This paper presents a first approximation of net CO2 fluxes from mineral soil due to land use, land‐use changes and forestry (LULUCF) activities in Brazil for the periods 1970–90 and 1975–95. The methodology employed is an adaptation of the approach proposed by the IPCC in ‘Revised 1996 guidelines for national greenhouse gas inventories’, which is based on the variations in soil C stocks as a function of changes in land‐use activities. The calculation was done separately for each Brazilian state and subsequently summarized for all of Brazil. The annual fluxes for Brazil indicate a net emission of CO2 to the atmosphere, which decreased from 93.3 Tg CO2 for the period 1970–90 to 46.4 Tg CO2 for the period 1975–95. This corresponded to yearly net emission rates of 11.0 g CO2 m−2 year−1 for the 1970–90 period and 5.5 g CO2 m−2 year−1 for the 1975–95 period. Within each administrative region, considerable differences in the yearly emission rates between the states could be observed. Several sources of uncertainties could be identified. The most important uncertainties were linked to the impact factor values, which represent changes in native C stock associated with conversion of the native vegetation to agricultural use.
No presente trabalho descreve-se a composição química dos óleos essenciais de Rollinia leptopetala R.E. Fries (Annonaceae) e as atividades larvicidas dos óleos essenciais, do extrato metanólico das raízes desta espécie e do alcalóide oxoaporfinico, liriodenina (1), frente às larvas no terceiro estágio do mosquito Aedes aegypti. O extrato metanólico mostrou-se ativo com CL 50 64,6 ± 1,5 ppm e uma forte atividade foi exibida para o composto (1), CL 50 3,6 ± 0,4 ppm. Os óleos essenciais das folhas e galhos também mostraram atividade com CL 50 104,7 ± 0,2 and 34,7 ± 0,3 ppm, respectivamente. Estes dados sugerem que R. leptopetala é fonte potencial de larvicidas naturais. A composição química do óleo essencial e as atividades descritas são comunicadas pela primeira vez.The aim of present study was to describe the chemical composition of the essential oils from the leaf and stem of Rollinia leptopetala R. E. Fries (Annonaceae) and to evaluate the larvicidal activities of these essential oils, of the methanol extract from roots of this plant and of the oxoaporphine alkaloid, liriodenine (1) against the third-instar of Aedes aegypti larvae. The methanol extract from the roots showed larvicidal activity with LC 50 64.6 ± 1.5 ppm. Higher activity was observed for the isolated alkaloid liriodenine (1), LC 50 3.6 ± 0.4 ppm. The essential oils from the leaves and stems, also exhibited larvicidal activity with LC 50 104.7 ± 0.2 and 34.7 ± 0.3 ppm, respectively. These results suggest R. leptopetala as a source of natural larvicidal compounds. This is the first report about the chemical composition and larvicidal activity of the leaf and stem essential oils of R. leptopetala. Keywords: Rollinia leptopetala, Annonaceae, essential oils, liriodenine, Aedes aegypti IntroductionAedes aegypti is the principal mosquito vector of dengue fever, including the hemorrhagic form, which is endemic to South East Asia, Central and South America, and West Africa.1 Between 50 and 100 million of cases are registered each year, causing thousands of deaths. 2The disease has high levels of mortality, and also inflicts great economic losses and social disruption in Brazil. Although some viral diseases, such as yellow fever, have been brought reasonably under control with a vaccine, no vaccine is so far available for dengue. Today, the only way of decreasing the incidence of this disease is by controlling the Aedes aegypti proliferation. This is not an easy task because the mosquitoes have developed resistance to the current synthetic insecticides that, in addition, are toxic to humans and the environment. The mosquito population control in the larval stage is much easier than in the adult Chemical Composition and Larvicidal Activity of Rollinia leptopetala (Annonaceae) J. Braz. Chem. Soc. 376 stage, and then new strategies are needed for controlling the proliferation of the larvae of A. aegypti. Several studies have focused on natural products as insecticides for controlling A. aegypti larvae. Alkaloids and essential oils from herbal plants have ...
A reatividade e estereosseletividade apresentadas por uma nova cepa de Candida tropicalis na redução de cetonas pró-quirais foram comparadas com cepas de microrganismos, estudadas em nosso laboratório, provenientes da biodiversidade brasileira. Neste caso, Candida tropicalis demonstrou-se como um agente redutor versátil e estereosseletivo na biorredução de uma série de cetonas aromáticas. Estes compostos pró-quirais foram convertidos aos correspondentes álcoois opticamente ativos com moderada a excelente estereopreferência dependendo da estrutura do substrato. Entre as cetonas utilizadas, as nitroacetofenonas foram enzimaticamente reduzidas aos correspondentes (S)-álcoois enantiopuros com completa conversão.The reactivity and stereoselectivity showed by a new strain of Candida tropicalis in the reduction of prochiral ketones have been compared with the ones previously attained in our laboratory using microorganisms from the Brazilian biodiversity. In this manner, Candida tropicalis has demonstrated its versatility as stereoselective agent in the bioreduction of a series of aromatic ketones. These prochiral compounds were converted into their corresponding optically alcohols with moderate to excellent stereopreference depending on the substrate structure. Among ketones tested, nitroacetophenones were enzymatically reduced to enantiopure (S)-alcohol with complete conversion. Keywords: alcohol dehydrogenases, biocatalysis, Candida tropicalis, ketones, yeast IntroductionChiral alcohols are an important class of organic substrates due to their properties as bioactive compounds and as starting materials for the synthesis of various biologically active materials.1 For example, enantiopure 1-phenylethanol is a chiral building block used in the fine chemical and pharmaceutical industries as an ophthalmic preservative, a solvatochromic dye, an inhibitor of cholesterol intestinal absorption and a mild floral fragrance. 2 In the synthesis of enantiopure chiral secondary alcohols, prochiral ketones are commonly used as starting materials using stereoselective chemical transformations or biocatalytic methods. Asymmetric reduction by chemical methods usually involves the use of expensive reagents or heavy metal catalysts.3 By contrast, biocatalysis applied to industrial processes has been shown as a very advantageous alternative to conventional chemical methods, and is widely used for the preparation of enantiomerically pure pharmaceuticals and other high added value compounds. 4 Enzymatic reduction of carbonyl groups represents one of the most important reactions employed in the synthesis of chiral alcohols. Enzymes that can be used for this transformation are oxidoreductases, which require the presence of a coenzyme, such as NADH or NADPH, which transfers the hydride anion to the carbonyl compound, being formed NAD + or NADP + . Whole cells of microorganisms can be also used in the enzymatic reduction of the carbonyl group. Each cell represents a small factory fully equipped for the reduction of the substrate bearing Candida...
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