Explosive growth of modern biology in recent times has created a new awareness in the unlimited biotechnical potential of natural products such as plants, microbes and animals. Among the natural products, plants possess great chemical versatility. Because of ecological necessity, the variety of secondary metabolites produced by plants is broader than those of other organisms. Plant derived pharmaceuticals and phytochemicals retain their historic significance in the drug industry. Such materials are being used in the treatment and prevention of human diseases such as cancer, AIDS, anti-ulcer, anti-inflammatory, cardiovascular, atherosclerosis and menopause diseases. A substantial portion of all the currently prescribed drugs are still derived directly or indirectly from plant sources. Many new potent drugs with novel structural features have been isolated. For example, the potent anti-tumor drug, Taxol from pacific yew tree (Taxus brevifolia), provides considerable effectiveness in the treatment of ovarian carcinoma. The study of natural products, not only provides us with novel bioactive compounds, but it lead to the understanding of natural process of great importance.

 Here at the Walker Cancer Research Institute (WCRI) Florida Division, the primary interest on cancer research is to explore the native plants of Florida and the surrounding region for potential sources of therapeutic agents which may have action for the remission of toxicological or carcinogenic problems of human health. Thus, a purpose oriented systematic search for bioactive compounds from, for example, Floridian plant, Licania michauxii Prance (Chrysobalanaceae) in this laboratory has resulted in the isolation of two novel ent-kaurane diterpenoids. Our extensive research experience on various bioactive natural products as well as 13C- and 2D-NMR studies is utilized to elucidate the molecular structure of two ent-kaurenoids. One of the diterpenoids was found to be cytotoxic to cultured human hepatoma (HepG2) and colon carcinoma (Caco-2) cells, respectively. Previously, WCRI investigated the methanolic extract of the roots of the aforesaid plant showed cytotoxicity against cultured human hepatoma (HepG2) and colon carcinoma (Caco-2) cells as well as inducing effect on heat shock protein (hsp) 70 mRNA (Cancer Letters, 149, 61, 2000). In addition to Floridian plants, WCRI is also investigating many samples (terrestrial plants and marine organisms) collected from India and terrestrial plant samples obtained from Greece and other European countries.