Abstract: The aim of this study was to elucidate the antichlamydial activity and mechanism of the natural product berberinein vitro. Firstly, the antichlamydial activity of berberine was evaluated. The data showed that berberine inhibited the formation of inclusion body and the titer of infectious progenies in a dose-dependent manner for bothChlamydia trachomatisL2 andChlamydia muridarumMoPn. Secondly, host cell viability was measured with CCK-8 kit to evaluate the cytotoxicity of the compound. No significant host cytotoxicity was observed when berberine concentration was not higher than 8 μmol/L. Then, the effect of berberine on the chlamydial infection process was examined by the pretreatment of compound with host cells orChlamydia. Pretreatment assays showed that berberine could weakly directly act onChlamydiabut not host cells to disturb the chlamydial infection process. Finally, the effect of berberine on the chlamydial proliferation process was analyzed. Later treatment and withdrawal assay revealed that the EB→RB transformation stage at 2－12 h of chlamydial period is the mainly target for berberine. The long-term tolerance assay displayed that berberine delayed the chlamydial development cycle, but could not kill it completely. In conclusion, berberine has a broad-spectrum antichlamydial activityin vitro, and its inhibitory effect on the proliferation period was stronger than that on the infection process.

Key words: Chlamydia, berberine, antichlamydial activity, infection process, proliferation process