Metabolomic analysis of the mechanism of action of yerba mate aqueous extract on Salmonella enterica serovar Typhimurium

Introduction Salmonella enterica serovar Typhimurium is a Gram- negative enteropathogen that infects millions of people worldwide each year; the emergence of drug- resistant strains has heightened the need for novel treatments. Aqueous extracts of yerba mate (Ilex paraguariensis) effectively inhibit drug- resistant S. Typhimurium in vitro. Some chemical constituents that contribute to the extract's antibacterial activity have been identified, but the mechanism of action of the extract is still unknown. Objectives This study sought to gain insight into the antibacterial mechanism of yerba mate extract against S. Typhimurium. Methods Assays for catalase activity and membrane permeability were used to select time points for an LC-MS metabolomics analysis of S. Typhimurium intracellular components. Results Yerba mate extract induced changes in central carbon metabolism in S. Typhimurium, reduced catalase activity by means other than direct inhibition, and did not change membrane integrity despite a significant increase in the production of a cell wall precursor. Additional significant differences were observed in the global metabolic regulators alpha-ketoglutarate and acetylphosphate, the energy-related molecule NAD(+), and in an unexpected match to the antibacterial compound yohimbine. Conclusion This work provides the first evaluation of the mechanism of action of yerba mate extract on S. Typhimurium, revealing a major impact on central carbon metabolism, catalase activity, and possible metabolic links to interference in energy production and membrane integrity. The putative identification of the antibacterial compound yohimbine and the many unidentified compounds provides additional avenues for future investigations of yerba mate compounds capable of traversing or binding to S. Typhimurium's membrane.