Higher Plant Terpenoids
Plants are phenomenally adept at biosyntheses of complex and potentially useful terpenoids. A considerable number of species from plant families rich in terpenoids, such as the Compositae, have been used in primitive cancer treatment from a pre-Christian period of unknown length. The possibilities for isolation of anticancer agents from the Compositae—and, for example, the Euphorbiaceae159—were anticipated at least 20 years ago by Hartwell at the U.S. National Cancer Institute (NCI), as noted in Chapter 2. Subsequent investigations of Compositae, particularly by Hertz and Kupchan, have led to a number of new sesquiterpenes capable of substantially inhibiting (ed50 < 10 μg/ml) the KB cell line. The application of this in vitro screening technique for bioassay markedly enhanced the facility with which such cytotoxic substances can be isolated. Unfortunately, in a significant number of cases, the cytotoxicity has not been translated into in vivo activity against the NCI’s lymphocytic leukemia P388 (the PS system, significant activity ≧ 125 T/C), Walker carcinosarcoma 256 (the WA system, significant activity ≦ 42 T/C), or lymphoid leukemia L1210 (the LE system, significant activity ≧ 125 T/C).
KeywordsBetulinic Acid Sesquiterpene Lactone Lymphoid Leukemia Cancer Chemotherapeutic Agent Biosynthetic Product
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