Important Anticancer Natural Products

Another important anticancer natural product is camptothecin, an alkaloid derived from the Chinese tree Camptotheca acuminata Descne. A semisynthetic water-soluble derivative of camptothecin known as ironotecan (Topotecin , Campto ) was introduced in Japan in 1994 for the treatment of lung, ovarian, and cervical cancers. Unlike Taxol, camptothecin acts by inhibition of the enzyme topoisomerase I. 

In the anticancer area, the use of natural products as direct agents or as novel lead compounds for the generation of synthetic or semisynthetic analogs has proved remarkably productive, and a recent survey showed that 62% of new anticancer agents over the last 10 years have been natural products or agents based on natural product models.7 Examples of clinically important plant-derived natural products are the vinca alkaloids vinblastine (4) and vincristine (5), the podophyllotoxin analogs etoposide (6) and teniposide (7), the diterpenoid paclitaxel (Taxol ) (8), and the camptothedn-derivative topotecan (9). 

Lactones and the macrocyclic lactones, like the y- and 5-lactones, are of importance since these ring systems are found widespread in nature. The simpler substituted lactones are important building blocks in the synthesis of many natural products, e.g. in the fields of antibiotics, anticancer pharmaceuticals, pheromones and prostaglandins to name but a few. 

Another area in which natural products have had a major impact on longevity and quality of life is in the chemotherapy of cancer (see Chapter 62). In fact, most major anticancer drugs are derived from plants or microorganisms. Important examples include bleomycin, doxorubicin, daunorubicin, vincristine, vinblastine, mitomycin, streptozocin, and most recently, paclitaxel... 

Approximately 60% of the world s population relies almost entirely on plants for medication. Natural products have long been recognized as an important source of therapeutically effective medicines. Of the 520 new drugs approved between 1983 and 1994, 39% were natural products or derived from natural products. Sixty percent to 80% of antibacterials and anticancer drugs were derived from natural products. 

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