Investigação dos constituintes químicos e busca de atividades biológicas nos resíduos madeireiros de Peltogyne catingae Ducke e Allantoma decandra (Ducke) S. A. Mori, Y. Y. Huang & Prance

Abstract

The Amazon harbors one of the largest forest covers in the world and sustains intense logging activity, which generates substantial volumes of residues that are generally underutilized. Several species exhibit high resistance to xylophagous organisms and remarkable wood durability, properties often associated with the presence and ecological role of secondary metabolites. In this context, aiming to add value to wood residues, the present study investigated the chemical constituents of wood residues (heartwood and sapwood) of Allantoma decandra and Peltogyne catingae and evaluated the biological activity of the isolated and characterized substances. Accordingly, the metabolic profiles of nonpolar and polar extracts were assessed by GC–MS and LC–MS, respectively. Polar extracts were fractionated by open-column chromatography using different stationary phases (silica gel and Sephadex LH-20), and promising fractions were analyzed by 1D and 2D Nuclear Magnetic Resonance (NMR) and LC–MS. These fractions were evaluated in vitro against three genera of fungi of medical (Candida spp. and Cryptococcus spp.) and medical/veterinary (Sporothrix spp.) relevance, as well as against a bacterium of importance to citriculture (Xanthomonas citri ssp. citri). As results, methyl esters of fatty acids were characterized in the nonpolar extract of A. decandra residues (with methyl 6-octadecenoate as the major constituent), while the polar extract yielded saturated (3) and unsaturated (4) fatty acid derivatives, a glycerol derivative (5), α-amyrin (6), β-amyrin (7), and four phenolic acids: gallic acid (1), 4-O-methylgallic acid (2), vanillic acid (8), and syringic acid (9). In the nonpolar extract of P. catingae residues, methyl esters of fatty acids were also identified (methyl 9,12-octadecadienoate as the major constituent), whereas the polar extract afforded seven modified flavonoids (peltogynoids): rel-(2,3-trans-3,4-trans)-peltogynol (10a), rel-(2,3-trans-3,4-trans)-mopanol (10b), rel-(2,3-trans-3,4-cis)-peltogynol B (10c), rel-(2,3-trans-3,4-cis)-mopanol B (10d), rel-(2,3-trans)-mopano (11), rel-(2,3-trans)-pubeschin (13), and rel-(2,3-trans-3,4-cis)-4-O-methylpeltogynol B (15), in addition to two flavanon-3-ols, rel-(2,3-trans)-3-O-methylfustin (12a) and rel-(2,3-cis)-3-Ometilfustin (12b), and one chalcone, (E)-butein (14). Among the antimicrobial assays, a fraction containing compounds 10a-d stood out, displaying MICs against Candida glabrata and C. tropicalis (40 µg/mL), C. krusei (20 µg/mL), Cryptococcus gattii (40 µg/mL), C. neoformans (5 µg/mL), Sporothrix brasiliensis (62.5 µg/mL, fungistatic effect), S. schenckii (31.25 µg/mL, fungicidal effect), and Xanthomonas citri ssp. citri (100 µg/mL, bactericidal effect). Additionally, the polar extract of P. catingae (PCM) stood out, exhibiting a MIC of 31.25 µg/mL and a fungicidal effect against S. brasiliensis and S. schenckii, as well as the 10b/10d mixture and compound 13, both showing a MIC of 62.5 µg/mL and a fungicidal profile against both evaluated strains. Thus, this study contributes to the knowledge of Amazonian biodiversity by adding chemical and biological value to the wood residues of A. decandra and P. catingae.