Comparison of Anti‐bacterial Activity of Four Kinds of Alkaloids in Rhizoma Coptidis Based on Microcalorimetry

Abstract

AbstractThe anti‐bacterial activities of four kinds of alkaloids in Rhizoma Coptidis, a traditional Chinese medicinal (TCM) herb, on Escherichia coli (E. coli) growth were investigated and compared by microcalorimetry. The four kinds of alkaloids were berberine, coptisine, palmatine and jatrorrhizine. The heat flow power‐time curves of E. coli growth in the presence of the four kinds of alkaloids were measured using an LKB‐2277 Bio‐activity monitor using a stop‐flow method, at 37°C. Then the thermal kinetic parameters such as, growth rate constant k, maximum power output of the log phase Pm,log and the stationary phase Pm,stat, growth inhibitory ratio I, generation time tg, total heat output of the log phase Qt,log and half‐inhibitory concentration of the drugs, IC50, were obtained from the curves. The four kinds of alkaloids had different anti‐E. coli activities. k, Pm,log and Qt,log of E. coli in the presence of the four kinds of alkaloids decreased with increasing concentrations of the alkaloids. Judged from the values of k, Pm,log, Qt,log, I and IC50, the experimental results revealed that the sequence of anti‐bacterial activities of the four kinds of alkaloids was berberine>coptisine>palmatine>jatrorrhizine. The functional groups methylenedioxy at C‐2 and C‐3 on phenyl ring improved anti‐bacterial activity more remarkably than methoxyl at C‐2 and C‐3 on the phenyl ring. However, the antibacterial activity did not vary significantly with methylenedioxy or methoxyl at C‐9 and C‐10 on the other phenyl ring.