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The antibacterial effect of Curcumin on Staphylococcus aureus growth was evaluated by microcalorimetry. The heat flow power-time curves and nine quantitative parameters of the S. aureus growth were applied to investigate the inhibitory effect with Curcumin. By analyzing these curves and some quantitative parameters using multivariate analytical methods, similarity analysis and principal component analysis, the antibacterial activity of Curcumin on S. aureus could be accurately evaluated from the change of the two main parameters, the second exponential growth rate constant k and the maximum heat flow power P. The main two thermal parameters played more important role in the evaluation: at low concentration (0-10.5 μg mL), Curcumin hardly influence the growth of S. aureus, while at high concentration (10.5-43.4 μg mL) it could notably inhibit the growth. All these illustrated that the antibacterial activity of Curcumin on S. aureus was enhanced with the increase of the concentration of this compound. This study might provide an useful method and idea accurately evaluate the antibacterial effects of Curcumin, which provides some useful methods for evaluate the nature antibacterial agents. [ABSTRACT FROM AUTHOR]

Using microcalorimetry, the characteristic metabolic heat flow power-time curves of S. aureus growth affected by Ursodesoxycholic acid and Hyodeoxycholic acid were measured at 37 °C. The thermal-kinetic parameters such as, growth rate constant k, the maximum power output ( P), the time corresponding to the maximum power output ( t), total heat-production Q, half inhibitory concentration of the drugs ( IC) were calculated from the growth curves. For both HDCA and UDCA, with the increasing of concentration, k, P, and Q decreased, meanwhile, k- c fit a linear equation, t was prolonged correspondingly. Principle component analysis, the results indicated t might be the main parameter in evaluating the antibacterial activity of HDCA and UDCA in microcalorimetric method. Combining with t and IC, the results revealed that the differences and trends of antibacterial activity of these bile acid derivatives were: HDCA > UDCA. Structure-activity relationship (SAR) analysis showed that the α-OH at C-3 and C-6 position at equal pace on the steroid nucleus enhanced the hydrophilicity of HDCA, which led to a stronger antibacterial effect than UDCA. In this study, a useful tool was provided to accurately evaluate the antibacterial effects of bile acid derivatives. The thermolysis curve recorded by microcalorimetry could provide a lot of kinetic and thermodynamic information for the study of growth process of living microbial, which could be helpful in the screening of high efficacy antibacterial agents. [ABSTRACT FROM AUTHOR]