β-Glucuronidase may contribute to the development of colon cancer. A reduction in the activity of this enzyme could inhibit the enterohepatic circulation of carcinogens, which is thought to reduce the risk of colon cancer. The purpose of this study was to investigate the effect of heat treatment on the β-glucuronidase inhibition activity of DOPA. Prior to heating, DOPA showed only a weak inhibitory effect on β-glucuronidase. After heating a DOPA solution at 100℃ for 10 min, the heat-treated DOPA (hDOPA) exhibited 48.5% inhibition at 10 µM. We performed a kinetic study on β-glucuronidase inhibition by hDOPA using Lineweaver-Burk analysis. The kinetics profile suggests that hDOPA competitively inhibits β-glucuronidase.