de filtro. A restri����o h��drica proporcionada pelos solutos e potenciais osm��ticos testados foi capaz de reduzir a germina����o e o comprimento das pl��ntulas em n��veis considerados satisfat��rios para a an��lise sanit��ria de sementes de algodoeiro, al��m de n��o interferir na recupera����o dos principais fungos sobre as sementes no teste de papel de filtro, revelando-se desta forma como uma alternativa eficaz em substitui����o ao uso do 2,4-D. O crescimento micelial dos fungos em meio agarizado foi reduzido nos potenciais osm��ticos a partir de -0,6 MPa. A recupera����o dos fungos fitopatog��nicos atrav��s do teste de incuba����o em papel de filtro n��o foi afetada pelo m��todo da restri����o h��drica.

Rela����es lineares m��ltiplas entre deslocamentos qu��micos em RMN 13C de haletos alif��ticos

Os deslocamentos qu��micos de RMN 13C de carbonos a , b , g e d de 17 conjuntos de haletos (F, Cl Br e I) alif��ticos, inclusive compostos mono, bi e tric��clicos, podem ser reproduzidos por uma equa����o linear de duas constantes e duas vari��veis do tipo : d R-X = A*d R-X1 + B*d R-X2 onde A e B s��o constantes obtidas por regress��o multilinear a partir de deslocamentos qu��micos de 13C; d R-X, o deslocamento qu��mico de 13C do composto com halog��nio (R-X); d R-X1 e d R-X2 deslocamentos qu��micos de outros haletos. Para brometos (R-X) alif��ticos a melhor correla����o foi obtida com os dados de fluoretos (R-X1) e iodetos (R-X2) com R2 de 0,9989 e desvio m��dio absoluto (DM) de 0,39ppm. Para cloretos (R-X) a melhor correla����o foi com dados de brometos (R-X1) e iodetos (R-X2) com R2 de 0,9960 e DM de 0,76ppm. Para fluoretos (R-X) a melhor correla����o foi com brometos (R-X1) e iodetos (R-X2) com R2 de 0,9977 e DM de 1,10ppm e para iodetos (R-X) foi com fluoretos (R-X1) e brometos (R-X2) com R2 de 0,9972 e desvio m��dio absoluto de 0,60 ppm.