Table 1.

The basic skeleton of the various classes and biological activity of flavonoids.

Classification	Flavonoid	Biological Activity	References
Flavanones	Naringenin (5,7-dihydroxy-2-(4-hydroxyphenyl)-chroman-4-one)	Antifibrinolytic, decreases pro-inflammatory cytokines in hepatocytes, antineoplastic activity (breast cancer, prostate cancer, lung cancer, and colon cancer), a promising treatment strategy against COVID-19, and therapeutic application in bone disorders and bone tissue engineered constructs	[11,12,13,14,15,16,17,18,19,20,62,63]
	Hesperitin ((2S)-5,7-dihydroxy-2-(3-hydroxy-4-methoxyphenyl)-2,3-dihydrochromen-4-one)	Anti-diabetic, antioxidant, anti-inflammatory, anticancer, antiviral, antibiofilm, antimicrobial, and cardiovascular protective activities	[21,22,23,24,25,64]
	Eriodictyol (2-(3,4-dihydroxyphenyl)-5,7-dihydroxy-2,3-dihydrochromen-4-one)	Cardiotonic, skin protection, antitumoral, antioxidant, anti-inflammatory, immunomodulatory, and hepatoprotective	[26,27,28]
	Silymarin (3,5,7-trihydroxy-2-[3-(4-hydroxy-3-methoxyphenyl)-2-(hydroxymethyl)-2,3-dihydro-1,4-benzodioxin-6-yl]-2,3-dihydrochromen-4-one)	Antioxidant, anti-inflammatory, and anticancer	[65]
Flavones	Apigenin (5,7-dihydroxy-2-(4-hydroxyphenyl)-chromen-4-one)	Neuroprotective	[32]
	Baicalein (5,6,7-trihydroxy-2-phenyl-4H-chromen-4-one)	Neuroprotective, antiviral activity, possible treatment agent against SARS-Cov2	[31,33,66]
	Wogonin (5,7-dihydroxy-8-methoxy-2-phenyl-4H-chromen-4-one)	Neuroprotective	[31,33]
	Luteolin (2-(3,4-dihydroxyphenyl)-5,7-dihydroxychromen-4-one)	Anti-inflammatory, antiallergy, and anticancer	[67]
	Chrysin (5,7-Dihydroxy-2-phenyl-4H-chromen-4-one)	Neuroprotective, anti-aging, skin protective, antioxidant, anti-inflammatory, anticancer, anti-diabetic, vasodilatory effect, and antihypertensive	[68,69,70,71]
	Acacetin (5,7-dihydroxy-2-(4-methoxyphenyl)-chromen-4-one)	Antiproliferative, neuroprotective, cardioprotective, anticancer, anti-inflammatory, anti-inflammatory diabetic, antimicrobial	[72]
	Diosmetin (5,7-dihydroxy-2-(3-hydroxy-4-methoxyphenyl)-chromen-4-one)	Antioxidant, anti-inflammatory, anti-apoptotic, and anticancer properties	[73]
Isoflavones	Genistein (5,7-dihydroxy-3-(4-hydroxyphenyl)-chromen-4-one)	Fungistatic, antibacterial, antiviral, anti-inflammatory, kidney protective, antioxidant, prevents angiogenesis, exerts estrogenic and/or antiestrogenic effects, and promising therapeutic application in bone disorders and bone tissue engineered constructs	[34,38,39,63,74,75,76,77]
	Daidzein (7-hydroxy-3-(4-hydroxyphenyl)-chromen-4-one)	Fungistatic, antibacterial, antiviral, antioxidant, prevents angiogenesis, exerts estrogenic and/or antiestrogenic effects, and promising therapeutic application in bone disorders and bone tissue engineered constructs	[34,38,39,63,77,78,79]
	Glycitein (7-hydroxy-3-(4-hydroxyphenyl)-6-methoxychromen-4-one)	Fungistatic, antibacterial, antiviral, antioxidant, prevents angiogenesis, and exerts estrogenic and/or antiestrogenic effects	[34,38,39,80,81]
	Formononetin (7-hydroxy-3-(4-methoxyphenyl)-chromen-4-one)	Fungistatic, antibacterial, antiviral, antioxidant, anti-inflammatory, neuroprotective, prevents angiogenesis, and exerts estrogenic and/or antiestrogenic effects	[34,38,39,82,83,84]
Flavonols	Quercetin (3,3,4,5,7-pentahydroxyflavone)	Downregulates malondialdehyde level and scavenges several free radicals (e.g., hydrogen peroxide, superoxide, and hydroxyl radicals), increases cell IFN-γ expression, decreases interleukine-4-positive cell expression, induces extrinsic and intrinsic pathways of apoptosis and autophagy, antimicrobial activity, inhibits biofilm formation, inhibits nucleic acid synthesis, antiviral activity, and possible treatment against SARS-Cov2	[41,42,43,44,45,66]
	Rutin (3,3′,4′,5,7-pentahydroxyflavone-3-rhamnoside)	Anti-inflammatory, anti-hypolipemiant, anti-atherosclerotic, antiallergic, anti-inflammatory, and antiviral	[46,47,48,49]
	Morin (2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxychromen-4-one)	Antioxidant, anti-inflammatory, anticancer, anti-diabetic, anti-inflammatory, antihypertensive, and gastric protector effects	[85]
	Kaempherol (3,5,7-trihydroxy-2-(4-hydroxyphenyl)-chromen-4-one)	Antioxidant, antimicrobial, and anti-inflammatory	[86,87]
	Myricetin (3,5,7-trihydroxy-2-(3,4,5-trihydroxyphenyl)-chromen-4-one)	Antioxidant, anti-inflammatory, anti-diabetic, anti-epileptic, anti-Alzheimer, anti-apoptotic, antithrombotic, neuroprotective, potential therapeutic agent against COVID-19, and hepatoprotective effect	[88,89,90]
Flavanols	Catechin (2-(3,4-dihydroxyphenyl)-3,4-dihydro-2H-chromene-3,5,7-triol)	Anti-inflammatory, anticancer, antiviral, antimicrobial, and protective cardiovascular properties	[50,51,52,53]
	Epigallocatechin (2-(3,4,5-trihydroxyphenyl)-3,4-dihydro-2H-chromene-3,5,7-triol)	Anti-inflammatory, anticancer, antiviral, antifungal, antimicrobial, and protective cardiovascular properties	[50,51,52,53,66]
	Afzelechin (2-(4-hydroxyphenyl)-3,4-dihydro-2H-chromene-3,5,7-triol)	Anti-inflammatory, anticancer, antiviral, antimicrobial, and protective cardiovascular properties	[50,51,52,53]
Anthocyanins	Cyanidin (2-(3,4-dihydroxyphenyl)-chromenylium-3,5,7-triol)	Immunomodulator and anti-inflammatory	[57,58,61]
	Delphinidin (2-(3,4,5-trihydroxyphenyl)-chromenylium-3,5,7-triol)	Anti-HER-2 effect, regulates the protein expression level of Bax and Bcl-2, inhibits the activation of NF-κB, induces G2/M phase arrest and apoptosis, pro-apoptotic, anti-proliferative effects, and anti-inflammatory	[59,60,61]
	Pelargonidin (2-(4-hydroxyphenyl)-chromenylium-3,5,7-triol)	Antioxidant and anti-inflammatory	[91,92,93]
	Petunidin (2-(3,4-dihydroxy-5-methoxyphenyl)-chromenylium-3,5,7-triol)	Antioxidant and anti-MIRI effects	[92,93]
	Malvidin (2-(4-hydroxy-3,5-dimethoxyphenyl)-chromenylium-3,5,7-triol)	Hypoglycemic, hypolipidemic, gastroprotective, hepatoprotective, antiadhesive, and antibiofilm effects	[94,95,96,97]