New research concludes that extracts from seaweed could be more effective than remdesivir, the current leading SARS-CoV-2 antiviral drug.

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Compounds extracted from brown seaweed might help treat COVID-19.

The authors published their research as a correspondence piece in the journal Cell Discovery. It lays the groundwork for future studies to corroborate the findings in humans.

SARS-CoV-2, like all viruses, reproduces by attaching to a host cell’s membrane, inserting its genetic material and using the cell’s resources to create replica viruses. In this way, it can spread throughout a person’s body.

One way to inhibit the spread of this virus between people is through handwashing. While it removes contaminated material, soap can also damage the outer envelope of a SARS-CoV-2 particle, which stops it from latching on to other cells.

Antiviral drugs that target SARS-CoV-2 often work differently. Rather than damaging the virus’s outer membrane, they bind with the component that attaches to the host’s cells. When this occurs, the virus is disarmed and cannot infect cells to replicate itself. This is how the current leading SARS-CoV-2 antiviral drug remdesivir works.

However, this manner of combating viruses leaves room for improvement. As Prof. Jonathan Dordick of the Rensselaer Polytechnic Institute in Troy, NY, a corresponding author of the new study, notes, “[w]e’re learning how to block viral infection, and that is knowledge we will need if we want to confront pandemics rapidly.”

“The reality is that we don’t have great antivirals. To protect ourselves against future pandemics, we will need an arsenal of approaches that we can quickly adapt to emerging viruses.”

– Prof. Jonathan Dordick

Previously published research from some of the authors of the current study suggests a possible source for an effective SARS-CoV-2 antiviral drug is seaweed.

Heparin is a common blood thinner that can be extracted from seaweed. The present study looked at three variants of heparin and two related fucoidans — a substance that can be obtained from brown seaweed — to see how effective they would be as decoys for SARS-CoV-2 in a laboratory setting.

The researchers applied the extracts to mammalian cells and measured enough for each one to reduce the effectiveness of the virus by 50%.

The researchers found that one of the fucoidans and two of the heparin extracts required a significantly lower concentration than remdesivir to reduce the virus’s effectiveness to 50%.

Furthermore, when used in high concentrations, a separate test found that none of the extracts showed any cellular toxicity, meaning they were likely to be safe.

According to Prof. Robert Linhardt, a co-author of the research, their findings could help discover new techniques to deliver the antiviral to COVID-19 patients.

“What interests us is a new way of getting at infection,” said Prof. Linhardt. “The current thinking is that the COVID-19 infection starts in the nose, and either of these substances could be the basis for a nasal spray. If you could treat the infection early, or even before you have the infection, you would have a way of blocking it before it enters the body.”

According to Prof. Dordick, the seaweed extracts may have use beyond COVID-19, and “could serve as a basis for an oral delivery approach to address potential gastrointestinal infection.”

The authors of the study researched the possibility of seaweed extract as a SARS-CoV-2 antiviral after studying the shape of the virus particles and how they function to deter a person’s normal antiviral defenses.

“It’s a very complicated mechanism that we quite frankly don’t know all the details about, but we’re getting more information,” said Prof. Dordick. “One thing that’s become clear with this study is that the larger the molecule, the better the fit. The more successful compounds are the larger sulfated polysaccharides that offer a greater number of sites on the molecules to trap the virus.”

While promising in theory, researchers need to corroborate the findings in living human cells to see if the extracts can form the basis of a new SARS-CoV-2 antiviral drug.