Synergistic Enhancement of Bioactive Release and Antibacterial Activity by NADES Extraction from Solid-State Fermentation-Pretreated Strychnos spinosa Lam.

Abstract

Strychnos spinosa Lam. is a sub-Saharan species whose resistant lignocellulosic cell wall matrix hinders efficient extraction of phenolic compounds using conventional methods. This study investigated the synergistic effects of solid-state fermentation (SSF) using Aspergillus Oryzae and Choline Chloride-Lactic acid based natural deep eutectic solvents (NADES) on the extraction of bioactive compounds from S . spinosa . Three extraction systems, non-fermented ethanol (NF-EtOH), non-fermented NADES (NF-NADES), and fermented NADES (F-NADES) were evaluated for total phenolic and flavonoid contents, antioxidant capacity, antibacterial activity and the underlying mechanism of bioactive release. F-NADES yielded the highest TPC (16.85 mg GAE/g) and extraction rate constant (K 2 = 0.02134 g/mg·min), significantly outperforming NF-EtOH (TPC = 10.25 mg GAE/g; K 2 = 0.01208 g/mg·min). TGA, FTIR, and SEM confirmed extensive disruption of the lignocellulosic matrix in F-NADES-treated residues. UPLC-Q-TOF-MS metabolite profiling revealed fermentation-driven bioconversion of phenolic glycosides into bioactive aglycones, including apigenin and luteolin. F-NADES demonstrated the most potent antibacterial activity, with MIC values of 0.78-6.50 mg/mL and MBC values of 1.56-12.50 mg/mL across all tested strains. Overall, the F-NADES approach offers a sustainable and highly efficient strategy for recovering bioactive compounds. • SSF-NADES integration enhanced bioactive metabolite recovery from S. spinosa leaves. • TGA, FTIR, and SEM confirmed F-NADES-driven lignocellulosic matrix deconstruction. • F-NADES surpassed ethanol in phenolic yield and extraction kinetics. • F-NADES drove enzymatic and oxidative bioconversion of phenolic metabolites. • F-NADES extracts exhibited potent antibacterial and antibiofilm activities.