Table 3.
Preclinical and human studies with dietary polyphenols on the gut and associated mechanisms (118).
| Experimental model/study | Polyphenol | Specific condition/concentration | Mechanism/effect | References |
|---|---|---|---|---|
| Bacteria culture | Epicatechin gallate | Incubation in pH 2.0 at 37°C for up to 3.5 h with different concentrations ranging from 2.4 to 8 mg/g | Methicillin-resistant S. aureus sensitizes to β-lactam antibiotics | (119) |
| Green tea and red wine polyphenols | Concentration ~50–100 mg/culture plate | Inhibits the VacA toxin of Helicobacter pylori | (120) | |
| Crude polyphenols | Different concentrations up to 5 mg/ml | Control of food-borne pathogenic bacteria without inhibitory effect on lactic acid bacteria growth | (121) | |
| Cell culture model | Ellagic acid, genistein, EGCG, resveratrol | Concentration 0.5–1 g/day | Decrease IL-1β-induced IL-8 secretion EGCG reduce the secretion of IL-6 and IL-8 Genistein lowers significantly the levels of IL-6 and MCP-1 |
(122, 123) |
| Green tea, cocoa, and red wine polyphenols | Concentration 0.5 mg/ml | Reduce basolateral IL-6 secretion from Caco-2 monolayers grown on Transwells and challenged with LPS | (124) | |
| Grape seed, cocoa, sugar cane, oak, mangosteen, and pomegranate polyphenolic extract | Concentration 0.5–4 mg/ml | Reduce IL-1β-induced IL-8 secretion | (125) | |
| Grifola frondosa water extract | Concentration <100 μg/ml | Inhibits TNF-α and induces MCP-1 and IL-8 in mRNA and protein levels | (126) | |
| Sardinian wine extracts | Concentration 50–100 μg/ml | Reduce oxysterol-induced IL-6 and IL-8 protein levels | (127) | |
| Quercetin and pinoresinol | Concentration 100–125 μM working solution | Decrease IL-1β-induced IL-6 and IL-8 levels | (128) | |
| Animal model | Resveratrol | Up to 20 mg/kg body weight | Stimulated fecal cell counts of Lactobacillus and Bifidobacterium sp | (114) |
| Reduces activities of fecal and host colonic mucosal enzymes, such as α-glucoronidase, nitroreductase, β-galactosidase, mucinase, and α-glucosidase | (129) | |||
| Increases TNF-α and IL-1b level Reduction in IL-10 in colon tissues |
(130) | |||
| Increases mucus production in goblet cells in colon mucosa of rat model | (131) | |||
| Decreases IFN-c, TNF-α, IL-6, and IL-1b in serum of mice with acute colitis | (132) | |||
| Quercetin | 100 mg/kg | Reduction of body weight Antidiabetic effect |
(133, 134) | |
| Chlorogenic acid | Different concentrations up to 6 mg/ml | Reduce concentrations of TNF-α and IFN-c in jejunum and colon of weaned rats | (135) | |
| Ellagic acid | Different concentrations up to 0.6 mg/g | Increases mucus production in goblet cells in colon mucosa of rat model of Crohn's disease | (136) | |
| Reduced the expression of TNF-α and IL-6 in rat colon tissues | (137) | |||
| Coffee and caffeic acid | Different concentrations up to 100 mg/kg | Inhibit colon cancer metastasis and cell transformation in mice by inhibiting TOPK (T-LAK cell-originated protein kinase) | (111) | |
| Curcumin | 120–200 μg/ml | Elevates fecal IgA in rats fed high-fat diet Downregulation of colonic IFN-c and TNF-α levels | (134, 138) | |
| Proanthocyanidin-rich red wine extract | ~250 mg kg−1 bw Administered to the rats by orally | Lower levels of Clostridium sp. and higher levels of Bacteroides, Lactobacillus, and Bifidobacterium sp | (139) | |
| Green tea polyphenol | 0.15% for 5 weeks | Reduction in the spontaneous release of IFN-c and TNF-α from colon and lamina propria lymphocytes | (140) | |
| Polyphenols algae | ~0.7 g (dry weight) | Decreased counts of Turcibacter and Akkermansia and increase in Alistipes | (141) | |
| Gallic acid | Different concentrations up to 200 mg/kg | Attenuate mRNA expression levels of TNF-α, IL-1β, IFN-c, IL-6, and IL-17 in colon | (142) | |
| Red wine polyphenol | Decrease the expression of zinc deficiency Induce TNF-α, cytokine-induced neutrophil Chemoattractant | (143) | ||
| Chinese propolis, Brazilian propolis | 100–200 mg/kg/twice daily for 12 weeks | Modulation of gut microflora composition Reduction of Bacteroides sp. | (144) | |
| Piceatannol | Increases in IL-1β, IL-6, and TNF-α in colon | (145) | ||
| Polyphenols (from fungi) | Modulation of gut microflora composition | (118) | ||
| Cocoa containing a total polyphenol | Reduces IgA and IL-6 in Peyer's patches and mesenteric lymph nodes | (146, 147) | ||
| Prunella vulgaris honey | ~20 μg/ml working concentration | Modulation of gut microflora composition, with increased Bacteroidetes/Firmicutes ratio Restoration of Lactobacillus sp. populations | (148) | |
| Pomegranate polyphenols | ~70 mg/ml working concentration | Reduce TNF-α and IL-1β mRNA, and TNF-α, IL-1β, and IL-6 protein levels in intestinal mucosa | (149) | |
| Aronia polyphenol, haskap polyphenol, bilberry polyphenol | Elevate the amount of fecal IgA in rats | (150) | ||
| Human study | Polyphenols (from spices) | Glucose uptake and control of appetite | (151) | |
| Dihydroxylated phenolic acid | Shows potent anti-inflammatory properties Reduce the secretion of TNF-α, IL-1β, and IL-6 |
(113) | ||
| Red wine | 150 ml/ day women 300 ml/day men |
Regular consumption results in a blood pressure reduction, increased lipid profile, and a decrease of uric acid Increase the proliferation of Bacteroides sp. |
(152) | |
| Green tea, fruits, vinegar wine | 700–900 ml/day green tea But not excessive |
Impact of weight reduction along with alteration in microflora of the gut | (153) | |
| Cocoa-derived flavanols | Wide range of concentrations depending upon health status | Increase growth and proliferation of Bifidobacterium sp. and Lactobacillus sp. | (41) | |
| (+)Catechin and (−)Epicatechin |
3 g/day | Inhibition of Clostridium histolyticum growth Growth of Lactobacillus sp. and Bifidobacterium sp. remained unchanged |
(39) | |
| Proanthocyanidin-rich grape extract | 100–300 mg/day | Important rise in bifidobacterial numbers | (40) |