Scientists find a seaweed extract that is better at blocking COVID-19 than remdesivir

Edible seaweeds or sea vegetables are already known to be an excellent source of food and nutrition among people across South-East Asia. Now, researchers at the Rensselaer Polytechnic Institute in the US have found that an extract of one particular seaweed could be a game-changer in the global pandemic caused by COVID-19.

Their study, published in the journal Cell Discovery, showed that the extract of an edible seaweed named Saccharina japonica outperformed antiviral drug remdesivir in blocking COVID-19 infection.

Blocking, how?

SARS-CoV-2, the virus that causes COVID-19, enters the body through the nose, eyes or mouth. Once inside, it tries to latch on to ACE-2 receptors which are present on our blood vessels, and in organs like the lungs, heart and kidneys. The seaweed extract RPI-27 offers the virus something else to latch on to—basically, it tricks the virus to leave the ACE-2 receptors alone and therefore "block" the infection.

Similar techniques and experiments have been successfully conducted against viruses that cause other infectious diseases, such as influenza type A, as well as dengue and Zika viral fever.

To be sure, blocking viruses in this way isn't the only way to stop or treat an infection: while some antiviral medicines prevent the virus from replicating (and let the body's immune system do the rest), others may block the virus from entering healthy cells in the first place. This study looked at the potential of medicines to block the COVID-19 virus.

The findings

RPI-27 was just one of the compounds these researchers were testing though: they also looked at the effectiveness of heparin, a common blood thinner, for blocking SARS-CoV-2. They found that while RPI-27 was more effective in blocking the new coronavirus infection in this way than the antiviral remdesivir by a factor of 9x, heparin was less effective. They also found that this seaweed extract (a type of fucoidans) was safe for human consumption.

COVID-19 has led to over 15 million infections and over 639,000 deaths worldwide, remdesivir, a drug originally created for the treatment of Ebola, is currently being used to reduce the duration of hospitalisation in COVID-19 patients.

As the scientific community continues its race towards developing a vaccine or finding a cure for COVID-19 or both, any good news should be linked to a reminder that we are some way off from finding a definitive treatment. This seaweed extract, too, would have to be tested and tried in the same way as other drugs like remdesivir. Only if it proves to be effective again and again and again—and safe—would it make it to the chemist's shop around the corner from your house.

Heparin also effective against SARS-CoV-2

Heparin also effective against SARS-CoV-2

The scientists used five different compounds to test their efficacy against the SARS-CoV-2 virus on mammalian cells: three variants of the common blood thinner named heparin, and two fucoidan or highly sulfated polysaccharides (RPI-27 and RPI-28)—extracted from the seaweed Saccharina japonica—were used in the experiments. The researchers conducted a type of dose-response study called EC50 on the cells—to find out the concentration at which each compound could block 50% of the virus' infectivity. The lower the value in the result, the more potent the compound.

The seaweed extract RPI-27 produced an EC50 value of about 83 nanomolar as compared to remdesivir's EC50 score of 770 nanomolar, producing a much stronger antiviral response than the drug being widely used in the treatment of the viral infection.

Heparin, on the other hand, yielded an EC50 value of 2.1 micromolar, which makes it one-third as active as remdesivir, while another variant of heparin produced an EC50 response of 5.0 micromolar. None of the compounds had any cellular toxicity, as confirmed by another test.

The findings of the new research suggest that even a common (an inexpensive) drug like heparin could be critical in the treatment of future COVID-19 patients by interfering with the virus's infectivity in the cells.

The study's findings were also in line with an earlier study that was published last month that researched the antiviral properties of seaweed polysaccharides, even as there is a severe lack of immunisation against the pandemic-causing coronavirus. The earlier study, published in the Journal of Applied Phycology said: "many species of marine algae contain significant quantities of complex structural sulphated polysaccharides that have been shown to inhibit the replication of enveloped viruses".

SARS-CoV-2 is an "enveloped virus": its basic structure can be broken down into three components: the genetic material of the virus or the single-strand RNA, the shell or envelope covering this strand and spike proteins that virus uses to gain entry into healthy cells. RPI-27 uses these spike proteins to bind with the virus, to block its entry into healthy cells.

Further, the researchers at the Rensselaer Polytechnic Institute expressed hope that the extract—if it proves useful in further trials and tests—may be delivered as a prophylactic (as a preventive measure) and painlessly through a nasal spray or orally as a pill.