Antineoplastic agents, 103. The isolation and structure of hypoestestatins 1 and 2 from the East African Hypoëstes verticillaris.

The East African shrub Hypoëstes verticillaris representing a heretofore chemically unexplored. Acanthaceae genus has been found to contain two new cell growth inhibitory (murine P-388 lymphocytic leukemia) phenanthroindolizidine alkaloids termed hypoestestatin 1 (1a) and hypoestestatin 2 (1b). Both substances were found to markedly inhibit growth of the murine P-388 cell line (ED50 = 10(-5) micrograms/ml). The structures of hypoestestatins 1 and 2 were assigned primarily on the basis of results from extensive spectral studies.