Sponges, Seaweeds and Sea Snails: A Treasure Trove of Undiscovered Medicines

Not many of us ever consider the origin of our medicine but if we stopped to wonder about where these magical treatments came from, our minds would probably turn to the jungle. Indeed, exotic plants found in the rainforest by intrepid explorers have been used in common medicines for centuries while even at home, many people turn to herbal remedies which come from local hedgerows or common herbs and roots. Yet very few of us consider the fact that some of our most recent medical breakthroughs have been found under the waves. With the oceans covering over two-thirds of the planet, it makes sense that they should host a whole treasure trove of potential medicines and cures.

The ocean’s medicinal potential has been known for centuries with the first evidence of humans using our ocean’s potions coming from almost 5,000 years ago in China. Over the course of our eclectic human history, sponges have been used to dress soldiers’ wounds, seaweed has been wrapped around inflamed warriors’ joints and even electric eels have been used to shock away extreme headaches. Simply floating in the salty water, breathing in sea air or looking out at the infinite horizon has long been thought to reduce common illnesses and now also improve mental health. Yet as our technology rapidly advances, we are increasingly moving away from exploration on land and plunging even deeper into the secrets held by the sea. The use of remotely operated vehicles and high quality scuba diving equipment is now helping us discover the ocean in a way that simply wasn’t possible 100 years ago. While rainforests host almost unbelievable diversity in their trees, flowers and tiny critters, oceans have their own highly diverse counterparts in the shape of bright sponges, corals and seaweeds, making the ocean the exciting new frontier in modern drug development.

The 1950s heralded the beginning of the marine pharmaceuticals industry when a shallow sponge resting in the tropical Caribbean Sea was investigated by scientists. They took two chemicals from the sponge and worked on them in the lab to eventually develop a revolutionary treatment for leukaemia and later in the 1980s, the drug which transformed HIV into a treatable condition. It seems safe to say that marine medicine started off with quite an incredible splash! So why is the ocean packed full of potential medicines? Most of the drugs we have developed from the ocean come from invertebrates which cannot move, for example corals and sponges which are fixed to the seabed. This means that these creatures are the easiest target for hungry predators as they cannot swim or put up a fight. Yet this means evolution has gifted them with powerful chemicals which they can emit to ward off any attackers and it is these substances which are so useful to us humans. Additionally, many of these invertebrates filter feed by sucking in water, taking in all the nutrients within it and then expelling the water back out. This feeding method means that they are highly likely to ingest any parasites or diseases which are suspended in the water and so they need a complex cocktail of chemicals to kill any potential bacteria which may make its way inside them. There is one more final trait which makes sponges and corals great for potential medicines. These creatures expand their range over their local patch of seabed but when two different species are competing to get a foothold on the same rugged bit of rock, they need an edge over their competitor. Therefore, many sponges and corals contain chemicals which hastily attack the dividing cells of a competing organism and this gives them great potential to treat rapidly expanding cancer cells.

One species which hosts a particularly toxic array of chemicals is the cone snail. In fact, the chemicals its tiny patterned shell hides can be deadly to humans, giving them the sinister nickname of ‘cigarette snail’ as once poisoned by this miniature mollusc, you only have time to smoke one cigarette before the toxins win against your body. One of the chemicals it houses is called omega-conopeptide and scientists have based the medicine ziconotide on this. This drug is an extremely powerful painkiller used for crippling, chronic pain as it blocks the nerves in the body which transmit pain signals. Ziconotide is much more powerful than morphine and thankfully all the toxic elements from the sea snail have been removed. Corals are now even considered to be used for bone grafts. A few decades ago, a scuba diving professor noticed how the porous structure of corals allowed water packed with nutrients to travel through the creature. He thought this would be a suitable model to base bone grafts on yet initial tests were unsuccessful as the coral never completely biodegraded within the body, leaving tiny pieces behind which attracted bacteria. Only recently have a new set of scientists found a potential solution. They have converted the calcium carbonate structure of coral into a more bone-like material called coralline hydroxyapatite which is now being trialled to understand if it is suitable for widespread use. Even the slimy seaweed which we overlook each time we take a trip to the sea is now being used in some countries as a new treatment to inhibit the progression of Alzheimer’s disease.

In fact, thousands of new compounds are isolated from the ocean each year and taken back to the lab to be analysed and tested, many of which are antibacterial, antifungal, antimalarial and anticancer. However, of course there is the ethical debate to be had. How can we balance drug development with marine conservation and animal rights? Modern scientific techniques allow us to extract the secrets from the ocean but leave the marine environment almost as we found it as once scientists have understood the DNA and chemicals at work within certain species, we can grow these chemical producing genes in laboratories in life forms such as bacteria and yeast, removing the need to harvest marine species on a major scale. For example, mangrove tunicate is a sea squirt which contains a compound used in chemotherapy. Yet to make just one gram of this essential drug, one tonne of sea squirts is needed. Thankfully though, scientists can artificially replicate the compound in laboratories, meaning this species remains untouched now we have understood its mysterious genetic make-up. In fact, some species we do not even have to touch at all, simply observing them is enough. Bottlenose dolphins observed in the Red Sea have been seen to rub their bodies along gorgonian corals, not just as a scratch but actually to self-medicate as the corals have been found to be covered in an antimicrobial mucus layer which can fight off infections.

While the ocean is delivering scientists with lots of exciting and promising samples, many of these products may not make it through the vigorous clinical trials and onto our shelves for another decade. Yet the sea promises to be worth the wait as it is giving us hope against the growing issue of antibiotic resistance. Some researchers are examining the slimy coating which covers the scales of some fish and has been found to destroy any bacteria in the water to help them fight diseases. By understanding the chemicals behind this gloopy substance, we could help reduce the spread of resistant bacteria and so far, some substances have been found which could be effective against MRSA.

So often our humble seaweeds, sponges and sea snails are forgotten about as we gaze in awe at our charismatic seals, dolphins and whales but these species could prove to be an incredible, essential resource in our future. 95% of our ocean remains unexplored and so it seems even more vital that we protect the ocean at all costs before we lose its hidden secrets and the potential medicines which could change the shape of our lives forever.

By Neve McCracken-Heywood