Plant-derived drugs

Traditional approaches to discovering anti-cancer therapeutics relied on identifying agents that were anti-proliferative with little or no cytotoxicity to normal cells. This approach, while successful, has yielded mainly cytotoxic drugs. Plant-derived compounds such as paclitaxel (Taxol ) [3,4] and vinca alkaloids (vincristine) [5] are two examples (Figure 1) of commercially used drugs identified using this approach. Paclitaxel is a stabilizer of tubulin and is marketed as Taxol for the treatment of breast and other cancers [6]. 

Furthermore, it has been observed that placental PGP is of great importance in limiting the fetal penetration of various potentially harmful or therapeutic compounds [64]. High PGP levels may have a role in the protection of fetuses from harmful tropical plant metabolites (from which many drugs are derived). An originally balanced polymorphism may have been preferentially selected by improved prenatal growth and development as well as improved postnatal health. This selective pressure may maintain the C allele in populations of African descent. 

For thousands of years, nature, especially plant life, was the pharmacy from which people obtained their medicines. Even today it is estimated that 40% of all drugs contain at least one plant-derived ingredient [1, 2]. 

Table 2. Plant-derived natural product-based drug candidates under clinical evaluation. 

Amin A, Gali-Muhtasib H, Ocker M, Schneider-Stock R. (2009) Overview of major classes of plant-derived anticancer drugs. Int J Biomed Sci 5 1-11. 

In recent years, however, some of the greatest emphasis has been placed on the search for anticancer and antiviral agents derived from natural products. Success in that area has not heen as great as that achieved in other helds. Since 1960, only seven plant-derived drugs have heen approved by the FDA for use as anticancer agents. Four of those drugs, vinblastine, vincristine, etoposide, and teniposide, were discovered in the 1950s. The last three—Taxol , topotecan, and irinotecan—were discovered and approved much more recently. 

PLANT-DERIVED NATURAL PRODUCTS IN DRUG DISCOVERY AND DEVELOPMENT AN OVERVIEW... 

When plant-derived natural products are examined specifically, it may be seen that they remain an invaluable but still incompletely exhausted resource for drug discovery purposes. Largely as a result of advances in natural product isolation techniques and spectroscopic methods for structural determination as well as the utilization of high-throughput bioassay... 

Plant-Derived Natural Products in Drug Discovery and Development... 

Table 1. Some Examples of Major Plant-derived Natural Product Drugs ...

Fig. 1. Structures of major plant-derived natural product drugs.

Balandrin MF, Kinghorn AD, Farnsworth NR, Plant-derived natural products in drug discovery An overview, in Kinghorn AD, Balandrin MF, eds., Human Medicinal Agents from Plants, Symposium Series No. 534, American Ghemical Society Books, Washington, DC, pp. 2—12, 1993. 

---