J Food Bioact

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

Journal website www.isnff-jfb.com

Review

Volume 3, Number , September 2018, pages 76-86

Anti-inflammatory effects of polymethoxyflavones from citrus peels: a review

Figure 1.
Possible anti-inflammatory signaling pathways of citrus PMFs.
Numbers refer to different compounds: (1) Nobiletin; (2) Tangeretin; (3) 5-Demethyltangeretin; (4) 3,5,6,7,8,3′,4′-Heptamethoxyflavone; (5) 5-Hydroxy-3,6,7,8,3′,4′-hexamethoxyflavone: (6) Sinensetin; (7) Pentamethylquercetin; (8) 5-Hydroxy-3,7,3′,4′-tetramethoxyflavone; (9) Sudachitin; (10) Tetramethyl-O-scutellarin.

Figure 2.
General chemical structures of polymethoxyflavones.

**Table 1.** The chemical structures and sources of selected citrus PMFs
Chemical name	Source	Reference
Nobiletin	sweet orange (Citrus sinensis), tangerine (Citrus tangerina), bitter orange (Citrus aurantium)	Li et al., 2014
Tangeretin	Citrus unshiu, Citrus depressa (Rutaceae), Citrus reticulata	Eun et al., 2017; Jang et al., 2013
5-Demethyltangeretin	sweet orange (Citrus sinensis), Scrophulariaceae (Limnophila geoffrayi), Limnophila aromatic, genus Oscimum	Li et al., 2006
3,5,6,7,8,3′,4′-Heptamethoxyflavone	Citrus genus, especially abundant in Citrus kawachiensis	Kou et al., 2013
5-Hydroxy-3,6,7,8,3′,4′-hexamethoxyflavone	sweet orange (Citrus sinensis), Hizikia fusiforme	Kang et al., 2013; Lai et al., 2007
Sinensetin	Citrus sunki Hort. ex Tanaka, Orthosiphon stamineus	Ko et al., 2010; Kang et al., 2013; Laavola et al., 2012
Pentamethylquercetin	Miaray Mandarin (Citrus miaray), Kaempferia parviflora Wall. ex Baker rhizomes, sea buckthorn (Hippophae rhamnoides)	Sae-wong et al., 2011; Uckoo et al., 2015; Wang et al., 2011
5-Hydroxy-3,7,3′,4′-tetramethoxyflavone	Miaray Mandarin (Citrus miaray), Kaempferia parviflora Wall. ex Baker rhizomes	Uckoo et al., 2015; Tewtrakul and Subhadhirasakul, 2008
Sudachitin	Citrus sudachi	Yuasa et al., 2012
Tetramethyl-O-scutellarin	unmatured Shiranuhi	Hyun et al., 2017

Table 1. The chemical structures and sources of selected citrus PMFs

Chemical name

Chemical Structure

Source

Reference

Nobiletin

sweet orange (Citrus sinensis), tangerine (Citrus tangerina), bitter orange (Citrus aurantium)

Li et al., 2014

Tangeretin

Citrus unshiu, Citrus depressa (Rutaceae), Citrus reticulata

Eun et al., 2017; Jang et al., 2013

5-Demethyltangeretin

sweet orange (Citrus sinensis), Scrophulariaceae (Limnophila geoffrayi), Limnophila aromatic, genus Oscimum

Li et al., 2006

3,5,6,7,8,3′,4′-Heptamethoxyflavone

Citrus genus, especially abundant in Citrus kawachiensis

Kou et al., 2013

5-Hydroxy-3,6,7,8,3′,4′-hexamethoxyflavone

sweet orange (Citrus sinensis), Hizikia fusiforme

Kang et al., 2013; Lai et al., 2007

Sinensetin

Citrus sunki Hort. ex Tanaka, Orthosiphon stamineus

Ko et al., 2010; Kang et al., 2013; Laavola et al., 2012

Pentamethylquercetin

Miaray Mandarin (Citrus miaray), Kaempferia parviflora Wall. ex Baker rhizomes, sea buckthorn (Hippophae rhamnoides)

Sae-wong et al., 2011; Uckoo et al., 2015; Wang et al., 2011

5-Hydroxy-3,7,3′,4′-tetramethoxyflavone

Miaray Mandarin (Citrus miaray), Kaempferia parviflora Wall. ex Baker rhizomes

Uckoo et al., 2015; Tewtrakul and Subhadhirasakul, 2008

Sudachitin

Citrus sudachi

Yuasa et al., 2012

Tetramethyl-O-scutellarin

unmatured Shiranuhi

Hyun et al., 2017

**Table 2.** Summary of *in vivo* and *in vitro* research work related to anti-inflammatory role of citrus PMFs
Citrus PMF	Inflammation Type	Cell line/Experiment system	Concentration	Treatment Duration	Effect	Reference
The up and down arrows represent enhancing and suppressing effects, respectively.
Nobiletin	Inflammatory bowel disease	Caco-2 cell	20, 40, 80 μM	36 hours	MLCK expression, Akt phosphorylation ↓ NF-κB level ↓	Xiong et al., 2015
		Sprague-Dawley male rats	20, 40 mg/kg	7 days	iNOS, COX-2 expression ↓ TNF-α, IL-1, IL-6 level ↓ MLCK, NF-κB activation ↓ PI3K expressions, Akt phosphorylation ↓	Xiong et al., 2015
		Human intestinal mast cells	45, 100 μM	1/4/18 hours	TNF, CXCL8, CCL3, CCL4 expression ↓ ERK1/2 phosphorylation ↓	Hagenlocher et al., 2017
		IL-10^−/− and wild-type mice	50 mg/kg	11 weeks	Colitis symptom, mast cells number ↓	Hagenlocher et al.,2018
		Human intestinal fibroblasts	5–100 µM	-	IL-6, TNF, CCL2 expression ↓	Hagenlocher et al.,2018
		RAW 264.7 macrophages	8–40 μM	24/48 hours	NO production ↓	Wu et al., 2017
		AOM-induced male F344 rats	0.1% in diet	40 weeks	IL-6, IL-1β, TNF-α levels ↓ COX-2 expression ↓	Wu et al., 2017
	Acute kidney injury	Cisplatin-treated adult male albino Wistar rats	5 mg/kg	10 days	Normalize morphological change of tubules TNF-α expression ↓	Malik et al., 2015
	Acute liver injury	LPS/GalN-treated male C57BL/6 mice	50, 100, 200 mg/kg	-	IL-1β, IL-6, TNF-α level ↓ iNOS, COX-2 expression ↓ NF-κB activation ↓ Nrf2 and HO-1 expression↑	He et al., 2016
	Acute lung injury	A549 cells	10⁻⁴, 10⁻³, 10⁻² mg/mL	24 hours	TNF-α, IL-6 production ↓ NF-κB p65, IκBα phosphorylation ↓	Li et al., 2018
		LPS-treated Kunming mice	10, 20 mg/kg	12 hours	TNF-α, IL-6, NO production ↓ iNOS expression ↓ NF-κB p65, IκBα phosphorylation ↓	Li et al., 2018
	Acute gastric lesion	Male Kunming mice	10, 20 mg/kg,	3 days	TNF-α, IL-6 level ↓ PEG₂ level ↑ p-ERK1/2, p-JNK, p-p38 expression ↓	Li et al., 2017
	Neuroinflammation	BV2 microglial cells	25–100 µM	20 hours	NO production ↓ iNOS expression ↓ TNF-α, IL-1β, and IL-6 level ↓	Ho and Kuo, 2014
		Male Sprague-Dawley rats	10, 25 mg/kg	3 days	TNF-α, IL-1β, IL-6, NF-κB, p-Akt level ↓ MMP9 expression ↓ Nrf2, HO-1 expression ↑	Bi et al., 2016; Zhang et al., 2016b
	Diabetic Cardiomyopathy	Male C57BL/6 mice	50 mg/kg	11 weeks	JNK, p38, NF-κB activation ↓	Zhang et al., 2016a
	Obesity-associated chronic inflammation	RAW 264.7 macrophages	10, 50, 100 µM	24 hours	TNF-α, NO, MCP-1 production ↓ iNOS, HO-1 expression ↓	Namkoong et al., 2017
Tangeretin	Inflammatory bowel disease	Male C57BL/6 mice	10, 20 mg/kg	3 days	NF-κB, MAPK activation ↓ iNOS, COX-2 expression ↓ TNF-α, IL-12, IL-17, IFN-γ expression ↓ IL-10 expression ↑	Eun et al., 2017
		Human intestinal mast cells	45, 100 μM	1/4/18 hours	IL-1β, TNF-α, CXCL8, CCL3, CCL4 expression ↓ ERK1/2 phosphorylation ↓	Hagenlocher et al., 2017
	Acute liver injury	Cisplatin-treated Wistar rats	100 mg/kg	7 days	TNF-α level ↓, IL-10 expression ↑ MAPK activation ↓	Omar et al., 2016
	Chronic kidney disease	Sprague-Dawley male rats	50, 100, 200 mg/kg	35 days	p-iNOS, p-IKKα/β, p-IκBα level ↓ p65 expression ↓ NO, IL-1β, IL-6, TNF-α production ↓	Wu et al., 2018
	Acute kidney injury	Cisplatin-treated Wistar rats	100 mg/kg	1 week	iNOS, TNF-α level ↓, IL-10, expression ↑ NF-κB activation ↓	Arab et al., 2016
	RSV-induced lung inflammation	Male BALB/c mice	25, 50, 100 mg/kg	3 days	IL-1β, IL-6 level ↓ NF-κB activation ↓	Xu et al., 2015
	Neuroinflammation	BV2 microglial cells	30, 50, 100 µM or 25–100 µM	1 or 20 hours	AMPK-SIRT1-NF-κB signaling ↓ NO, TNF-α, IL-6, IL-1β level ↓ iNOS, MMP-3, MMP-8 expression ↓	Ho and Kuo, 2014; Lee et al., 2016
	LPS-induced inflammation	RAW 264.7 macrophages	6–30 μM	24 hours	NO, PGE₂, IL-1β, IL-6 level ↓ iNOS, COX-2 expression ↓	Funaro et al., 2016
5-Demethyltangeretin	Skin inflammation	DMBA/TPA-treated female mice	1, 5 μmol	0.5 hour	COX-2 expression ↓ NF-κB activation ↓ PI3K, Akt phosphorylation ↓	Ma et al., 2014
3,5,6,7,8,3′,4′-Heptamethoxyflavone	Neuroinflammation	C57BL/6 strain mice	25, 50 or 100 mg/kg	5 or 10 days	Reduce hypertrophied form of microglia IL-1β expression ↓	Okuyama et al., 2014; Okuyama et al., 2015
	LPS-induced inflammation	Human Peripheral blood monocytes	3.7–100 μM	0.5 hour	TNF-α (IC₅₀ = 5 μM), MIP-1α (IC₅₀ = 7.3 μM), IL-10 (IC₅₀ = 12.3 μM) production ↓	Manthey et al., 1999
5-hydroxy-3,6,7,8,3′,4′-hexamethoxyflavone	Neuroinflammation	BV2 microglial cells	10, 20, 30 μM	2 hours	iNOS expression ↓ NO level ↓ NF-κB activation ↓ Nrf2-dependent HO-1 expression ↑	Kang et al., 2013
	Skin inflammation	TPA-treated female ICR mice	1, 3 μmol	0.5 hour	iNOS, COX-2 expression ↓ NF-κB activation ↓ STAT3, p38, ERK MAPK, PI3K, Akt phosphorylation ↓	Lai et al., 2007
Sinensetin	LPS-induced inflammation	RAW 264.7 macrophages Murine J774 macrophages	50 μM	1 hour	TNF-α, PGE₂, COX-2, iNOS, NO, IL-Iβ, IL-6 expression ↓	Laavola et al., 2012; Shin et al., 2012;
Pentamethylquercetin	LPS-induced inflammation	Mouse peritoneal macrophages	IC₅₀∼26 μM	20 hours	NO production ↓	Matsuda et al., 2003
5-hydroxy-3,7,3′,4′-tetramethoxyflavone	LPS-induced inflammation	RAW 264.7 macrophages	100 μM	5–20 minutes	iNOS, COX-2 expression ↓	Sae-wong et al., 2009
		RAW 264.7 macrophages	IC₅₀∼16μM	48 hours	NO, PGE₂ production ↓	Tewtrakul et al., 2009; Tewtrakul and Subhadhirasakul, 2008
Sudachitin	LPS-induced inflammation	RAW 264.7 macrophages	10, 30 μM	24 hours	TNF-α, NO production ↓ iNOS expression ↓	Yuasa et al., 2012
Tetramethyl-O-scutellarin	LPS-induced inflammation	RAW 264.7 macrophages	25, 50, 100 μM	24 hours	PGE₂, TNF-α, IL-1β, IL-6 level ↓ NO production ↓	Hyun et al., 2017

Table 2. Summary of in vivo and in vitro research work related to anti-inflammatory role of citrus PMFs

Citrus PMF

Inflammation Type

Cell line/Experiment system

Concentration

Treatment Duration

Effect

Reference

The up and down arrows represent enhancing and suppressing effects, respectively.

Nobiletin

Inflammatory bowel disease

Caco-2 cell

20, 40, 80 μM

36 hours

MLCK expression, Akt phosphorylation ↓ NF-κB level ↓

Xiong et al., 2015

Sprague-Dawley male rats

20, 40 mg/kg

7 days

iNOS, COX-2 expression ↓ TNF-α, IL-1, IL-6 level ↓
MLCK, NF-κB activation ↓
PI3K expressions, Akt phosphorylation ↓

Xiong et al., 2015

Human intestinal mast cells

45, 100 μM

1/4/18 hours

TNF, CXCL8, CCL3, CCL4 expression ↓
ERK1/2 phosphorylation ↓

Hagenlocher et al., 2017

IL-10^−/− and wild-type mice

50 mg/kg

11 weeks

Colitis symptom, mast cells number ↓

Hagenlocher et al.,2018

Human intestinal fibroblasts

5–100 µM

IL-6, TNF, CCL2 expression ↓

Hagenlocher et al.,2018

RAW 264.7 macrophages

8–40 μM

24/48 hours

NO production ↓

Wu et al., 2017

AOM-induced male F344 rats

0.1% in diet

40 weeks

IL-6, IL-1β, TNF-α levels ↓ COX-2 expression ↓

Wu et al., 2017

Acute kidney injury

Cisplatin-treated adult male albino Wistar rats

5 mg/kg

10 days

Normalize morphological change of tubules
TNF-α expression ↓

Malik et al., 2015

Acute liver injury

LPS/GalN-treated male C57BL/6 mice

50, 100, 200 mg/kg

IL-1β, IL-6, TNF-α level ↓ iNOS, COX-2 expression ↓
NF-κB activation ↓ Nrf2 and HO-1 expression↑

He et al., 2016

Acute lung injury

A549 cells

10⁻⁴, 10⁻³, 10⁻² mg/mL

24 hours

TNF-α, IL-6 production ↓ NF-κB p65, IκBα phosphorylation ↓

Li et al., 2018

LPS-treated Kunming mice

10, 20 mg/kg

12 hours

TNF-α, IL-6, NO production ↓ iNOS expression ↓
NF-κB p65, IκBα phosphorylation ↓

Li et al., 2018

Acute gastric lesion

Male Kunming mice

10, 20 mg/kg,

3 days

TNF-α, IL-6 level ↓ PEG₂ level ↑
p-ERK1/2, p-JNK, p-p38 expression ↓

Li et al., 2017

Neuroinflammation

BV2 microglial cells

25–100 µM

20 hours

NO production ↓ iNOS expression ↓
TNF-α, IL-1β, and IL-6 level ↓

Ho and Kuo, 2014

Male Sprague-Dawley rats

10, 25 mg/kg

3 days

TNF-α, IL-1β, IL-6, NF-κB, p-Akt level ↓
MMP9 expression ↓ Nrf2, HO-1 expression ↑

Bi et al., 2016; Zhang et al., 2016b

Diabetic Cardiomyopathy

Male C57BL/6 mice

50 mg/kg

11 weeks

JNK, p38, NF-κB activation ↓

Zhang et al., 2016a

Obesity-associated chronic inflammation

RAW 264.7 macrophages

10, 50, 100 µM

24 hours

TNF-α, NO, MCP-1 production ↓ iNOS, HO-1 expression ↓

Namkoong et al., 2017

Tangeretin

Inflammatory bowel disease

Male C57BL/6 mice

10, 20 mg/kg

3 days

NF-κB, MAPK activation ↓ iNOS, COX-2 expression ↓
TNF-α, IL-12, IL-17, IFN-γ expression ↓ IL-10 expression ↑

Eun et al., 2017

Human intestinal mast cells

45, 100 μM

1/4/18 hours

IL-1β, TNF-α, CXCL8, CCL3, CCL4 expression ↓
ERK1/2 phosphorylation ↓

Hagenlocher et al., 2017

Acute liver injury

Cisplatin-treated Wistar rats

100 mg/kg

7 days

TNF-α level ↓, IL-10 expression ↑ MAPK activation ↓

Omar et al., 2016

Chronic kidney disease

Sprague-Dawley male rats

50, 100, 200 mg/kg

35 days

p-iNOS, p-IKKα/β, p-IκBα level ↓ p65 expression ↓
NO, IL-1β, IL-6, TNF-α production ↓

Wu et al., 2018

Acute kidney injury

Cisplatin-treated Wistar rats

100 mg/kg

1 week

iNOS, TNF-α level ↓, IL-10, expression ↑ NF-κB activation ↓

Arab et al., 2016

RSV-induced lung inflammation

Male BALB/c mice

25, 50, 100 mg/kg

3 days

IL-1β, IL-6 level ↓ NF-κB activation ↓

Xu et al., 2015

Neuroinflammation

BV2 microglial cells

30, 50, 100 µM or 25–100 µM

1 or 20 hours

AMPK-SIRT1-NF-κB signaling ↓
NO, TNF-α, IL-6, IL-1β level ↓
iNOS, MMP-3, MMP-8 expression ↓

Ho and Kuo, 2014; Lee et al., 2016

LPS-induced inflammation

RAW 264.7 macrophages

6–30 μM

24 hours

NO, PGE₂, IL-1β, IL-6 level ↓ iNOS, COX-2 expression ↓

Funaro et al., 2016

5-Demethyltangeretin

Skin inflammation

DMBA/TPA-treated female mice

1, 5 μmol

0.5 hour

COX-2 expression ↓ NF-κB activation ↓
PI3K, Akt phosphorylation ↓

Ma et al., 2014

3,5,6,7,8,3′,4′-Heptamethoxyflavone

Neuroinflammation

C57BL/6 strain mice

25, 50 or 100 mg/kg

5 or 10 days

Reduce hypertrophied form of microglia
IL-1β expression ↓

Okuyama et al., 2014; Okuyama et al., 2015

LPS-induced inflammation

Human Peripheral blood monocytes

3.7–100 μM

0.5 hour

TNF-α (IC₅₀ = 5 μM), MIP-1α (IC₅₀ = 7.3 μM), IL-10 (IC₅₀ = 12.3 μM) production ↓

Manthey et al., 1999

5-hydroxy-3,6,7,8,3′,4′-hexamethoxyflavone

Neuroinflammation

BV2 microglial cells

10, 20, 30 μM

2 hours

iNOS expression ↓ NO level ↓ NF-κB activation ↓
Nrf2-dependent HO-1 expression ↑

Kang et al., 2013

Skin inflammation

TPA-treated female ICR mice

1, 3 μmol

0.5 hour

iNOS, COX-2 expression ↓ NF-κB activation ↓
STAT3, p38, ERK MAPK, PI3K, Akt phosphorylation ↓

Lai et al., 2007

Sinensetin

LPS-induced inflammation

RAW 264.7 macrophages
Murine J774 macrophages

50 μM

1 hour

TNF-α, PGE₂, COX-2, iNOS, NO, IL-Iβ, IL-6 expression ↓

Laavola et al., 2012; Shin et al., 2012;

Pentamethylquercetin

LPS-induced inflammation

Mouse peritoneal macrophages

IC₅₀∼26 μM

20 hours

NO production ↓

Matsuda et al., 2003

5-hydroxy-3,7,3′,4′-tetramethoxyflavone

LPS-induced inflammation

RAW 264.7 macrophages

100 μM

5–20 minutes

iNOS, COX-2 expression ↓

Sae-wong et al., 2009

RAW 264.7 macrophages

IC₅₀∼16μM

48 hours

NO, PGE₂ production ↓

Tewtrakul et al., 2009; Tewtrakul and Subhadhirasakul, 2008

Sudachitin

LPS-induced inflammation

RAW 264.7 macrophages

10, 30 μM

24 hours

TNF-α, NO production ↓ iNOS expression ↓

Yuasa et al., 2012

Tetramethyl-O-scutellarin

LPS-induced inflammation

RAW 264.7 macrophages

25, 50, 100 μM

24 hours

PGE₂, TNF-α, IL-1β, IL-6 level ↓ NO production ↓

Hyun et al., 2017