Coffee Cascara as a Source of Natural Antimicrobials: Chemical Characterization and Activity Against ESKAPE Pathogens

Coffee cascara is a byproduct of coffee production traditionally used for infusions and animal feed. In this study, aqueous extracts of cascara from three different sources (Cas1-Cas3) were analyzed for their polyphenol and flavonoid content, as well as the concentrations of key individual bioactive compounds including caffeine, trigonelline, chlorogenic acid, and protocatechuic acid. Among the tested samples, Cas1 exhibited the highest total polyphenol (802.2 mg GAE/L) and flavonoid (134.7 mg QE/L) contents. The antibacterial activity of these extracts and an artificial mixture of the four compounds were evaluated against ESKAPE pathogens. Cas1 exhibited the most promising antibacterial effect, with minimal bactericidal concentration (MBC) values as low as 0.03 mg/mL for S. aureus and A. baumannii, and 0.26 mg/mL for P. aeruginosa. The artificial mixture, despite containing higher concentrations of the major compounds, exhibited reduced efficacy (MBC of 0.04 mg/mL for S. aureus and 0.15 mg/mL for A. baumannii, respectively), highlighting the superior activity of the native extracts. These results indicate that cascara extracts possess strong antibacterial activity, which correlates with their content of bioactive compounds, mainly polyphenols and alkaloids. The pronounced efficacy of the native extracts compared to the artificial mixture suggests that minor constituents in cascara may synergistically contribute to antibacterial effects. The present study highlights the potential of cascara aqueous extracts as natural multi-component antimicrobial agents, particularly against clinically relevant pathogens such as A. baumannii.