published_or_final_version / Chemistry / Master / Master of Science

Tropical forests contain the greatest biotic diversity of any biome, and those of South-east Asia are amongst the most diverse and tree species rich. I studied the speciose understorey tree genus, Aporosa (Euphorbiaceae), at two c. 50 ha plots in Malayisa, at Lambir Hills National Park, Sarawak, and at Pasoh Forest Reserve Peninsular Malaysia, where 17 and 12 species co-occur, respectively. The aim of this study was to determine which factors influence the spatial distribution of Aporosa species, what limits their abundance, and ultimately what are the mechanisms of coexistence among the species of this genus. Using a method of second-order spatial pattern analyses based on Ripley's K function to test for non-random spatial distributions, and to test for spatial associations between species (using a bivariate method) I found that Aporosa species formed spatially distinct assemblages at both sites. A randomization procedure suggested that these assemblages were explained by biases in the distribution of species in relation to habitat types. Soil type, as determined by parent material, was an important determinant of habitat preferences, although topography and forest stmcture also accounted for some variation. I found measurable effects of position on soil and especially topographic types on mortality and recruitment rates of many Aporosa species. Growth rates over a 5-8 year period varied between species, but, perhaps due to the short time interval and the correlation between abiotic variables, they were a poor indicator of habitat preference as defined by bias in a species' distribution. Aporosa species exhibit a range of morphological, anatomical and biochemical properties, and I found evidence that both habitat partitioning and density-dependent mortality of juveniles occurred. These are both mechanisms contributing to the maintenance of species richness. A severe drought had differential effects on mortality rates of Aporosa species and may be important in determining species' spatial distributions and abundance. Therefore disturbance events are also likely to be important mechanisms, as are non-equilibrium random population fluctuations, between ecologically similar species.

Thesis (M. Sc.)--University of Hong Kong, 1968. / Typewritten.

Thesis (M. Sc.)--University of Hong Kong, 1968. / Typewritten.

No description available.

No description available.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1951. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Inaugural dissertation (Ph. D.)--Vereinigten Friedrichs-Universität Halle - Wittenberg. / Bibliography : p. [51]

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Submitted by Pedro Barros (pedro.silvabarros@ufpe.br) on 2018-08-29T21:29:27Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Jéssica de Andrade Gomes Silva.pdf: 2120791 bytes, checksum: f8dff5a8f7f03f7a24db2d78615fe1f1 (MD5) / Approved for entry into archive by Alice Araujo (alice.caraujo@ufpe.br) on 2018-09-10T19:23:08Z (GMT) No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Jéssica de Andrade Gomes Silva.pdf: 2120791 bytes, checksum: f8dff5a8f7f03f7a24db2d78615fe1f1 (MD5) / Made available in DSpace on 2018-09-10T19:23:08Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Jéssica de Andrade Gomes Silva.pdf: 2120791 bytes, checksum: f8dff5a8f7f03f7a24db2d78615fe1f1 (MD5) Previous issue date: 2017-07-20 / CAPES / Croton heliotropiifolius Kunth constitui uma espécie endêmica do Nordeste Brasileiro. É popularmente conhecida por suas propriedades medicinais de alívio da dor de estômago, na disenteria e antitérmico. O presente trabalho avaliou o estudo fitoquímico e biológico do extrato metanólico de folhas de C heliotropiifolius. Investigações fitoquímicas foram realizadas por cromatografia em camada delgada, cromatografia líquida de alta eficiência, espectrofotometria de UV-visível e espectroscopia de Infravermelho por Transformação de Fourier (FT-IR). Para as atividades biológicas, foram empregados os métodos de difusão em ágar na a avaliação antimicrobiana, o método de sequestro de radicais livres usando o DPPH (2,2-difenil-1-picril-hidrazil) para a atividade antioxidante e as atividades citotóxicas foram analisadas através do método MTT (brometo de 3-(4,5-dimetiltiazol-2-il)-2,5-difeniltetrazólio em linhagens tumorais e para a investigação da capacidade citotóxica contra eritrócitos, foi realizado o ensaio hemolítico in vitro de fragilidade osmótica, seguido de análise morfológica dos eritrócitos. Análises fitoquímicas do extrato por cromatografia em camada delgada e líquida de alta eficiência identificaram a presença de compostos fenólicos: flavonoides (ácido gálico) e taninos hidrolisáveis. Foi demontrada a ausência de alcaloides, cumarinas e saponinas. Bem como, no espectro de UV-visível e de infravermelho do extrato, que demosntram bandas de absorção em 268, 316, 406 nm e 1661 cm⁻¹, respectivamente; o que validou os achados cromatográficos. Nos ensaios biológicos, a avaliação antimicrobiana contra cepas Staphylococcus aureus (ATTCC 12692) e Candida albicans (ATCC-76645) mostrou resistência ao extrato. Na atividade antioxidante foram demonstrados valores de 10,67%, 13,92%, 20,31 % com nível de significância de p<0,001. A atividade citotóxica mostrou baixo percentual de inibição celular para as linhagens tumorais NCI-H292, MCF-7, Hep-2 e moderado para HL-60. A investigação da capacidade citotóxica contra eritrócitos apresentou baixa atividade hemolítica, tendo a maior concentração (1000 μg/mL) exibido percentual de 2,95% e significância de p<0,001. A morfologia dos eritrócitos manteve-se preservada. Deste modo, a espécie C. heliotropiifolius demonstrou baixo nível de citotoxicadade, capacidade antioxidante e presença de compostos fenólicos, o que possibilita o isolamento do ácido gálico em estudos futuros. / Croton heliotropiifolius Kunth is an endemic species of the Brazilian Northeast. It is popularly known for its medicinal properties of relief of stomach pain, dysentery and antipyretic. The present work evaluated the phytochemical and biological study of the methanolic extract of leaves of C heliotropiifolius. Phytochemical investigations were performed by thin-layer chromatography, high performance liquid chromatography, UV-visible spectrophotometry and Fourier Transform Infrared (FT-IR) spectroscopy. For the biological activities, agar diffusion methods were used in the antimicrobial evaluation, the free radical sequestration method using DPPH (2,2-diphenyl-1-picrylhydrazyl) for the antioxidant activity and the cytotoxic activities were Were analyzed by MTT (3- (4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide in tumor cell lines and for the investigation of cytotoxic capacity against erythrocytes, the in vitro hemolytic assay of osmotic fragility , Followed by a morphological analysis of the erythrocytes Phytochemical analyzes of the extract by high efficiency liquid and thin layer chromatography identified the presence of phenolic compounds: flavonoids (gallic acid) and hydrolyzable tannins The absence of alkaloids, coumarins and saponins was demonstrated. As in the UV-visible and infrared spectra of the extract, which show absorption bands at 268, 316, 406 nm and 1661 cm⁻¹, respectively. Which validated the chromatographic findings. In the biological assays, antimicrobial evaluation against strains Staphylococcus aureus (ATTCC 12692) and Candida albicans (ATCC-76645) showed resistance to the extract. In the antioxidant activity, values of 10.67%, 13.92%, 20.31% were demonstrated, with a significance level of p <0.001. Cytotoxic activity showed a low percentage of cell inhibition for the NCI-H292, MCF-7, Hep-2 and moderate to HL-60 tumor lines. Investigation of the cytotoxic capacity against erythrocytes showed low hemolytic activity, with the highest concentration (1000 μg / mL) presented a percentage of 2.95% and significance of p <0.001. The erythrocyte morphology remained preserved. In this way, the C. heliotropiifolius species showed low levels of cytotoxicity, antioxidant capacity and the presence of phenolic compounds, which makes it possible to isolate gallic acid in future studies.