Comparison of anti-bacterial activity of three types of di-O-caffeoylquinic acids in Lonicera japonica flowers based on microcalorimetry

The anti-bacterial activities of three types of di-O-caffeoylquinic acids(diCQAs) in Lonicera japonica flowers, a traditional Chinese medicine(TCM), on Bacillus shigae growth were investigated and compared by microcalorimetry. The three types of diCQAs were 3, 4-di-O-caffeoylquinic acid(3, 4-diCQA), 3, 5-di-O-caffeoylquinic acid(3, 5-diCQA), and 4, 5-di-O-caffeoylquinic acid(4, 5-diCQA). Some qualitative and quantitative information of the effects of the three diCQAs on metabolic power–time curves, growth rate constant k, maximum heat-output power Pm, and the generation time tG, total heat output Qt, and growth inhibitory ratio I of B. shigae were calculated. In accordance with a thermo-kinetic model, the corresponding quantitative relationships of k, Pm, Qt, I and c were established. Also, the half-inhibitory concentrations of the drugs(IC50) were obtained by quantitative analysis. Based on the quantity–activity relationships and the IC50 values, the sequence of inhibitory activity was 3, 5-diCQA > 4, 5-diCQA > 3, 4-diCQA. The results illustrate the possibility that the caffeoyl ester group at C-5 is the principal group that has a higher affinity for the bacterial cell, and that the intramolecular distance of the two caffeoyl ester groups also has an important influence on the anti-bacterial activities of the diCQAs.

The anti-bacterial activities of three types of di-O-caffeoylquinic acids （diCQAs） in Lonicerajaponica flowers, a traditional Chinese medicine （TCM）, on Bacillus shigae growth were investigated and compared by microcalorimetry. The three types of diCQAs were 3, 4-di-O-caffeoylquinic acid （3, 4-diCQA）, 3, 5-di-O-caffeoylquinic acid （3, 5-diCQA）, and 4, 5-di-O-caffeoylquinic acid （4, 5-diCQA）. Some qualitative and quantitative information of the effects of the three diCQAs on metabolic power-time curves, growth rate constant k, maximum heat-output power Pro, and the generation time tG, total heat output Qt, and growth inhibitory ratio I of B. shigae were calculated. In accordance with a thermo-kinetic model, the corresponding quantitative relationships of k, Pm, Qt, I and c were established. Also, the half-inhibitory concentrations of the drugs （IC50） were obtained by quantitative analysis. Based on the quantity-activity relationships and the IC50 values, the sequence of inhibitory activity was 3, 5-diCQA 〉 4, 5-diCQA 〉 3, 4-diCQA. The results illustrate the possibility that the caffeoyl ester group at C-5 is the principal group that has a higher affinity for the bacterial cell, and that the intramolecular distance of the two caffeoyl ester groups also has an important influence on the anti-bacterial activities of the diCQAs.