The CoviD-19 saga: Seaweed Extract rivals Remdesivir

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Gulaman lovers, hear hear!

Those who love seaweed might be in for some exciting news on recent scientific developments around these marine plants in the context of the pandemic.

A range of polysaccharides extracted from edible seaweed, in new lab trials, have been shown to at least match the efficacy of remdesivir, the current standard antiviral used to combat Covid-19.

Heparin is a common blood thinner that can be extracted from seaweed, as well as fucoidans. In the July 2020 study published in Cell Discovery, Nature, Paul S. Kwon and co-authors tested the antiviral activity in three variants of heparin (heparin, trisulfated heparin, and a non-anticoagulant low molecular weight heparin) and two fucoidans (RPI-27 and RPI-28) extracted from the seaweed Saccharina japonica.

All five compounds are long chains of sugar molecules known as sulfated polysaccharides.

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

Tricking the Virus

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. The spike protein on the surface of SARS-CoV-2 latches onto the ACE-2 receptor, a molecule on the surface of human cells.

Once secured, the virus inserts its own genetic material into the cell, hijacking the cellular machinery to produce replica viruses. In this way, it can spread throughout a person’s body.

"Heparin" by Sixflashphoto is licensed under CC BY 4.0
“Heparin” by Sixflashphoto is licensed under CC BY 4.0

One way to inhibit the spread of this virus between people is through hand-washing. 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 (the spike) 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.

The study shows that the polysaccharides from the seaweed extract can act as “decoy molecules” which are attacked by the virus instead of human cells, neutralizing the virus before it degrades naturally.

Robert Linhardt, a Rensselaer professor of chemistry and chemical biology, explains that the current thinking of Covid-19 infection starting in the nose could mean the seaweed extracts being studied could be a basis for a nasal spray. The researchers are considering the extract as an early treatment or even a prophylaxis for infection prevention.

The researchers note that its distinction from Remdesivir is it’s mode of delivery. Remdesivir is delivered intravenously, while fucoidans can be administered orally and is generally safe. Meanwhile heparin is not orally bioavailable. Jonathan Dordick, one of the researchers and a professor of chemical and biological engineering at Rensselaer, added that an oral delivery approach may address potential gastrointestinal infection of CoviD-19.

The researchers suggested that treatment of fucoidans, nebulized heparin, or possibly TriS-heparin in combination with or without current antiviral therapies, should be assessed first in human primary epithelial cells and then in human patients suffering from Covid-19.

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