The bark of the tree speciesMyrcia eximiaDC., which occurs in secondary forests in the Brazilian Amazon, is described for the first time. The aim was to provide a broad knowledge of its composition, to add value, and to direct uses to the bark of this species based on its polyphenolic content and antioxidant capacity. The bark is formed by conducting phloem, nonconducting phloem, and rhytidome. In addition, dead phloem occurs between the periderms. The average chemical composition of the bark was 45.6% total extractives, 1.4% suberin, 1.7% ash, and 21.1% lignin. The ethanol-water extract had a high content of flavonoids and condensed tannins [300.8 and 877.3 mg catechin equivalents (CE) g⁻¹of the extract, respectively]. High-performance liquid chromatography (HPLC) was used to quantify the presence of rutin, quercetin, and gallic, ferulic, and o-coumaric acids. The bark extract showed strong 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) free radical scavenging activity, which was superior to that of the commercial antioxidant butylated hydroxytoluene (BHT), with an IC₅₀of 85.2 μg mL⁻¹. Based on these results, it is evident that the bark ofM. eximiafrom the Brazilian Amazon rainforest is a new and potential natural source of phenolic compounds and antioxidants, and its extracts can be used in the food and pharmaceutical industry and in various condensed tannin-based products.

Tannins from Myrcia splendens from the Amazon rainforest were used for the first time in the formulation of a urea-tannin-formaldehyde (UTF) resin. The objective was to evaluate the effect of different tannin proportions on the glue line performance in Pinus sp. woods, glued with UTF adhesive. The tannins were extracted in a water bath, using 1500 mL of water and 100g of dry bark (liquor/bark 15:1), with addition of 3% Na2SO3, at a temperature of 70 °C for three hours. The adhesives formulations were based on the gradual replacement of mass of the urea-formaldehyde (UF) adhesive by tannin powder, totalizing four compositions and one control treatment. UTF adhesives were evaluated for their physicochemical properties, shear bond strength (wet and dry) and wood failure. The addition of M. splendens tannins to the urea formaldehyde adhesive promoted an increase in glue line strength. The proportion of 5.0% of tannins proved to be ideal in the formulation of the UTF adhesive, considering all the parameters evaluated. Thus, this study proves the potential use of Amazonian tannins from Myrcia splendens in the partial composition of more sustainable UTF adhesives.

This study investigated the influence of particle size and solvent on the extraction efficiency of phenolic compounds and antimicrobial activity of bark extracts from Anacardium occidentale, Stryphnodendron adstringens, and Myrcia eximia, native to the Caatinga, Cerrado, and Amazon biomes, respectively. Extractions were performed using deionized water and 70% methanol in four particle size ranges (28, 35, 60, and 80 mesh). The levels of condensed tannins, total phenols, and flavonoids were measured, along with the antimicrobial activity against Gram-positive and Gram-negative bacterial strains. Extracts obtained with methanol showed higher yields in phenolic compounds compared to water, with Myrcia eximia showing the highest flavonoid content. Antimicrobial activity was more evident against Gram-positive bacteria (Staphylococcus aureus and Listeria monocytogenes), especially for Myrcia eximia extracts. These findings highlight the potential use of forest residues to obtain bioactive compounds with antimicrobial properties.

The aim was to evaluate the potential of the stem bark of Byrsonima spicata, Croton matourensis, Myrcia splendens, Tapirira guianensis and Vismia guianensis as a source of value-added macromolecules to contribute to the bioeconomy in the Amazon. The barks were collected from secondary forests in the state of Pará, Brazil, and analysed for the first time for anatomical and chemical composition. High-performance microscopic images showed the presence of a rhytidome composed of one to seven layers of periderms. The bark had a significant presence of extractives soluble in ethanol and water (from 29.3 to 46.1 %). Lignin content ranged from 19.0 to 33.4 %. The optical emission spectrometer showed a rich mineral composition, particularly in calcium (2.9–20.6 g kg⁻¹ of bark). High tannin content was quantified, especially in B. spicata (19.1 %) and M. splendens (29.9 %). The composition of the bark suggests that it can be used to obtain potentially valuable phenolic compounds with chemical functionalities and bioactivities. After this extraction, the lignin-rich solid residue is suitable for a thermochemical valorisation, while the high nutrient levels make soil amendment an interesting application. A sustainable bark removal may therefore generate local income and contribute to the conservation of these Amazonian species.

The bark anatomy was analysed, as was the overall chemical composition (extractives, lignin, suberin, ash and polysaccharides), and a quantitative elemental analysis was performed of the bark and two tannin extracts (extracted with water only and with a mixture of water and Na₂SO₃). The phenolic composition and antioxidant activity of the bark extracts were quantified. The results indicated that the bark is composed of conductive phloem, nonconductive phloem, rhytidome, crystals and secretory cells. The average chemical composition was 15.9 % extractives, 35.3 % total lignin, 1.9 % suberin, 15.4 % ash and 31.5 % polysaccharides. The condensed tannin yield in the extract obtained with water alone was 5.1 %, and that in the treatment with water and Na₂SO₃ was 8.1 %. The ethanol-water extract had a high phenolic content (112.6 mg GAE g⁻¹ extract). The bark extract showed strong antioxidant activity, reaching 83.5 % inhibition of DPPH free radicals, which was higher than the value of 75.0 % for the commercial antioxidant BHT at the same concentration. These results demonstrate that Protium tenuifolium is a potential natural Amazonian source of phenolic compounds and antioxidants and can be used for medicinal purposes and the production of various sustainable products, such as cosmetics.