Antimicrobial potential of Miscanthus × giganteus extracts: linking in vitro and in silico activity with in situ efficacy in milk

Abstract

Miscanthus × giganteus is a high-biomass, low-input crop whose potential as a source of antimicrobial compounds remains insufficiently explored. This study investigated the phytochemical composition, antioxidant and antimicrobial properties of methanolic (MeOH) and dichloromethane (DCM) extracts obtained from roots, rhizomes, stems, and leaves, integrating in vitro assays with molecular modelling and validation in a food matrix. Targeted UHPLC-MS/MS analysis revealed marked organ- and solvent-dependent differences in phenolic composition, with p-coumaric acid predominating in roots and rhizomes, while leaves were particularly enriched in 5-O-caffeoylquinic acid and isoorientin. MeOH root extract exhibited the strongest overall antioxidant potential, consistent with its high phenolic content. The extracts displayed broad antimicrobial activity against foodborne and pathogenic bacteria, filamentous fungi, and Candida spp., with antibacterial MIC and MBC values of 0.23–1.88 and 0.47–3.75 mg mL−1, respectively, and activities frequently comparable or superior to commercial food preservatives. Molecular docking, 100 ns molecular dynamics simulations, and MM-PBSA analyses identified isoorientin as a particularly promising antimicrobial constituent, showing stable interactions with microbial targets, including Bacillus cereus DltA. Guided by the phytochemical, antimicrobial, and in silico findings, the MeOH leaf extract was further evaluated against B. cereus in milk. At 2 mg mL−1, bacterial growth was inhibited by 97% after 24 h and remained suppressed by 81% after 48 h. These findings identify M. × giganteus as a sustainable source of bioactive compounds and demonstrate that its antimicrobial activity can be retained in a complex food matrix, supporting further development of Miscanthus-derived natural preservation strategies.