Antioxidant, Enzyme-Inhibitory and Antimicrobial Activity of Underutilized Wheat and Maize Crop Residues

Global wheat and maize production, which reached two billion tonnes in 2021, generates significant agricultural waste with largely untapped potential. This study investigates the bioactive properties of ethanol extracts from wheat and maize harvest residues, their ethyl acetate fractions, and their principal compounds. In vitro assays (DPPH, ABTS, FRAP, and TRC) revealed variable antioxidant capacities among the samples, with ferulic acid demonstrating the strongest free-radical scavenging and reducing effects, often surpassing those of standard antioxidant controls. Enzyme inhibition assays identified the flavonoid tricin as the most effective inhibitor of α-glucosidase, acetylcholinesterase, and butyrylcholinesterase, while the flavonolignan mixture of salcolins A and B showed the highest inhibitory activity against α-amylase and tyrosinase. Antimicrobial testing using the broth microdilution method resulted in minimum inhibitory concentrations (MICs) ranging from 31.25 µg/mL to >1000 µg/mL. Gram-positive bacteria showed the highest susceptibility, Candida albicans exhibited variable sensitivity, and Gram-negative bacteria were resistant in the tested concentration range. Bioactivity increased in the order of extracts, fractions, and then individual compounds. These findings suggest that wheat and maize residues possess notable bioactive properties, highlighting their potential as sources of valuable and pharmacologically active compounds.