Prospecção de plantas aromáticas na região do médio e baixo Solimões.

Abstract

The vast Amazon region is composed by various ecosystems resulting in a great diversity of species. Its dimensions impose restrictions on the access to many of its resources, keeping them unknown as sources of a great potential for discovery and production of natural products, and sources of raw materials for various industry sectors which can generate resources for local traditional populations in a sustainable way. This paper was made under the auspices of the PIATAM project, which studied species occurring in the region of middle and lower Solimões River, found in lowland, flooded, lake and land ecosystems. Focusing on the objective of phytochemical studies guided by the pursuit of essential oils (EOs), antileishmanial, antitumoral, antioxidant substances and inhibitors of acetylcholinesterase, samples were taken from specimens, looking for aromatic plants and in some cases plants for medicinal purposes. Over 88 species were collected; the samples produced more than 300 fractionated samples from the 78 botanically identified species, which are distributed in 32 families and 57 genera, mainly concentrated in the Lauraceae (15 species), Annonaceae (7), Fabaceae (7), Piperaceae (6), Lamiaceae (5) and Verbenaceae (4) families. A total seventyone EOs were extracted from: branches (19), leaves (37), bark (6), wood (2) and other plant parts (7); forty-eight ethanolic extracts were also obtained from: branches (16), leaves (17), roots (2), bark (10) and other parts (3). The EOs were extracted by hydrodistillation and seventy-eight of them were analyzed by gas chromatography coupled to mass spectrometry (GC-FID, GC-MS) for the determination of their chemical compositions. Twenty-five of the analyzed EOs were chemically identified and are presented here. Among the identified substances, a large percentage (44.09%) corresponded to sesquiterpene hydrocarbons; the oxygenated monoterpenes represented 24.12%, oxygenated sesquiterpenes 16.56%, monoterpene hydrocarbons 7.87%, and other classes of substances 7.35%. The substance most frequently observed was β-pinene. The best EO yields were observed in the species Piper tuberculatum (2.44%) and Calyptranthes spruceana (2.31%); the leaves were the plant parts that showed better EO and ethanolic extract yields. Some EOs were evaluated for antiparasitic activity against Leishmania amazonensis; a higher activity was observed in EOs consisting predominantly of sesquiterpenes, especially the EOs obtained from the leaves of louro mamuí (IC50 = 28.6 μg / mL). Against Trypanosoma cruzi, Alpinia speciosa had the best LC50 (4.5 μg / mL) followed by Epaltes sp. (5.5 μg / mL). Two major constituents of these two species: terpinen-4-ol (Alpinia speciosa, 29%) and α-gurjunene (Epaltes sp., 12.3%) can be contributors to the significant trypanosomicide activities observed. To evaluate the antioxidant potential of extracts and EOs, assays were performed using DPPH; extracts showed better inhibitory concentrations (IC50) than EOs, the better IC50 being found in the extracts from C. spruceana and Ouratea discophora (5.85 and 7.01 μg / mL, respectively), highlighting also: Nectandra cuspidata (bark: 8.64 μg / mL), Pleurotherium parviflorum (bark: 9.84 μg / mL), Lauracea spp. (bark: 10.72 μg / mL) and Ocotea cernua (bark: 11.81 μg / mL). The antioxidant activity was higher in extracts of bark, followed by extracts of branches, with a lower expression in extracts of leaves. The acetylcholinesterase inhibitory activity was observed in several of the tests performed, highlighting the EO obtained from branches of Nectandra amazonum and the extract of C. spruceana. Several plant extracts used in folk medicine were tested in a single dose of 50 μg / mL regarding the inhibition of tumor cell growth: SF-295 (human glioblastoma), HCT-8 (human colon) and MDAMB-435 (human breast); the bark extract from Himatanthus sucuuba presented some of the best inhibition percentages, respectively: 43.07, 65.87 and 63.25%.