Estudo fitoquímico e avaliação das atividades antimicrobiana e tripanocida das flores e folhas de Combretum lanceolatum Pohl ex. Eichler (Combretaceae)

Abstract

The most numerous genus of the family Combretaceae is Combretum, with approximately 370 species. Pharmacological studies on extracts of these species had display antioxidant activity, anti-diabetic, anti-inflammatory, antifungal and anticancer properties, showing great pharmacological potential for this family. Phytochemical studies of plants of the genus, showed a wide range of secondary metabolites, including triterpenes, flavonoids, lignans among others. Combretum lanceolatum Pohl specie occurs from north to south of Brazil, and also in Paraguay, popularly known as “mel de pomba”, “pombeiro vermelho” and “remela de macaco”. From the chemical-pharmacology point of view, the species is little known. Previous studies in the crude ethanolic extract of flowers of C. lanceolatum, in our group research and coworkers, showed high antidiabetic activity, besides the presence of flavonoids, quercetin-3-O-methyl quercetin, isorhamnetin, and dilenetina. Motivated by these results and by the diverse range of pharmacological activity described in the genus, this work aims to carry out chemical studies, as to isolate and identify the fraction (s) / substance (s) correlating their pharmacological aspects. The plant material (leaves and flowers) were extracted with EtOH. The crude ethanol extract (EBEtOHF1 e EBEtOHF2) were suspended in MeOH: H2O (3: 1, 1L) solution and subjected to partition with solventes, followed by serial column chromatography on silica gel, providing the isolation/identification of 10 compounds: new cycloartane triterpenes: Lanceolatoside I, II, III, IV, V and VI and 4 known flavonoids: quercetin, 3- O-methyl-quercetin, isoramnetin and dilenetin. Trypanocidal activity was performed by in vitro assays of intracellular amastigote forms of T. cruzi using inhibition tests with benzonidal. EBEtOHF1 and EBEtOHF2 had a significant IC50 value: 73.16% (± 1.25) for EBEtOHF2 and 84.16% (± 1.15) for EBEtOHF1 compared to benzonidazole [87.25% (± 1.05)]. FHMeOH was inactive. The FAcOEt presented extremely high activity, being 97.54 (± 0.23), above of the standard drug used. The FDCM presented considerable activity, with 68.65 (± 1.70). The IC50 values for the isolated compounds tested, in the concentration of 50 μg/mL: quercetin (114), isoramnetina (115), 3-O-methylquercetin (116) and dilenetin (117) were respectively, 80.98% (± 2.61), 78.05% (± 2.18), 88.03% (± 0.33) and 85.70% (± 1.27) compared to the benzonidazole standard 87.25% (± 1.05). The EBETOHF1, FDCMF1, FDCMF2 and FT show strong active against two pathogens: S. aureus and K pneumonia, and presented moderate activity against P. aeruginosa.