A group from The City University of New York, USA, etc. has reported that GRFT/Carrageenan combination could provide higher antiviral activity against SARS-CoV-2 than using GRFT or Carrageenan independently.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8400000/
GRFT is a homodimeric lectin of 121 aminoacids and six carbohydrate-binding sites with high affinity for high mannose arrays. These mannose arrays are frequently found in viral spikes of important pathogens like HIV, HSV, hepatitis C virus (HCV), ebola virus, and members of the Coronaviridae family. The ability to block HIV in vitro, at picomolar concentrations, makes GRFT one of the most potent molecules inhibiting HIV replication.
Carrageenan is a kind of salfated polysaccharide (repeated structures of galactopyranose disaccharides) and three type of carrageenans are known (κ-Carrageenan (κ-CG), ι-Carrageenan (ι-CG), and λ-Carrageenan (λ-CG)). CG shows antiviral activity, and is generally recognized as safe (GRAS) by the Food and Drug Administration.
The half-maximal effective concentration (EC50) values for GRFT, CG, those mixtures measured against SARS-CoV-2 are summarized below.
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GRFT, 20.6µg/mL
ι-CG, 7.5µg/mL
λ-CG, 6.1µg/mL
ι-CG + GRFT (1:5), 0.2µg/mL
λ-CG + GRFT (1:5), 0.4µg/mL
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Let’s expect in vivo studies to be done to confirm this in vitro experimental results obtained with a cell-based pseudoviral infection assay.