Bark of Astronium lecointei Ducke trees from the Amazon: chemical and structural characterization

Abstract

The bark of the Astronium lecointei Ducke tree, a species native to the Brazilian Amazon, was characterized in relation to anatomical and chemical features. The chemical composition was studied for the first time. The bark of A. lecointei has a periderm with thick phellem layer and the phloem has abundant sieve tube members and a conspicuous presence of sclerified nodules of sclereids. The mean chemical composition of A. lecointei bark was 5.8% ash, 12.9% total extractives that were principally polar compounds soluble in water and ethanol, 32.7% lignin, 1.8% suberin, and 46.9% polysaccharides. The ethanol and water extracts contained phenolics compounds (77.1 mg gallic acid equivalents/g extract), flavonoids (58.7 mg catechin equivalents/g extract) and tannins (7.3 mg catechin/g extract) and showed moderate antioxidant capacity. Extractives were present preferentially in the finest fraction with enrichment in the water-soluble portion. The main phenolic constituents found in the bark extract are chlorogenic acid (49.1%), gallic acid (46.8%), o-coumaric acid (2.7%) and trans-cinnamic acid (1.4%). The bark showed high calcium concentration (267 mg/g) and had 103 mg/g nitrogen and 46 mg/g potassium. Based on the potential use of polar extractives, polysaccharides and lignin, bark from A. lecointei is suggested as a valuable resource of raw material for production of high-value products.