Medical and Health Documents

This document has been written in an attempt to provide an insight for the herbalist about allopathic research and use of plants in oncology. It is by no means comprehensive, and is not meant to imply any endorsement of the techniques or principles. It also is not meant to imply any a prioridisapproval or criticism.

Sample

Few compounds reach clinical trials. A low therapeutic index (the ratio of maximum tolerated dose to minimum effective dose), undesirable side-effects or high toxicity may outweigh beneficial tumor-inhibitory activity. Of 25, 000 screens conducted annually by the NCI (including both synthetic and natural materials), only 8-12 compounds are likely to be selected for pre-clinical testing, and only 6-8 may go on to clinical trials.

The random-selection screening program for natural products was terminated by the NCI in 1983. In over 25 years, the program did not identify a single agent for use in the allopathic treatment of cancer. Nevertheless, the number of cytotoxic and anti-tumor agents identified was enormous. The NCI has certainly not lost confidence in the potential of natural products as leads for new anti-cancer agents. Instead of the random-selection screening program, anew screening system was begun in 1986, reducing the scale of the operation, and concentrating on the less thoroughly investigated groups of organisms, including plants, marine animals, fungi and cyanobacteria.

When found using the approach outlined above, tumor-inhibiting constituents are often new to science, and span a wide range of structure. Occasionally, however, they are well known but had not been screened the correct way. Examples relevant to the phytotherapist include usneic acid (Usnea spp.), ellagic acid (Quercus spp.), the anthraquinone aloe-emodin (Cascarasagrada), juglone (Juglans spp.), pyrrolizidine alkaloids, aristolochicacid (Aristolochia spp.), hellebrigenin (Helleborus niger: Black Hellebore), the well known alkaloids used to treat gout from the Autumn Crocus (Colchicum autumnale) and cucurbitacins found in species of Euphorbia, Hypericum and Ecbalium elaterium (the squirting cucumber).

An interesting finding in such research concerns the controversial pyrrolizidinealkaloids, known for their hepatotoxic properties, especially to grazinganimals. Those found in Senecio spp., however, have shown antitumoractivities at dose levels lower than that which is toxic. Indicine-N-oxidefrom Heliotropium indicum (a botanical relative of Comfrey) showedno marked hepato-toxicity, possessed significant anti-tumor activity, and went to clinical trials. The compound showed substantial activity in acute leukemia, but hepatotoxicity was more severe than expected, and the cause is not known.

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