Seasonality of the biological potential of extracts of Merostachys neesii Rupr. (Poaceae: Bambusoideae)

• Ano de defesa: 2019
• Autor(a) principal: Moreira, Fernanda Anselmo
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Anticholinesterase activity; Antioxidant activity; Atividade anticolinesterásica; Atividade antioxidante; Bambusoideae; Flavonoid; Flavonoide; Nutritional value; Sazonalidade; Seasonality; Valor nutricional
• Link de acesso: http://www.teses.usp.br/teses/disponiveis/41/41132/tde-05032020-091446/

Bamboos have been used as a food resource and for the treatment of diseases for centuries. In regions where fodder is scarce in some seasons, these grasses can be used as supplementary forage. Furthermore, bamboo shoots are a very popular food in Asian cuisine and have received increasing attention due to their nutritional value and health benefits. Bamboo culms and leaves are also nutritionally important. Culms have been used as a source of fiber for food supplements, while bamboo leaf extract (AOB, antioxidant of bamboo leaves extract) has been certificated as a natural food antioxidant. The main bioactive constituents in these plants are phenolic compounds, mainly phenolic acids and flavones C-glycosides. Several factors are known to affect the production of secondary metabolites, including seasonality. Thus, the knowledge of how seasonal changes can affect secondary metabolite content and, consequently, the biological potential of plant extracts is important in the study of medicinal plants. Brazil has one of the largest diversity of bamboo species in the world and is the center of diversity of many genera, among them Merostachys Spreng. This genus has 53 species (47 natives) and so far, only three species have been studied regarding their chemical composition and biological activity. Thus, M. neesii, an endemic bamboo species from the Atlantic Rain Forest, was chosen for this study. The main objectives of this study were to contribute to the phytochemical knowledge of the Brazilian native flora, to help in the search for bioactive compounds and to contribute to the understanding of how seasonality can affect the production of secondary metabolites. As the main results, it was observed that M. neesii presented similar chemical composition to other bamboo species. Were identified 65 compounds, most of them described for the first time for the genus. The main classes of compounds found were soluble carbohydrates, organic acids, catecholamines, fatty acids, phytosterols, triterpenes (lupenone), and flavonoids, especially flavones C-glycosides derived from apigenin and tricin. The evaluation of the nutritional composition of M. neesii revealed that this species has potential as supplementary forage as well as a food additive. Moreover, extracts of this species, especially leaf infusion, showed antiradicalar and iron-reducer activity. However, these extracts exhibited low acetylcholinesterase inhibitory activity. Regarding seasonal changes, there was no significant difference between seasons on the nutrient contents, except for the lipid content of leaves that was higher in the rainy season than in the dry season. There were some variations among harvestings for phytosterol, flavonoid contents, and antioxidant activity, but there was no clear variation pattern. Thus, climate factors were not relevant to determine these changes. Finally, there was a moderate correlation between antioxidant activity and flavonoids for culms. Other classes of phenolic compounds, probably phenolic acids, may be involved in the antioxidant activity, especially in leaf infusion, which was the most active extract. Although phenolic acids were detected in leaf and culm extracts, they were not evaluated in the present study. Thus, further studies on phenolic composition should be performed for a better understanding of the antioxidant activity of these extracts, as well as their phenolic composition