Investigation of the anti-fungal activity of coptisine on Candida albicans growth by microcalorimetry combined with principal component analysis

Aims: This study investigated the anti-fungal activity of coptisine on Candida albicans growth. Methods and Results: The metabolic power-time curves of Candida albicans growth at 37 degrees C affected by coptisine were measured by microcalorimetry using an LKB-2277 Bioactivity Monitor with stop-flow mode. Then, the diameter of inhibitory zones in the agar layer was observed using agar cup method, and the minimal inhibitory concentration (MIC) of coptisine on Candida albicans growth was determined by serial dilution method. From the principal component analysis on nine quantitative parameters obtained from the power-time curves, we could easily evaluate the anti-fungal activity of coptisine by analysing the change of values of the main two parameters, growth rate constant k and maximum power output in the log phase P-m,P- log. The results showed that coptisine had strong anti-fungal activity: at a low concentration (45 mu g ml<SU-1</SU) began to inhibit the growth of Candida albicans and at a high concentration (500 mu g ml<SU-1</SU) completely inhibited Candida albicans growth. Coptisine gave big inhibitory zones with diameters between 11 and 43 mm within test range, and the MIC of it was 1000 mu g ml<SU-1</SU. Conclusions: Coptisine had strong anti-fungal activity on Candida albicans growth. The method of microcalorimetry applied for the assay of anti-fungal activity of coptisine was quantitative, sensitive and simple. Significance and Impact of the Study: This work will provide useful information for the development of chemical biology policy in the use of anti-microbials in food and drug production.