Mango is rich in polyphenols including gallotannins and gallic acid, among others. The bioavailability of mango polyphenols, especially polymeric gallotannins, is largely dependent on the intestinal microbiota, where the generation of absorbable metabolites depends on microbial enzymes. Mango polyphenols can favorably modulate bacteria associated with the production of bioactive gallotannin metabolites including Lactobacillus plantarum, resulting in intestinal health benefits. In several studies, the prebiotic effects of mango polyphenols and dietary fiber, their potential contribution to lower intestinal inflammation and promotion of intestinal integrity have been demonstrated. Additionally, polyphenols occurring in mango have some potential to interact with intestinal and less likely with hepatic enzymes or transporter systems. This review provides an overview of interactions of mango polyphenols with the intestinal microbiome, associated health benefits and underlying mechanisms.

Açaí (Euterpe oleracea Mart.) berries, characterized by high polyphenol concentrations (predominantly anthocyanins), have demonstrated anti-inflammatory and anti-diabetic activities. The study objective was to determine the modulation of lipid and glucose-metabolism, as well as oxidative stress and inflammation, by an açaí-beverage (containing 1139 mg L⁻¹ gallic acid equivalents of total polyphenolics) in 37 individuals with metabolic syndrome (BMI 33.5 ± 6.7 kg m⁻²) who were randomized to consume 325 mL twice per d of a placebo control or açaí-beverage for 12 weeks. Anthropometric measurements, dietary intake, and blood and urine samples were collected at baseline and after 12 weeks of consumption. Two functional biomarkers, plasma level of interferon gamma (IFN-γ) and urinary level of 8-isoprostane, were significantly decreased after 12 weeks of açaí consumption compared to the placebo control (p = 0.0141 and 0.0099, respectively). No significant modification of biomarkers for lipid- and glucose-metabolism was observed in this study. Findings from this small pilot study provide a weak indication that the selected dose of açaí polyphenols may be beneficial in metabolic syndrome as only two biomarkers for inflammation and oxidative stress were improved over 12 weeks. Follow-up studies should be conducted with higher polyphenol-doses before drawing conclusions regarding the efficacy of açaí polyphenols in metabolic syndrome.

Sargassum thunbergii (Mertens ex Roth) Kuntze (ST) is a brown alga rich in indole-2-carboxaldehyde. This study aimed to investigate the anti-obesity effects of ethanol extract from ST in in vitro and in vivo models. In 3T3-L1 cells, ST extract significantly inhibited lipid accumulation in mature adipocytes while lowering adipogenic genes (C/epba and Pparg) and enhancing metabolic sensors (Ampk, Sirt1), thermogenic genes (Pgc-1a, Ucp1), and proteins (p-AMPK/AMPK and UCP1). During animal investigation, mice were administered a chow diet, a high-fat diet (HF), or an HF diet supplemented with ST extract (at dosages of 150 and 300 mg/kg bw per day) for 8 weeks (n = 10/group). ST extract administration decreased weight gain, white adipose tissue weight, LDL-cholesterol, and serum leptin levels while improving glucose intolerance. In addition, ST extract increased the expression of Ampk and Sirt1 in adipose tissue and in the liver, as well as p-AMPK/AMPK ratio in the liver, compared to HF-fed mice. The abundance of Bacteroides vulgatus and Faecalibacterium prausnitzii in the feces increased in response to ST extract administration, although levels of Romboutsia ilealis decreased compared with those in HF-fed mice. ST extract could prevent obesity in HF-fed mice via the modulation of AMPK activation and gut microbiota composition.

Scytosiphon lomentaria (SL) is a brown seaweed with antioxidant and anti-inflammatory properties; however, its effects on obesity are unknown. In this research, we investigated the anti-obesity properties and underlying mechanisms of the SL extract in vitro and in vivo. In 3T3-L1 preadipocytes, SL extract inhibited lipid accumulation, decreased the expression of Acc1, C/ebpa, Pparg mRNA and p-ACC1, and increased the expression of Ucp1 mRNA, UCP1 and p-AMPK. In animal experiments, mice were fed a chow diet, a high-fat diet (HF; 60% of calories as fat), and high-fat diet with SL extract (150 and 300 mg/kg body weight) for eight weeks (n = 10/group). SL extract reduced HF-induced weight gain, epididymal fat weight, fat cell size, LDL-C, leptin, fasting glucose, and glucose tolerance. In addition, SL extract had comparable effects on mRNA expression in WAT and liver to those observed in vitro, thereby inhibiting p-ACC1/ACC1 and increasing p-AMPK/AMPK and UCP1 expression. Furthermore, SL extract decreased HF-induced Firmicutes/Bacteroidetes ratio and reversed HF-reduced Bacteroides spp., Bacteroides vulgatus, and Faecalibacterium prausnitzii. These findings suggest that SL extract can aid in weight loss in mice fed a high-fat diet by altering adipogenic and thermogenic pathways, as well as gut microbiota composition.

Ulcerative colitis is a chronic inflammatory bowel disease characterized by colonic mucosal inflammation, intestinal microflora imbalance, and intestinal permeability. It is essential to develop natural compounds with anti-inflammatory and intestinal bacterial imbalance correction properties. The brown alga Sargassum horneri is rich in polyphenols, such as fucoxanthin and chromene, which have antioxidant, anti-inflammatory, and anti-cancer properties. In results, S. horneri ethanol extract (SHE) reduced TNF-α and IL-6 levels as well as Pi3k/Mtor/S6k mRNA expression in LPS-treated RAW264.7 and Caco-2 cells. In addition, SHE treatment decreased the expression of genes associated with inflammation and the mTOR axis in the co-culture system while increasing the expression of tight junction factors. In a mouse model of dextran sulfate sodium (DSS)-induced colitis, SHE treatment improved intestinal length, histological scores, and the expression of genes related to tight junctions while decreasing the expression of genes related to inflammatory markers and the mTOR axis. The gut microbiota of mice treated with SHE exhibited a decrease in the ratio of Firmicutes to Bacteroidota, which had been increased by DSS treatment and an increase in beneficial bacteria. Therefore, SHE consumption may be a useful natural alternative, as it improves gut microbiota, alleviates colitis symptoms, and prevents their onset.