Cuminaldehyde\nPotentiates Antiproteolytic Peptide\nEfficacy via Parallel Pathways of Enhanced Inner Membrane-Damaging\nActivity and Inhibition of Bacterial Energy Metabolism

Antimicrobial peptides (AMPs) offer potential as antibiotic\nalternatives,\nbut high cost, off-site cytotoxicity, and poor stability limit their\napplication. Combining AMPs with adjuvants holds promise in surmounting\nthese limitations. Among potentiators, terpenoids account for the\nhighest proportion, yet their potential to enhance the AMPs efficacy\nand underlying mechanism remain unclear. Hence, we investigated the\npotential of monoterpenoids to enhance the efficacy of antiproteolytic\nAMPs N1 (NalAArIILrWrFR). Cuminaldehyde potentiated N1 activity against\nall tested strains, with FICI from 0.375 to 0.094. N1/cuminaldehyde\ncombination also worked synergistically against drug-resistant bacteria,\nexhibited a low incidence of resistance development, and was not synergistically\ntoxic to eukaryotes. Furthermore, cuminaldehyde enhanced N1 stability\nin salts, serum, and proteases. Mechanistically, cuminaldehyde enhanced\nthe inner-membrane-damaging activity of N1 and inhibited bacterial\nenergy metabolism. Finally, cuminaldehyde enhanced the efficacy of\nN1 against ETEC K88-induced enteritis in mice. Collectively, cuminaldehyde\nmay be a promising N1 adjuvant to combat bacterial infections and\ncircumvent antibiotic resistance.