Antimicrobial activity, physicochemical properties, antioxidant capacity, and elemental composition of yerba mate (Ilex paraguariensis)

Yerba mate ( Ilex paraguariensis ) has attracted considerable interest because of its diverse bioactive properties. To provide an integrated characterization beyond the evaluation of a single biological property, this study investigated the antimicrobial and physicochemical characteristics of water, ethanol, and methanol extracts, together with the antioxidant capacity and elemental composition of yerba mate. Antimicrobial activity was evaluated against foodborne pathogenic bacteria ( Bacillus subtilis , Escherichia coli , Enterococcus faecalis , and Staphylococcus aureus ) and yeast species ( Candida albicans and Saccharomyces cerevisiae ) using the agar well diffusion method. The water, ethanol, and methanol extracts were tested at their experimentally determined extract concentrations rather than after normalization to a common dry-extract concentration. The results revealed that the extracts exhibited no antifungal activity but showed varying levels of antibacterial effects among the tested extracts and microorganisms. Under the tested experimental conditions, the methanol extract produced the largest inhibition zones, particularly against S. aureus (18.67 mm) and B. subtilis (18.33 mm), and showed the lowest MIC value (43.75 µg/mL). Physicochemical analyses showed that the methanol extract had the highest pH (5.31) and the lowest oxidation–reduction potential (113.83 mV), whereas the ethanol extract had the lowest pH (4.86) and the highest oxidation–reduction potential (137.13 mV). For the single analyzed extract condition at 5 mg/mL, the total phenolic content was 12.80 µg GAE/mL, with a ferric reducing antioxidant power of 0.89 µM FeSO 4 ·7H 2 O equivalents and a DPPH radical scavenging activity of 59.07%. Because solvent-specific antioxidant measurements were not available, these results do not permit comparison among the water, ethanol, and methanol extracts. Elemental analysis by ICP-MS showed that potassium (3320.54 ppm), magnesium (1079.60 ppm), and calcium (726.35 ppm) were the most abundant measured elements, while Pb, Cd, and As were detected at relatively low concentrations in the dried plant material; however, dietary exposure was not assessed. Overall, extracts prepared from the analyzed commercial yerba mate material using different solvents exhibited different levels of in vitro antibacterial activity under the tested experimental conditions; however, because the extracts were not evaluated at an identical dry-extract concentration, these differences cannot be attributed exclusively to the extraction solvent. However, because no food-matrix or shelf-life experiments were performed, further validation using food-compatible extracts in real food systems is required before preservative applications can be proposed. Further studies should focus on identifying the bioactive compounds responsible for the observed activities and evaluating concentration-dependent responses using food-compatible extracts.