Effect of flavonoids on protease activities in human skeletal muscle tissue in vitro

The effect of a representative range of flavonoid compounds on the activities of a range of proteolytic enzyme types in human skeletal muscle tissue was determined in vitro. All of the proteases showed some degree of inhibition by all of the flavonoid compounds investigated, with IC50 values (concentration of flavonoid required to inhibit initial activity of muscle proteases by 50%) for various enzyme/flavonoid combinations ranging from approx. 50 micromol/l to 2 mmol/l. These data demonstrate that in addition to their well described antioxidant characteristics, flavonoids also possess novel antiproteolytic inhibitory activity in vitro, which may in part explain some of the beneficial effects of these plant derived compounds in vivo.