Do medicines come from the sea?

While most drugs derived from natural sources currently come from terrestrial (land-based) organisms, research suggests that marine invertebrates produce more antibiotic, anti-cancer, and anti-inflammatory substances than any group of terrestrial organisms.

The deep-sea sponge, Forcepia species, produces a series of compounds called lasonolides, which exhibit promising biomedical properties for the treatment of pancreatic cancer.

The deep-sea sponge, Forcepia species, produces a series of compounds called lasonolides, which exhibit promising biomedical properties for the treatment of pancreatic cancer. Download image (jpg, 42 KB).

People who are not familiar with ocean exploration often believe that the primary reason for investigating deep-sea ecosystems is little more than scientific curiosity. This perspective quickly changes, however, when they learn that these ecosystems are the source of promising new drugs for treating some of the most deadly human diseases.

Most drugs in use today come from nature. Aspirin, for example, was first isolated from the willow tree. Penicillin was discovered from common bread mold. To date, almost all of the drugs derived from natural sources come from land-dwelling organisms. But recently, systematic searches for new drugs have shown that marine invertebrates produce more antibiotic, anti-cancer, and anti-inflammatory substances than any group of terrestrial organ­isms. Particularly promising invertebrate groups include sponges, tunicates, ascidians, bryozoans, octocorals, and some molluscs, annelids, and echi­noderms.

Some chemicals produced by marine animals that may be useful in treating human diseases include:

  • Ecteinascidin: Extracted from tunicates; being tested in humans for treatment of breast and ovarian cancers and other solid tumors
  • Discodermalide: Extracted from deep-sea sponges belonging to the genus Discodermia; anti-tumor agent
  • Bryostatin: Extracted from the bryozoan, Bugula neritina; potential treatment for leukemia and melanoma
  • Pseudopterosins: Extracted from the octocoral (sea whip) Pseudopterogorgia elisabethae; anti-inflammatory and analgesic agents that reduce swelling and skin irritation and accelerate wound healing
  • w-conotoxin MVIIA: Extracted from the cone snail, Conus magnus; potent pain-killer

A striking feature of this list is that all of the organisms (except the cone snail) are sessile (non-moving) invertebrates. To date, this has been true of most marine invertebrates that produce pharmacologically active substances. Several reasons have been suggested to explain why sessile marine animals are particularly productive of potent chemicals. One possibility is that they use these chemicals to repel predators, because they are basically “sitting ducks.” Another possibility is that since many of these species are filter feeders, they may use powerful chemicals to repel parasites or as antibiotics against disease-causing organisms.

Competition for space may explain why some of these invertebrates produce anti-cancer agents. If two species are competing for the same piece of bottom space, it would be helpful to produce a substance that would attack rapidly dividing cells of the competing organism. Since cancer cells often divide more rapidly than normal cells, the same substance might have anti-cancer properties.