This thesis describes phytochemical studies on Buxus macowanii, a medicinal plant collected from South Africa and the fungal transformation of glycyrrhetinic acid (71), a triterpenoid found in Glycyrrhiza plants. The crude methanolic extract of B. macowanii was active in the acetylcholinesterase inhibition assay (IC50 = 30 μg/mL). Chemical investigation of its alkaline dichloromethane extract afforded five novel triterpenoidal alkaloids, 31-hydroxybuxatrienone (56), macowanioxazine (57), 16α-hydroxyma- cowanitriene (58), macowanitriene (59), and macowamine (60), along with two known Buxus bases, Nb-demethylpapillotrienine (61) and moenjodaramine (62). Compounds 56, 57, and 61 exhibited different level of AChE inhibitory activities with compound 56 being significantly active (IC50 = 8.0 μM). Glycyrrhetinic acid (71) was incubated with Curvularia lunata (ATCC 12017) for ten days to afford one metabolite which was characterized by NMR spectral data as known biotransformed product, 3-oxo-glycyrrhetinic acid (85). This metabolite was previously obtained through biotransformation of 71 by using other fungi.

No description available.

Thesis (MAppSc) -- University of South Australia, 1992

Hamburg, Techn. University, Diss., 2008.

Universiẗat, Diss.--Münster, 1994.

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Pavlostathis, Spyros G.; Committee Member: Huang, Ching-Hua; Committee Member: Hughes, Joseph B.; Committee Member: Sobecky, Patricia A.; Committee Member: Spain, Jim C.

Dresden, Techn. Universiẗat, Diss., 2008.

Thesis (doctoral)--Universiẗat, Jena, 2003.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 87-92).

Made available in DSpace on 2014-06-11T19:29:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-08-25Bitstream added on 2014-06-13T20:19:06Z : No. of bitstreams: 1 souza_dd_me_araiq.pdf: 1205391 bytes, checksum: efe0f12f0564d2daba3992d3a42bc863 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A biotransformação utilizando microorganismos é uma ferramenta útil para substituir uma reação química de difícil execução, sendo possível catalisar régio e enantioseletivamente uma extensa gama de substratos xenobióticos, sobretudo na produção de compostos de interesse comercial. Nesta pesquisa foi utilizado como agente da biotransformação o fungo do gênero Curvularia isolado de uma planta endêmica do cerrado brasileiro (Ocootea corimbosa) pelo grupo NuBBE do Instituto de Química da UNESP de Araraquara. O ensaio foi realizado em duas etapas, na primeira foi feita uma triagem sobre alguns substratos escolhidos com o objetivo de determinar quais substratos eram promissores para a ocorrência da biotransformação e o melhor tempo de ensaio para estes substratos. Na segunda etapa da pesquisa foram selecionados a canfora, o mentol e o limoneno como substratos promissores. Os experimentos foram realizados com o intuito de avaliar a biotransformação de forma a verificar a presença de produtos biotransformados pelo fungo. Dessa forma foi realizada, em cada ensaio, uma etapa semipreparativa, onde os produtos da biotransformação foram analisados e identificados em mistura. As análises foram realizadas por CG-EM e RMN-H1 e RMN-C13 obtendo-se sempre um padrão para comparação. Para o ensaio com o limoneno foi verificado a presença um derivado dihidroxilado (1,2 limoneno diol) atestando a capacidade do fungo em bioidroxilar substratos exógenos. Para o mentol foi isolado e identificado um metabolito secundário inédito na literatura, que não havia sido isolado em trabalhos posteriores utilizando o fungo Curvularia sp. Para a cânfora foi possível constatar, em mistura, a presença de derivados monohidroxilados do substrato de partida. Esse foi o primeiro trabalho de biotransformação utilizando fungos isolados de uma planta endêmica... / The biotransformation using microorganisms is a useful tool to substitute a chemical reaction of difficult execution, being been possible enantioselectiv to catalyze regal and an extensive xenobiotic substratum gamma, over all in the composite production of commercial interest. In this research fungi of isolated the Curvularia sort of an endemic plant of the Brazilian open pasture (Ocootea corimbosa) for the NuBBE group of the Institute of Chemistry of the UNESP of Araraquara was used as agent of the biotransformation. The assay was carried through in two stages, in the first one a selection on some substrata chosen with the objective was made to determine which substratct was promising for the occurrence of the biotransformation and optimum time of assay for these substract. In the second stage of the research they had been selected the camphor, menthol and the limonene as promising substract. The experiments had been carried through with intention to evaluate the biotransformação of form to verify the presence of products biotransformad for fungi. Of this form it was carried through, in each assay, a semipreparativ stage, where the products of the biotransformation had been analyzed and identified in mixture. The analyses had been carried through by CGEM and RMN-H1 and RMN-C13 getting itself always a standard for comparison. For the assay with the limonene one derivative was verified the dihydroxilation presence (1,2 limoneno diol) certifying the capacity of fungi in to biohydroxilation exogen substract. For menthol isolated and an unknown secondary metabolit in the literature was identified, that had not been isolated in posterior works using fungi Curvularia sp. For the camphor it was possible to evidence, in mixture, the presence of monohydroxilations derivatives of the departure substratum. This was the first work of biotransformation using fungis... (Complete abstract click electronic access below)