Curcuma longa L. constituents inhibit sortase A and Staphylococcus aureus cell adhesion to fibronectin

The inhibitory activity of Curcuma longa L. (turmeric) rhizome constituents against sortase A, a bacterial surface protein anchoring transpeptidase, from Staphylococcus aureus ATCC 6538p was evaluated. The activity of the isolated compounds (1-4) was compared to that of the positive control, p-hydroxymecuribenzoic acid (pHMB). The biologically active components of C. longa rhizome were characterized by spectroscopic analysis as the curcuminoids curcumin (1), demethoxycurcumin (2), and bisdemethoxycurcumin (3). Curcumin was a potent inhibitor of sortase A, with an IC₅₀ value of 13.8 ± 0.7 μg/mL. Bisdemethoxycurcumin (IC₅₀ = 31.9 ± 1.2 μg/mL) and demethoxycurcumin (IC₅₀ = 23.8 ± 0.6 μg/mL) were more effective than pHMB (IC₅₀ = 40.6 ± 1.2 μg/mL). The three isolated compounds (1-3) showed no growth inhibitory activity against S. aureus strain Newman, with minimum inhibitory concentrations (MICs) greater than 200 μg/mL. Curcumin also exhibited potent inhibitory activity against S. aureus cell adhesion to fibronectin. The suppression of fibronectin-binding activity by curcumin highlights its potential for the treatment of S. aureus infections via inhibition of sortase activity. These results indicate that curcumin is a possible candidate in the development of a bacterial sortase A inhibitor.