Functional Foods for Health: The Interrelated Antioxidant and Anti-Inflammatory Role of Fruits, Vegetables, Herbs, Spices and Cocoa in Humans

Author(s): Mauro Serafini, Ilaria Peluso

Journal Name: Current Pharmaceutical Design

Volume 22 , Issue 44 , 2016


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Functional Foods for Health: The Interrelated Antioxidant and Anti-Inflammatory Role of Fruits, Vegetables, Herbs, Spices and Cocoa in Humans

Mauro Serafini* and Ilaria Peluso

Functional Foods and Metabolic Stress Prevention Laboratory, Centre for Food and Nutrition, Council for Agricultural Research and Economics, Rome, Italy

Abstract: The health benefits of plant food-based diets could be related to both integrated antioxidant and anti-inflammatory mechanisms exerted by a wide array of phytochemicals present in fruit, vegetables, herbs and spices. Therefore, there is mounting interest in identifying foods, food extracts and phytochemical formulations from plant sources which are able to efficiently modulate oxidative and inflammatory stress to prevent diet-related diseases. This paper reviews available evidence about the effect of supplementation with selected fruits, vegetables, herbs, spices and their extracts or galenic formulation on combined markers of redox and inflammatory status in humans.

Keywords : Antioxidants, human, functional foods, inflammation, oxidative stress, plant foods.


Article Information

Identifiers and Pagination:

Year: 2016
Volume: 22
Issue: 44
First Page: 6701
Last Page: 6715
Publisher Id: CPD-22-44-6701
DOI: 10.2174/1381612823666161123094235

Article History:

Received Date: September 08, 2015

Accepted Date: November 15, 2016

* Address correspondence to this author at the Functional Foods and Metabolic Stress Prevention Laboratory, Centre for Food and Nutrition, Council for Agricultural Research and Economics, Via Ardeatina 546, 00176 Rome, Italy; Tel: +39-065149451; E-mail: serafini_mauro@yahoo.it

1. INTRODUCTION

The regulation of endogenous antioxidant defences, including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX), involves the interaction with antioxidant responsive elements (ARE) which are present in the promoter regions of most of the genes inducible by oxidative stress [1]. In particular, nuclear factor-erythroid 2-related factor 2 (Nrf2) is the transcription factor responsible for both constitutive and inducible expression of ARE-regulated genes [2]. Under physiological conditions, Nrf2 is bound to kelch-like protein-1 (KEAP1) and is thereby sequestered in the cytoplasm; however, in the presence of oxidative stress, Nrf2 dissociates from KEAP1, translocates into the nucleus and induces the transcription of antioxidant enzymes. Oxidative stress represents also a key stimulus for the activation of nuclear factor- kappa B (NF-κB), which appears in the cytoplasm of non-stimulated cells forming a complex with its inhibitor IκB. Following stimulation, NF-κB is activated by phosphorylation and degradation of IκB, thus migrating to the nucleus, stimulating gene expression and inducing the synthesis of inflammatory cytokines. The close link between oxidative and inflammatory stress in the mechanisms of body defences against stress, is further highlighted in the oxidative burst of leucocytes, the innate immune response involving the activation of NADPH-oxidase (NOX) and myeloperoxidase (MPO) yielding a massive production of Reactive Oxygen Species (ROS) and Reactive Nitrogen Species (RNS) [3]. However, the presence of an excessive and uncontrolled ROS and cytokines production, a condition defined as “low-grade chronic inflammation” takes place and is associated with pre-pathological conditions such as obesity and degenerative diseases [4, 5].

Inflammatory and oxidative stress can rise also as a direct consequence of unbalanced dietary life style, such as the ingestion of high fat and high carbohydrate meals [6, 7]. Increase in postprandial lipopolysaccharide (LPS) and Toll-like receptor-4 (TLR4) is associated with increased levels of inflammatory cytokines, such as interleukin (IL)-6, IL-17 and tumor necrosis factor-alpha (TNF-α) [8], which in turn activate oxidative burst [9]. Given these premises, the importance of the diet, as inducer or preventer of inflammatory and oxidative stress, is paramount.

A large body of epidemiological and clinical evidence provides a solid rationale for the health benefits of diets based on foods of vegetable origin [10], thanks to their content of bioactive ingredients such as vitamins and flavonoids. In fact, flavonoids and their metabolites, in addition to their direct free radical scavenging capacity [11], impair the production of ROS and RNS by neutrophils and other phagocytic cells through the inhibition of NOX, MPO and inducible-Nitric Oxide Synthases (iNOS) [3]. However, herbs and spices used for culinary purposes also represent an excellent, source of phytochemicals [12, 13]. Antioxidant and anti-inflammatory activities have been reported in vitro and in animal models for ginger (Zingiber officinale) [14], milk thistle (Silybum marianum) [15], hawthorn (Crataegus monogyna) [16, 17], passion flower (Passiflora edulis) [18] and chamomile (Matricaria chamomilla) [19, 20]. Therefore the health benefits of plant food-based diets could be related to both integrated antioxidant and anti-inflammatory mechanisms exerted by a wide array of phytochemicals present in fruit, vegetables, herbs and spices [21 - 24]. On this basis, there is mounting interest in identifying foods, food extracts and phytochemicals formulations from plant sources which are able to efficiently modulate oxidative and inflammatory stress to prevent diet-related diseases [25]. This paper reviews available evidence about the effect of supplementation with selected fruits, vegetables, herbs, spices, cocoa, beverages with mixed plant food composition as well as extracts and galenic formulation, on combined markers of redox and inflammatory status in humans.

2. OVERVIEW OF IDENTIFIED STUDIES

We performed a search on MEDLINE and Google Scholar Databases for literature of human studies by using the search terms: (fruit* OR vegetable* OR herb* OR spice* OR cocoa) AND antioxidant AND (cytokines OR CRP) AND (subjects OR patients).

A total of 88 interventions from 74 studies reporting both markers of redox/oxidative and inflammatory status after consumption of plant-derived products were collected. Dietary interventions were grouped according to different categories, specifically vegetables (Table 1) [26 - 31], fruits (Table 2) [32 - 54], grape seeds (Table 3) [55 - 59], herbs (Table 4) [60 - 65], green tea (Table 5) [66 - 70], spices (Table 6) [71 - 78], beverages with mixed composition (Table 7) [8, 79 - 82] extracts with mixed composition (Table 8) [83 - 93] and cocoa products (Table 9) [66, 94 - 97]. Selection of the plant foods was performed on the basis of available human data on both oxidative and inflammatory markers: for example, raspberry, blackberry and olives were not included due to the lack of combined information. Of these interventions, 69 were given over a long-term (from five days to 1 year). Studies were extremely variable in their experimental design: 44 were parallel, 17 were cross-over and 13 were longitudinal studies. The number of participants enrolled in individual trials ranged from 8 [29, 45] to 121 [73], and enrolled subjects were characterized by extremely variable features and health status: either healthy subjects or patients with asthma, cancer, infections, hemodialysis, rheumatoid arthritis, sepsis, acute respiratory distress syndrome, cardiovascular disease (CVD, hypertension, diabetes, dyslipidemia and metabolic syndrome and subjects with risk factors for CVD (i.e. smoking habit, overweight/obesity, old age). A limited number of studies evaluated the effect of the tested product in acute models of oxidative stress such as postprandial status (high energy meal, two studies) or physical exercise (five studies).

Table 1. Overview of the reviewed intervention studies with vegetables and vegetable extracts in humans: characteristics, study design and effect on markers of redox, oxidative and inflammatory status.

Treatment Dose/day
Standardization
Subjects (healthy status and no.) Study design and duration Markers of red-ox/ oxidative status Markers of inflammatory status Refs.
Carrot (juice) 16 fl oz Healthy
17
Longitudinal, 3 months NEAC↑
MDA↓
CRP and IL-1↔ [26]
Tomato (juice) 280 ml
(11.6 mg of lycopene/100 ml)
Healthy women
25
Longitudinal, 2 months TBARS ↓
NEAC ↔
Adiponectin ↑ [27]
Tomato-derived Lyc-O-Mato (capsules) 45 mg lycopene Asthmatic
79
Parallel, 14 weeks IsoP↔ CRP ↑
IL-6, IL-8 and TNF-α ↔
[28]
Tomato-derived Lyc-O-Mato (capsules). 30 mg lycopene Obese
8
Longitudinal, 4 weeks Dienes ↔ CRP, TNF-α and IL-6 ↔ [29]
Tomato-derived Lyc-O-Mato (drink). 250 ml
(5.7 mg of lycopene, 3.7 mg of phytoene, 2.7 mg of phytofluene, 1 mg of β-carotene, and 1.8 mg α-tocopherol)
Healthy
26
Crossover, 26 days IsoP↔ TNF-α and IFN-γ ex vivo ↓ [30]
Tomato-derived Lyc-O-Mato (extract) 80 mg lycopene Healthy
18 males
Longitudinal, 1 week;
postprandial (3h)
MDA ↔
MDA ↔
CRP↔
CRP↔
[31]

CRP: C reactive protein; IFN-γ: interferon gamma; IL: interleukin; IsoP: isoprostanes; MDA: malondialdehyde; NEAC: non-enzymatic antioxidant capacity; TBARS: thiobarbituric acid reactive substances; TNF-α: tumor necrosis factor alfa.

As expected, multiple biomarkers were used to monitor different aspects of redox/oxidative and inflammatory status in biological fluids and cells. Markers of redox status included non- enzymatic antioxidant capacity (NEAC, n=29), reduced glutathione (GSH, n=8) or ratio of reduced/oxidized glutathione (GSH/GSSG) (n=1), antioxidant enzymes (n=29) (e.g. SOD, CAT and GPX), markers of lipid peroxidation (n=77) [i.e. oxidized low density lipoproteins (oxLDL), isoprostanes (IsoP), malondialdehyde (MDA), thiobarbituric acid reactive substances (TBARS), peroxides, 4-hydroxy-nonenal (4-HNE) and conjugated dienes], pro-oxidant- antioxidant balance (PAB, n=1), 8-hydroxy-2'–deoxyguanosine (8-OHdG, n=2) and markers of protein oxidation (n=15). Inflammatory markers included C-reactive protein (CRP, n=69), heat shock protein 70 (HSP70, n=1), inflammatory cytokines (n=49), adiponectin (n=8) and markers of innate immunity-mediated ROS generation (n=10) [i.e. the oxidative burst, subunit p22phox of the NOX, iNOS and MPO].

3. STUDIES ON COMBINED ANTIOXIDANT AND ANTIINFLAMMATORY EFFECT OF VEGETABLES AND VEGETABLE EXTRACTS

Table 1 describes the reviewed intervention studies on the combined antioxidant and anti-inflammatory effects of vegetables and vegetable extracts.

Three months of supplementation with carrot [26] juice decrease marker of lipid oxidation, increase plasma antioxidant defenses but did not show any effect on inflammatory markers in healthy subjects. On the contrary, drinking 280 mL of tomato juice for two months [27] decreased markers of lipid oxidation, without affecting antioxidant capacity status, but increasing the anti-inflammatory adiponectin in healthy subjects. On the other hand, tomato-derived Lyc-o-Mato supplement did not affect peroxidation markers, neither in the form of drink [30] nor as supplement [28, 31]. Besides Lyc-o-Mato increased CRP production in asthmatic subjects [28] without affecting plasma cytokines concentration in obese and asthmatic subjects [28, 29], but decreasing the ex-vivo production of interferon (IFN)-γ and TNF-α in healthy subjects [30].

Although only 28.6% (2/7) of the interventions improved the markers of red-ox or inflammatory status, however it must be taken into account that some of the intervention studies were not controlled for placebo [26, 27, 29, 31] and 4 studies out of seven were conducted on healthy subjects, supposedly not affected by oxidative/inflammatory chronic conditions.

4. STUDIES WITH FRUITS, FRUIT JUICES, GRAPE SEEDS AND THEIR EXTRACTS

Within juice (Table 2), pomegranate juice (100cc/day, 1 year) [48] and concentrated juice (50g/day, four weeks) [44] decreased IL-6 [44, 48, 51] or MPO [50, 51], concomitantly increasing NEAC [44] or decreasing lipo-peroxidation and protein oxidation markers [48, 50] in type 2 diabetic patients [44], hemodialysis subjects [50, 51] and overweight/obese subjects [48].

Cranberry juice (0.7 liters for 60 days in parallel design) significantly reduced markers of protein and lipid oxidation and increased the anti-inflammatory adiponectin in patients with metabolic syndrome [35].

In the study by Basu et al. [34], 480 mL of cranberry juice, in a similar period of time (8 weeks) and in patients with metabolic syndrome, decreased oxidative stress markers (oxLDL and MDA), increase plasma NEAC and in agreement with results from Simao’s [35], the juice did not affect CRP and IL-6 levels, while adiponectin levels were not measured in this study. On the contrary, when cranberry was given as dried powder for 6 months, it neither affected the markers of redox/oxidative status nor CRP in men with urinary tract infections [33]. Bilberry juice, in a parallel study on subjects with at least one risk factor for CVD was effective in modulating inflammatory markers without any impact on redox status or lipid oxidation [32]. On the contrary, in type 2 diabetic patients, freeze-dried strawberry 50g/day consumption for 6 weeks decreased CRP and MDA and increased NEAC [42].

One and half rio red grapefruit consumption for 6 weeks in parallel design, failed to display any effect on isoprostanes and CRP levels neither in obese nor in subjects with metabolic syndrome [54]. However, it is extremely interesting to notice that subjects with high baseline isoprostanes levels experienced a significant reduction in response to grapefruit consumption, highlighting once more the importance of a detectable oxidative/inflammatory stress for a significant effect [54, 98]. Marotta et al. [38, 39] showed that supplementation with 9 and 6 g of fermented papaya for 6 months in patients with HCV-related cirrhosis translated in an improvement of marker of redox status, in a decrease in marker of oxidative stress and in a parallel anti-inflammatory effect on TNF-α and TNF-α ex vivo production. In a different group of subjects, chronic consumption of 9 g of fermented papaya for 3 months decreased TNF-α and IL-6, increase Hsp-70 without changes in antioxidant enzymes in elderly subjects [37]. A quite surprising increase of oxidative burst in PBMN was described in Type 2 diabetic obese after supplementation with 9 g of sachets of fermented papaya [36]. Barona et al. [43] observed an increase of iNOS in subjects without dyslipidemia and a decrease in those individuals with dyslipidemia after 4 weeks of consumption of 46 g of freeze-dried whole grape powder. Also plasma adiponectin concentrations followed opposite outcomes based on dyslipidemia category (Table 2), whereas IL-6, IL-8, TNF-α, SOD, GPX, oxLDL and IsoP did not differ significantly between treatment periods regardless of dyslipidemia classification. On the contrary GPX increased in patients with Rheumatoid Arthritis after the consumption of pomegranate extract (500 mg) for 8 weeks [50].

Table 3 describes intervention trials with grape seeds in different forms: as capsules [55, 57], tablets [58] or added in yoghurt [56].

In the study by Kar et al. [58] where 600 mg of grape seeds extract was given to 32 diabetics for 4 weeks, showed a combined effect in increasing antioxidant status (GSH), and decreasing inflammation (CRP). In agreement with Kar’s findings, 200 mg of monomeric and oligomeric flavanols from grape seeds increased the GSH/GSSG ratio and decreased TNF-α in smokers. Higher doses of grape seed extract, 1300 mg and 2 g, did not show any effect on selected markers of redox, oxidative and inflammatory status [55, 56]. Nevertheless, two grams of grape seeds extracts displayed an antioxidant effect, decreasing isoprostanes and lipid oxidation, after fructose ingestion in overweight obese patients [57].

5. STUDIES WITH HERBS, GREEN TEA AND THEIR EXTRACTS

Overall, herb extracts are extremely effective in modulating oxidative and inflammatory status as shown in four studies out of the five identified (Table 4).

Ginseng-based steroid Rg1 (5 mg) decreased lipid oxidation and inflammatory TNF-α in healthy subjects after exercise [60] and ginsenosides, intravenously injected, decreased lipid oxidation and IL-6 and LPS production [62].

On the contrary, capsules of ginseng extracts did not affect CRP levels and antioxidant status [61]. Between the selected herbs, extracts of Silybum marianum (milk thistle) decreased CRP in subjects with Type 2 diabetes in concomitance with an increase in NEAC and antioxidant enzymes (SOD and GPX), as well as with decreases in MDA levels [63]. Also the hydro alcoholic nettle (Urtica dioica) extract, 100 mg/kg of body weight for 8 weeks supplementation, increased NEAC and decreased IL-6 and CRP in patients with type 2 diabetes [64, 65].

Green tea extracts modulate both markers of oxidation and inflammation, as shown in three studies out of the four identified; at least one marker of inflammation was actively improved in all studies (Table 5).

In particular, in hemodialysis patients the decrease in peroxides levels of two different doses of green tea extract (455 and 910 mg) was associated with the reduction of markers of inflammation IL8 and TNF-α receptor, CRP and TNF-α both after acute and chronic consumption [70]. Similar results were obtained with 1 g of green tea extract in a longitudinal study of 3 and 6 months with a decline in oxLDL and of p22phox [69]. Furthermore green tea extract (379 mg) increased NEAC, concomitantly with a reduction of TNF-α and CRP after 3 months of supplementation in obese and hypertensive patients [68].

6. STUDIES WITH SPICES EXTRACTS

Spices often used for culinary purposes, namely curcumin and ginger, showed the capability to improve both oxidative stress and inflammatory status (Table 6).

Capsules of curcuminoids decreased lipid oxidation and CRP levels in patients undergoing coronary artery bypass [73]. Decrease of CRP and IL-8 concentration but with no antioxidant effect, was obtained with 200 mg of curcumin in healthy subjects [71].

Studies conducted with ginger involved patients with Type 2 diabetes [77], subjects on peritoneal dialysis [76], or patients with acute respiratory distress syndrome [78]. In two of these studies, ginger consumption improved redox and inflammatory markers. In another 4-week study on diabetic patients, with a randomized, controlled design, turmeric (2g) as an adjunct to standard metformin therapy determined a significant reduction in lipid peroxidation and MDA, reduced CRP and enhanced total antioxidant status [74].

7. STUDIES WITH BEVERAGES AND EXTRACTS WITH MIXED PLANT FOOD COMPOSITION

Among different beverages, a mixed fruits juice did not affect neither TBARS nor CRP levels in healthy subjects after 12 weeks of 120 ml daily [79], whereas ingestion of 300 mL of citrus-based juice with added A. melanocarpa extract for 6 months reduced both oxLDL and CRP in patients with metabolic syndrome [80] (Table 7).

Table 2. Overview of the reviewed intervention studies with fruits, fruit juices and fruits extracts in humans: characteristics, study design and effect on markers of redox, oxidative and inflammatory status.

Treatment Dose/day
Standardization
Subjects (healthy status and no.) Study design and Duration Markers of red-ox/ oxidative status Markers of inflammatory status Refs.
Bilberry (juice) 330 ml At least one risk factor for cardiovascular disease
62
Parallel, 4 weeks NEAC, lipid peroxidation and GSH ↔ CRP and IL-6 ↓
IL-1, IL-2, IL-12, IL-17 and IFN-γ ↔
TNF-α ↑
[32]
Cranberries (dried powder) 1500 mg Men with urinary tract infection
42
Parallel, 6 months NEAC, SOD, MDA, GSH, GPX, CAT and AOPP ↔ CRP ↔ [33]
Cranberry (juice) 480 ml
(polyphenols 458 mg)
Metabolic syndrome
31
Parallel, 8 weeks NEAC ↑
MDA ↓
oxLDL,↓
CRP↔
IL6↔
[34]
Cranberry (juice) 0,7 litres
(polyphenols
104mg/100ml)
Metabolic syndrome
56
Parallel, 60 days Lipid peroxidation and AOPP ↓ Adiponectin ↑
CRP, TNF-α, IL-1 and IL-6 ↔
[35]
Fermented papaya (sachets) 9 g Type 2 diabetic obese
17
Longitudinal, 2 and 6 weeks 4-HNE ↔
Carbonils ↔
Oxidative burst ↑ [36]
Fermented papaya (supplement). 9 g Elderly
40
Crossover, 3 months SOD, GPX and GSH ↔ TNF-α and IL-6 ↓
CRP ↔
Hsp-70 ↑
[37]
Fermented papaya (supplement). 9 g HCV-related cirrhosis
50
Longitudinal, 6 months GSH and GPX↑
MDA and 8-OHdG↓
TNF-α↓ [38]
Fermented papaya (supplement). 6 g HCV-related cirrhosis
32
Parallel, 6 months 4-HNE ↓
GSH ↑
TNF-α ex vivo ↓ [39]
Freeze-dried Strawberry 50g
(polyphenols 2.0g)
Women with metabolic syndrome
16
Longitudinal, 4 weeks 4-HNE, MDA ↓
oxLDL ↔
CRP and adiponectin ↔ [40]
Freeze-dried strawberry 25 g (low)
(polyphenols 1.0g)
50g (high)
(polyphenols 2.0g)
Obese with elevated serum lipids
60
Parallel, 12 weeks MDA and HNE ↓
MDA and HNE ↓
CRP ↔
CRP ↔
[41]
Freeze-dried strawberry 50g
(polyphenols 2.0g)
Type 2 diabetic
36
Parallel, 6 weeks NEAC ↑
MDA ↓
CRP ↓ [42]
Freeze-dried whole grape (powder) 46 g
(polyphenols 580 mg/100 g)
Dyslipidemia
11
Non-dyslipidemia
13
Crossover, 4 weeks oxLDL, IsoP, SOD and GPX↔
oxLDL, IsoP, SOD and GPX↔
TNF-α, IL-6, IL-8 and NOX↔
adiponectin↑
iNOS↓
TNF-α, IL-6, IL-8 and NOX↔
adiponectin↓
iNOS↑
[43]
Pomegranate (concentrated juice) 50 g
(polyphenols 6.3 mg/100 g).
Type 2 diabetic
31
Longitudinal, 4 weeks NEAC ↑ IL-6 and adiponectin ↓
TNF-α and CRP ↔
[44]
Pomegranate (capsules) 2 capsules (1.5g polyphenol). obese with type 2 diabetes
8
healthy
9
Longitudinal, 4 weeks 4-HNE, MDA ↓
oxLDL ↔
4-HNE, MDA, oxLDL ↔
CRP ↔
CRP ↔
[45]
Pomegranate (extract) 1g
(600–755 mg of gallic acid equivalents)
Hemodialysis
33
Parallel, 6 months NEAC, AOPP, 8-OHdG and ox-LDL↔ IL-6 and CRP ↔ [46]
Pomegranate (extract) 2 capsules (500 mg, 40% ellagic acid) Rheumatoid arthritis
55
Parallel, 8 weeks MDA ↔
GPX ↑
CRP ↔ [47]
Pomegranate (extract) 100mg Overweight/obese
42
Parallel, 30 days MDA ↓ CRP and IL-6 ↓ [48]
Pomegranate juice + pomegranate (extract) 100 mL Juice
1,050 mg extract
Hemodialysis
20
Crossover
4 weeks juce followed by 4 weeks extract or 4 weeks extract followed by 4 weeks juice), immediately before each dialysis treatment
IsoP ↔ CRP and IL-6 ↔ [49]
Pomegranate (juice) 100ml
(polyphenols 0.7mmol/100 cc juice).
Hemodialysis
27
Parallel, during the first hour of a dialysis session AOPP ↓ MPO ↓ [50]
Pomegranate (juice) 100 cc
(polyphenols 0.7mmol/100 cc juice).
Hemodialysis
49
Parallel, during each dialysis (3 times/ week), 1 year MDA, AOPP and carbonyls ↓ TNF-α, IL-6 and MPO ↓ [51]
Red grape (concentrated juice) 100ml
(polyphenols 0.64 g)
Hemodialysis
38
Healthy
15
Parallel, 2 weeks NEAC ↑
oxLDL ↓
NEAC ↑
oxLDL ↓
CRP ↔
CRP ↔
[52]
Red grape (concentrated juice) 100ml
(polyphenols 0.64 g)
Hemodialysis
16
Parallel, 2 weeks oxLDL ↓ CRP ↔
ROS ↓
[53]
Rio red grapefruit Half 3 times/day Obese
74
Metabolic syndrome
29
Parallel, 6 weeks IsoP ↔
IsoP ↔
CRP ↔
CRP ↔
[54]

4-HNE: 4-hydroxynonenal; 8-OHdG: 8-hydroxy-2' –deoxyguanosine; AOPP: advanced oxidation protein products; CAT: catalase; CRP: C reactive protein; GPX: glutathione peroxidase; GSH: reduced glutathione; Hsp-70: heat shock protein 70; IFN-γ: interferon gamma; IL: interleukin; iNOS: inducible nitric oxide synthase; IsoP: isoprostanes; MDA: malondialdehyde; NEAC: non-enzymatic antioxidant capacity; NOX: NADPH-oxidase; oxLDL: oxidized low density lipoproteins; ROS: reactive oxygen species; SOD: superoxide dismutase; TNF-α: tumor necrosis factor alfa; HCV: Hepatitis C Virus.

Table 3. Overview of the reviewed intervention studies with grape seeds in humans: characteristics, study design and effect on markers of redox, oxidative and inflammatory status.

Treatment Dose/day
Standardization
Subjects (healthy status and no.) Study design and duration Markers of red-ox/ oxidative status Markers of inflammatory status Refs.
Grape seeds (capsules) 1300 mg CVD risk factors
50
Crossover, 1 month NEAC, MDA and IsoP↔ CRP and IL-6 ↔ [55]
Grape seed extract (added in yoghurt) 2 g CVDrisk factors
35
Crossover, 4 weeks oxLDL and IsoP↔ CRP↔ [56]
Grape seed extract (capsules) 2 g Overweight/obese first degree relatives of type 2 diabetic patients
38
Parallel, 8 weeks
+ 6d fructose
week 8:
carbonils ↓
IsoP and TBARS ↔
after fructose:
IsoP and TBARS↓
week 8:
CRP ↔
after fructose:
CRP ↔
[57]
Grape seed extract (tablets) 600 mg Type 2 diabetes
32
Crossover, 4 weeks NEAC ↔
GSH ↑
CRP ↓ [58]
Monomeric and oligomeric flavanols from grape seeds (capsules) 200 mg Male smokers
25
Parallel, 8 weeks NEAC, SOD, CAT, GPX and IsoP↔
GSH/GSSG ↑
CRP ↔
TNF-α ↓
[59]

CAT: catalase; CRP: C reactive protein; CVD: cardiovascular; GPX: glutathione peroxidase; GSH: reduced glutathione; GSSG: oxidized glutathione; IL: interleukin; IsoP: isoprostanes; MDA: malondialdehyde; NEAC: non-enzymatic antioxidant capacity; oxLDL: oxidized low density lipoproteins; SOD: superoxide dismutase; TBARS: thiobarbituric acid reactive substances; TNF-α: tumor necrosis factor alfa.

Table 4. Overview of the reviewed intervention studies with herbs extracts in humans: characteristics, study design and effect on markers of redox, oxidative and inflammatory status.

Treatment Dose/day
Standardization
Study design and duration Study design and
duration
Markers of red-ox/ oxidative status Markers of inflammatory status Refs.
Ginseng based steroid Rg1 (capsule) 5 mg Rg1 Healthy
12
Crossover, one night and one hour before exercise TBARS ↓ IL6 ↔
TNF- α ↓
[60]
Ginseng extract (capsule) 250 mg, four capsules/day
(7 mg ginsenosides)
Hyperlipidemic
36
Parallel, 8 weeks PAB ↔ CRP↔ [61]
Ginsenosides (intravenously) 1.5 mL/kg (equal to 1.35 mg/kg ginsenosides and 0.15 mg/kg aconite alkaloid). Children undergoing heart surgery for congenital heart defects
24
Parallel, 2 minutes before the start of cardiopulmonary bypass (CPB) and throughout the course of CPB. MDA (1 and 2h after reperfusion) ↓ IL-6 and LPS (1 and 2h after reperfusion)↓ [62]
Silybum marianum (L.) Gaertn. (silymarin) extract (tablets) 140 mg silymarin three times/day Type 2 diabetes
40
Parallel, 45 days SOD↑
GPX↑
NEAC ↑
MDA↓
CRP↓ [63]
Nettle (Urtica dioica) (extract) 100 mg /kg of body weight 50
type 2 diabetes
Parallel, 8 weeks NEAC ↑
SOD ↑
MDA↔
GPX↔
CRP and IL-6↓
TNF-α ↔
[64, 65]

CRP: C reactive protein; GPX: glutathione peroxidase; IL: interleukin; NEAC: non-enzymatic antioxidant capacity; LPS: lipopolysaccharide; MDA: malondialdehyde; PAB: Pro-oxidant- Antioxidant Balance; SOD: superoxide dismutase; TBARS: thiobarbituric acid reactive substances; TNF-α: tumor necrosis factor α.

Table 5. Overview of the reviewed intervention studies with green tea and green tea extracts in humans: characteristics, study design and effect on markers of redox, oxidative and inflammatory status.

Treatment Dose/day
Standardization
Subjects (healthy status and no.) Study design and duration Markers of red-ox/ oxidative status Markers of inflammatory status Refs.
Green tea (Beverage) 2.4 g instant green tea
(297.9 mg catechins)
Obese
19
Crossover, 5 days IsoP ↓ CRP and IL6 ↔ [66]
Green tea extract (Beverage) 159 mg total catechins in 450ml Male cyclists
9
Crossover, 21 days,
After exercise (2h)
oxLDL and
TBARS ↔
After exercise: oxLDLand
TBARS ↔
CRP ↓
IL6 ↔
After exercise:
CRP and IL6 ↔
[67]
Green tea extract (capsule) 379 mg (208 mg EGCG) Obese, hypertensive patients
9
Parallel, 3 months NEAC ↑ TNF-α ↓
CRP ↓
[68]
Green tea extract (capsule) 1 g (483 mg of Camelia Sinensis powder and 100 mg of leaf extracts for a total of 68 mg catechins) Chronic dialysis
20
Longitudinal, 3 and 6 months oxLDL ↓ (only in 9 patients) P22phox ↓ [69]
Green tea extract (Tablets) 455 and 910 mg of catechins during a single hemodialysis session. Haemodialysis patients
44
Crossover, bolus, 1 and 3h post-dialysis
Parallel, 7 months
peroxides ↓
peroxides ↓
IL-8 and TNF-α receptor↓
CRP and TNF-α↓
[70]

CRP: C reactive protein; EGCG: epigallocatechingallate; IL: interleukin; IsoP: isoprostanes; NEAC: non-enzymatic antioxidant capacity; oxLDL: oxidized low density lipoproteins; TBARS: thiobarbituric acid reactive substances; TNF-α: tumor necrosis factor alfa.

Table 6. Overview of the reviewed intervention studies with spices extracts in humans: characteristics, study design and effect on markers of redox, oxidative and inflammatory status.

Treatment Dose/day
Standardization
Subjects (healthy status and no.) Study design and duration Markers of red-ox/ oxidative status Markers of inflammatory status Refs.
Curcumin (phytosome) 200 mg Healthy
19
Parallel, 48 hours prior and 24 hours after running test NEAC↔
CAT ↔
GPX ↔
CRP ↓ (24h)
IL-8 ↓ (2h)
MPO ↔
[71]
Curcumin extracts (powder) 400 mg (80 mg curcumin) Healthy
38
Parallel, 4 weeks NEAC↑ CAT↑
SOD ↔
CRP ↔
MPO↑
[72]
Curcuminoids (capsules) 4 g Undergoing coronary artery bypass grafting
121
Parallel, 3 days before the surgery and 5 days after surgery MDA↓ CRP↓ [73]
Turmeric (capsules) 2 g Type 2 diabetes on metformin therapy
60
Parallel, 4 weeks. NEAC ↑
MDA↓
GSH, GPX, CAT and carbonyls ↔
CRP↓ [74]
Turmeric (capsules) 2.8 g Overweight and obese women
98
Parallel, 4 weeks IsoP and oxLDL↔ CRP, IL-6, IL-8 and TNF-α ↔ [75]
Ginger (capsule) 1000 mg Peritoneal dialysis
36
Parallel, 10 weeks MDA↔ CRP↔ [76]
Ginger (capsules) 3 g Type 2 diabetes
45
Parallel, 3 months NEAC↑
MDA↓
CRP↓ [77]
Ginger extract (enteral feeding) 120 mg Acute respiratory distress syndrome
32
Parallel, 5 and 10 days GSH (day 5)↑ IL-1 ↔
IL-6 (day 5)↓
TNF-α ↔
[78]

CAT: catalase; CRP: C reactive protein; GPX: glutathione peroxidase; GSH: reduced glutathione; IL: interleukin; IsoP: isoprostanes; MDA: malondialdehyde; MPO: myeloperoxidase; NEAC: non-enzymatic antioxidant capacity; oxLDL: oxidized low density lipoproteins; SOD: superoxide dismutase; TNF--α: tumor necrosis factor alfa.

Table 7. Overview of the reviewed intervention studies with beverages with mixed plant food composition in humans: characteristics, study design and effect on markers of redox, oxidative and inflammatory status.

Treatment Dose/day
Standardization
Subjects (healthy status and no.) Study design and
duration
Markers of
red-ox/ oxidative status
Markers of inflammatory status Refs.
Mixed fruit beveragea 120 ml Healthy
14
Longitudinal, 12 weeks TBARS ↔ CRP↔ [79]
Citrus-based juice with melanocarpab. 300 ml Metabolic syndrome
33
Parallel, 6 months oxLDL↓ CRP↓ [80]
Mixed fruit and vegetable beverageb 360 mg/L polyphenols; 170 mg total proanthocyanidins and 9 mg anthocyanins in single dose Healthy
20
Parallel, acute (0-4h) IsoP↓
NEAC↑
CRP↔ [81]
Pineapple, black currant and plum. 500 ml (32 mg anthocyanins, 2.5 mg flavan-3-ols and 20 mg flavonols) Overweight
14
Crossover, acute, post-prandial with high fat and carbohydrates meal (0-8h) IsoP↔
NEAC↔
TNF- α, IL-6 and IL-17↓ [8, 82]

CRP: C reactive protein; IFN: interferon; IL: interleukin; IsoP: isoprostanes; MDA: malondialdehyde; NEAC: non-enzymatic antioxidant capacity; TBARS: thiobarbituric acid reactive substances; TNF- α: tumor necrosis factor alfa. Mixed fruit beveragea: Acai pulp, pomegranate, wolfberry, camu camu, passion fruit, aronia, acerola, bilberry, apricot, purple grape, white grape, lychee, banana, kiwi, pear, cranberry, blueberry and prune. Citrus-based juiceb. juice citrus (95%) with 5% of A. melanocarpa extract. Mixed fruit and vegetable beveragec: Coffee fruit extract, grape seed, North American wild blueberry, quercetin, resveratrol, bilberry, raspberry, cranberry, prune, tart cherry, strawberry, grape seed extract, broccoli sprouts, broccoli, tomato, carrot, spinach, kale, brussels sprout, pomegranate extract and acai pulp) dissolved in a blend of juices (grape, pomegranate, pear, apple, strawberry, chiloensis; acai, yumberry, rubra; cupuacu and camu and a standardized extract of Ashwagandha).

On the other hand, after acute consumption of a polyphenol-rich beverage containing an extremely variegate variety of mixed fruit and vegetable extracts improve redox markers without affecting CRP levels in healthy subjects [81].

On the contrary, half liter of a mixed fruit-based drink decreased the postprandial inflammatory stress induced by a high fat meal (1361 calories) without affecting redox markers in overweight subjects [8, 82] as displayed in Table 7.

As described in Table 8, when supplements with mixed composition were administered as capsules, tablets, powder or by infusion, three studies showed a combined effect on both markers of redox/oxidative and inflammatory status.

In particular, five weeks of supplementation with capsules containing resveratrol, tomato extract, green tea extract, antioxidant vitamins, fish oil and polyunsaturated fatty acids (PUFA), decreased isoprostanes concentration concomitantly with a reduction of IL-18 in overweight subjects [83]. After 8 weeks of consumption of capsules containing powder concentrate derived from acerola cherry, apple, bilberry, blackberry, black currant, blueberry, beetroot, broccoli, cabbage, carrot, Concord grape, cranberry, elderberry, kale, orange, peach, papaya, parsley, pineapple, raspberry, red currant, spinach and tomato, were found a decrease in protein (carbonyls) and lipid (oxLDL) oxidative damage, as well as the exercise-induced increase of TNF-α [87]. Furthermore, 8 weeks of supplementation with capsule containing curcuminoids (1g) + piperine (10 mg) was able to modulate SOD in conjunction with a decrease in lipid peroxidation (MDA) and the inflammatory CRP [91]. In the study from Soare et al. [92] providing an extremely variegate composition of functional ingredients, ranging from resveratrol, to fish oil to green, black and white tea etc. for 6 months failed to show any results on redox/oxidative and inflammatory status. Negative results were also obtained by Nieman et al. [90], with green tea, blueberry and soy protein extracts, and by Braga et al. [93] with green tea extracts and vitamin C and E, in healthy and cancer patients, where only an effect on plasma NEAC was observed in Braga’s study. However, all these three studies suffered from potential bias due to lack or improper placebo. In particular, placebo was prepared from Soy protein isolate containing 1.38 mg/g gallic acid equivalents (GAE) in the study of Nieman et al. [90], it was a concentrate orange juice in the study of Braga et al. [93] and, in the study from Soare et al. [92] placebo was lacking and both groups received a daily multivitamin/mineral supplement. Studies from Gupta et al. [84] and Mahmoodpoor et al. [89] failed to display any effect on antioxidant status but showing a decrease of levels of CRP in patients with dyslipidaemia and TNF-α in patients with sepsis, respectively. A limited effect on SOD and LDL oxidation was observed after two months of supplementation with capsules containing a wide array of fruit and vegetables [85] or 24 weeks with capsules containing ginseng roots, mulberry and banana extracts [86] in healthy subjects and type 2 diabetes patients, respectively.

Table 8. Overview of the reviewed intervention studies with extracts with mixed composition in humans: characteristics, study design and effect on markers of redox, oxidative and inflammatory status.

Treatment Dose/day
Standardization
Subjects (healthy status and no.) Study design and
Duration
Markers of red-ox/ oxidative status Markers of inflammatory status Refs.
Capsule containing antioxidants, plant-food extracts and PUFA Four capsules
(resveratrol 6.3 mg, tomato extract (3.75 mg lycopene), green tea extract 94.5 mg, a-tocopherol 90.7 mg, vitamin C 125 mg, eicosapentaenoic acid (EPA) 380 mg, docosahexaenoic acid(DHA) 260 mg, other PUFA 60 mg)
Overweight
36
Crossover, 5 weeks IsoP↓ CRP ↔
IL-18 ↓
MPO ↑
[83]
CHOLACTIV
(capsule)
Two capsule
Leucoselect® Phytosome® 250 mg; policosanol 15 mg; tomato extract (lycopene≥ 10%) 75mg; Oenothera biennis oil (cis-γ-linolenic acid≥9%) 250 mg)
Dyslipidemia
60
Parallel, 6 weeks SOD ↔
GPX ↔
MDA ↔
CRP ↓ [84]
Fruits and vegetables capsules (FV)a
FVB: FV with the addition of mixed berry juice powderb
Three twice a day with meal Healthy
117
Parallel, 60 days SOD↑
SOD↑
CRP↔
CRP↔
[85]
Capsule containing: ginseng roots, mulberry leaf water extract and banana leaf water extract. 6 g Impaired glucose tolerance or mild T2D
94
Parallel, 24 weeks oxLDL↓ CRP↔ [86]
Capsule containing powder concentrate derived from fruits and vegetablesc Three twice a day with meal
(6 capsules)
(7.5mg β-carotene, 200mg vitamin C, 60 mg α-tocopherol)
Overweight and obese pre-menopausal women
42
Parallel, 8 weeks
Pre- and post-30 min exercise
8 weeks:
Carbonyls and oxLDL↓
MDA↔
Post-exercise:
Carbonyls, oxLDL and MDA↔
8 weeks:
TNF- α and IL-6↔
Post-exercise:
TNF- α ↓
IL-6↔
[87]
Vitamins, minerals and mixed plant extractsd (Tablets) 2 tablets Healthy
42
Longitudinal, 4 weeks oxLDL↓
IsoP↔
CRP↔ [88]
Infusion of IMOD (urtica, carotenoids, urea, and selenium) 125 mg of IMOD* Severe sepsis
16
Parallel, 14 days NEAC, lipid peroxidation and SH ↔ TNF-α↓
IL-1, IL-2, IL-6↔
[89]
Powder containing: green tea extract, blueberry pomace extract, Soy protein complex Soy protein complex
40 g.
2, 136 mg GAE.
Healthy
31
Parallel, 2 weeks
2.5-h exercise (3-day exercise period).
NEAC, carbonyls and IsoP↔
NEAC, carbonyls and IsoP↔
CRP, TNF-α IL-6 and IL-8 ↔
CRP, TNF-α IL-6 and IL-8 ↔
[90]
Curcuminoids + piperine (capsules) curcuminoids (1g) + piperine (10mg) Metabolic syndrome
100
Parallel, 8 weeks SOD↑
MDA↓
CRP↓ [91]
Mixed plant extracts and fish oil capsules) One each supplement/day
100 mg of resveratrol, a complex of 800 mg each of green, black, and white tea extract, 250 mg of pomegranate extract, 650 mg of quercetin, 500 mg of acetyl-l-carnitine, 600 mg of lipoic acid, 900 mg of curcumin, 1 g of sesamin, 1.7 g of cinnamon bark extract, and 1.0 g fish oil
Healthy
54
Parallel, 6 months Carbonyls ↔ CRP, TNF- α and IL-6↔ [92]
Powder containing green tea extract (1g) + vitamin C and E Twice/day and one hour before surgery‡ Cancer patients
36
Parallel, three doses† NEAC ↑
IsoP↔
CRP ↔ [93]

CRP: C reactive protein; GPX: glutathione peroxidase; IL: interleukin; IsoP: isoprostanes; MDA: malondialdehyde; MPO: myeloperoxidase; NEAC: non-enzymatic antioxidant capacity; oxLDL: oxidized low density lipoproteins; PUFA: polyunsaturated fatty acids; SH: sulphydrils; SOD: superoxide dismutase; TNF- α: tumor necrosis factor alfa; T2D: Type 2 diabetes. a: capsules blended fruit and vegetable juice powder concentrate derived from acerola cherry, apple, beet, broccoli, cabbage, carrot, cranberry, kale, orange, peach, papaya, parsley, pineapple, spinach, and tomato; b: bilberry, blackberry, black currant, blueberry, cranberry, Concord grape, elderberry, raspberry and red currant; c: acerola cherry, apple, bilberry, blackberry, black currant, blueberry, beetroot, broccoli, cabbage, carrot, Concord grape, cranberry, elderberry, kale, orange, peach, papaya, parsley, pineapple, raspberry, red currant, spinach and tomato; d: Citrus bioflavonoids, green coffee bean extract, pomegranate whole fruit extract, grape seed extract, blueberry fruit extract, green tea leaf extract, bitter melon fruit extract, prune skin extract, watercress herb 4:1 extract, Chinese cinnamon bark powder, Indian gum Arabic tree bark and heart wood extract, rosemary extract and artichoke leaf extract; *: in 100 ml of DW5% infused over 1 hour on the first day, then 8 ml of IMOD in 100 ml/d; ‡ pancreaticoduodenectomy; †: 2 the day before the operation and the third the day of surgery 3 h before the anaesthesia.

8. STUDIES WITH COCOA PRODUCTS

Table 9 describes the reviewed intervention studies with cocoa products, including dark chocolate, beverages and creams. Within these interventions decreases in peroxidation markers were observed in healthy [94], obese [66] and pre-hypertensive or stage-1 hypertensive subjects with high cholesterol [95]. In particular, the consumption of a cocoa beverage with a medium content of flavanols (400mg /day) for 5 days decreased IsoP, CRP and IL-6 levels in obese subjects, whereas beverages with lower (180mg/day) or higher (900mg/day) flavanols content increased IL-6 levels [66]. IL-6 did not decrease [95] after the consumption of a cocoa cream product (78g of cocoa + 30g hazelnuts + 2g phytosterols + 20 g fiber) that decreased levels of oxLDL and CRP [95]. Furthermore, others reported decreased levels of the anti-inflammatory IL-10 after the consumption of a cocoa powder (45.3mg flavanols) with 400 mL of semi-skimmed milk in both normo- and moderate hyper-cholesterolaemic subjects [96, 97].

9. DISCUSSION

In this paper, for the first time, we reviewed available evidence about the effect of supplementation with selected fruits, vegetables, herbs, spices and their extracts or galenic formulations on combined markers of redox and inflammatory status in humans. Overall, 30.7% (27/88) of the interventions did not show any positive effect on any markers, while in the remaining 69.3% (61/88) there was an improvement of at least one of the two category markers. Among the 61 interventions showing an effect on the selected markers, 44.2% (27/61) improved both markers of redox and inflammatory status. More specifically, markers of red-ox and oxidative status change after the interventions as follows: NEAC increased in 48.3% (14/29), GSH in the 50.0% (4/8), antioxidant enzymes in the 31.0% (9/29), whereas marker of protein oxidation and markers of lipid peroxidation decreased in the 33.3% (5/15) and 48.0% (37/77), respectively. For what concerning markers of inflammatory stress, CRP decreased after intervention in 24.6% of the studies (17/69), the 44.9% (22/49) of the interventions reported decreases in at least one inflammatory cytokines, whereas 40.0% of the interventions (4/10) reported increased in markers of ROS generation [i.e. the oxidative burst, iNOS and MPO].

Table 9. Overview of the reviewed intervention studies with cocoa products in humans: characteristics, study design and effect on markers of redox, oxidative and inflammatory status.

Treatment Dose/day
Standardization
Subjects (healthy status and no.) Study design and duration Markers of red-ox/ oxidative status Markers of inflammatory status Refs.
Dark chocolate +
Cocoa beverage
36.9 g (Procyanidin 4.56mg/g)
+
30.9 g (Procyanidin 15.6mg/g)
Healthy
25
Longitudinal, 6 weeks treatment and 6-weeks washout period NEAC, IsoP ↔ .
oxLDL ↓
CRP ↔
Ex vivo IL-1β, IL-6, TNF-α ↔
[94]
Cocoa
beverages
180 mg flavanols (low),
400 mg flavanols (medium)
900 mg flavanols (high)
Obese
19
Crossover, 5 days IsoP ↔ .
IsoP ↓
IsoP ↔ .
CRP↔, IL-6 ↑
CRP ↓, IL6↓
CRP ↔, IL-6 ↑
[66]
Cocoa
cream products
78 g of:
A: cocoa;
B: cocoa + hazelnut (30 g);
C: cocoa + hazelnuts + phytosterols (2 g);
D:cocoa+hazelnuts+phytosterols+ fiber (20 g).
Pre-hypertensive or stage-1 hypertensive, high cholesterol
113
Parallel, 4 weeks oxLDL ↔
oxLDL ↔
oxLDL ↔
oxLDL ↓
CRP and IL-6 ↔
CRP and IL-6 ↔
CRP and IL-6 ↔
CRP ↓, IL-6 ↔
[95]
Cocoa powder 45.3 mg flavanols
/ 400 mL semi-skimmed milk
Moderately hypercholesterolaemic
20
Healthy
24
Cross-over, 4 wks NEAC, MDA, Carbonyls ↔
NEAC, MDA, Carbonyls ↔
IL-10 ↓
IL-1β, IL-6, IL-8, TNF-α ↔
IL-10 ↓
IL-1β, IL-6, IL-8, TNF-α ↔
[96,
97]

CRP: C reactive protein; IL: interleukin; IsoP: isoprostanes; MDA: malondialdehyde; NEAC: non-enzymatic antioxidant capacity; oxLDL: oxidized low density lipoproteins; TNF-α: tumor necrosis factor alfa.

Some considerations are essential for a more comprehensive evaluation of these findings. First, the high heterogeneity of the reviewed studies should be taken into account, as they involved not only wide and very different sources of food, food extracts and supplements, but also different doses, length of supplementation and characteristics of the subjects. Moreover, identified studies presented different robustness and designs, and sometimes a limited sample size. For what concerns the length of the study, in one-day trial it is possible having a clear experimental window of the investigated phenomenon, free of any interference from diet, physical activity and homeostatic controls. On the other hand, when dealing with long-term intervention studies, all the potential bias due to subjects variability, selection criteria, study design, food/extract/ galenic composition must be taken into account. The choice of the biomarkers and the type of measurements also represent an enormous source of variability: markers of redox status can include assessment of endogenous antioxidant (NEAC, single antioxidants, enzymes etc.), while markers of oxidative stress status might involve lipid peroxidation (oxLDL, MDA, isoprostanes, and others) and markers for inflammatory stress are mainly CRP and cytokines. All these markers respond differently to the different types of supplementation, providing different physiological meanings. In our view, in order to obtain a clearer picture of the phenomenon, it is preferable to assess a battery of biomarkers for three interconnected but different responses. For lipid oxidation, despite isoprostane levels being considered a gold standard, it will be also useful to assess other markers such as LDL oxidation or hydro-peroxides levels in order to obtain more complete information. At the same time, the assessment of antioxidant status should include markers for NEAC [Ferric Reducing Antioxidant Potential (FRAP), Total-radical Trapping Antioxidant Parameter (TRAP) and oxygen radical absorbance capacity (ORAC)], endogenous antioxidants (GSH, uric acid and thiols) and endogenous enzymes, preferably in cellular systems (CAT, SOD, GPX). With respect to the inflammatory response it is crucial to understand the role that every single cytokine plays in the different type of pathology or metabolic conditions, keeping in mind that their supposedly low or undetectable levels in healthy and young people could be raised by specific stressors such as post-prandial stress or strenuous physical exercise.

In long term studies we need to consider the existence of physiological mechanism of homeostatic control for both oxidative and inflammatory stress, aimed to tune the antioxidant network and to optimize inflammatory response to the stress. As we showed in previous works [98, 99], in healthy condition such as the absence of specific risk factors for oxidative stress (smoking, obesity, old age etc.), the body require a minimum dose of nutritional antioxidant to maintain physiological red-ox homeostasis, translating in a lack of effect on markers of antioxidant status following long term supplementation. We showed that 58% of the intervention studies conducted with fruit, vegetables, tea, wine, cocoa-products, olive oil and galenic flavonoids, reported a lack of effect in healthy subjects [99] with an effect size of 0.367 (p<0.001;n=1450) [98]. On the contrary when the studies were conducted on subjects characterized by different CVD risk factors (smoking, hypercholesterolemia, metabolic syndrome, hypertension etc.) involving the existence of an oxidative/inflammatory stress, the percentage of efficiency rise to 70% of the intervention studies and effect size of 0.937 (p<0.001;n=526) [98, 99].

A detailed description of the nutritional, antioxidant as well as bioactive ingredient composition of the tested food or extracts is crucial for characterizing the tested matrix and for defining the “effective dose” able to display an antioxidant/anti-inflammatory effect in humans. However, most of the studies lack this information and the majority of the compounds present in the food or in the extracts were not identified. However, between the different ingredients, flavonoids, with their considerable in vitro antioxidant capacity [100 - 102], might play a role in the modulation of redox-regulated genes as well as in the anti-inflammatory activity of plant foods [103, 104]. Flavonoids, such as catechins from green tea, curcumin from turmeric and grape seed procyanidins [1, 104 - 106] exert their anti-inflammatory and antioxidant effects through the activation of Nrf2, inducing the antioxidant enzymes transcription, and the inhibition of NF-kB, key transcription factors in inflammatory responses. In this framework, it must be taken into account that not only flavonoids, but also other bioactive phytochemicals like triterpenes, centella saponin, asiaticoside, and sceffoleoside, asiatic acid, madecassic acid, phenolic acid avenanthramides and others can affect Nrf2 and/or NF-κB pathways [107 - 109]. The mechanism suggested for Nrf2 and/or NF-κB modulation by polyphenols, phenolic acids, saponins and triterpenoids is the interaction of electrophiles with cysteine residues of KEAP1 I-κB and/or I-kappa kinases (IKK) [110 - 119].

However, due to the extensive metabolic activity during digestion, leading to different metabolites endowed with different bioactive ingredients from parental compounds, it is still unclear which are the bioactive ingredients or metabolites responsible of the effect and their relevance in humans [98, 99, 120].

CONCLUSION

In this review, we have shown that some fruits, vegetables, herbs, spices, cocoa and their extracts display a perceived functional activity increasing antioxidant status and at the same time modulating oxidative and inflammatory stress in humans. Interestingly, the modulatory effect of plant foods seems much more efficient in subjects characterized by different risk factors and high level of inflammatory and oxidative stress. In order to fully identify the food items, their functional ingredients as well as the mechanism of action able to display mutual antioxidant/anti-inflammatory activities, more evidence in humans is needed. Meanwhile, it is highly recommended to fully utilize the “functional heritage“ of the wide array of different phytochemicals with multi-factorial synergistic interactions contained in fruits, vegetables, herbs and spices and their extracts to efficiently prevent the raise of oxidative and inflammatory stress, major determinants of degenerative diseases.

LIST OF ABBREVIATIONS

4-HNE = 4-hydroxynonenal
8-OHdG = 8-hydroxy-2'–deoxyguanosine
ARE = Antioxidant responsive elements
CAT = catalase
CRP = C-reactive protein
CVD = cardiovascular disease
FRAP = ferric Reducing Antioxidant Potential
GAE = gallic acid equivalents
GPX = glutathione peroxidase
GSH = glutathione
GSH/GSSG = ratio of reduced/oxidized glutathione
HSP70 = heat shock protein 70
IFN = interferon
IkB = inhibitor of NF-kB
IKK = I-kappa kinases
IL = interleukin
iNOS = inducible nitric oxide synthases
IsoP = isoprostanes
KEAP1 = kelch-like protein-1
LPS = lipopolysaccharide
MDA = malondialdehyde
MPO = myeloperoxidase
NEAC = non-enzymatic antioxidant capacity
NF-kB = nuclear factor- kappa B
NFR2 = nuclear factor-erythroid 2-related factor 2
NOX = NADPH-oxidase
ORAC = oxygen radical absorbance capacity
oxLDL = oxidized low density lipoproteins
PAB = pro-oxidant- antioxidant balance
PUFA = polyunsaturated fatty acids
RNS = reactive nitrogen species
ROS = reactive oxygen species
SOD = superoxide dismutase
TBARS = thiobarbituric acid reactive substances
TLR4 = toll-like receptor-4
TNF-α = tumour necrosis factor-alpha
TRAP = total-radical trapping antioxidant parameter

CONFLICT OF INTEREST

The authors confirm that this article content has no conflict of interest.

ACKNOWLEDGEMENTS

Editorial assistance was provided by Luca Giacomelli, PhD, on behalf of Content Ed Net; this assistance was funded by PGT Healthcare.

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