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 (1H and 13C) 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.