Abstract: The purpose of this research was to evaluate the radiation protective effects of different constituents of Sijunzi Decoction on BALB/c mice. One hundred and ninety two BALB/c mice aged 6—8 weeks were divided by random number table method into normal control group, model group, Sijunzi Decoction water extract group, alcohol extract group, and groups of the supernatant of 50%, 60%, 70%, 80% alcohol to precipitate of aqueous extract, respectively. Radiation-damaged mice model were single-irradiated by 3.5 Gy ⁶⁰Co γ rays, and the extracts of Sijunzi Decoction were administered intragastrically before and after the irradiation. The activity index including peripheral hemogram, thymus index and bone marrow micronucleus rate were examined. The results showed that, compared to the radiation model group, the WBC counts of the group with the supernatant of 80% alcohol to precipitate of aqueous extract(p<0.05) were increased significantly at 3 d after irradiation, while the mice bone marrow micronucleus rates were obviously reduced by the water extract, alcohol extract and the supernatant of 50%, 60%, 70% alcohol to precipitate of aqueous extract(p<0.05). At 7 d after irradiation, the mice thymus indices were elevated in the groups with the supernatant of 70%, 80% alcohol to precipitate of aqueous extract(p<0.05), whereas the mice bone marrow micronucleus rates were reduced in the same way by the water extract, the alcohol extract as well as the supernatant of 60%, 70%, 80% alcohol to precipitate of aqueous extract(p<0.05). The largest reductions in the mice bone marrow micronucleus rates were observed in the groups of the supernatant of 70%, 80% alcohol to precipitate of aqueous extract. The above results indicate that the supernatant of 70%, 80% alcohol to precipitate of aqueous extract could possibly be the major radiation protective constituents of Sijunzi Decoction. This conclusion provides not only the basis for the studies on the anti-radiation chemical constituents of Sijunzi Decoction and on its anti-radiation effect mechanism, but also the scientific evidence for the new anti-radiation drug development in traditional Chinese medicine.

Key words: Sijunzi Decoction, BALB/c mice, radiation damage, active constituent