Silvia de Sousa Freitas

Phytochemistry and quantification of polyphenols in extracts of the Asteraceae weeds from Diamantina, Minas Gerais state, Brazil

Plantas daninhas Asteraceae sao ricas em substâncias quimicas com atividades biologicas e farmaceuticas. Os objetivos deste trabalho foram descrever a fitoquimica e quantificar os polifenois em extratos etanolicos de folhas de 12 especies de plantas daninhas Asteraceae coletadas em Diamantina, Minas Gerais, Brasil. A triagem de extratos de Asteraceae revelou a presenca de taninos, esteroides, triterpenos, antocianinas e flavonoides. O conteudo de fenois totais foi alto para extratos de Lychnophora ericoides (147,97 ± 2,66), Lepidaploa lilacina (141,11 ± 1,99) e Eremanthus elaeagnus (134,61 ± 7,81) e baixo em extratos de Lychnophora ramosissima (32,65 ± 0,70) e Lychnophora sp. (54,03 ± 0,73). Extratos de plantas daninhas Asteraceae de Diamantina podem ter potencial em estudos biologicos que estao a procura para pesticidas e drogas.

Decomposition Dynamics of Typha angustifolia under Aerobic Conditions

The study of the Typha species has gained attention in tropical areas due to their rapid growth, nutrient release, and contribution to detritus in lakes. Analysis of the degradation of Typha angustifolia has shown that the first stage of decomposition is marked primarily by the release of soluble compounds, indicating that microorganisms have a minor influence at this stage. In subsequent stages, microorganisms act by degrading and consuming phenolic compounds and phosphorus. The remaining compounds form humic substances and are retained in the detritus. Thus, microorganisms significantly degrade organic matter, resulting in a two-fold increase in decomposition. Different forms of phosphorus could be detected in the remaining mass by 31P NMR (nuclear magnetic resonance). By comparing the 31P NMR data between the samples with and without the antibiotic, we can better understand the slow decomposition process of Typha angustifolia.

Effects of astilbin from Dimorphandra mollis (Fabaceae) flowers and Brazilian plant extracts on Sitophilus zeamais (Coleoptera: Curculionidae)

Abstract Botanical extracts can be an alternative to synthetic insecticides for pest management, owing to their efficiency and environmental safety. The lethal times (LT50 and LT90), loss of grain weight, and repellence of Sitophilus zeamais (Coleoptera: Curculionidae) were evaluated when extracts from 5 plant species from the Brazilian Cerrado biome [Adenocalymma nodosum (Bignoniaceae) leaves, astilbin from Dimorphandra mollis (Fabaceae) flowers, Psychotria prunifolia (Rubiaceae) leaves, Senna obtusifolia (Fabaceae) leaves, and Tithonia diversifolia (Asteraceae) flowers] were applied to a surface and to food. The weevils exposed to a surface treated with extracts from T. diversifolia flowers (106.43 h) and P. prunifolia leaves (119.68 h) at 2% (m.v-1) presented the lowest LT50 and LT90 values, respectively. Corn grains treated with the extract from P. prunifolia leaves at 2% (w.w-1) exhibited fastest mortality of S. zeamais individuals with lower values of LT50 and LT90 than the other treatments. All the botanical extracts repelled S. zeamais after 30 min of application; however, the extracts from S. obtusifolia leaves, P. prunifolia leaves, and T. diversifolia flowers at 2% (m.v-1) repelled this insect after 6 min. Moreover, at 90 and 120 min after the beginning of the experiment, the extracts from P. prunifolia leaves and T. diversifolia flowers repelled the adult weevils. The extracts from A. nodosum leaves, P. prunifolia leaves, and T. diversifolia flowers applied to corn grains showed class III repellency according to the Preference Index for S. zeamais and less grain weight loss, when compared with astilbin from D. mollis flowers and S. obtusifolia leaves. Therefore, it was concluded that the extracts from T. diversifolia flowers and P. prunifolia leaves were the most promising in controlling S. zeamais, with the potential for application in programs for the integrated management of this pest.