Improved recovery of galloyl metabolites from mango (Mangifera indica L.) in human plasma using protein precipitation with sodium dodecyl sulfate and methanol.

Extraction of polyphenolic metabolites from blood fractions can be challenging since compound recovery can be limited by chemical structure, polarity, and protein-binding affinity of analytes. Gallic acid and its metabolites exhibit particularly low recoveries from plasma and can lead to an underestimation of their bioavailability from foods. A modified method to extract free gallic acid and its metabolites from human plasma aided by sodium dodecyl sulfate and acidified methanol (SDS-MeOH) was applied to extract free gallic acid and its metabolites from human plasma after a single consumption of 400 g of mango (cv. Ataulfo) pulp by 10 healthy male and female subjects. The use of SDS-MeOH facilitated extraction of significantly (p < 0.05) more pyrogallol, free gallic acid, 4-O-methylgallic acid, and ethyl gallate with recovery rates exceeding 80% in standard recovery from human blood plasma when compared to conventional methods that rely on solvent extraction or solid phase extraction. The method was reproducible and precise for standards from 50 to 500 µg/L. In pharmacokinetic plasma samples five predominant metabolites of gallic acid were tentatively characterized by HPLC-MS and absorption kinetics evaluated over 8 h for catechol-O-sulfate, 4-O-methylgallic acid-3-O-sulfate, and pyrogallol-O-sulfate, methylpyrogallol-O-sulfate, and 4-O-methylgallic acid with AUC0-8h of 9520 ± 3370, 6030 ± 1310, 5990 ± 1690, 4020 ± 1040, and 2790 ± 1190 µg/L h respectively. Plasma extraction was rapid and reproducible with superior recovery rates compared to conventional methods when evaluating polar phenolic metabolites.

Body Mass Index as a Determinant of Systemic Exposure to Gallotannin Metabolites during 6-Week Consumption of Mango (Mangifera indica L.) and Modulation of Intestinal Microbiota in Lean and Obese Individuals.

SCOPE: This human clinical pilot trial investigated pharmacokinetics of gallotannin-metabolites and modulation of intestinal microbiota in healthy lean and obese individuals after 6 weeks of daily mango consumption. METHODS AND RESULTS: Participants are divided into three groups: Lean Mango (LM: n = 12; BMI = 22.9 kg m-2 ), Obese Mango (OM: n = 9; BMI = 34.6 kg m-2 ), and Lean Control (LC: n = 11; BMI = 22.1 kg m-2 ). LM and OM consumed 400 g of mango per day for 6 weeks. LC consumed mango only on Days 0 and 42. After 6 weeks, LM experienced increased systemic exposure (AUC0-8h ) to gallotannin-metabolites, 1.4-fold (p = 0.043). The greatest increase is 4-O-methyl-gallic acid, 3.3-fold (p = 0.0026). Cumulative urinary excretion of gallotannin-metabolites significantly increased in LM and OM, but not LC. For OM, qPCR data show increased levels of tannase-producing Lactococcus lactis and decreased levels of Clostridium leptum and Bacteroides thetaiotaomicron, bacteria associated with obesity. LM experienced an increased trend of fecal levels of butyric (1.3-fold; p = 0.09) and valeric acids (1.5-fold; p = 0.056). Plasma endotoxins showed a decreased trend in LM and OM. CONCLUSION: Continuous mango intake significantly increased systemic exposure to gallotannin- metabolites and induced an increased trend for fecal short-chain fatty acids in lean but not obese individuals. This pharmacokinetic discrepancy may result in BMI-associated reduced gallotannin-derived health benefits.

Obesity-Associated Diseases Biomarkers Are Differently Modulated in Lean and Obese Individuals and Inversely Correlated to Plasma Polyphenolic Metabolites After 6 Weeks of Mango (Mangifera indica L.) Consumption.

SCOPE: Mangos are a rich source of gallotannin-derived polyphenols that may exert anti-inflammatory effects relevant to obesity-related chronic diseases. This randomized human clinical study investigated the influence of daily mango supplementation for 6 weeks on inflammation and metabolic functions in lean and obese individuals. METHODS AND RESULTS: Lean (n = 12, body mass index [BMI] 18-26.2 kg m-2 ) and obese (n = 9, BMI >28.9 kg m-2 ) participants, aged 18-65 years received daily 400 g of mango pulp for 6 weeks. Inflammatory cytokines, metabolic hormones, and lipid profiles were examined in plasma before and after 6 weeks. In lean participants, systolic blood pressure was lowered by 4 mmHg after 6 weeks. In obese participants, hemoglobin A1c (HbA1c) and plasminogen activator inhibitor-1 (PAI-1) were reduced by 18% and 20%, respectively. Obese participants showed decreased plasma concentrations (area under the curve [AUC] 0-8h ) of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1). Correlation analysis indicates that the beneficial effects of mango supplementation on pro-inflammatory cytokines, PAI-1 and HbA1c, are associated with systemic exposure to polyphenolic metabolites. CONCLUSIONS: Mango supplementation improves the plasma levels of pro-inflammatory cytokines and metabolic hormones in obese participants. There is a crucial need to investigate the role of lowered polyphenolic absorption in obese individuals on their efficacy in reducing biomarkers for inflammation and other risk factors for chronic diseases.

Mango polyphenolics reduce inflammation in intestinal colitis-involvement of the miR-126/PI3K/AKT/mTOR axis in vitro and in vivo.

This study sought to elucidate the mechanisms underlying the anti-inflammatory effect of mango (Mangifera Indica L.) polyphenolics containing gallic acid and gallotanins, and the role of the miR-126/PI3K/AKT/mTOR signaling axis in vitro and in vivo. Polyphenolics extracted from mango (var. Keitt) were investigated in lipopolysaccharide (LPS)-treated CCD-18Co cells. Rats received either a beverage with mango polyphenolics or a control beverage, and were exposed to three cycles of 3% dextran sodium sulfate (DSS) followed by a 2-wk recovery period. The mango extract (10 mg GAE/L) suppressed the protein expression of NF-κB, p-NF-κB, PI3K (p85ß), HIF-1α, p70S6K1, and RPS6 in LPS-treated CCD-18Co cells. LPS reduced miR-126 expression, whereas, the mango extract induced miR-126 expression in a dose-dependent manner. The relationship between miR-126 and its target, PI3K (p85ß), was confirmed by treating cells with miR-126 antagomiR where mango polyphenols reversed the effects of the antagomiR. In vivo, mango beverage protected against DSS-induced colonic inflammation (47%, P = 0.05) and decreased the Ki-67 labeling index in the central and basal regions compared to the control. Mango beverage significantly attenuated the expression of pro-inflammatory cytokines such as TNF-α, IL-1ß, and iNOS at the mRNA and protein level. Moreover, the expression of PI3K, AKT, and mTOR was reduced, whereas, miR-126 was upregulated by the mango treatment. These results suggest that mango polyphenols attenuated inflammatory response by modulating the PI3K/AKT/mTOR pathway at least in part through upregulation of miRNA-126 expression both in vitro and in vivo; thus, mango polyphenolics might be relevant as preventive agents in ulcerative colitis. © 2016 Wiley Periodicals, Inc.

Polyphenolics from mango (Mangifera indica L.) suppress breast cancer ductal carcinoma in situ proliferation through activation of AMPK pathway and suppression of mTOR in athymic nude mice.

The objective of this study was to assess the underlying mechanisms of mango polyphenol decreased cell proliferation and tumor volume in ductal carcinoma in situ breast cancer. We hypothesized that mango polyphenols suppress signaling along the AKT/mTOR axis while up-regulating AMPK. To test this hypothesis, mango polyphenols (0.8 mg gallic acid equivalents per day) and pyrogallol (0.2 mg/day) were administered for 4 weeks to mice xenografted with MCF10DCIS.com cells subcutaneously (n=10 per group). Tumor volumes were significantly decreased, both mango and pyrogallol groups displayed greater than 50% decreased volume compared to control. There was a significant reduction of phosphorylated protein levels of IR, IRS1, IGF-1R, and mTOR by mango; while pyrogallol significantly reduced the phosphorylation levels of IR, IRS1, IGF-1R, p70S6K, and ERK. The protein levels of Sestrin2, which is involved in AMPK-signaling, were significantly elevated in both groups. Also, mango significantly elevated AMPK phosphorylation and pyrogallol significantly elevated LKB1 protein levels. In an in vitro model, mango and pyrogallol increased reactive oxygen species (ROS) generation and arrested cells in S phase. In silico modeling indicates that pyrogallol has the potential to bind directly to the allosteric binding site of AMPK, inducing activation. When AMPK expression was down-regulated using siRNA in vitro, pyrogallol reversed the reduced expression of AMPK. This indicates that pyrogallol not only activates AMPK, but also increases constitutive protein expression. These results suggest that mango polyphenols and their major microbial metabolite, pyrogallol, inhibit proliferation of breast cancer cells through ROS-dependent up-regulation of AMPK and down-regulation of the AKT/mTOR pathway.

Pyrogallol, an absorbable microbial gallotannins-metabolite and mango polyphenols (Mangifera Indica L.) suppress breast cancer ductal carcinoma in situ proliferation in vitro.

Mango is rich in bioactive absorbable polyphenols, but also contains considerable amounts of unabsorbable gallotannins at varying degrees of polymerization. Gallotannins are not absorbable upon consumption and have rarely been considered in the discussion of health benefits of polyphenols. Therefore, the objective of this study was to investigate the anti-proliferative activities of the major microbial metabolite of gallotannins, pyrogallol (PG) and a low molecular weight fraction of mango (Mangifera Indica L.) polyphenols (ML) and involved pathways including the AKT/mTOR signaling axis in an in situ breast cancer cell line, MCF10DCIS.COM. Fluorouracil (5-FU), a widely used genotoxic cancer therapeutic, was used a positive control and in combination with ML and PG to assess potential interactions. Concentrations that were non-cytotoxic in non-cancer cells were identified in non-cancer mammary fibroblasts (MCF-12F) and only non-cytotoxic dietarily relevant concentrations were selected for the investigation in MCF10DCIS.COM cancer cells. In addition to proliferation and viability, mRNA and expression of total and phosphorylated protein were investigated. Results show that both, ML and PG significantly reduced proliferation in MCF10DCIS.COM, but did not significantly reduce viability following a 48 h exposure. ML significantly reduced mRNA expression of mTOR and HIF-1α, while PG significantly reduced mRNA of IGF-1R, AKT, mTOR and HIF-1α. ML and PG reduced total protein expression of IGF-1R, IR, AKT, mTOR, and P70S6K. In addition, PG reduced IRS protein. Both treatments also had an effect on phosphorylated protein levels, with PG significantly reducing IGF-1R, AKT, and P70S6K levels. ML had a similar effect and significantly decreased IR, AKT, and P70S6K phosphorylation levels. Within the low concentration-range, ML and PG did not interact with the cytotoxic activities of 5-FU. Overall, the AKT/mTOR signaling axis appears to be implicated as causal in decreased proliferation induced by diet-relevant concentrations of ML and PG.

Urinary metabolites from mango (Mangifera indica L. cv. Keitt) galloyl derivatives and in vitro hydrolysis of gallotannins in physiological conditions.

SCOPE: The absorption, metabolism, and excretion of mango galloyl derivatives (GD) has not yet been investigated in humans, and studies investigating repeated dosages of polyphenols are limited. METHODS AND RESULTS: In this human pilot trial, healthy volunteers (age = 21-38 y, n = 11) consumed 400 g/day of mango-pulp (cv. Keitt) for 10 days, and seven metabolites of gallic acid (GA) were characterized and quantified in urine excreted over a 12 h period. Pyrogallol-O-sulfate and deoxypyrogallol-O-sulfate were found to be significantly more excreted between days 1 and 10 (p < 0.05) from 28.5 to 55.4 mg and 23.6 to 47.7 mg, respectively. Additionally, the in vitro hydrolysis of gallotannins (GTs) was monitored at physiological pH and temperature conditions, and after 4 h a significant (p < 0.05) shift in composition from relativity high to low molecular weight GTs was observed. CONCLUSION: Seven metabolites of GA were identified in the urine of healthy volunteers, and two microbial metabolites were found to be significantly more excreted following 10 days of mango consumption. Mango GTs were also found to release free GA in conditions similar to the intestines. GTs may serve as a pool of pro-GA compounds that can be absorbed or undergo microbial metabolism.

Pre-heating and polyphenol oxidase inhibition impact on extraction of purple sweet potato anthocyanins.

Purple sweet potatoes (PSP) have been used as a natural food colorant with high acylated anthocyanins concentrations. Commercially extracting pigments from PSP can be challenging due to firm texture and high polyphenol oxidase (PPO) content. These studies evaluated hot water immersions (30, 50, 70, and 90°C for 10 min) as pre-heating treatments and addition of PPO inhibitors (citric acid, oxalic acid, and sodium borate) to aqueous extraction solutions to aid pigment recovery. Predominant PSP anthocyanins included acylated cyanidin or peonidin derivatives. Non-pigmented cinnamates acted as oxidase substrates and induced co-oxidation reactions with anthocyanins. Pre-heating PSP significantly increased polyphenolic yields in a temperature-dependent manner, consistent with tissue softening and PPO inactivation. The use of solvent modifiers in the extraction solution associated with heat helped minimize enzyme action and increased polyphenolic recovery. Minimizing the impact of PPO with heat was critical to the extraction and recovery of PSP anthocyanins, suitable for food use.

Phytochemical composition and effects of commercial enzymes on the hydrolysis of gallic acid glycosides in mango (Mangifera indica L. cv. 'Keitt') pulp.

A detailed characterization of mango pulp polyphenols and other minor phytochemicals was accomplished for the first time in the cultivar 'Keitt' whereby the identification and semiquantification of five hydroxybenzoic acids, four cinnamic acids, two flavonoids, and six apocarotenoids was accomplished. Among the most abundant compounds were two monogalloyl glucosides (MGG) identified as having an ester- or ether-linked glucose, with the ester-linked moiety present in the highest concentration among nontannin polyphenolics. Additionally, the impact of side activities of three commercial cell-wall degrading enzymes during 'Keitt' mango pulp processing was evaluated to determine their role on the hydrolysis of ester- and ether-linked phenolic acids. The use of Crystalzyme 200XL reduced the concentration of ester-linked MGG by 66%, and the use of Rapidase AR 2000 and Validase TRL completely hydrolyzed ether-linked MGG after 4 h of treatment at 50 °C. Fruit quality, in vivo absorption rate, and bioactivity of mango phytochemicals rely on their chemical characterization, and characterizing changes in composition is critical for a complete understanding of in vivo mechanisms.