Evaluación de la actividad antimicrobiana del d-limoneno frente a Escherichia Coli y docking molecular

Abstract

Antimicrobial resistance, particularly in Escherichia coli strains producing extended-spectrum β-lactamases (ESBL) such as the CTX-M-15 enzyme, represents one of the greatest threats to global public health. Given the loss of efficacy of conventional antibiotics, there is a pressing need to explore natural compounds like d-limonene, whose lipophilic structure suggests potential for disrupting bacterial membranes and inhibiting resistance enzymatic systems. To test this hypothesis, a multidisciplinary approach was employed, including broth microdilution to determine cell viability (ATCC 25922), disk diffusion assays to measure synergy with antibiotics (ATCC 35218), and molecular docking simulations with the 1ZG4 protein. Results revealed dose-dependent antimicrobial activity with a Half-Maximal Inhibitory Concentration (IC50) of 14.95 mg/mL, identifying a biphasic biological behavior characterized by an adaptive or hormetic effect at low doses (1-8 mg/mL) and marked inhibition starting at 16 mg/mL. In synergy tests, d-limonene (64 mg/mL) significantly enhanced the action of gentamicin (+3 mm) and ceftriaxone (+2 mm). Complementarily, docking predicted a binding affinity of -4.96 kcal/mol at the CTX-M-15 catalytic site, stabilized by hydrophobic interactions. It is concluded that d-limonene acts through a dual mechanism of membrane disruption and competitive enzymatic inhibition by occlusion, positioning itself as a promising adjuvant to restore the therapeutic efficacy of antibiotics against multi-resistant strains.