Inhibition of the bacterial surface protein anchoring transpeptidase sortase by isoquinoline alkaloids

The inhibitory activity of Coptis chinensis rhizome-derived material was evaluated against sortase, a bacterial surface protein anchoring transpeptidase, from Staphylococcus aureus ATCC 6538p and compared to that of four commercially available isoquinoline alkaloids. The biologically active constituent of C. chinensis extract was characterized as the isoquinoline alkaloid, berberine chloride, by spectral analysis. The isolate was a potent inhibitor of sortase, with an IC 50 value of 8.7 μg/ml and had antibacterial activity against Gram-positive bacteria with a minimum inhibitory concentration (MIC) in the range of 50-400 μg/ml. Among the four isoquinoline alkaloids tested, berberine chloride had strong inhibitory activity. These results indicate that berberine is a possible candidate for the development of a bacterial sortase inhibitor.