he aim of the present study was to optimize the extraction conditions of green tea aqueous extract [green tea concentration (G) and extraction temperature (T)]. Response surface methodology was applied to determine the highest radical scavenging activity (RSA), Ferric reducing antioxidant power (FRAP) and reducing power (RP) of the prepared green tea extract. Effect of green tea aqueous extract prepared using the optimal conditions on the liver cirrhosis retardation in rats was also investigated. Two-factors central composite design was established to determine the effects of G or T and radical scavenging holding time as independent variables on RSA, FRAP and RP as dependent variables. The optimum G, T and holding time with maximum RSA were 1.0 %, 88.7 °C for 25 min, with a predicted RSA of 81.3 % (r2=0.9115) compared to the BHT, which had a scavenging value of 87.4 % at concentration 150 ppm and holding time 30 min The same predicted concentration and temperature obtained with the highest FRAP and RP were 2.566 and 1.687 with r2 0.9780 and 0.9550, respectively. The phenolic and flavonoid contents were 81.2 mg gallic acid equivalent and 33.5 mg quercetin equivalent per 100 ml green tea extract. The extract prepared at optimal conditions was used for treatment of cirrhotic rats by CCl4. Insignificant (P≥0.05) differences were observed between the green tea group and control group in obtained total protein or albumin values. Total protein and albumin were dramatically decreased in the group treated by CCL4. 
The same trend was observed with studying the transaminase enzymes. Histopathological sections appeared the effect of green tea extract on the retardation of liver cirrhosis in rats.