Sérgio Augusto de Loreto Bordignon

Benzopyrans from Hypericum polyanthemum

From the aerial parts of Hypericum polyanthemum Klotzsch ex Reichardt (Guttiferae), three chromenes, 6-isobutyryl-5,7-dimethoxy-2,2-dimethyl-benzopyran; 7-hydroxy-6-isobutyryl-5-methoxy-2,2-dimethyl-benzopyran and 5-hydroxy-6-isobutyryl-7-methoxy-2,2-dimethyl-benzopyran were isolated. Their structures were determined by NMR spectroscopic analyses.

Germination and growth inhibitory effects of Hypericum myrianthum and H. polyanthemum extracts on Lactuca sativa L.

Germination and growth inhibitory effects of ethanolic crude extracts of Hypericum myrianthum and H. polyanthemum aerial parts on lettuce (Lactuca sativa) were investigated. The germination was retarded in all the tested concentrations. After seven days the final germination percentage of the most concentrated extracts was significantly reduced by both extracts in comparison with the control. The radicles length was significantly affected showing necrosis. Both species present phenolic compounds as the main components and they could be responsible for the inhibition of the germination and growth of Lactuca sativa.

Anti-tumour Screening of Brazilian Plants

Organic and aqueous extracts of 145 Brazilian plants (538 extracts) from 34 families were evaluated for anti-tumour activity against the human tumour cell lines HT29 and NCIH460. Of the extracts tested, 117 (22%) demonstrated cytotoxicity against one or both of the cell lines at a concentration of 100µg/ml. Of special interest are the families Anacardiaceae, Annonaceae, Asteraceae, Celestraceae, Leguminosae (Fabaceae), Meliaceae and Myrtaceae, which contain a high proportion of active species. On the basis of these results we are further examining the cytotoxic species, with the objective of isolating and identifying the active phytochemicals. These results also confirm the continuing importance of natural product screening models, alongside targeted drug development, in the discovery of new anti-neoplastic pharmacophores.

Palinologia de níveis do Holoceno da Planície Costeira do Rio Grande do Sul (localidade de Passinhos), Brasil

Este trabalho apresenta os resultados da analise palinologica de 51 amostras obtidas em um testemunho de sondagem de 270 cm de espessura, realizado na localidade de Passinhos, municipio de Osorio, Planicie Costeira do Rio Grande do Sul, Brasil. Ao longo do perfil foram selecionadas tres amostras para datacao com 14C e a mais basal forneceu uma idade de 10.600±90 anos A.P. Foram identificados 71 palinomorfos, agrupados conforme seus respectivos habitos e/ou habitats e tratados estatisticamente de modo a fornecer diagramas polinicos de porcentagem e concentracao. As quatro zonas palinologicas identificadas evidenciam a gradativa colmatacao de um lago e as mudancas vegetacionais dai decorrentes e, finalmente, os efeitos da colonizacao humana. Permitiram, ainda, sua correlacao com dados anteriores, obtidos em outras areas da Planicie Costeira. Palavras-chave: Palinologia, Holoceno, Rio Grande do Sul, Brasil.

Palynological analysis of a late Holocene core from Santo Antônio da Patrulha, Rio Grande do Sul, Southern Brazil

A sedimentar core collected at Santo Antônio da Patrulha, Rio Grande do Sul State, southmost Brazil, was submitted to pollen analysis to provide the vegetational history of this region, and the paleoecological and paleoclimatic changes. A total of 98 taxa of palynomorphs was identified from 35 subsamples. Three radiocarbonic datings were obtained along a section of 115 cm depth, including the basal age of 4730 ± 50 yr BP. Pollen diagrams and cluster analysis were performed based on palynomorphs frequencies, demonstrating five distinct phases (SAP-I to SAP-V), which reflected different paleoecological conditions. The predominance of plants associated with grasslands in the phase SAP-I suggests warm and dry climate conditions. A gradual increasing of humidity conditions was observed mainly from the beginning of the phase SAP-III, when the vegetation set a mosaic of grasslands and Atlantic rainforest. Furthermore, the presence of some forest taxa ( Acacia-type, Daphnopsis racemosa, Erythrina-type and Parapiptadenia rigida-type), from the phase SAP-IV, is interpreted as an influence of the seasonal semideciduous forest in the study region. From the phase SAP-V (ca. 4000 yrs BP), the vegetation became similar to the modern one (extant Atlantic rainforest Biome), especially after 2000 yrs BP (calibrated age).

Screening of Brazilian plants for the presence of peroxides

Chloroform or dichloromethane extracts of 357 southern Brazilian plant species were tested for the presence of peroxides by thinlayer chromatography, using the spray reagent from Huber & Frohlke. From the species tested, 71 (20%) showed positive results and most of them (56%) are Asteraceae species. The species tested were mainly from Asteraceae, but 55 more families were screened, in a total of 77 genera surveyed.

Late Holocene Vegetation History and Early Evidence of Araucaria angustifolia in Caçapava do Sul in the Lowland Region of Rio Grande do Sul State, Southern Brazil

Little is known about the southernmost occurrence of small areas with Araucaria angustifolia populations in Cacapava do Sul in low elevated areas of Rio Grande do Sul State, about 130 km to the south of to the highlands of southern Brazil where the main distribution of Araucaria is found. This occurrence is about 130 km further south to the main area of Araucaria angustifolia which is on the highlands in southern Brazil. The question is whether this occurrence is natural, due to indigenous peoples, or due to plantation by post-Columbian settlers. To trace the origin of this little known southernmost existence of Araucaria angustifolia trees is of particular interest for conservation issues. To address this question we did a vegetation survey and studied a 150 cm-long radiocarbon dated sediment core from the Fazenda da Monica by pollen analysis. The vegetation survey of the study area indicates that also other typical taxa of the Araucaria forest as well as the Atlantic lowland rainforest are found in the present-day semi-deciduous forest, such as Podocarpus, Ilex, Myrsine and Prunus for the former, and Alchornea, Moraceae, Arecaceae, and Myrtaceae for the later. The pollen record, due to bad pollen preservation, starts only after 44 cm core depth, which is about 515 cal yr BP old (AD 1490), indicating that Araucaria angustifolia as well as other Araucaria forest and Atlantic rainforest taxa occurred in this area since the beginning of the pollen record. The occurrence of these taxa can be seen as natural and not introduced during the post-Columbian colonisation. First settlers at the beginning of the 19th century reduced existing population of Araucaria markedly and in particular since about AD 1950. The population of Araucaria angustilfolia before the post-Columbian settlement was much larger than today.