Objective: To study the different purgative effects and molecular mechanisms among different components of processed Rhez Radix et Rhizoma (extracts from Rhez Radix et Rhizoma

cooked Rhez Radix et Rhizoma and Rhez Radix et Rhizoma carbon). Method: Mice were randomly divided into control group and treatment groups with different components of processed Rhez Radix et Rhizoma at a dose of 10 g·kg-1. The different samples were administered to mice for observing the purgative number

the first purgative time

the 5 hour purgative times and defecation quantity. The effects on small intestinal propulsion were determined by propulsion rate of charcoal powder in mice. The effects on Na+-K+-ATPase in rat colon wall cell membrane were determined after the rat was treated for 5 days. Result: The mice showed no purgative effect after be administered with different components of the processed Rhez Radix et Rhizoma except the component 2 and 3.As the total number of defecation in mice was concerned

except the cooked Rhez Radix et Rhizoma component 2 and 3 as well as the Rhez Radix et Rhizoma component 4 and Rhez Radix et Rhizoma carbon component 4

other components were significantly higher compared with the controls (P<0.05 or P<0.01). Compared with the Rhez Radix et Rhizoma component 2

the number of defecation for the cooked Rhez Radix et Rhizoma component 2 was significantly less (P<0.05). Compared with the Rhez Radix et Rhizoma component 3

the number of defecation for the cooked Rhez Radix et Rhizoma component 3 and the Rhez Radix et Rhizoma carbon component 3 was significantly less (P<0.01). Compared with control group

the Rhez Radix et Rhizoma component 2 and 3 could significantly promote the intestinal propulsion (P<0.05)

while the other components also had the same tendency. Among the different components of the same procesed Rhez Radix et Rhizoma

the intestinal propulsions of the Rhez Radix et Rhizoma component 2 and 3 were higher than the cooked Rhez Radix et Rhizoma component 2 and 3 respectively (P<0.05). All the components of the processed Rhez Radix et Rhizoma could inhibit Na+-K+-ATPase in cell membrane of colon wall

among them the Rhez Radix et Rhizoma component 2 and 3 and the Rhez Radix et Rhizoma carbon component 3 showed the significant inhibitory effect compared with the control group (P<0.05 or P<0.01). Among the component 2

the highest inhibition for Na+-K+-ATPase appeared from Rhez Radix et Rhizoma

compared with the processed Rhez Radix et Rhizoma and the Rhez Radix et Rhizoma carbon (P<0.05 or P<0.01). Among the component 3

the lowest inhibition for Na+-K+-ATPase appeared from Rhez Radix et Rhizoma

with significance between that of the processed Rhez Radix et Rhizoma (P<0.05). Conclusion: The Rhez Radix et Rhizoma component 2 and 3 possess the strongest purgative effects and the inhibitory action on Na+-K+-ATPase is potentially the molecular mechanism.