Life has originated from the oceans that cover over 70% of the earth’s surface and contain highly ecological, chemical and biological diversity starting from microorganisms to vertebrates. This diversity has been the source of unique chemical compounds, which hold tremendous pharmaceutical potential. New trends in drug discovery from natural sources emphasize on investigation of the marine ecosystem to explore numerous complex and novel chemical entities.
Among the first bioactive compounds from marine sources, spongouridine and spongothymidine from the Caribbean sponge (Cryptotheca crypta), were isolated serendipitously in the early 1950s. They were approved as an anticancer drug (cytosine arabinoside, Ara-C) and an antiviral drug (adenine arabinoside, Ara-A), respectively, 15 years later. The secondary metabolites of marine organisms have been studied extensively over the past 30 years, since a small number of academic chemists began to isolate and elucidate novel compounds from marine sources in the 1970’s.
Drug discovery research from marine organisms has been accelerating and now involves interdisciplinary research including biochemistry, biology, ecology, organic chemistry, and pharmacology. These entities are the sources of new leads for treatment of many diseases such as cancer, AIDS, inflammatory conditions, and a large variety of viral, bacterial and fungal diseases. Because of the highly chemical and physical harsh conditions in marine environment, the organisms produce a variety of molecules with unique structural features and exhibit various types of biological activities.
Majority of the marine natural products have been isolated from sponges, coelenterates (sea whips, sea fans and soft corals), tunicates, opisthobranch molluscs (nudibranchs, sea hares, etc. ), echinoderms (starfish, sea cucumbers, etc. ) and bryozoans (moss animals) . Sponges, the most primitive multicellular invertebrates, considered as a gold mine during the past 50 years, have fascinated scientists for isolation of promising bioactive compounds for human welfare.
Published literature, patents and other scientific records on the genotoxicity and anticancer potentials of marine compounds revealed that few compounds have gone through preclinical evaluations. Interestingly, cytarabine (Cytostar-U) also known as Ara-C, a compound isolated from the Caribbean sponge Cryptotheca crypta currently being used with other anticancer drugs in the treatment of acute myelocytic leukaemia (AML) and lymphomas is one of the very few marine anticancer drugs studied in long-term clinical study.
Acyclovir, which was synthetically known as Ara-A, was modeled based on sponge-derived spongothymidine or spongouridine. Ara-A is the first sponge-derived antiviral compound in the market. Polyketide Calyculin A (a selective inhibitor of protein phosphatase 1, isolated from sponge Discodermia calyx),Okadaic acid, a potent inhibitor of protein phosphatases, especially protein phosphatases 1 and 2 respectively isolated from Luffariella variabilis and Halichondria okadai has reached the market undergoing from basic research to long phases of clinical study.
Saclike filter feeder tunicates have been reported to be an importent source in drug discovery. Study of marine organisms for their bioactive potential, being an important part of marine ecosystem, has picked up the rhythm in recent years with the growing recognition of their importance in human life. This interdisciplinary study of the life in the oceans ensures an exciting new frontier of scientific discovery and economic opportunity. By Malti . S. Dumbani, K. M. K COLLEGE OF PHARMACY.