Synthesis and antimicrobial activity of 9-o-substituted palmatine derivatives
Chemistry and Chemical Engineering School, Henan University of Technology, Zhengzhou 450001, Henan, P. R. China
Z C Li Chemistry and Chemical Engineering School, Henan University of Technology, Zhengzhou 450001, Henan P. R. China E-mail: [email protected]
A series of new palmatine derivatives with alkyl or alkyl with N-heterocyclic structures were designed and synthesized at C-9-O according to the principle of association. These compounds were characterised by 1 H NMR, 13 C NMR, ESI-MS and elemental analysis, and tested for their antimicrobial activity in vitro to evaluate structure-activity relationships. The results indicated that 9-O-substituted palmatine derivatives exhibit varying degrees of antimicrobial activity. Antibacterial activities of compounds (3a-f) against Gram +ve bacteria increased 2- to 64-fold than that of palmatine. The compounds (3a-f) possessed relatively weaker inhibitory effects against Gram −ve bacteria and fungi than that against Gram +ve bacteria. Antimicrobial activities of compounds (5a-e) are lower than that of compounds (3a-f). Compound 3d showed the highest antimicrobial activity of all the compounds. The LD 50 values of compounds (3a-f) decreased as the alkyl side chain was elongated. Compound 3f showed least toxicity.