Evaluation of Antioxidant-Rich Mexican Oregano (Lippia graveolens) Infusion and Carvacrol: Impact on Metabolic Activity and Cytotoxicity in Breast Cancer Cell Lines

Background/Objectives: The search for natural alternatives in breast cancer (BC) management has spurred interest in plant-derived extracts, particularly oregano variants and their bioactive compound carvacrol (Cv). However, Mexican oregano (Lippia graveolens) infusion (MoI) remains unexplored. This study aimed to chemically characterize MoI and compare its anticancer effects with Cv across BC cell lines, including aggressive triple-negative (TN) subtypes. Methods: MoI was analyzed for composition, antioxidant capacity (ABTS, DPPH, FRAP, total phenols/flavonoids), and phytochemical profile (FTIR, HPLC). Anticancer activity was assessed via MTT and LDH assays. Results: MoI exhibits strong antioxidant capacity and concentration-dependent antiproliferative effects, with IC50 values ranging from 0.08 to 0.18 mg/mL across BC lines, significantly higher (i.e., less cytotoxic) than Cv IC50 of 121–211 µM. Importantly, MoI displayed markedly lower cytotoxicity toward non-cancerous cells (IC50 0.18 mg/mL) compared to Cv (IC50 110 µM). Conclusions: While both agents reduced metabolic activity, Cv induced a more acute suppression. These findings position MoI as a promising, selective candidate for BC therapy, particularly for poor-prognosis subtypes like TN BC, warranting further mechanistic investigation.