Anatomical and chemical characterization of the bark of two Amazonian tree species

The barks of Schizolobium parahyba var. amazonicum and Zanthoxylum ekmanii from the Brazilian Amazon were anatomically and chemically characterized to assess their potential as renewable industrial raw materials. Anatomically, both species showed distinct secondary phloem organization: S. parahyba var. amazonicum had fibers in small isolated groups, dilated rays, and astrosclereids, whereas Z. ekmanii exhibited fibers arranged in tangential bands and narrower rays. Chemically, both barks were rich in polysaccharides (53–60 %) and lignin (22–24 %), with moderate extractive contents. Condensed tannin yields ranged from 0.7–1.8 %, while total phenolic contents were 14.5 and 26.3 mg GAE g −1 extract, with DPPH IC 50 values of 124.4 and 86.7 μg mL −1 , indicating weak-to-moderate antioxidant activity. Calcium (Ca), potassium (K), and nitrogen (N) were the most abundant mineral elements, suggesting a role as potential nutrient sources. Altogether, the integrated anatomical, chemical, and mineral profiles identify these Amazonian bark residues as lignocellulosic feedstocks with potential for biorefineries, bio-based materials, and soil nutrient recovery within sustainable tropical forestry chains.