Carbohydrate moiety is found in many anticancer nature products. To explore the
carbohydrate moiety of
daunorubicin in enhancing anticancer efficacy, several
daunorubicin derivatives bearing
disaccharide (1-8) have been synthesized. Their cytotoxicities were tested in
leukemia K562 and
colon cancer SW620 cells.
Topoisomerase II (
topo II)
poisoning was performed with the in vivo complex of topoisomerase bioassay. In both cell lines, compounds with various terminal 2,6-dideoxy
sugars (compounds 1, 3, 5, and 8) showed 30- to 60-fold higher anticancer activity than compounds with 2-deoxy- or 6-deoxy
sugar (compounds 6 and 7). Compounds with an alpha-linkage between two
sugar units (compound 3) showed 35-fold higher anticancer activity than compounds with a beta-linkage (compound 4). In addition, the anticancer activities of these compounds correlated with their ability to target
topo II mediated genomic DNA damage in vivo. Compounds 1 and 3 with 2,6-dideoxy
sugars produced more covalent
topo-
DNA complex than compounds with 2-deoxy
sugar (6) and 6-deoxy
sugar (7). Compounds with an alpha-configuration of terminal 2,6-dideoxy
sugar (compounds 1 and 3) showed higher
topo II
poisoning than their counterparts with the beta-configuration (compounds 2 and 4). These results indicate that
sugar moieties in
daunorubicin play a significant role in its anticancer activity and
topo II inhibition. The second
sugar of
disaccharide daunorubicin should possess 2,6-dideoxy with alpha-linkage to the first
sugar to exhibit better anticancer activity.