Table 4.

The role of polyphenols against SARS-CoV, MERS-CoV, and SARS-CoV-2.

Polyphenols	Representative	Form/Source	Virus	Mechanism	Reference
Phenolic acids
Hydrobenzoic acids	Gallic acid	Tetra-O-galloyl-β-D glucose from Galla chinensis	SARS-CoV	Avidly binds with surface spike protein of SARS-CoV.	Yi et al. (2004)
	Hydrobenzoic acid	Desmethoxyreserpine	SARS-CoV-2	Inhibit replication of 3CLpro, and entry.	Kesel (2005)
Flavonoids
Flavonols	Kaempferol	Kaempferol derivatives, Kaempferol	SARS-CoV	Inhibit 3a ion channel of CoVs.	Schwarz et al. (2014)
			MERS-CoV, SARS-CoV	Inhibit PLpro.	Park et al. (2017)
				Inhibit SARS-3CLpro activity.
	Quercetin	Quercetin, Quercetin 3-β-D-glucoside, isobavachalcone, and helichrysetin	MERS	Inhibit cleavage activity of MERS-3CLpro enzyme.	Jo et al. (2019)
		Quercetin, Quercetin-β-galactoside	MERS-CoV, SARS-CoV	Inhibit PLpro.	Park et al. (2017)
				Inhibit SARS-3CLpro activity.
		Quercetin and TSL-1 from Toona sinensis Roem	SARS-CoV	Inhibit the cellular entry of SARS-CoV.	Chen et al. (2008)
		Quercetin	SARS-CoV-2	PLpro and 3CLpro enzyme.	Park et al. (2013)
	Myricetin	Myricetin	SARS-CoV	Inhibit nsP13 by affecting the ATPase activity.	Yu et al. (2012)
				SARS-CoV helicase inhibitor.
	Herbacetin	Herbacetin	MERS	Inhibit cleavage activity of MERS-3CLpro enzyme.	Jo et al. (2019)
			SARS-CoV	block the enzymatic activity of SARS-CoV 3CLpro.	Jo et al. (2020)
	Papyriflavonol A	Broussonetia papyrifera	MERS-CoV, SARS-CoV	Inhibit PLpro.	Park et al. (2017)
	Kazinol A, B, F and J, and broussoflavan A			Inhibit SARS-3CLpro activity.
	Amentoflavone,	Torreya nucifera leaves	SARS-CoV 3CL pro inhibitor		Ryu, Park, et al. (2010)
	Kaempferol, quercetin, luteolin-7-glucoside, demethoxycurcumin, naringenin, apigenin-7-glucoside, oleuropein, curcumin, catechin, epicatechingallate, zingerol, gingerol, and allicin	Traditional herbs	Inhibitors of SARS-CoV-2-Mpro	block the enzymatic activity of SARS-CoV 3CLpro.	Khaerunnisa et al. (2020)
Flavones	Apigenin	Ocimum basilicum	SARS-CoV	Inhibit PLpro.	Pandey et al. (2020)
				Inhibit SARS-CoVpro activity.
	Baicalin	Scutellaria baicalensis	SARS-CoV	Inhibit Angiotensin-converting enzyme.	Chen and Nakamura (2004)
	Scutellarein	Scutellaria lateriflora	SARS-CoV	Inhibit nsP13 by affecting the ATPase activity.	Yu et al. (2012)
	Rhoifolin	Rhus succedanea.	SARS-CoV	Inhibit SARS-3CLpro activity.	(Gong et al., 2008; Nguyen et al., 2012)
	Luteolin	luteolin, from Veronicalina riifolia	SARS-CoV	Avidly binds with surface spike protein of SARS-CoV.	Yi et al. (2004)
	Daidzein	Plant-derived phenolic compounds and Root extract of Isatis indigotica	SARS-CoV	Not active.	Lin et al. (2005)
	30-(3-methylbut-2-enyl)-30,4,7-trihydroxyflavone	Broussonetia papyrifera	MERS-CoV, SARS-CoV	Inhibition of cysteine proteases CoV	Park et al. (2017)
	neobavaisoflavone	Psoralea corylifolia	SARS-CoV	Inhibitory activity toward SARS-CoV PLpro.	Kim et al. (2014)
Flavanones	Herbacetin,	Plant-derived phenolic compounds and Root extract of Isatis indigotica,	SARS-CoV	Inhibit the cleavage activity of the SARS-3CLpro enzyme.	Jo et al. (2020); Lin et al. (2005)
	Rhoifolin pectolinarin Tetra-O-galoyl-β-d-glucose (TGG) luteoline
	Pelargonidin	Pimpinella anisum	SARS-CoV-2	Binding affinities to 3C-like protease of SARS-CoV-2	Hasan et al. (2020)
	Bavachinin	Psoralea corylifolia	SARS-CoV	Inhibitory activity toward SARS-CoV PLpro.	Kim et al. (2014)
Anthocyanidins	10 polyacylated and monomeric anthocyanins	Bure components	SARS-CoV-2	Constructively network with catalytic dyad residues of 3CLpro of SARS-CoV-2.	Khalifa, Nawaz, et al. (2020)
Flavanols	Epigallocatechin gallate	Green tea	SARS-CoV	Inhibit SARS-3CLpro activity.	(Gong et al., 2008; Nguyen et al., 2012)
	Gallocatechin gallate and epicatechingallate	Green tea	SARS-CoV	Inhibit SARS-3CLpro activity.	(Gong et al., 2008; Nguyen et al., 2012)
	gallocatechin-3-gallate	Green tea	SARS-CoV	Inhibit SARS-3CLpro activity.	Ghosh, Chakraborty, Biswas, and Chowdhuri (2020)
Chalcone	Isoliquiritigenin	Glycyrrhiza glabra	MERS-CoV, SARS-CoV	Inhibit PLpro.	Park et al. (2017)
				Inhibit SARS-3CLpro activity.
	Broussochalcone B, broussochalcone A, and 4-hydroxyisolonchocarpin	Broussonetia papyrifera	MERS-CoV, SARS-CoV	Inhibit PLpro.	Park et al. (2017)
				Inhibit SARS-3CLpro activity.
	isobavachalcone	Psoralea corylifolia	SARS-CoV	inhibitory activity toward SARS-CoV PLpro.	Kim et al. (2014)
	4’ -O-methylbavachalcone	Broussonetia papyrifera	MERS-CoV, SARS-CoV	Inhibit PLpro.	Park et al. (2017)
				Inhibit SARS-3CLpro activity.
Tannins	19 hydrolysable tannins	Bure components	SARS-CoV-2	Efficacious and selective anti-COVID-19 therapeutic compounds.	Khalifa, Zhu, et al. (2020)