Biological activities and physicochemical characterization of alkaline lignins obtained from branches and leaves of Buchenavia viridiflora with potential pharmaceutical and biomedical applications

In this work, we investigated in vitro different biological activities of alkaline lignins extracted from the species Buchenavia viridiflora, a tree from the Amazon rainforest used as a wood product. The chemical composition results for the twig and leaves were, respectively (%): cellulose (30.88 and 24. 28), hemicellulose (21.62 and 23.03), lignin (29.93 and 25.46), extractives (13.06 and 20.52), and ash (4.51 and 6.72). The yield was higher for the lignin of the branches (67.9 %) when compared to the leaves (60.2 %). Lignins are of the GSH type, low molecular weight and thermally stable. They promoted moderate to low antioxidant activity, highlighting the lignin of the branches, which presented an IC₅₀ of 884.56 μg/mL for the DPPH assay and an IC₅₀ of 14.08 μg/mL for ABTS. In the cytotoxicity assays, they showed low toxicity against macrophage cells (IC₅₀ 28.47 and 22.58 μg/mL). In addition, they were not cytotoxic against splenocytes and erythrocytes at concentrations ranging from 100 to 6.25 μg/mL. These were able to promote splenocyte proliferation and induce the production of anti-inflammatory cytokines. And inhibit the growth of tumor cells with IC₅₀ ranging from 12.63 to values >100 μg/mL and microbial at a concentration of 512 μg/mL. Finally, they showed antiparasitic activity by inhibiting the growth of chloroquine-sensitive and resistant Plasmodium falciparum strains. These findings reinforce that the lignins in this study are promising for potential pharmaceutical and biomedical applications.