Amplification of DNA-binding affinities of protoberberine alkaloids by appended polyamines

This communication describes a synthetic approach toward the amplification of the moderate DNA-binding affinities of protoberberine alkaloids. Specifically, three protoberberine derivatives bearing two to six primary amino groups at the 3- and 9-positions of protoberberine were synthesized and characterized by NMR (H-1 and C-13) and HRMS. Studies on their affinities toward calf thymus (CT) DNA by ethidium bromide (EB) displacement and spectrophotometric titration experiments indicate that these polyamino protoberberines show more than 103-fold enhanced DNA-binding affinities relative to palmatine and thus are exploitable as strong DNA-binders. (c) 2006 Elsevier Ltd. All rights reserved.