Abstract:

BACKGROUND: Studies have confirmed that the active ingredients of Paeonia lactiflora Pall. have better inhibitory effects on Candida albicans, but its monomer paeoniflorin has not been reported whether it can inhibit Candida albicans biofilm.
OBJECTIVE: To observe the effect of paeoniflorin on Candida albicans biofilm in vitro.
METHODS: Paeoniflorin solution at different concentrations of 4, 2, 1, 0.5, 0.25 g/L was prepared using RPMI-1640 according to 2-fold dilution method. Chlorhexidine was diluted with RPMI-1640 to different concentrations, including 2%, 1%, 0.5%, 0.25%, 0.125%. We compared the effects of different concentrations of chlorhexidine and paeoniflorin on diameter of Candida albicans by agar diffusion method. MTT assay was used to detect the effect of different concentrations of chlorhexidine or paeoniflorin on the cell adhesion of Candida albicans as well as their inhibitory effects on Candida albicans biofilms. Confocal laser scanning microscope and LIVE/DEAD BacLight Bacterial Viability Kits were combined to observe the changes of Candida albicans biofilms under normal or intervention conditions. 
RESULTS AND CONCLUSION: Both chlorhexidine and paeoniflorin possessed bacteriostatic ability, and their bacteriostatic ring diameters were positively correlated with drug concentrations. Significant differences in the bacteriostatic ring diameter were observed between chlorhexidine and paeoniflorin, except between 2 g/L paeoniflorin and 1%, 2% chlorhexidine. Paeoniflorin at different concentration could inhibit cell adhesion of Candida albicans as well as inhibit Candida albicans biofilm. The inhibition rate was also positively correlated with 
drug concentrations. Under normal conditions, most of bacteria in the biofilms were alive, and there was a small amount of dead bacteria after 48 hours. After intervention with paeoniflorin, the proportion of dead bacteria in the biofilms was increasing along with the concentrations of paeoniflorin. Compared with the chlorhexidine, paeoniflorin showed a lower bacteriostatic activity. These findings indicate that paeoniflorin has an obvious inhibitory action in Candida albicans biofilms in vitro.

Key words: biocompatible materials, Candida albicans, biofilms, drugs, Chinese herbal