Effect of berberine alkaloids on Bifidobacterium adolescentis growth by microcalorimetry

The inhibitory effects of three berberine alkaloids (BAs) from Coptis chinensis Franch on Bifidobacterium adolescentis growth were investigated by microcalorimetry. The growth rate constant (k) and maximum heat-output power (Pmax) decreased and peak time of maximum heat-output power (tp) prolonged with the increase of BAs concentration. Half inhibitory ratios (IC50) BAs were respectively 790.3 (berberine), 339.6 (coptisine) and 229.8 mu L-1 (palmatine), which indicated the sequence of their antimicrobial activity: berberine < coptisine < palmatine. Combined with previous findings, the sequence which could show the bioactivity of Bacillus shigae and Escherichia coli was: berberine > coptisine > palmatine. The structure-function relationship of BAs indicated that the functional group methylenedioxy or methoxyl at C2 and C3 might be the major group inducing the activities of BAs on E. coli and B. adolescentis. Meanwhile, the substituent groups at C2, C3, C9 and C10 almost had equal effect on B. shigae.