Table 3.

Summary of antiviral activity among carrageenans with each respective proposed mechanism of action and remarks on molecular weight and sulfate content of the tested compound.

Sulfated Polysaccharide	Virus Strain	Antiviral Activities	Proposed Mechanism of Action	Toxicity (Cell)	Remarks on Molecular Weight and Sulfate Content	Refs.
	CP (%)
ι-Carrageenan	HRV2	100% 2	ι-Carrageenan inhibits HRV2 entry to infect HeLa cell line	>1000 µg/mL (HeLa)		[11]
κ-Carrageenan		62% 2
λ-Carrageenan		55% 2
	log TCID50 1
ι-Carrageenan	HRV2	<2 2
κ-Carrageenan		~6 2
λ-Carrageenan		~6 2
	Viral Replication Inh. at 5 µg/mL
ι-Carrageenan	HRV1A	>99%	Reduces production of HRV particles on HeLa cell line	>500 µg/mL (HNep)		[11]
	HRV14	>99%
	HRV16	>99%
	HRV83	>99%
	HRV84	>99%
	Neutralization Activity
ιCarrageenan	SARS-CoV-2 Spike pseudotyped lentivirus	79% 3	Inhibits cell entry of the SARS-CoV-2 spike pseudotyped lentivirus	>100 µg/mL (Vero B4)	1. High molecular weight Fucoidan from U. pinnatifida and F. vesiculosus shows less than 50% reduction in infection 2. Polymer without sulfate found to be inactive	[88]
κ-Carrageenan		~80% 4
λ-Carrageenan		~80% 4
	EC50 (µg/mL)
λ-Carrageenan	SARS-CoV-2	0.9	1. Neutralizing viral glycoprotein HA 2. Blocking the VP harboring viral ribonucleoprotein complexes	>300 µg/mL (MDCK)	λ-carrageenan (1025 kDa) shows better solubility in cold water than other carrageenans because of its higher sulfate content	[90]
	Influenza A (H1N1)	0.3
	Influenza A (H3N2)	0.3
	Influenza B	1.4

CP = cell protection; HRV = human rhinoviruses followed with each respective strain number; HeLa = human cervical epithelial carcinoma cell line; HNep = human nasal epithelial cells; Vero B4 = embryonic African green monkey kidney cells; HA = hemagglutinin; VP = viral particles; MDCK = Madin–Darby canine kidney cells; ¹ value of viral replication inhibition; ² at 200 µg/mL concentration; ³ includes 2.6 µg/mL IC₅₀ for ι-carrageenan and percent neutralization obtained at 10 µg/mL; ⁴ at 100 µg/mL.