NOVEL CYTO-TOXIC AND ANTITUMOR AGENTS .4. WITHAFERIN-A - RELATION OF ITS STRUCTURE TO THE INVITRO CYTO-TOXIC EFFECTS ON P388-CELLS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 31  (1) , 31-36
Abstract
In vitro effects of withaferin A and its 9 new derivatives [2,3-dihydrowithaferin A, 2,3-dihydro-27-deoxywithaferin A, 2,3,24,25-tetrahydro-27-deoxywithaferin A, 4-dehydrowithaferin A, withaferin A diacetate, 15 .beta.-hydroxywithaferin A, 12 .beta.-hydroxywithaferin A, UN-R1 and UN-R2] on [mouse leukemia] P388 cells were studied. The cytotoxicity was calculated from the utilization of precursors in protein and nucleic acid (NA) synthesis and from capacity to suppress cell proliferation. The most potent agents proved to be 4-dehydrowithaferin A and withaferin A diacetate exhibited an equal inhibitory effect on thymidine, uridine and L-valine incorporation. They stopped cell proliferation and, at the same time, killed the cells. Cytotoxicity was due to a double bond at position C2-3, by dissociating this bond the cytotoxicity markedly decreased in all derivatives. A dissociation of the double bond at C24-25 or a removal of OH group from C27 did not cause any significant changes in the biological effects of the derivatives. An addition of a carbonyl group at C4 increased the effects of the agent. An addition of OH groups to the molecule of withaferin A resulted chiefly in a qualitative change in the action of derivatives manifested by a significant decrease in L-valine inhibition. As withaferin A promptly reacted with L-cysteine, one of the possible target sites in the cell might be the SH groups of enzymes which react with the lactone and epoxide groups of the agent.