In Coral Reefs, Natural Medicines that Can Save Your Life Are Discovered.

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People commonly look to coral reefs as a potential source of future wonder drugs. It falls short of expectations. In coral reefs, researchers discover new complex compounds almost everywhere they look. These molecules have promise for treating a wide range of illnesses and ailments, including cancer, HIV, Alzheimer's disease, chronic pain, and wrinkles. Researchers in coral reefs have identified over 20,000 distinct molecules with the potential to be utilized as pharmaceuticals, and the number of compounds on this list grows by more than 1,000 every year.

Why are potential medications so abundant in coral reefs?

Any natural creature's day-to-day life is dangerous, but this is especially true for species that live on coral reefs and are unable to evacuate by swimming away, such as sponges, anemones, and many different types of mollusks, as well as the corals themselves. These species are referred regarded as "sessile" because they cannot move at all, like a coral polyp, or can only move very slowly, like certain sponges. Corals and their sessile companions have had to turn to additional ways of defense against invading animals, illnesses, and parasites, as well as direct risks of physical injury such as being devoured. This is due to the ability of fish, most crustaceans, octopi, and squid to flee when threatened.

Although visible protection systems like spines, shells, and stone exoskeletons are amazing, they can only protect an organism so much. Instead, many coral reef creatures, notably marine sponges and corals have turned to chemical warfare to defend themselves against illnesses, other competitors, and predators.

Coral reef habitats are a remarkable treasure trove of chemical defense mechanisms. Some of the defensive chemicals are produced directly by the animals, while others are produced by microbes with which the animals have formed mutually advantageous alliances. Depending on the chemical and the circumstances, reef animals can use the compounds to keep other animals out of their personal space, to assist themselves in healing from an injury, to protect against environmental threats such as ultraviolet radiation, to discourage other animals from snacking on them, and to prevent algae and other oozing microorganisms from growing a slimy coat over them, a process known as "biofouling."

Coral reefs have been in our oceans since the Devonian period, some 410 million years ago. However, the average age of a living coral reef today is only 10–20,000 years. Corals had been present for around 90 million years before they started building reefs, while sea sponges had been there for at least 100 million years before corals appeared. This suggests that coral reef species have had at least 600 million years to develop a range of chemical defenses against the shifting and diverse threats they confront.

Over the period of more than a half-billion years, how many unique chemical compounds have reef species developed? Since the late 1990s, when scientists began really researching the pharmaceutical potential of coral reefs, they have discovered around 500 new compounds per year. On an annual basis, that figure has almost doubled since then.

Every year, scientists find new substances in coral reef creatures. Steroids and terpenes, as well as acids and alkaloids, are examples of these compounds. Sea sponges are the most abundant source of these chemicals found in reefs, followed by corals and other microbes including fungus and cyanobacteria. (Because sponges lack circulatory and nervous systems, their cellular activity is mostly coordinated by chemical transfer.)

Most of these chemicals have little medical use. However, treatments for coral reefs are being created that are already saving lives. Researchers discovered spongothymidine and spongouridine in Tectitethya crypta, a Caribbean reef sponge. Cytarabine, a chemotherapy medicine derived from spongothymidine that saved Arden O'Connor's life, was already in clinical use in 1969. Cytarabine was frequently given to patients whose leukemia had become resistant to previous therapies. Cytarabine has been linked to a few cases of apparent full remission in people whose cancer was terminal at the time of treatment.

Vidarabine, a spongouridine-derived antiviral medication, is effective against herpes simplex and varicella-zoster; however, acyclovir, which is less irritating to patients, has largely taken its place in recent years.

Eribulin is a synthetic medication that was created by making a minor change to the molecule Halichrondin B. Halichrondin B was first isolated in 1986 from the marine sponge Halichondria okadai. Eribulin was created as a cancer treatment. Eribulin, which was approved by the FDA for use in clinical trials in 2010, has been shown to be effective in treating liposarcomas as well as metastatic breast tumors, both of which are often fatal.

Antillogorgia elisabethae, also known as "sea whip," is a glycoside chemical found in the Caribbean coral Antillogorgia elisabethae. It is an effective anti-inflammatory that is mild enough to be used in cosmetics.

It is not unusual for microorganisms found among corals to be the source of potential new medications. A fungus culture taken from the coral Echinogorgia rebekka in the South China Sea was found to have antibacterial properties in a 2011 study. One of the substances discovered was shown to be extremely effective in eliminating the bacteria Micrococcus tetragenus. Secondary respiratory infections caused by this bacterium can lead to blood poisoning.

The cyanobacterium Lyngbya, which was discovered in a coral off the coast of Fort Lauderdale, Florida, may hold some promise as a source of novel antiviral medications that could be used to combat HIV and other diseases. This is due, in part, to the fact that Lyngbya contains a number of potential protease inhibitor medications, which interfere with viral reproduction. One reason for this is that Lyngbya contains a molecule that, according to some reports, is capable of disabling protease inhibition. This opens the door to the development of more powerful antiviral medications, assuming researchers can figure out how to turn them off. The protease inhibitors found in Lingbya appear to reduce the appetites of animals that may consume the cyanobacteria. This could be a defense mechanism against predators.

Other organisms, in addition to marine sponges, coral, and microbes, are capable of producing potentially new drugs. The crinoid Colobometra perspinosa, also known as the black feather star, produces compounds that have the ability to kill cancer cells. Ziconotide, a painkiller derived from the venom of a reef-dwelling predatory sea snail, is an effective last-ditch effort for patients who have reached the end of their opiates. The Elysia rufescens reef sea slug feeds on Bryopsis algae, which produce the chemical kahalalide F. The kahalalide F protects the algae and sea slugs from predatory fish attacks. Furthermore, it shows great promise in the treatment of advanced melanomas.

Furthermore, reefs could help to solve the growing problem of antibiotic resistance. Over the last decade, studies on the chemical algeferin, which is secreted by Agelas sponges, have revealed that it can ostensibly turn off bacterial resistance to antibiotics. As a result, microorganisms become more vulnerable to our increasingly antiquated arsenal of antibacterial drugs like ciprofloxacin. Because algeferin does not directly harm bacteria, researchers believe bacteria will develop resistance to it over time. Antibiotic-resistant pathogens such as Pseudomonas aeruginosa and MRSA can be rendered susceptible to algeferin.

Because coral reefs are already under threat, using organisms from coral reefs poses a significant challenge. They don't need the pharmaceutical industry to clearcut them for miracle drugs, as poachers did in the 1990s when it was discovered that the trees contained a promising chemotherapy drug called taxol.

Potential drugs found in coral reef organisms are frequently found in very low concentrations within the tissues of the animals. This raises the possibility of unsustainable overharvesting, similar to what happened with Pacific yew, endangering the coral reef ecosystem. If a few square meters of sponges are required to extract one dose of a drug that a person may take twice a day for the rest of her life, that person will be responsible for significant sponge deforestation over the course of her lifetime.

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References

1. clarke chris. We’re Finding Amazing, Life-Saving Natural Medicines in Coral Reefs. KCET. 2017 Mar 23 [accessed 2022 May 17]. https://www.kcet.org/shows/earth-focus/discovering-life-saving-medicines-in-coral-reefs

2. Peixoto RS, Sweet M, Bourne DG. Customized Medicine for Corals. Frontiers. 2001 Jan 1 [accessed 2022 May 17]. https://www.frontiersin.org/articles/10.3389/fmars.2019.00686/full

3. Medicine - Coral Reef Alliance. Coral Reef Alliance. 2021 Sep 14 [accessed 2022 May 17]. https://coral.org/en/coral-reefs-101/why-care-about-reefs/medicine/

4. DANIEL CAMILO THOMPSON POO. Did you know coral reefs produce medicine? | Interamerican Association for Environmental Defense (AIDA). Interamerican Association for Environmental Defense (AIDA). 2018 May 28 [accessed 2022 May 15]. https://aida-americas.org/en/blog/did-you-know-coral-reefs-produce-medicine

5. ANDREW W. BRUCKNER. Life-Saving Products from Coral Reefs. Issues in Science and Technology. 1970 Jan 1 [accessed 2022 May 14]. https://issues.org/p_bruckner-coral-reefs-importance/

6. Moore E. The Coral Reef Medicine Cabinet • Eat BlueTM. Eat BlueTM. 2020 Dec 23 [accessed 2022 May 17]. https://www.eat.blue/ocean-health/the-coral-reef-medicine-cabinet/