Synthesis and cytotoxicity evaluation of 13-n-alkyl berberine and palmatine analogues as anticancer agents

By introducing long carbon-chain alkyl groups at the C-13 position of berberine and palmatine, 13-n-hexyl/13-n-octyl berberine and palmatine chloride analogues 4a-d were synthesized and examined by MTT assays for cytotoxic activity in seven human cancer cell lines (7701QGY, SMMC7721, HepG2, CEM, CEM/VCR, KIII, Lewis), yielding IC₅₀ values of 0.02 ± 0.01-13.58 ± 2.84 μM. 13-n-Octyl palmatine (compound 4d) gave the most potent inhibitor activity, with an IC₅₀ of 0.02 ± 0.01 μM for SMMC7721. In all cases, the 13-n-alkyl berberine and palmatine analogues 4a-d were more cytotoxic than berberine and palmatine. In addition, compounds 4a-d also exhibited more potent cytotoxicity than berberine and palmatine in mice with S180 sarcoma xenografted in vivo. The primary screening results indicated that the 13-n-hexyl/13-n-octyl berberine and palmatine analogues might be valuable source for new potent anticancer drug candidates.