Preliminary Evaluation of Cytotoxic and Metabolic Modulatory Activities of <i>Mentha cordifolia</i> Opiz Leaf Crude Extract on Human Peripheral Blood Mononuclear Cells

Mentha cordifolia Opiz (yerba buena) is traditionally used for its antimicrobial and therapeutic properties. The cytotoxic and metabolic modulatory effects of the buffered leaf crude extract of M. cordifolia Opiz on human peripheral blood mononuclear cells (PBMCs) were evaluated using a Water-Soluble Tetrazolium (WST-8)–based colorimetric assay. Phytochemical characterization revealed a total phenolic content of 0.1304 mg GAE/g extract. Among the tested concentrations (25–200 µg/mL), the extract exhibited minimal-to-mild cytotoxic effects, with no evident dose-dependent toxicity. Because the same donors were evaluated across all treatment conditions, repeated-measures one-way analysis of variance (ANOVA) was performed using donor identity as the repeated factor. The Shapiro–Wilk test did not indicate a significant deviation from normality ( W = 0.9855, p = .9891), which supported the use of a parametric analysis. Repeated-measures one-way ANOVA revealed a statistically significant overall effect of treatment on the PBMC metabolic activity ( F (5,10) = 6.441, p = .0063). Post hoc paired comparisons using Bonferroni correction demonstrated that the positive control (PC) exhibited significantly increased metabolic activity relative to the negative control (adjusted p = .025), whereas no other pairwise comparisons reached statistical significance after multiple-comparison correction. Under phytohemagglutinin-stimulated conditions, the 50 and 100 µg/mL concentrations showed comparatively moderate metabolic activity, whereas the 200 µg/mL concentration demonstrated reduced metabolic activity relative to that of the PC. The PC demonstrated increased metabolic activity, confirming the assay’s responsiveness. Inter-individual variability in metabolic responses was observed among the donors, particularly at higher extract concentrations. The modest metabolic modulatory activity observed may be related to the phytochemical composition of the buffered extract. Overall, this preliminary in vitro study extends our previous findings and highlights the low cytotoxicity and modest donor-dependent metabolic modulatory effects of M. cordifolia Opiz, warranting further mechanistic and phytochemical investigations to confirm these findings.