Avaliação das atividades antibacteriana e antiplasmódica de espécies de annonaceae da amazônia: estudo fitoquímico bioguiado de Guatteria Citriodora

Abstract

The rapid growth of resistance of bacteria and malaria parasites against currently available drugs creates an urgent need for new therapeutic approaches. The Annonaceae family, because its history in ethnomedicine and chemical and pharmacological potential, evidenced in the literature, represents a promising natural source of biological active molecules to combat these diseases. In the present study we evaluated, preliminarily, antiplasmodial activities of hydroalcoholic extracts of the leaves of Unonopis guatterioides, Anaxagorea brevipes, Duguetia riparia, Tetrameranthus duckei, Annona exsucca, Xylopia benthamii and Guatteria citriodora species. Among the evaluated species, only Guatteria citriodora showed potential antiplasmodial activity with IC50 equal to 1.0685 and p-value of 0.540. The evaluation of antiplasmodial activity of hexane fractions (FHF and FHG), alkaloidic (FAF and FAG) and neutral (FNF and FNG) derived from the partitioning of the crude hydroalcoholic extracts of leaves (EHBF) and branches (EHBG) of this species, directed the phytochemical studies for promising fractions, so the alkaloid fractions were selected. In addition, the antibacterial activities of EHBF and EHBG, FHF and FHG, FAF and FAG, FNF and FNF and essential oils of the leaves were also evaluated. The evaluation of antiplasmodial activity were performed against Plasmodium falciparum by flow cytometry, and for the antimicrobial activity the technique of agar disk diffusion were used against several gram positive and gram negative pathogenic bacteria. The fractions FHG, FAF and FAG proved to be the most active for antiplasmodial activity with IC50 of 1.035 μg.mL-1 (p-value 0.57), 1.0685 μg.mL-1 (p-value 0.54) e 0.332 μg.mL-1 (p-value 0.26), respectively. Bacillus subtilis proved to be very sensitive front FAF and FAG showing zone of inhibition of 22 mm and 21mm respectively, both fractions with minimum inhibitory concentration (MIC) equal to 62.5 μg.mL-1. Enterococcus faecalis showed moderately sensitive to FAF with xix inhibition zone of 17 mm and MIC equal to 125 μg.mL-1. A significant antibacterial activity was observed for the essential oils from the leaves, against Gram-negative bacteria Escherichia coli and Salmonella typhimurium EPEC which proved moderately sensitive to essential oils since they showed inhibition halos between the average of 11 and 13 mm, respectively, both with CIM equal to 125 μg.mL-1. The alkaloid fractions of leaves and twigs of Guatteria citriodora species selected by phytochemical study were analyzed by ESI-IT-MS and their chromatographic profile revealed the presence of several ion pair mass, which were consistent with the presence of protonated ions of aporphine alkaloids. From the chromatographic fractionation of these fractions seven alkaloids were isoleted, and they were identified by nuclear magnetic resonance of 1H and 13C (1D and 2D), such as the alkaloids: liriodenine, lyisicamine, O-methylmoschatoline and 3-methoxyoxoputerine (oxoaporphine), 3-methoxyguadiscidine (aporphine), palmatine (protoberberine) and guattescidine (7-hydroxy-7-methylaporphine). With the exception of liriodenine and O-methylmoschatoline, isolated from the bark of G. citriodora by Rabelo (2008), other structures are reported for the first time in the species. The antiplasmodial activities in vitro of FAF and FAG fractions are promising and may be associated with their alkaloidal constituents, which encourages deeper studies including in vivo investigations to establish its true efficacy and toxicity, providing data to obtaining new antimalarial drugs from vegetable source.