Inhibition of sortase, a bacterial surface protein anchoring transpeptidase, by beta-sitosterol-3-O-glucopyranoside from Fritillaria verticillata

A glucosylsterol, beta-sitosterol-3-O-glueopyranoside, has been isolated as an active principle with sortase inhibitory effect from the bulbs of Fritillaria verticillata by bioassay-guided chromatographic fractionation. The isolate was a potent inhibitor of sortase, with an IC50 value of 18.3 mug/ml and had antibacterial activity against Bacillus subtilis, Staphylococcus aureus, and Micrococcus leuteus with MIC values of 50, 200, and 400 mug/ml, respectively, indicating that this compound is a possible candidate for the development of a bacterial sortase inhibitor. In addition, sitosterol was found to be inactive upon sortase and bacterial cell growth. These results suggest that the inhibitory potency of flsitosterol-3-O-glucopyranoside is sensitively dependent upon the glucopyranoside side chain moiety.