Alkaline lignin from Crataeva tapia leaves: in vitro antimicrobial, antibiofilm, cytotoxic evaluation and potential application in pharmaceutical tablets.

The lignin extracted from the leaves of Crataeva tapia was investigated for its antimicrobial activity and potential use in solid pharmaceutical formulations. The leaves contained 35% cellulose, 23.4% hemicellulose, 17.3% lignin, 19.1% extractives, and 4.7% ash. The extraction yield after acid precipitation was 67.8%. Cytotoxicity assays in RAW 264.7, J774, Vero, V79, and HepG2 cells showed low toxicity (IC50 >1000 µg/mL) and no hemolytic activity (<10%). Lignin exhibited MIC values ranging from 512 to >1024 µg/mL, with no MBC or MFC detected. The best antibacterial result was observed against Staphylococcus aureus UFPEDA-709 (MIC 512 µg/mL), comparable to oxacillin. Among Candida strains, notable results were obtained for HAM11 (128 µg/mL; fluconazole 0.5 µg/mL) and HAM13 (128 µg/mL; fluconazole 4 µg/mL). No synergism was observed against bacteria, but additive and synergistic effects were detected in HAM11 and HAM13, respectively. Lignin reduced HAM13 biofilm formation by 16%. Ergosterol assays suggested its action on fungal cell walls and membranes. Tablets containing lignin showed hardness of 5.5 Kgf/cm², friability of 0.93%, and disintegration in 36.2 min, while those without lignin showed 4.6 Kgf/cm², 0.15%, and 31 min, respectively. These findings highlight C. tapia lignin as a versatile and promising biomaterial for sustainable fluconazole-based formulations and adjuvant therapies.