Microcalorimetry and turbidimetry to investigate the anti-bacterial activities of five fractions from the leaves of Dracontomelon dao on P. aeruginosa

As a healthcare-associated pathogen with the resistance to anti-bacterial agent, P. aeruginosa has caused prevalent public burden and should not be ignored. Facing the realistic situation, developing novel anti-P. aeruginosa agents is urgent. Leaves of Dracontomelon dao were extensively used in southern China to treat various infectious diseases 1000 years ago. And in the study, the heat flow power–time (HFP–time) curves generated by P. aeruginosa which were disturbed by the five fractions (PE, CHCl₃, EtOAc, n-BuOH and Vestiges fraction) from them were investigated through microcalorimetry, and then, some thermal kinetic parameters were obtained from the curves to characterize the metabolism of P. aeruginosa. The parameters were analyzed by principal component analysis (PCA), and the anti-P. aeruginosa activities of the five fractions were systematically compared and evaluated. The results showed that five fractions all expressed respective anti-P. aeruginosa effects in a dose-dependent manner and especially the performance of EtOAc fraction with half-inhibitory concentration (IC50) of 18.06 μg mL⁻¹. Simultaneously, the prospective performance of EtOAc fraction was confirmed by turbidimetry. Based on the promising anti-P. aeruginosa activities of EtOAc fraction, it could be developed as a novel anti-bacterial agent used in practice for treating certain infectious diseases.