Sodium-Periodate-Mediated Harringtonine Derivatives and Their Antiproliferative Activity against HL-60 Acute Leukemia Cells.

Harringtonine (HT) is a naturally occurring alkaloid isolated from the plant genus Cephalotaxus. It possesses antileukemic activity and has been clinically utilized for the treatment of acute leukemia and lymphoma. Sodium periodate (NaIO4 ) was reacted with HT to produce five HT derivatives including four novel compounds. Their antiproliferative activity against HL-60 acute promyelocytic leukemia cells revealed that the presence of the C-5' methyl group enhances the antiproliferative activity because the IC50 values of the HT derivatives, including HT1 (5'-de-O-methylharringtonine), were at least 2000 times higher (>100 μM) than that of HT (∼47 nM). In addition, an indirect competitive enzyme-linked immunosorbent assay (icELISA) using a monoclonal antibody against HT (mAb 1D2) revealed that these antiproliferative activities were related to their cellular uptake. These results indicated that esterification of HT1 at the C-4' carboxylic acid group may enhance the antiproliferative activity of HT.