The isoquinoline alkaloids were isolated from traditional Chinese drugs of Phellodendri Cortex, Radix Stephaniae Tetrandrae,
Corydalis Yanhusuo and Corydalis Bungeana. The power-time curves of growth of E. coli at different concentrations of isoquinoline alkaloid at 37�C were determined by a 2277 Thermal Activity Monitor. The rate
constant of bacteriostastic activity was calculated. The relationship between growth rate constant and concentration was established.
The optimum bacteriostastic concentration was determined. Experimental results have indicated that all the isoquinoline alkaloids
isolated from the four kinds of traditional Chinese drugs have bacteriostastic activity and the order is Phellodendri Cortex>Radix
Stephaniae Tetrandrae>Corydalis Yanhusuo>Corydalis Bungeana.