Estudo estrutural e farmacognóstico de Scutellaria agrestis A. St.-Hil. ex Benth. (Lamiaceae): uma planta medicinal utilizada por populações ribeirinhas do Amazonas

Abstract

Scutellaria agrestis (trevo-roxo) is a plant widely used by the riverine population of the Amazon state in the treatment of earaches, fever, diarrhea and high blood pressure. This work aimed to perform anatomical, histochemical, pharmacological and phytochemical analysis of the vegetative organs of S. agrestis, in order to investigate the active principle of this plant. Individuals of S. agrestis were collected in two locations, the first of them being the riverine communities Nossa Senhora das Graças and Nossa Senhora de Nazaré, located in the Solimões river, in Manacapuru, state of Amazonas, and the second one, the medicinal garden of Nilton Lins University, in Manaus, Amazonas state. Samples of vegetative organs were processed according to usual techniques of light microscopy and scanning electron microscopy for anatomical study of the plant and ontogenetic study of plant trichomes. The metabolites synthesized by secretory structures were detected and histolocalized by phytochemical and histochemical tests. An aqueous extract was prepared from the leaf of the studied species and experiments were performed to investigate the acute toxicity in vivo and in vitro, and the analgesic and/or anti-inflammatory actions in vivo. Numerous glandular trichomes are seen in both leaf and stem of S. agrestis. The epidermis of the vegetative organs of this plant contains anthocyanins in the vacuole, except for the adaxial leaf epidermis. The leaf is amphihypostomatic, with diacitic stomata. The leaf blade has uniseriate epidermis, dorsiventral mesophyll and hydathodes are present along the margin. The midrib has a plan- convex shape, with vascular tissue arranged in an open arc. The petiole has a concave-convex shape, collateral vascular system. The stem is square-shaped with prominent vertices, evident endoderm, collateral vascular system and parenchymatous pith. The root is protostelic, with endoderm highlighted by suberified Casparian strips; cells of exodermis, cortex and endodermis have mucilage and phenolic content. The ontogeny of trichomes of S. agrestis follows the pattern for the family. The secretory structures responsible for the synthesis of substances are peltate and capitate glands and the secretory epidermis. Such structures are the site of secretion of the active principle of the plant, producing phenols (phenols, hydrolysable tannins, coumarins and several classes of flavonoids such as anthocyanins, anthocyanidines, chalcones, aurones, flavones, flavonols, xanthones, leucoanthocyanidines, flavanones, flavanonols), terpenes (essential oils, free steroids, saponins), total lipids, proteins and acids. The aqueous extract of S. agrestis leaf showed analgesic and anti-inflammatory response to the pain signal, but does not present antiedematogenic activity and has no toxic components, so it is a vegetal drug with scientific support, giving a toxicological margin of safety for the improvement of studies with this species. The results of this research provide botanical and pharmacognostic data, contributing to the knowledge of this plant biology. Keywords: trevo-roxo, ontogeny of secretory structures, histochemistry, phytochemistry, biological assays.