Antineoplastic agents. 398. Isolation and structure elucidation of cephalostatins 18 and 19

Abstract

Continued investigation of murine leukemia (P-388) active fractions from the African marine worm Cephalodiscus gilchristi has resulted in the discovery of cephalostatins 18 (1b) and 19 (1c). The structures were determined by interpretation of their highfield (500 MHz) 1H, 13C, and 2D NMR and HRMS. Both of these new methoxy steroidal alkaloids exhibited strong activity against the murine P-388 lymphocytic leukemia cell line (ED50 ca. 10(-3) microg/mL), a mini panel of human cancer cell lines (GI50 <10(-3) microg/mL), and the U.S. National Cancer Institute's 60 human cancer cell line panel (mean panel GI50 ca. 10(-9) M).