Bioactive Molecules of Marine Invertebrates from South-West Indian Ocean: Status and Perspectives

Marine invertebrates produce a large number of unique and structurally diversified natural products which represent a major source of bioactive molecules, particularly for pharmaceuticals leads. This great potential has elicited worldwide scientific and economic interests in searching novel drugs from marine invertebrates. These efforts have resulted in several thousands of novel marine natural products exhibiting a wide range of bioactivities such as anticancer, antiviral, antifungal, and antibacterial properties. To date, the pioneering countries in marine natural products discovery such as USA, Japan, Australia, and Spain are benefiting from the great commercial and social value of such research. Since the early 1990s, the Chemistry Laboratory of Natural Substances and Food Sciences (LCSNSA, University of La Réunion) has been trying to gain a foothold in this field of research. The laboratory which is located at Reunion Island is at a strategic location for the research of natural bioactive molecules. Indeed, with a series of islands scattered in the western Indian Ocean along the southeast coast of Africa (Madagascar, Seychelles, the Comoros, Mayotte, Mauritius, Eparses islands), Reunion Island belongs to a global biodiversity hotspot. This paper will therefore provide an outline of the contribution made by the LCSNSA to marine natural products research in the west of Indian Ocean. Over the last 15 years, our research programs were more precisely concentrated on marine invertebrates from Reunion Island, Mayotte, and Madagascar. Among the numerous marine invertebrates encountered in these areas, sponges, ascidians, and soft corals have predominated in all our collection expeditions and have therefore received special attention from our research group. More than 100 new compounds showing relevant bioactivity were isolated. Among these compounds, a series of guanidine alkaloids, designated netamines A-S were isolated from a Madagascan sponge, Biemna laboutei. Absolute configurations of netamines I and J determined via a joint experimental and theoretical circular dichroism study are also discussed in this paper.