Ilex paraguariensis (Yerba Mate): A Narrative Review of Bioactive Compounds, Biological Activities, and Green Extraction Technologies

Background: Ilex paraguariensis (yerba mate) is a widely consumed botanical beverage rich in caffeoylquinic acids, methylxanthines, flavonoids, and saponins. However, the large number of biological effects attributed to yerba mate has made it difficult to distinguish mechanistic promise from clinically relevant evidence. Methods: This structured narrative review searched PubMed/MEDLINE, Scopus, Web of Science Core Collection, ScienceDirect, Wiley Online Library, and Google Scholar for literature published from January 2015 through June 2026. Predefined thematic search blocks, eligibility criteria, staged screening, data extraction, and design-appropriate methodological appraisal were applied. Results: The most coherent evidence concerns antioxidant and anti-inflammatory mechanisms and possible metabolic effects, including lipid, glycemic, and body-weight-related outcomes. However, much of the evidence remains preclinical, while human studies are limited, heterogeneous in dose and formulation, and generally of short duration. Safety depends on total caffeine exposure, preparation temperature, processing-related contaminants, individual susceptibility, and concurrent medication use. Very-hot consumption and smoke-derived polycyclic aromatic hydrocarbons represent avoidable risks. Conclusions: Yerba mate may represent a functional beverage and source of bioactive ingredients, but therapeutic claims remain unsupported. Responsible use requires control of caffeine dose, beverage temperature, processing contaminants, and exposure in vulnerable populations. Future research should prioritize standardized preparations, long-term safety assessment, dose–response characterization, and adequately powered clinical trials.