A microcalorimetric method to determine antimicrobial effects of two bile acid derivatives on Staphylococcus aureus

• Published in: Journal of thermal analysis and calorimetry 2012-06, Vol.108 (3), p.1293-1301
• Main Authors: Li, Xingfeng, Jin, Cheng, Liu, Wei, Zhou, Jian, Kong, Weijun, Dai, Bing, Wang, Jiabo, Yan, Dan, Zhao, Yanling, Luo, Yun, Xiao, Xiaohe
• Format: Article
• Language: English
• Subjects: Analysis; Analytical Chemistry; Antibacterial agents; Antibiotics. Antiinfectious agents. Antiparasitic agents; Bacteriology; Biological and medical sciences; Chemistry; Chemistry and Materials Science; Deoxycholic acid; Fundamental and applied biological sciences. Psychology; Growth, nutrition, cell differenciation; Inorganic Chemistry; Measurement Science and Instrumentation; Medical sciences; Methods; Microbiology; Pharmacology. Drug treatments; Physical Chemistry; Polymer Sciences; Staphylococcus aureus; Staphylococcus aureus infections
• ISSN: 1388-6150; 1588-2926; 1572-8943
• DOI: 10.1007/s10973-011-1436-6

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 m ), the time corresponding to the maximum power output ( t p ), total heat-production Q t , half inhibitory concentration of the drugs ( IC 50 ) were calculated from the growth curves. For both HDCA and UDCA, with the increasing of concentration, k , P m , and Q t decreased, meanwhile, k – c fit a linear equation, t p was prolonged correspondingly. Principle component analysis, the results indicated t p might be the main parameter in evaluating the antibacterial activity of HDCA and UDCA in microcalorimetric method. Combining with t p and IC 50 , 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.