Lignin From Dinizia excelsa: Isolation, Characterization, and Evaluation of Antioxidant, Cytotoxic, Antitumor, Antimicrobial, and Immunomodulatory Activities

ABSTRACT Alkaline lignin extracted from Dinizia excelsa wood was characterized by Fourier‐transform infrared (FTIR), ultraviolet–visible (UV–Vis), NMR, gel permeation chromatography (GPC), and thermogravimetric analysis (TGA). Spectra revealed a predominance of guaiacyl units, giving a highly condensed structure with notable thermal stability. Biological assays showed moderate antioxidant activity and no cytotoxicity toward normal cells (viability ≥90.00%). In contrast, significant antitumor effects were observed against MCF‑7 and Jurkat cell lines, together with antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa . The lignin also stimulated splenocyte proliferation and boosted secretion of IL‑2, IL‑4, IL‑10, and IFN‑γ, indicating an immunomodulatory profile. These results position D. excelsa lignin as a promising phenolic metabolite source for biomedical applications and highlight the importance of Amazonian biodiversity in the search for new bioactive compounds.