Antitumor potential of natural products from Mediterranean ascidians

With regard to drug discovery and development, natural products marine sources started to attract interest from pharmaceutical companies and research institutions only 40 years ago, with the advent of high performance liquid chromatography (HPLC), and the new NMR and Mass techniques. Since then, marine sources have provided well over 18,000 different natural products many of them being structurally unique and absent in terrestrial organisms. Incidence of biological activity in marine derived compounds is high, especially with regard to cytotoxicity where marine-derived extracts surpass those of terrestrial origin. It is no surprise therefore that marine natural products have their stronghold in the area of anti-cancer chemotherapy as indicated by the list of compounds currently under clinical investigation. Ascidians, invertebrates belonging to the subphylum Urochordata (Tunicata), are renowned for their great chemical diversity and, during the last 25 years, they have been shown to produce an array of cytotoxic molecules. Among the first six marine-derived compounds that have reached clinical trials as antitumor agents, three are derived from ascidians [1], as evidence of the high potential of these organisms as a new source of antitumor compounds. In the course of our research activities on marine ascidians from the Mediterranean Sea, we discovered a number of new molecules with different structural features but all endowed with antiproliferative or cytotoxic activity. [2-6]. Reported in this communication are some of our recent results on the chemistry and bioactivity of these natural products, which strongly support the hypothesis that ascidians natural products could play a highly significant role in anticancer drug discovery and development process.