J Food Bioact

Journal of Food Bioactives, ISSN 2637-8752 print, 2637-8779 online

Journal website www.isnff-jfb.com

Review

Volume 15, September 2021, pages 39-50

Phenolic compounds in cereal grains and effects of processing on their composition and bioactivities: a review

**Table 1.** Chemical composition of the major cereal grains produced worldwide (whole grain)
	Wheat	Rye	Maize	Barley	Oats	Rice	Millet
Adapted from Koehler and Wieser (2013).
Moisture (g/100g)	12.6	13.6	11.3	12.1	13.1	13.0	12.0
Protein (g/100g)	11.3	9.4	8.8	11.1	10.8	7.7	10.5
Lipids (g/100g)	1.8	1.7	3.8	2.1	7.2	2.2	3.9
Available carbohydrates (g/100g)	59.4	60.3	65.0	62.7	56.2	73.7	68.2
Fiber (g/100g)	13.2	13.1	9.8	9.7	9.8	2.2	3.8
Minerals (g/100g)	1.7	1.9	1.3	2.3	2.9	1.2	1.6
Thiamine (B1) (mg/kg)	4.6	3.7	3.6	4.3	6.7	4.1	4.3
Riboflavin (B20 (mg/kg)	0.9	1.7	2.0	1.8	1.7	0.9	1.1
Nicotinamide (mg/kg)	51.0	18.0	15.0	48.0	24.0	52.0	18.0
Panthothenic acid (mg/kg)	12.0	15.0	6.5	6.8	7.1	17.0	14.0
Vitamin B6 (mg/kg)	2.7	2.3	4.0	5.6	9.6	2.8	5.2
Folic acid (mg/kg)	0.9	1.4	0.3	0.7	0.3	0.2	0.4
Tocols (mg/kg)	41.0	40.0	66.0	22.0	18.0	19.0	40.0

Table 1. Chemical composition of the major cereal grains produced worldwide (whole grain)

Wheat

Rye

Maize

Barley

Oats

Rice

Millet

Adapted from Koehler and Wieser (2013).

Moisture (g/100g)

12.6

13.6

11.3

12.1

13.1

13.0

12.0

Protein (g/100g)

11.3

9.4

8.8

11.1

10.8

7.7

10.5

Lipids (g/100g)

1.8

1.7

3.8

2.1

7.2

2.2

3.9

Available carbohydrates (g/100g)

59.4

60.3

65.0

62.7

56.2

73.7

68.2

Fiber (g/100g)

13.2

13.1

9.8

9.7

9.8

2.2

3.8

Minerals (g/100g)

1.7

1.9

1.3

2.3

2.9

1.2

1.6

Thiamine (B1) (mg/kg)

4.6

3.7

3.6

4.3

6.7

4.1

4.3

Riboflavin (B20 (mg/kg)

0.9

1.7

2.0

1.8

1.7

0.9

1.1

Nicotinamide (mg/kg)

51.0

18.0

15.0

48.0

24.0

52.0

18.0

Panthothenic acid (mg/kg)

12.0

15.0

6.5

6.8

7.1

17.0

14.0

Vitamin B6 (mg/kg)

2.7

2.3

4.0

5.6

9.6

2.8

5.2

Folic acid (mg/kg)

0.9

1.4

0.3

0.7

0.3

0.2

0.4

Tocols (mg/kg)

41.0

40.0

66.0

22.0

18.0

19.0

40.0

**Table 2.** Phenolic composition of highly-produced cereal grains
Cereal	Variety	Phenolic content	Major phenolics identified	Reference
Wheat	Waxy (bran)	Total phenolic acids: 952–1,386 µg/g	Ferulic, p-coumaric, vanillic, syringic, t-cinnamic, caffeic, p-hydroxybenzoic acids	Jonnala et al., 2010
Winter (whole grain)	Total phenolic acids: 4.2–182.3 µg/g	Ferulic, p-coumaric, syringic, vanillic, sinapic acids	Vaher et al., 2010; Ross et al., 2003a
Winter (bran)	Total phenolic acids: 17.7–532.4 µg/g	Ferulic, p-coumaric, syringic, vanillic, sinapic acids
Spring (flour)	Total phenolic acids: 0.7–58.1 µg/g	Ferulic, p-coumaric, syringic, vanillic, sinapic acids
Spring (whole grain)	Total phenolic acids: 2.8–132.8 µg/g	Ferulic, p-coumaric, syringic, vanillic, sinapic acids
Spring (bran)	Total phenolic acids: 18.5–268.9 µg/g	Caffeic, ferulic, p-coumaric, syringic, vanillic, sinapic acids
Miscellaneous	Lignans: 5–20 mg/100 g; Alkylresorcinols: 489–642 mg/g	7-hydroxymatairesinol, syringaresinol, secoisaloriciresinol, lariciresol, and matairesinol; 5-n-nonadecylresorcinol (C19:0), 5-n-heneicosylresorcinol (C21:0)
Rice	Brown (dehulled)	Free Total phenolics: 32.0–39.0 mg gallic acid equivalent (GAE)/100 g. Free Total Flavonoids: 26.0–31.0 mg catechin equivalent (CE)/100 g. Total Free Proanthocyanidin: 7.0–7.8 mg CE/100 g. Total Insoluble-bound Phenolics: 42.3–50.0 mg GAE/100 g. Total Insoluble-bound Flavonoids: 45.2–50.8 mg CE/100 g	Vanillic, syringic, salicylic acid, p-coumaric, ferulic, sinapic acids and their derivatives	Zhou et al., 2014; Zhang et al., 2019
	Black (dehulled)	Free total phenolics: 4.31–36.52 mg GAE/100 g. Esterified total phenolics: 6.41–40.83 mg GAE/100 g. Insoluble-bound total phenolics: 38.55–62.55 mg GAE/100 g. Cyanidin-3-O-glucoside: 12.03–1,106 mg/kg. Peonidin-3-O-glucoside: 3.54–311.12 mg/kg	Protocatechuic, 2,5-dihydroxybenzoic acid, p-hydroxybenzoic, vanillic, syringic, p-coumaric, ferulic, sinapic, and isoferulic acids	Shao et al., 2018
Rye	Miscellaneous	Lignans: 10–20 mg/100 g. Alkylresorcinols: 720–761 mg/g	Syringaresinol, pinoresinol, lariciresinol, isolariciresinol, 7-hydroxymatairesinol, mairesinol, secoisolariciresinol; 5-n-heptadecylresorciol (C17:0), 5-n-nonadecylresorcinol (C19:0), 5-n-heneicosylresorcinol (C21:0); mallic, p-hydroxybenzoic, and ferulic acids; vitexin, quercetin	Zanella et al, 2017; Pihlava et al., 2018; Ross et al., 2003a; Rao et al., 2020
Oat	Echidna, Williams, Yallara	Total phenolic content: 33.47–87.74 mg GAE/100 g	Syringaresinol, pinoresinol, lariciresinol, isolariciresinol, 7-hydroxymatairesinol, mairesinol, secoisolariciresinol; 5-n-heptadecylresorciol (C17:0), 5-n-nonadecylresorcinol (C19:0), 5-n-heneicosylresorcinol (C21:0); mallic, p-hydroxybenzoic, and ferulic acids; vitexin, quercetin; ferulic, chlorogenic, p-coumaric, and hydroxybenzoic acids; vixetin, rutin, quercetin, catechin, epicatechin; prodelphinidin B, prodelphinidin B3, procyanidin B2	Zanella et al, 2017; Pihlava et al., 2018; Ross et al., 2003a; Rao et al., 2020; Madhujith and Shahidi, 2009; Ge et al., 2021, Rao et al., 2020
Barley	Falcon, AC Metcalfe, Tyto, Tercel, Phoenix, Peregrine, naked barley, Compass, Hindmarsh, Gairdner	Free total phenolics: 0.18–0.42 mg ferulic acid equivalents (FAE)/g. Soluble conjugate phenolics: 0.42–0.81 mg FAE/g. Insoluble-bound total phenolics: 2.03–3.36 mg FAE/g. Total proanthocyanidins: 8.94–20.71 mg CE/100 g
Maize	Purple	Total phenolic content: 69.1–229.1 mg GAE/g. Total anthocyanin content: 17–93.5 mg C3G/g	o-Coumaric, caffeic, vanillic, protocatechuic, and ferulic acids; rutin, luteolin, quercetin, naringenin, and kaempferol; cyanidin-3-glucoside, pelargonidin-3-O-glucoside, peonidin-3-O-glucoside, cyaniding-3-(6′-malonylglucoside), pelargonidin-3-(6′-malonylglucoside), and peonidin-3-(6′-malonylglucoside	Zhang et al. (2019)
Millet	Kodo (whole grain)	Free total phenolics: 16.2 µmol ferulic acid equivalent (FAE)/g. Esterified total phenolics: 2.02 µmol FAE/g. Etherified total phenolics: 1.55 µmol FAE/g. Insoluble-bound total phenolics: 81.6 µmol FAE/g	Gallic, protocatechuic, vanillic, syringic, p-hydroxybenzoic, p-coumaric, chlorogenic, caffeic, ferulic acids; catechin, epicatechin, myricetin, kaempferol, quercetin, luteolin	Chandrasekara and Shahidi, 2011a, b
Foxtail (whole grain)	Free total phenolics: 4.49 µmol ferulic acid equivalent (FAE)/g. Esterified total phenolics: 0.37 µmol FAE/g. Etherified total phenolics: 0.32 µmol FAE/g. Insoluble-bound total phenolics: 11.6 µmol FAE/g	o-Coumaric, caffeic, vanillic, protocatechuic, and ferulic acids; rutin, luteolin, quercetin, naringenin, and kaempferol; cyanidin-3-glucoside, pelargonidin-3-O-glucoside, peonidin-3-O-glucoside, cyaniding-3-(6′-malonylglucoside), pelargonidin-3-(6′-malonylglucoside), and peonidin-3-(6′-malonylglucoside	Zhang et al. (2019)
Sorghum	White (whole grain)	Free phenolic acids: 123 µg/g. Insoluble-bound phenolic acids: 622.9 µg/g	Gallic, protocatechuic, p-hydroxybenzoic, vanillic, caffeic, p-coumaric, ferulic, and cinnamic acids; catechin, epicatechin, procyanidin B1, apigenin, luteolin	Dykes and Rooney, 2006
		Gallic, protocatechuic, p-hydroxybenzoic, vanillic, caffeic, p-coumaric, ferulic, and cinnamic acids; catechin, epicatechin, procyanidin B1, apigenin, luteolin	Dykes and Rooney, 2006

Table 2. Phenolic composition of highly-produced cereal grains

Cereal

Variety

Phenolic content

Major phenolics identified

Reference

Wheat

Waxy (bran)

Total phenolic acids: 952–1,386 µg/g

Ferulic, p-coumaric, vanillic, syringic, t-cinnamic, caffeic, p-hydroxybenzoic acids

Jonnala et al., 2010

Winter (whole grain)

Total phenolic acids: 4.2–182.3 µg/g

Ferulic, p-coumaric, syringic, vanillic, sinapic acids

Vaher et al., 2010; Ross et al., 2003a

Winter (bran)

Total phenolic acids: 17.7–532.4 µg/g

Ferulic, p-coumaric, syringic, vanillic, sinapic acids

Spring (flour)

Total phenolic acids: 0.7–58.1 µg/g

Ferulic, p-coumaric, syringic, vanillic, sinapic acids

Spring (whole grain)

Total phenolic acids: 2.8–132.8 µg/g

Ferulic, p-coumaric, syringic, vanillic, sinapic acids

Spring (bran)

Total phenolic acids: 18.5–268.9 µg/g

Caffeic, ferulic, p-coumaric, syringic, vanillic, sinapic acids

Miscellaneous

Lignans: 5–20 mg/100 g; Alkylresorcinols: 489–642 mg/g

7-hydroxymatairesinol, syringaresinol, secoisaloriciresinol, lariciresol, and matairesinol; 5-n-nonadecylresorcinol (C19:0), 5-n-heneicosylresorcinol (C21:0)

Rice

Brown (dehulled)

Free Total phenolics: 32.0–39.0 mg gallic acid equivalent (GAE)/100 g. Free Total Flavonoids: 26.0–31.0 mg catechin equivalent (CE)/100 g. Total Free Proanthocyanidin: 7.0–7.8 mg CE/100 g. Total Insoluble-bound Phenolics: 42.3–50.0 mg GAE/100 g. Total Insoluble-bound Flavonoids: 45.2–50.8 mg CE/100 g

Vanillic, syringic, salicylic acid, p-coumaric, ferulic, sinapic acids and their derivatives

Zhou et al., 2014; Zhang et al., 2019

Black (dehulled)

Free total phenolics: 4.31–36.52 mg GAE/100 g. Esterified total phenolics: 6.41–40.83 mg GAE/100 g. Insoluble-bound total phenolics: 38.55–62.55 mg GAE/100 g. Cyanidin-3-O-glucoside: 12.03–1,106 mg/kg. Peonidin-3-O-glucoside: 3.54–311.12 mg/kg

Protocatechuic, 2,5-dihydroxybenzoic acid, p-hydroxybenzoic, vanillic, syringic, p-coumaric, ferulic, sinapic, and isoferulic acids

Shao et al., 2018

Rye

Miscellaneous

Lignans: 10–20 mg/100 g. Alkylresorcinols: 720–761 mg/g

Zanella et al, 2017; Pihlava et al., 2018; Ross et al., 2003a; Rao et al., 2020

Oat

Echidna, Williams, Yallara

Total phenolic content: 33.47–87.74 mg GAE/100 g

Syringaresinol, pinoresinol, lariciresinol, isolariciresinol, 7-hydroxymatairesinol, mairesinol, secoisolariciresinol; 5-n-heptadecylresorciol (C17:0), 5-n-nonadecylresorcinol (C19:0), 5-n-heneicosylresorcinol (C21:0); mallic, p-hydroxybenzoic, and ferulic acids; vitexin, quercetin; ferulic, chlorogenic, p-coumaric, and hydroxybenzoic acids; vixetin, rutin, quercetin, catechin, epicatechin; prodelphinidin B, prodelphinidin B3, procyanidin B2

Zanella et al, 2017; Pihlava et al., 2018; Ross et al., 2003a; Rao et al., 2020; Madhujith and Shahidi, 2009; Ge et al., 2021, Rao et al., 2020

Barley

Falcon, AC Metcalfe, Tyto, Tercel, Phoenix, Peregrine, naked barley, Compass, Hindmarsh, Gairdner

Free total phenolics: 0.18–0.42 mg ferulic acid equivalents (FAE)/g. Soluble conjugate phenolics: 0.42–0.81 mg FAE/g. Insoluble-bound total phenolics: 2.03–3.36 mg FAE/g. Total proanthocyanidins: 8.94–20.71 mg CE/100 g

Maize

Purple

Total phenolic content: 69.1–229.1 mg GAE/g. Total anthocyanin content: 17–93.5 mg C3G/g

o-Coumaric, caffeic, vanillic, protocatechuic, and ferulic acids; rutin, luteolin, quercetin, naringenin, and kaempferol; cyanidin-3-glucoside, pelargonidin-3-O-glucoside, peonidin-3-O-glucoside, cyaniding-3-(6′-malonylglucoside), pelargonidin-3-(6′-malonylglucoside), and peonidin-3-(6′-malonylglucoside

Zhang et al. (2019)

Millet

Kodo (whole grain)

Free total phenolics: 16.2 µmol ferulic acid equivalent (FAE)/g. Esterified total phenolics: 2.02 µmol FAE/g. Etherified total phenolics: 1.55 µmol FAE/g. Insoluble-bound total phenolics: 81.6 µmol FAE/g

Gallic, protocatechuic, vanillic, syringic, p-hydroxybenzoic, p-coumaric, chlorogenic, caffeic, ferulic acids; catechin, epicatechin, myricetin, kaempferol, quercetin, luteolin

Chandrasekara and Shahidi, 2011a, b

Foxtail (whole grain)

Free total phenolics: 4.49 µmol ferulic acid equivalent (FAE)/g. Esterified total phenolics: 0.37 µmol FAE/g. Etherified total phenolics: 0.32 µmol FAE/g. Insoluble-bound total phenolics: 11.6 µmol FAE/g

Zhang et al. (2019)

Sorghum

White (whole grain)

Free phenolic acids: 123 µg/g. Insoluble-bound phenolic acids: 622.9 µg/g

Gallic, protocatechuic, p-hydroxybenzoic, vanillic, caffeic, p-coumaric, ferulic, and cinnamic acids; catechin, epicatechin, procyanidin B1, apigenin, luteolin

Dykes and Rooney, 2006

Gallic, protocatechuic, p-hydroxybenzoic, vanillic, caffeic, p-coumaric, ferulic, and cinnamic acids; catechin, epicatechin, procyanidin B1, apigenin, luteolin

Dykes and Rooney, 2006

**Table 3.** Effect of common cereal processing techniques on their phenolic composition
Cereal	Process	Effect	Reference
Barley	Infrared and hot air drying (60 °C)	Infrared drying released bound phenolics, increasing the phenolic content in regards to the hot air drying and original samples	Ge et al., 2021
Millet	Dehulling	Reduction of total phenolic content. Reduction of oxygen radical absorbance capacity and hydroxyl-radical scavenging capacity. Reduction of the concentration of p-coumaric and ferulic acids	Chandrasekara and Shahidi, 2011a, b
Rice	Parboiling	Release of bound phenolics, increasing the contents of p-coumaric, syringic, protocatechuic, and ferulic acids compared to raw sample	Thammapat et al., 2016
Wheat	Steam explosion (215 °C for 120 s)	Increased concentration of soluble phenolic acids	Liu et al., 2016
Brown rice, wheat, and oat	Extrusion cooking	Enhanced content of insoluble-bound phenolics. Increased bioaccessibility of wheat phenolics	Zeng et al., 2016
Maize	Roasting (17 min)	Decreased total phenolic and flavonoid contents. Diminished free radical scavenging activity and iron chelating ability	Oboh et al., 2010

Table 3. Effect of common cereal processing techniques on their phenolic composition

Cereal

Process

Effect

Reference

Barley

Infrared and hot air drying (60 °C)

Infrared drying released bound phenolics, increasing the phenolic content in regards to the hot air drying and original samples

Ge et al., 2021

Millet

Dehulling

Reduction of total phenolic content. Reduction of oxygen radical absorbance capacity and hydroxyl-radical scavenging capacity. Reduction of the concentration of p-coumaric and ferulic acids

Chandrasekara and Shahidi, 2011a, b

Rice

Parboiling

Release of bound phenolics, increasing the contents of p-coumaric, syringic, protocatechuic, and ferulic acids compared to raw sample

Thammapat et al., 2016

Wheat

Steam explosion (215 °C for 120 s)

Increased concentration of soluble phenolic acids

Liu et al., 2016

Brown rice, wheat, and oat

Extrusion cooking

Enhanced content of insoluble-bound phenolics. Increased bioaccessibility of wheat phenolics

Zeng et al., 2016

Maize

Roasting (17 min)

Decreased total phenolic and flavonoid contents. Diminished free radical scavenging activity and iron chelating ability

Oboh et al., 2010