Estudo químico e atividade larvicida, antioxidante e antibacteriana de Pourouma guianensis Aubl. (Urticaceae)

Abstract

This work describes the isolation of some chemical constituents and evaluation of larvicidal (4th instar larvae of Aedes aegypti L.), free radical scavenging (DPPH) and antibacterial (microdilution method) activities of leaves, bark and stem of Pourouma guianensis Aubl. (Urticaceae). The phytochemical study performed with the extracts with positive results in trials led to the isolation of two triterpenes (3 ,19 -dihydroxyurs-12-en-28-oic and 2 ,3 ,19 -trihydroxyurs-12-en-28-oic acids, known as pomolic and euscaphic acids, respectively), reported for the first time in this genus, and two benzoic acid derivatives (3-methoxy-4-hydroxybenzoic and 3,4-dihydroxybenzoic acids, known as vanillic and protececuic acids, respectively), described for the first time in the species under study. All compounds had their structures identified on the basis of their NMR spectral data and by comparison with literature data. In the larvicidal assays, among the samples of leaves, bark and stem tested, moderate activity (mortality > 50% < 75%) were observed only in some of the fractions from the stem [Hexane-CHCl3 1:1 (58.5%), CHCl3 (71.11%) and EtOAc (60.0 and 53.33%; ppt and ssb, respectively)]. In the antioxidant assays, when compared with positive standard used (ascorbic acid, gallic acid and BHT), only two fractions from leaves [CHCl3 (312.01 ± 1.55 μg/mL) and EtOAc (CI50 120.76 ± 1.85 μg/mL)] and stem [CHCl3 (372.47 ± 4.28 μg/mL) and EtOAc-MeOH 1:1 (360.68 ± 1.05 μg/mL)] showed promising results. In the antibacterial assays, among the samples tested, the best results were obtained only with extracts from leaves and stem against Staphylococcus aureus and Enterococcus faecallis (MIC 125-500 mg/mL). Among the evaluated samples from bark, only a few extracts showed a weak activity against S. aureus and E. faecallis (CIM 1000 mg/mL). Regarding Gram-negative bacteria used, all extracts were inactive against Klebsiella pneumoniae and only some extracts showed weak activity against Pseudomonas aeruginosa (CIM 1000 mg/mL). The results obtained in this study will contribute to extend the chemotaxonomy and the biological potential of the genus Pourouma.