Abstract
For seeking novel antibacterial agents with high efficacy and low toxicity to deal with drug resistance, the effects of Salvia miltiorrhizae from various sources on Escherichia coli were evaluated by microcalorimetry coupled with chemometrics. Firstly, the heat-flow power-time curves of E. coli growth affected by different S. miltiorrhizae samples were recorded. Then, some crucial quantitative thermo-kinetic parameters including growth rate constant, heat-flow power and heat output, etc. were obtained from theses curves and were further investigated by some powerful chemometric techniques including similarity analysis, multivariate analysis of variance, hierarchical clustering analysis and principle component analysis. By analyzing the principle parameters, growth rate constant of the second exponential phase (k2) and the heat-flow output powers of the second highest peak (P2), together with the derived parameter inhibitory ratio (I, %), it could be quickly concluded that the tested S. miltiorrhizae samples from different sources in China exhibited strong antibacterial effects on E. coli and the samples from Beijing city exhibited the strongest anti-E. coli effects, which might be used as novel and underlying antibacterial candidates for the resistance of E. coli to the existing drugs in practice. This study provides a useful tool and helpful idea to accurately and rapidly evaluate the antibacterial effects of some complex matrices, offering some references for exploring new antibacterial agents.
Highlights
In recent decades, more and more attentions have been paid on Traditional Chinese Medicines (TCMs) because of their complementary therapeutic efficacy to Western medicines, and their abilities to solve some primary problems that have not yet been solved by traditional therapy, such as resistance of some microbes to the existing antibacterial agents which has led to increasing challenges for doctors and researchers, as well as has become an increasingly important and pressing global attention (Zhao et al 2015)
The purpose of this study was to determine the antibacterial activities of S. miltiorrhizae on E. coli by using microcalorimetry coupled with some helpful chemometric methods including similarity analysis (SA), multivariate analysis of variance (MANOVA), hierarchical clustering analysis (HCA) and principle component analysis (PCA)
Metabolic heat-flow power (HFP)‐t curves of E. coli growth Performing the microcalorimeter, the normal metabolic thermogenic curve of E. coli growth in the LB culture medium at 37 °C in the absence of any substances was determined in Fig. 1, which presented two stages and four representative phases: the first exponential growth phase (A–B), a stationary phase (B–C), the second exponential growth phase (C–D), and a decline phase (D–E)
Summary
More and more attentions have been paid on Traditional Chinese Medicines (TCMs) because of their complementary therapeutic efficacy to Western medicines, and their abilities to solve some primary problems that have not yet been solved by traditional therapy, such as resistance of some microbes to the existing antibacterial agents which has led to increasing challenges for doctors and researchers, as well as has become an increasingly important and pressing global attention (Zhao et al 2015). Escherichia coli, a kind of gram-negative bacteria that were widely existed in the environment, which have brought serious hazards to the intestinal tract of humans and animals to cause various infections and foodborne diseases such as peritonitis, cholecystitis, cystitis, bloody and non-bloody diarrhea, and so on (Müller et al 2001). These pathogenic E. coli are responsible for hemolytic colitis infections that lead to the hemolytic uremic syndrome, and result in high levels of morbidity and mortality in general population, especially for impressionable groups including infants, children, and the elderly (Kong et al 2012). Developing new antibacterial agents with high efficacy and low toxicity for the resistant E. coli is in great urgency.
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