Abstract: Objective To compare the acute toxicity of Qing'e pills and their separated prescriptions aqueous extract in mice and to explore the mechanism of prescription compatibility so as to provide data for safe and rational drug use in clinic. Methods According to the classical principle of "monarch, minister, assistant and guide" and the seven-emotion compatibility of Chinese medicine, as well as the theory of nature, taste and indications, Qing'e pills were divided into five groups: combination 1 (salt Eucommia ulmoides Oliver+salt Psoralea corylifolia L+fried Juglans regia L.), combination 2 (salt Eucommia ulmoides Oliver+salt Psoralea corylifolia L), combination 3 (salt Psoralea corylifolia L + Alliumsativum L.), combination 4 (salt Psoralea corylifolia L+fried Juglans regia L. + Alliumsativum L.), and combination 5 (Qing'e pills). The aqueous extract of Qing'e pills was prepared, and the contents of psoralen and isopsoralen in each drug group were detected by HPLC. The classical experimental method for acute toxicity was used to compare the difference in acute toxicity between Qing'e pills and their separated prescriptions aqueous extract. Results The contents of psoralen in the water extracts of combination 1, combination 2, combination 3, combination 4 and combination 5 were 0.156 3%, 0.172 6%, 0.104 8%, 0.050 3% and 0.083 8% respectively, compared with 0.160 6%, 0.158 9%, 0.096 0%, 0.036 6% and 0.062 3% respectively for isopsoralen. The maximum tolerated dose (MTD) value of each group was 165.32, 156.52, 156.00, 118.78 and 129.84 g/(kg·d),respectively, which were equivalent to 779.77, 892.94, 1779.6, 956.8 and 538.59 times the daily dosage per kilogram of body weight of 70 kg people. The main toxic symptoms of mice were depression, inactivity, ataxia, stiffness, and proneness to clonic convulsion. The mice in each group had different degrees of redness and swelling in ears, tails and eyes. Conclusion The acute toxicity of combinations mentioned above is not so severe as that of salt Psoralea corylifolia L, suggesting that the prescriptions of Qing 'e pills combined according to the prescription structure of traditional Chinese medicine can reduce the acute toxicity of Psoralea corylifolia L. The compatibility of traditional Chinese medicine can ensure effective safety control. The mechanism of detoxification needs to be further studied.

Key words: Qing'e pills, compatibility and toxicity reduction, salt Psoralea corylifolia L., acute toxicity, normal mice, aqueous extract