The novel proapoptotic activity of nonnatural enantiomer of Lentiginosine

D-(−)-Lentiginosine [(−)-4], the nonnatural enantiomer of the iminosugar indolizidine alkaloid L-(+)-lentiginosine, acts as apoptosis inducer on tumor cells of different origin, in contrast to its natural enantiomer. Although D-(−)-4 exhibited a proapoptotic activity towards tumor cells at level lower than the chemotherapeutic agent, SN38, it was less proapoptotic towards normal cells and less cytotoxic. Apoptosis induced by D-(−)-4 was caspase-dependent, as shown by the increased expression and activity of caspase- 3 and -8 in treated cells, and by inhibition following treatment with the pan caspase inhibitor, ZVAD-FMK. This study highlighted how a natural iminosugar alkaloid and its synthetic enantiomer, which were simply known for their inhibition against a fungal glucoamylase, could behave in a complete different way when tested towards cell growth and death of cells of different origin.