Figure 2.

Effect of pterostilbene in the activity of New Delhi metallo‐β‐lactamase‐1 (NDM‐1). Pterostilbene was added to PBS containing 10‐mM ZnCl₂ (pH 7.4) in a 96‐well plate to reach the final concentrations of 4, 8, 16, and 32 μg·ml⁻¹ and incubated with the purified NDM‐1 for 10 min. Then 25‐μM nitrocefin (dissolved in sterile water) was added for another incubation at 37°C for 30 min. The absorbance of each sample was read at 492 nm by a microplate reader at room temperature, and residual activity was calculated. The samples without inhibitors (shown as 0 μg·ml⁻¹ pterostilbene) or NDM‐1 served as positive controls or negative controls, respectively. Residual activity = (A − A₀) /(A₁₀₀ − A₀) × 100%, where A represents the absorbance of samples at 492 nm and A₀ and A₁₀₀ represent 0% and 100% activity as determined in the negative controls and positive controls, respectively. All data are mean ± SD, n = 5. * P < .05, significantly different from the positive control group; one‐way ANOVA followed by a Dunnett t test. Pt, pterostilbene