Structure elucidation of in vivo and in vitro metabolites of mangiferin

The Anti-Diabetic Effects of Medicinal Plants Belonging to the Liliaceae Family: Potential Alpha Glucosidase Inhibitors

Background

Diabetes mellitus is a complex metabolic disorder that has an enormous impact on people's quality of life and health. Although there is no doubt about the effectiveness of oral hypoglycemic agents combined with lifestyle management in controlling diabetes, no individual has ever been reported to have been completely cured of the disease. Globally, many medicinal plants have been used for the management of diabetes in various traditional systems of medicine. A deep look in the literature has revealed that the Liliaceae family have been poorly investigated for their antidiabetic activity and phytochemical studies. In this review, we summarize medicinal plants of Liliaceae utilized in the management of type II diabetes mellitus (T2DM) by inhibition of α-glucosidase enzyme and phytochemical content.

Methods

The literature search was conducted using databases including PubMed, ScienceDirect, and Google Scholar to find the significant published articles about Liliaceae plants utilized in the prevention and treatment of antidiabetics. Data were filtered to the publication period from 2013 to 2023, free full text and only English articles were included. The keywords were Liliaceae OR Alliaceae OR Amaryllidaceae AND Antidiabetic OR α-glucosidase.

Results

Six medicinal plants such as Allium ascalonicum, Allium cepa, Allium sativum, Aloe ferox, Anemarrhena asphodeloides, and Eremurus himalaicus are summarized. Phytochemical and α-glucosidase enzymes inhibition by in vitro, in vivo, and human studies are reported.

Conclusion

Plants of Liliaceae are potential as medicine herbs to regulating PPHG and prevent the progression of T2DM and its complication. In silico study, clinical application, and toxicity evaluation are needed to be investigated in the future.

Pharmacological properties of mangiferin: bioavailability, mechanisms of action and clinical perspectives

This review aims to provide an in-depth analysis of the pharmacological properties of mangiferin, focusing primarily on its bioavailability and mechanisms of action, and its potential therapeutic applications, especially in the context of chronic diseases. We conducted a comprehensive examination of in vitro and in vivo studies, as well as clinical trials involving mangiferin or plant extracts containing mangiferin. The primary source of mangiferin is Mangifera indica, but it's also found in other plant species from the families Anacardiaceae, Gentianaceae, and Iridaceae. Mangiferin has exhibited a myriad of therapeutic properties, presenting itself as a promising candidate for treating various chronic conditions including neurodegenerative disorders, cardiovascular diseases, renal and pulmonary diseases, diabetes, and obesity. Despite the promising results showcased in many in vitro studies and certain animal studies, the application of mangiferin has been limited due to its poor solubility, absorption, and overall bioavailability. Mangiferin offers significant therapeutic potential in treating a spectrum of chronic diseases, as evidenced by both in vitro and clinical trials. However, the challenges concerning its bioavailability necessitate further research, particularly in optimizing its delivery and absorption, to harness its full medicinal potential. This review serves as a comprehensive update on the health-promoting and therapeutic activities of mangiferin.

Comprehensive Profiling of Mangiferin Metabolites In Vivo and In Vitro Based on the "Drug Metabolite Clusters" Analytical Strategy

Mangiferin, a natural flavonoid compound with multiple biological activities (e.g., anti-inflammatory, anti-oxidant, anti-diabetic, and anti-tumor), has gained increased research interest in recent years. Nevertheless, the metabolic processing of mangiferin has not been fully investigated. In this study, a rapid and efficient analytical strategy named "Drug Metabolite Clusters" was applied for comprehensive profiling of mangiferin metabolites in rat plasma, urine, and feces samples in vivo following oral administration and liver microsomes in vitro. First, the biological samples were pretreated with methanol, acetonitrile, and solid phase extraction (SPE) for further liquid chromatography-mass spectrometry (LC-MS) analysis. Second, the raw data were acquired using ultra-high performance liquid chromatography quadrupole exactive orbitrap high-resolution mass spectrometry (UHPLC-Q-Exactive Orbitrap HRMS) under the positive and negative full-scan/dd MS² modes. Third, mangiferin and its basic metabolites (norathyriol, trihydroxyxanthone, and dihydroxyxanthone) were selected as mangiferin metabolite cluster centers by referring to the relevant literature. Subsequently, according to the pyrolysis law of mass spectrometry, literature reports, and reference material comparison, especially the diagnostic product ions (DPIs), the candidate metabolites were accurately preliminarily identified, and mangiferin metabolite clusters based on metabolite cluster center changes were formed. As a result, a total of 67 mangiferin metabolites (mangiferin included) were detected, including 29 in plasma, 48 in urine, 12 in feces, and 6 in liver microsomes. Among them, trihydroxyxanthones were first detected in rat urine samples after oral mangiferin. We found that mangiferin mainly underwent deglucosylation, dehydroxylation, methylation, glucuronidation, sulfation, and other composite reactions in rats. Herein, we have elucidated the metabolites and metabolic pathways of mangiferin in vivo and in vitro, which provided an essential theoretical basis for further pharmacological studies of mangiferin and a comprehensive research method for the identification of drug metabolites.

Therapeutic potential of mangiferin against kidney disorders and its mechanism of action: A review

There is a swing in research developments concerning the utilization of natural products as effective pharmacotherapeutic agents due to their comparatively lower toxicities than synthetic compounds. Among natural products, mangiferin is a natural C-glucosyl xanthonoid polyphenol with remarkable pharmacological activities. Emerging evidence indicates the therapeutic benefits of mangiferin against various kidney disorders, including renal injury, diabetic nephropathy, renal fibrosis, hyperuricemic nephropathy, and lupus nephritis, in experimental animal models. The mangiferin induced antioxidant response resulting in vital functions, such as protection against renal inflammation, inhibits renal cell apoptosis, activates autophagy, causes immunomodulation, regulates renal urate transporters and modulates cell signalling pathways. The purpose of this review provide a brief overview of the in vitro/in vivo reno-protective effect of mangiferin and the underlying mechanism(s) in protecting against kidney disorders. Understanding the pharmacological actions of mangiferin is prominence due to its excellent therapeutic potential in managing kidney disorders. Thus, in addition to this review, in-silico molecular docking is performed against nuclear factor kappa B (NF-κB) and soluble epoxide hydrolase (sEH) to study the mechanism of action of mangiferin. It is believed that mangiferin is a safe reno-protective molecule. The observed positive effects are attributed to the inhibition of inflammation caused by NF-κB and sEH upregulation and oxidative stress activation. Studies on the efficacy and safety of mangiferin in clinical trials are further warranted to confirm its medicinal potential as therapeutic agent for kidney disorders in humans.

Mangiferin: a review of dietary sources, absorption, metabolism, bioavailability, and safety

Mangiferin is a potential candidate for use in nutraceutical and functional food applications due to its numerous bioactivities. However, the low bioavailability of mangiferin is a major limitation for establishing efficacy for use. This review describes current information on known food sources and factors that influence mangiferin contents, absorption, and metabolism features, and recent progress that has come from research efforts to increase the bioavailability of mangiferin. We also list patents that targeted to enhance mangiferin bioavailability. Mangifera indica L. is the major dietary source for mangiferin, a xanthone that varies widely in different parts of the plant and is influenced by many factors that involve plant propagation and post-harvest processing. Mangiferin absorption occurs mostly in the small intestine by passive diffusion with varying absorption capacities in different segments of the gastrointestinal tract. Recent research has led to the development of novel technologies to encapsulate mangiferin in nano/microparticle carrier systems as well as generate mangiferin derivatives to improve solubility and bioavailability. Preclinical studies reported that mangiferin < 2000 mg/kg is generally nontoxic. The safety and the increase in bioavailability are key limiting factors for developing successful applications for mangiferin as a nutritional dietary supplement or nutraceutical.

Aerobic bioconversion of C-glycoside mangiferin into its aglycone norathyriol by an isolated mouse intestinal bacterium

Norathyriol is an aglycone of a xanthonoid C-glycoside mangiferin that possesses different bioactive properties useful for humans compared to mangiferin. Mangiferin is more readily available in nature than norathyriol; thus, efficient mangiferin conversion into norathyriol is desirable. There are a few reports regarding mangiferin C-deglycosylation because of the C-C bond resistance toward acid, alkaline, and enzyme hydrolysis. In this study, we isolated a mangiferin-deglycosylating bacterium strain KM7-1 from the mouse intestine. 16S rDNA sequencing indicated that KM7-1 belongs to the Bacillus genus. Compared to the taxonomically similar bacteria, the growth characteristic of facultative anaerobic and thermophilic resembled, yet only Bacillus sp. KM7-1 was able to convert mangiferin into norathyriol. Resting cells of Bacillus sp. KM7-1 obtained from aerobic cultivation at 50 °C showed high norathyriol formation from 1 m m of mangiferin. Norathyriol formation can be conducted either under aerobic or anaerobic conditions, and the reaction depended on time and bacterial amount.

Mangiferin and organ fibrosis: A mini review

Fibrosis is the end stage of many chronic diseases, which results in organ function failure and high mortality. Mangiferin is a major constituent in mango and other 16 plants, and has been shown a variety of pharmacological effects, such as antioxidant, antibacterial, anti-tumor, anti-inflammation. The emerging evidence has shown that mangiferin can improve renal interstitial fibrosis, pulmonary fibrosis, myocardial fibrosis and hepatic fibrosis through the inhibition of inflammation, oxidative stress and fibrogenesis effects, indicating that mangiferin is promising therapeutic choice for organ fibrosis. The aim of this review is to summarize the therapeutic effects of mangiferin on fibrosis of various organs and the underlying mechanisms.

Therapeutic potential of mangiferin in the treatment of various neuropsychiatric and neurodegenerative disorders

Xanthones are important chemical class of bioactive products that confers therapeutic benefits. Of several xanthones, mangiferin is known to be distributed widely across several fruits, vegetables and medicinal plants. Mangiferin has been shown to exert neuroprotective effects in both in-vitro and in-vivo models. Mangiferin attenuates cerebral infarction, cerebral edema, lipid peroxidation (MDA), neuronal damage, etc. Mangiferin further potentiate levels of endogenous antioxidants to confer protection against the oxidative stress inside the neurons. Mangiferin is involved in the regulation of various signaling pathways that influences the production and levels of proinflammatory cytokines in brain. Mangiferin cosunteracted the neurotoxic effect of amyloid-beta, MPTP, rotenone, 6-OHDA etc and confer protection to neurons. These evidence suggested that the mangiferin may be a potential therapeutic strategy for the treatment of various neurological disorders. The present review demonstrated the pharmacodynamics-pharmacokinetics of mangiferin and neurotherapeutic potential in several neurological disorders with underlying mechanisms.

Mangiferin promotes intestinal elimination of uric acid by modulating intestinal transporters

Increasing evidence shows that the intestinal tract plays an important role in maintaining urate homeostasis and might be a potential therapeutic target for hyperuricaemia. However, uric acid-lowering drugs available in the clinic do not target intestinal excretion as a therapeutic strategy. We previously reported that mangiferin had potent hypouricaemic effects in hyperuricaemic animals. However, the underlying mechanisms are not completely clear. Here, we investigated the effects of mangiferin on the intestinal excretion of urate and its underlying mechanisms. The data revealed that mangiferin concentration-dependently promoted the intestinal secretion of endogenous urate in in situ intestinal closed loops in normal and hyperuricaemic mice, as well as inhibited the absorption of exogenous uric acid perfused into the intestinal loops in rats. Administration of mangiferin not only decreased the serum urate levels in the hyperuricaemic mice but also increased the protein expression of ATP-binding cassette transporter, subfamily G, member 2 (ABCG2) and inhibited the protein expression of glucose transporter 9 (GLUT 9) in the intestine. These findings suggested that intestinal ABCG2 and GLUT9 might be pivotal and possible action sites for the observed hypouricaemic effects. Moreover, no significant changes in intestinal xanthine oxidoreductase activities were observed, suggesting that mangiferin did not affect intestinal uric acid generation in the hyperuricaemic mice. Overall, promoting intestinal elimination of urate by upregulating ABCG2 expression and downregulating GLUT9 expression might be an important mechanism underlying mangiferin lowering serum uric acid levels. Mangiferin supplementation might be beneficial for the prevention and treatment of hyperuricaemia.

A pervasive scientific overview on mangiferin in the prevention and treatment of various diseases with preclinical and clinical updates

Natural products are increasing used in preventing and treating various diseases. Mangiferin belongs to the xanthone family, and has potential antiangiogenic, anticancer, immunomodulatory and anti-inflammatory activity along with the antioxidant activity. It is also used in the treatment of cardiac problem, diabetes and neurodegenerative disease. Finding of various researchers proves that mangiferin has a broad spectrum therapeutic application. Motive of this review is to describe the various studies performed on mangiferin for its different pharmacological activities. It also discusses various challenges associated with mangiferin such as stability and bioavailability. Strategies and approaches to improve bioavailability of mangiferin have also been discussed. Both research and review articles were used to write the manuscript. They were collected from various search engines like Pub Med, Science Direct and Google Scholar, using keywords like mangiferin, polyphenol, bioavailability enhancement, solubility enhancement, and antioxidant. Mangiferin being a potent antioxidant is effective in the treatment of various diseases. With novel drug delivery approaches we can overcome poor solubility and bioavailability problem which eventually can result to better utilisation of mangiferin in treating a variety of diseases and make mangiferin a revolutionary drug.

Mangiferin-Loaded Polymeric Nanoparticles: Optical Characterization, Effect of Anti-topoisomerase I, and Cytotoxicity

Mangiferin is an important xanthone compound presenting various biological activities. The objective of this study was to develop, characterize physicochemical properties, and evaluate the anti-topoisomerase activity of poly(lactic-co-glycolic acid) (PLGA) nanoparticles containing mangiferin. The nanoparticles were developed by the emulsion solvent evaporation method and the optimal formulation was obtained with a response surface methodology (RSM); this formulation showed a mean size of 176.7 ± 1.021 nm with a 0.153 polydispersibility index (PDI) value, and mangiferin encapsulation efficiency was about 55%. The optimal conditions (6000 rpm, 10 min, and 300 μg of mangiferin) obtained 77% and the highest entrapment efficiency (97%). The in vitro release profile demonstrated a gradual release of mangiferin from 15 to 180 min in acidic conditions (pH 1.5). The fingerprint showed a modification in the maximum absorption wavelength of both the polymer and the mangiferin. Results of anti-toposiomerase assay showed that the optimal formulation (MG4, 25 µg/mL) had antiproliferative activity. High concentrations (2500 µg/mL) of MG4 showed non-in vitro cytotoxic effect on BEAS 2B and HEPG2. Finally, this study showed an encapsulation process with in vitro gastric digestion resistance (1.5 h) and without interfering with the metabolism of healthy cells and their biological activity.

Effects of Benzophenones from Mango Leaves on Lipid Metabolism

The mango tree (Mangifera indica L.) is a tropical, perennial, woody evergreen plant belonging to the Anacardiaceae. In traditional medicine, dried mango tree leaves were considered useful in treating diabetes and respiratory infections. In this paper, we review the phytochemical research on mango leaves and the mechanisms of benzophenones in lipid metabolism regulation. Thirty-six benzophenones have been isolated from mango leaves; among them, mangiferin is the major compound. Structure-activity relationships of benzophenones in lipid accumulation and the mechanisms of action of mangiferin in lipid metabolism are summarized. After oral administration, mangiferin is partly converted to its active metabolite, northyariol, which contributes to the activation of sirtuin-1 and liver kinase B1 and increases the intracellular AMP level and AMP/adenosine triphosphate ratio, followed by AMP-activated protein kinase phosphorylation, leading to increased phosphorylation of sterol regulatory element-binding protein-1c. Current evidence supports ethnopharmacological uses of mango leaves in diabetes and points toward potential future applications.

Metabolism, pharmacokinetics, and hepatic disposition of xanthones and saponins on Zhimu treatments for exploratively interpreting the discrepancy between the herbal safety and timosaponin A3-induced hepatotoxicity

Timosaponin A3, a saponin in Zhimu, elicited hepatotoxicity via oxidative stress. However, the clinical medication of Zhimu has been historically regarded as safe, probably associated with the antioxidants it contains. However, the related information on the in vivo levels of timosaponin A3 and antioxidants remained unclear on Zhimu treatments. Therefore, a combination of the in vitro metabolism, including microbiota-mediated and liver-mediated metabolism, and in vivo pharmacokinetics and hepatic disposition, was conducted for three xanthones (neomangiferin, mangiferin, and norathyriol) and three saponins (timosaponin B2, timosaponin B3, and timosaponin A3) on Zhimu treatments. Consequently, following oral administration of Zhimu decoction to rats, those saponins and xanthones were all observed in the plasma with severe liver first-pass effect, where mangiferin was of the maximum exposure. Despite the ignorable content in the herb, timosaponin A3 elicited sizable hepatic exposure as the microbiota-mediated metabolite of saponins in Zhimu. The similar phenomenon also occurred to norathyriol, the microbiota-mediated metabolite of xanthones. However, the major prototypes in Zhimu were of limited hepatic exposure. We deduced the hepatic collection of norathyriol, maximum circulating levels of mangiferin, and timosaponin B2 and mangiferin interaction may directly or indirectly contribute to the whole anti-oxidation of Zhimu, and then resisted the timosaponin A3-induced hepatotoxicity. Thus, our study exploratively interpreted the discrepancy between herbal safety and timosaponin A3-induced hepatotoxicity. However, given the considerable levels and slow eliminated rate of timosaponin A3 in the liver, more attention should be paid to the safety on the continuous clinical medication of Zhimu in the future.

Absorption, Metabolism, and Pharmacokinetics Profiles of Norathyriol, an Aglycone of Mangiferin, in Rats by HPLC-MS/MS

Norathyriol, an aglycone of mangiferin, is a bioactive tetrahydroxyxanthone present in mangosteen and many medicinal plants. However, the biological fate of norathyriol in vivo remains unclear. In this study, the absorption and metabolism of norathyriol in rats were evaluated through HPLC-MS/MS. Results showed that norathyriol was well absorbed, as indicated by its absolute bioavailability of 30.4%. Besides, a total of 21 metabolites of norathyriol were identified in rats, including methylated, glucuronidated, sulfated and glycosylated conjugates, which suggested norathyriol underwent extensive phase II metabolism. Among those metabolites, 15 metabolites were also identified in hepatocytes incubated with norathyriol, indicating the presence of hepatic metabolism. Furthermore, glucuronide and sulfate conjugates, rather than their parent compound, were found to be the main forms existing in vivo after administration of norathyriol, as implicated by the great increase of exposure of norathyriol determined after hydrolysis with β-glucuronidase and sulfatase. The information obtained from this study contributes to better understanding of the pharmacological mechanism of norathyriol.

Inhibition of UGT2B7 Enzyme Activity in Human and Rat Liver Microsomes by Herbal Constituents

The co-use of conventional drug and herbal medicines may lead to herb-drug interaction via modulation of drug-metabolizing enzymes (DMEs) by herbal constituents. UDP-glucuronosyltransferases (UGTs) catalyzing glucuronidation are the major metabolic enzymes of Phase II DMEs. The in vitro inhibitory effect of several herbal constituents on one of the most important UGT isoforms, UGT2B7, in human liver microsomes (HLM) and rat liver microsomes (RLM) was investigated. Zidovudine (ZDV) was used as the probe substrate to determine UGT2B7 activity. The intrinsic clearance (V_max/K_m) of ZDV in HLM is 1.65 µL/mg/min which is ten times greater than in RLM, which is 0.16 µL/mg/min. Andrographolide, kaempferol-3-rutinoside, mitragynine and zerumbone inhibited ZDV glucuronidation in HLM with IC₅₀ values of 6.18 ± 1.27, 18.56 ± 8.62, 8.11 ± 4.48 and 4.57 ± 0.23 µM, respectively, hence, herb-drug interactions are possible if andrographolide, kaempferol-3-rutinoside, mitragynine and zerumbone are taken together with drugs that are highly metabolized by UGT2B7. Meanwhile, only mitragynine and zerumbone inhibited ZDV glucuronidation in RLM with IC₅₀ values of 51.20 ± 5.95 μM and 8.14 ± 2.12 µM, respectively, indicating a difference between the human and rat microsomal model so caution must be exercised when extrapolating inhibitory metabolic data from rats to humans.

Mangiferin Improves Hepatic Lipid Metabolism Mainly Through Its Metabolite-Norathyriol by Modulating SIRT-1/AMPK/SREBP-1c Signaling

Objective: Mangiferin (MGF) is a natural xanthone, with regulation effect on lipid metabolism. However, the molecular mechanism remains unclear. We purposed after oral administration, MGF is converted to its active metabolite(s), which contributes to the effects on lipid metabolism. Methods: KK-A^y mice were used to validate the effects of MGF on lipid metabolic disorders. Liver biochemical indices and gene expressions were determined. MGF metabolites were isolated from MGF administrated rat urine. Mechanism studies were carried out using HepG2 cells treated by MGF and its metabolite with or without inhibitors or small interfering RNA (siRNA). Western blot and immunoprecipitation methods were used to determine the lipid metabolism related gene expression. AMP/ATP ratios were measured by HPLC. AMP-activated protein kinase (AMPK) activation were identified by homogeneous time resolved fluorescence (HTRF) assays. Results: MGF significantly decreased liver triglyceride and free fatty acid levels, increased sirtuin-1 (SIRT-1) and AMPK phosphorylation in KK-A^y mice. HTRF studies indicated that MGF and its metabolites were not direct AMPK activators. Norathyriol, one of MGF's metabolite, possess stronger regulating effect on hepatic lipid metabolism than MGF. The mechanism was mediated by activation of SIRT-1, liver kinase B1, and increasing the intracellular AMP level and AMP/ATP ratio, followed by AMPK phosphorylation, lead to increased phosphorylation level of sterol regulatory element-binding protein-1c. Conclusion: These results provided new insight into the molecular mechanisms of MGF in protecting against hepatic lipid metabolic disorders via regulating SIRT-1/AMPK pathway. Norathyriol showed potential therapeutic in treatment of non-alcoholic fatty liver disease.

In Vitro Bioaccessibility and Effect of Mangifera indica (Ataulfo) Leaf Extract on Induced Dyslipidemia

Cardiovascular diseases (CVDs) are the leading causes of death in the world, and epidemiological evidence points to dietary habits, stress, and obesity as major risk factors promoting pathological conditions like atherosclerosis, hypertension, and thrombosis. Current therapeutic approaches for CVDs rely on lifestyle changes and/or the use of drug agents. However, since the efficacy of such interventions is often limited by poor compliance and/or significant side effects, continued research on new preventive and therapeutic approaches is much needed. Our study is aimed to determine the bioaccessibility, total content of phenolic compounds, and antioxidant capacity (DPPH·, ABTS^·+) of a methanolic extract from Mangifera indica L. leaves (MEM), and its lipid-lowering effect on an induced dyslipidemia model in Wistar rats. Our results showed that mangiferin is the main component of MEM. The extract showed a total content of polyphenol compounds of 575.28 gallic acid equivalents per dry matter basis (GAE/g db), antioxidant activity 77.68 μmol Trolox equivalents per gram (TE/g) db as measured by DPPH· and 20,630 μmol TE/g db by ABTS^·+, and 12% of phenolic compounds were bioaccessible, and 100 mg/kg of MEM reduced hyperlipidemia levels induced in Wistar rats. Further study on the potential use of MEM as a nutraceutical to prevent CVDs in high-fat diet consumers is required.

Mangiferin: a natural miracle bioactive compound against lifestyle related disorders

The current review article is an attempt to explain the therapeutic potential of mangiferin, a bioactive compound of the mango, against lifestyle-related disorders. Mangiferin (2-β-D-glucopyranosyl-1,3,6,7-tetrahydroxy-9H-xanthen-9-one) can be isolated from higher plants as well as the mango fruit and their byproducts (i.e. peel, seed, and kernel). It possesses several health endorsing properties such as antioxidant, antimicrobial, antidiabetic, antiallergic, anticancer, hypocholesterolemic, and immunomodulatory. It suppresses the activation of peroxisome proliferator activated receptor isoforms by changing the transcription process. Mangiferin protects against different human cancers, including lung, colon, breast, and neuronal cancers, through the suppression of tumor necrosis factor α expression, inducible nitric oxide synthase potential, and proliferation and induction of apoptosis. It also protects against neural and breast cancers by suppressing the expression of matrix metalloproteinase (MMP)-9 and MMP-7 and inhibiting enzymatic activity, metastatic potential, and activation of the β-catenin pathway. It has the capacity to block lipid peroxidation, in order to provide a shielding effect against physiological threats. Additionally, mangiferin enhances the capacity of the monocyte-macrophage system and possesses antibacterial activity against gram-positive and gram-negative bacteria. This review summarizes the literature pertaining to mangiferin and its associated health claims.

Characterization of 2,3-diarylxanthones by electrospray mass spectrometry: gas-phase chemistry versus known antioxidant activity properties

RATIONALE

Xanthones (XH) are a class of heterocyclic compounds widely distributed in nature that hold numerous noteworthy biological and antioxidant activities. Therefore, it is of utmost importance to achieve relevant detailed structural information to understand and assist prediction of their biological properties. The potential relationship between radical-mediated xanthone chemistry in the gas phase and their promising antioxidant activities has not been previously explored.

METHODS

Protonated xanthones XH1-9 were generated in the gas phase by electrospray ionization (ESI) and the main fragmentation pathways of the protonated XH1-9 formed due to collision-induced dissociation (CID) were investigated.

RESULTS

In the CID-MS/MS spectra of [M+H](+) ions of XH1, XH2 and XH4 the product ions formed due to H2 O elimination corresponding to the base peak of the spectra. For the remaining six xanthones (XH3, XH5-9), showing the most promising biological profile, the product ion produced with the highest relative abundance (RA) corresponded to the one formed through concomitant loss of H2 O plus CO. Indicative of an inexistent or lower biological activity is the combined loss of CO plus O unique to the CID-MS/MS spectra of XH1, XH2, XH4, and XH5. The product ion formed by loss of 64 Da (concomitant loss of two molecules of H2 O plus CO) is only observed for xanthones containing a catechol unit (XH3 and XH6-9). This product ion has the highest RA for the most potent scavenger of reactive oxygen and nitrogen species XH9 that contains two of these catechol moieties.

CONCLUSIONS

A strong relationship between some of the biological activities of the studied 2,3-diarylxanthones and their ESI-MS/MS fragmentation spectra was found. The multivariate statistical analysis results suggest that the selected MS features are related to the important biological features. Copyright © 2016 John Wiley & Sons, Ltd.

Pharmacokinetics of mangiferin and its metabolite-norathyriol, Part 2: Influence of UGT, CYP450, P-gp, and enterobacteria and the potential interaction in Rhizoma Anemarrhenae decoction with timosaponin B2 as the major contributor

The poor bioavailability of mangiferin (MGF) is a major obstacle on its further development. Aimed to illustrate the underlying mechanism and improve its poor exposure, the compared PK profiles of MGF and norathyriol (NTR) after different MGF preparation were performed: pure MGF, the Rhizoma Anemarrhenae (Zhi-mu) decoction, MGF, and timosaponin B2 (TB-2) combination. Furthermore, the potential contributing factors, including uridine diphosphoglucuronosyltransferase (UGT), cytochrome P450 (CYP450), P-gp, and enterobacterial were investigated by comparing the PK profiles with and without the corresponding inhibitors or in different rat models. After taking MGF, CYP450 and UGT inhibition could decrease MGF and NTR exposure; P-gp inhibition slightly enhanced (48%) MGF exposure, whereas more apparent for the improved NTR exposure (302%); enterobacterial inhibition almost completely stopped the NTR production, but no such effect was observed for MGF. Compared with the limited improvement by the abovementioned inhibition, the MGF and NTR exposure could significantly increase by 11.5- and 5.9-fold in the Zhi-mu decoction compared with the MGF treatment, probably contributed to TB-2 as an absorption enhancer because the MGF and TB-2 combination produced a similar level of improvement on the PK paremeters of MGF and NTR to the herb treatment. Likewise, most of the effects by UGT, CYP450, P-gp, and enterobacteria followed a similar variation tendency between them. Therefore, the poor bioavailability of MGF possibly mainly attributed to its poor membrane permeability, but not transporters or metabolic enzymes, and the compatibility of MGF and TB-2 could probably expand the prospective application of MGF by improving its bioavailability. © 2016 BioFactors, 42(5):545-555, 2016.

Pharmacokinetics of mangiferin and its metabolite-Norathyriol, Part 1: Systemic evaluation of hepatic first-pass effect in vitro and in vivo

Mangiferin (MGF), a glucoside of xanthone existing in phytomedicines and food, is increasingly attracting attention on diabetes treatment, while the underlying mechanism leading to its low oral bioavailability is unclear. Norathyriol (NTR), an active metabolite with hypoglycemic activity and its exposure after MGF dosing remains unclear. Hence, a rapid and sensitive LC-MS/MS method was established and validated to determine MGF and NTR and applied in the PK study in rats. Correspondingly, the in vitro experiments on temperature-dependent uptake, and MGF metabolism in hepatocyte and enterobacteria samples were performed. Results revealed that hepatic first-pass effect slightly contributed to the poor bioavailability of MGF, based on the MGF exposure in portal vein plasma was nearly similar to that in systemic plasma, and the MGF accumulation in the liver was limited, so was that of NTR. Correspondingly, the in vitro study revealed the MGF uptake was mainly dependent on poor passive transport, possibly leading to its limited hepatic metabolism and accumulation. Moreover, the NTR exposure remained considerably low (C_max  < 3 ng/mL, AUC_NTR /AUC_MGF  < 3%) in plasma after single MGF dosing, corresponding to its tiny proportion (0.1%) of MGF in MGF-incubated enterobacteria samples. However, given the low generation and elimination rates of NTR, NTR might accumulate in plasma and exert effects after repeated MGF dosing, although requires further study. This work is the first systemic study on PK profiles of MGF and NTR in vitro and in vivo, which is important for the interpretation on the poor bioavailability and pharmacodynamics of MGF. © 2016 BioFactors, 42(5):533-544, 2016.

Mangiferin: A xanthonoid with multipotent anti-inflammatory potential

Over the last era, small molecules sourced from different plants have gained attention for their varied and long-term medicinal benefits. Their advantageous therapeutic effects in diverse pathological complications lead researchers to give an ever-increasing emphasis on them and discover their novel therapeutic potentials. Among these, the heat stable, xanthonoid group of organic molecules has gained special importance with distinctive regards to the bioactive molecule mangiferin due to its solubility in water. Mangiferin, a yellow polyphenol having C-glycosyl xanthone structure, is widely present in different edible sources like mango, and possesses numerous biological activities. Extensive research with this molecule shows its antioxidant, anti-inflammatory, antidiabetic, anticancer, antimicrobial, analgesic, and immunomodulatory properties. Thus, it provides protection against a wide range of physiological disorders. The C-glucosyl linkage and polyhydroxy groups in mangiferin's structure contribute essentially to its free radical-scavenging activity. Moreover, its ability in regulating various transcription factors like NF-κB, Nrf-2, etc. and modulating the expression of different proinflammatory signaling intermediates like tumor necrosis factor-α, COX-2, etc. contribute to its anti-inflammatory, anticancer, and antidiabetic potentials. In this comprehensive article, information has been provided about the sources, chemical structure, metabolism, and different biological activities of mangiferin with special emphasis on the underlying cellular signal transduction pathways. Insights into an in-depth assessment of mangiferin's anti-inflammatory therapeutic potential have also been discussed in detail. On an overall perspective, this review aims to stage mangiferin's diversified therapeutic applications and its emerging possibility as a promising drug in future based on its anti-inflammatory property. © 2016 BioFactors, 42(5):459-474, 2016.

Hypouricaemic action of mangiferin results from metabolite norathyriol via inhibiting xanthine oxidase activity

Context Mangiferin has been reported to possess a potential hypouricaemic effect. However, the pharmacokinetic studies in rats showed that its oral bioavailability was only 1.2%, suggesting that mangiferin metabolites might exert the action. Objective The hypouricaemic effect and the xanthine oxidase inhibition of mangiferin and norathyriol, a mangiferin metabolite, were investigated. Inhibition of norathyriol analogues (compounds 3-9) toward xanthine oxidase was also evaluated. Materials and methods For a dose-dependent study, mangiferin (1.5-6.0 mg/kg) and norathyriol (0.92-3.7 mg/kg) were administered intragastrically to mice twice daily for five times. For a time-course study, mice received mangiferin and norathyriol both at a single dose of 7.1 μmol/kg. In vitro, inhibition of test compounds (2.4-2.4 mM) against xanthine oxidase activity was evaluated by the spectrophotometrical method. The inhibition type was identified from Lineweaver-Burk plots. Results Norathyriol (0.92, 1.85 and 3.7 mg/kg) dose dependently decreased the serum urate levels by 27.0, 33.6 and 37.4%, respectively. The action was more potent than that of mangiferin at the low dose, but was equivalent at the higher doses. Additionally, the hypouricaemic action of them exhibited a time dependence. In vitro, norathyriol markedly inhibited the xanthine oxidase activities, with the IC50 value of 44.6 μM, but mangiferin did not. The kinetic studies showed that norathyriol was an uncompetitive inhibitor by Lineweaver-Burk plots. The structure-activity relationships exhibited that three hydroxyl groups in norathyriol at the C-1, C-3 and C-6 positions were essential for maintaining xanthine oxidase inhibition. Discussion and conclusion Norathyriol was responsible for the hypouricaemic effect of mangiferin via inhibiting xanthine oxidase activity.

Comprehensive Evaluation of the Metabolism of Genipin-1-β-d-gentiobioside in Vitro and in Vivo by Using HPLC-Q-TOF

To examine the metabolism of genipin-1-β-d-gentiobioside (GG), its distribution and biotransformation in vivo and in vitro were investigated. Urine, plasma, feces, and various organs were collected after oral administration of GG to normal rats and pseudo-germ-free rats to evaluate GG metabolism in vivo. GG was incubated with intestinal flora and primary hepatocytes in vitro to investigate microbial and hepatic metabolism. Using HPLC-Q-TOF-LC/MS, 11 metabolites of GG were absolutely or tentatively identified in terms possible elemental compositions, retention times, and characteristics of fragmentation patterns corresponding to eight biotransformations: deglycosylation, hydroxylation, sulfate conjugation, glucuronidation, hydrogenation, demethylation, glycosylation, and dehydration. Fewer metabolites were detected in pseudo-germ-free rats than in conventional rats. Moreover, geniposide and genipin were generated by the deglycoslation of intestinal bacteria. Geniposidic acid was detected in rat primary-hepatocyte incubation. This study first explores the metabolism of GG in vivo and in vitro. The results can aid the elucidation of PK profiles and clinical usage of gardenia fruit.

Metabolite profiling of Zi-Shen pill in rat biological specimens by UPLC-Q-TOF/MS

This study aimed to profile the chemical constituents of Zi-Shen pill (ZSP) and its metabolites in plasma, urine, and prostate tissue, after administration into rats. Based on the chromatographic retention behavior, fragmentation patterns of chemical components, published literatures, and literature databases, an UPLC-Q-TOF/MS (LC-TOF/MS) method was established to identify the components of ZSP and its metabolites in biological samples. A total of 101 compounds were identified and tentatively characterized from the ZSP, including alkaloids, xanthones, and timosaponins. Except for 33 prototype components, 22 metabolites were detected in the plasma, urine, and prostate, and mainly came from Phellodendri Amurensis Cortex and Anemarrhenae Rhizoma. It was found that glucuronidation and sulfation were the major metabolic processes of xanthones, while oxidation, demethylation, and glucuronidation were the major metabolic pathways of alkaloids. In summary, the present study provided important chemical information on the metabolism of ZSP, indicating that alkaloids might be able to be absorbed into the prostate. The results provided a basis for further studies of the mechanisms of action for ZSP.

Laminaria japonica increases plasma exposure of glycyrrhetinic acid following oral administration of Liquorice extract in rats

The present study was designed to investigate the effects of Laminaria japonica (Laminaria) on pharmacokinetics of glycyrrhetinic acid (GA) following oral administration of Liquorice extract in rats. Following oral administrations of single-dose and multi-dose Liquorice extract and Liquorice-Laminaria extract, respectively, plasma samples were obtained at various times and the concentrations of GA, liquiritigenin, and isoliquiritigenin were measured by LC-MS. The effects of Laminaria extract on pharmacokinetics of GA were also investigated, following single-dose and multidose of glycyrrhizic acid (GL). The effects of Laminaria extract on intestinal absorption of GA and GL were studied using the in situ single-pass intestinal perfusion model. The metabolism of GL to GA in the contents of small and large intestines was also studied. The results showed Liquorice-Laminaria extract markedly increased the plasma concentration of GA, accompanied by a shorter Tmax. Similar alteration was observed following multidose administration. However, pharmacokinetics of neither liquiritigenin nor isoliquiritigenin was affected by Laminaria. Similarly, Laminaria markedly increased concentration and decreased Tmax of GA following oral GL were observed. The data from the intestinal perfusion model showed that Laminaria markedly increased GL absorption in duodenum and jejunum, but did not affect the intestinal absorption of GA. It was found that Laminaria enhanced the metabolism of GL to GA in large intestine. In conclusion, Laminaria increased plasma exposures of GA following oral administration of liquorice or GL, which partly resulted from increased intestinal absorption of GL and metabolism of GL to GA in large intestine.

Mangiferin and its aglycone, norathyriol, improve glucose metabolism by activation of AMP-activated protein kinase

CONTEXT

Mangiferin has been reported to possess antidiabetic activities. Norathyriol, a xanthone aglycone, has the same structure as mangiferin, except for a C-glucosyl bond. To our best knowledge, no study has been conducted to determine and compare those two compounds on glucose consumption in vitro.

OBJECTIVE

In this study, the effects of norathyriol and mangiferin on glucose consumption in normal and insulin resistance (IR) L6 myotubes were evaluated. Simultaneously, the potential mechanism of this effect was also investigated.

MATERIALS AND METHODS

Normal or IR L6 myotubes were incubated with norathyriol (2.5 ∼ 10 μM, 0.625 ∼ 2.5 μM), mangiferin (10 ∼ 40 μM, 2.5 ∼ 10 μM) or rosiglitazone (20 μM) and/or 0.05 nM insulin for 24 h, respectively. The glucose consumption was assessed using the glucose oxidase method. Immunoblotting was performed to detect protein kinase B (PKB/Akt) and AMP-activated protein kinase (AMPK) phosphorylation in L6 myotubes cells.

RESULTS

Norathyriol and mangiferin treatment alone increased the glucose consumption 61.9 and 56.3%, respectively, in L6 myotubes and made additional increasing with 0.05 nM insulin. In IR L6 myotubes, norathyriol treatment made increasing with or without insulin, mangiferin treatment also made increasing but only when co-treated with insulin. Immunoblotting results showed that norathyriol and mangiferin produced an increase of 1.9 - and 1.8-fold in the phosphorylation levels of the AMPK, but not in Akt.

DISCUSSION AND CONCLUSION

Our findings suggest that norathyriol and mangiferin could improve the glucose utilization and insulin sensitivity by up-regulation of the phosphorylation of AMPK. Norathyriol may be considered as an active metabolite responsible for the antidiabetic activity of mangiferin.

Antioxidant properties and hyphenated HPLC-PDA-MS profiling of Chilean Pica mango fruits (Mangifera indica L. Cv. piqueño)

Antioxidant capacities and polyphenolic contents of two mango cultivars from northern Chile, one of them endemic of an oasis in the Atacama Desert, were compared for the first time. Twenty one phenolic compounds were detected in peel and pulp of mango fruits varieties Pica and Tommy Atkins by HPLC-PDA-MS and tentatively characterized. Eighteen compounds were present in Pica pulp (ppu), 13 in Pica peel (ppe) 11 in Tommy Atkins pulp (tpu) and 12 in Tommy Atkins peel (tpe). Three procyanidin dimers (peaks 6, 9 and 10), seven acid derivatives (peaks 1–4, 11, 20 and 21) and four xanthones were identified, mainly mangiferin (peak 12) and mangiferin gallate, (peak 7), which were present in both peel and pulp of the two studied species from northern Chile. Homomangiferin (peak 13) was also present in both fruit pulps and dimethylmangiferin (peak 14) was present only in Tommy pulp. Pica fruits showed better antioxidant capacities and higher polyphenolic content (73.76/32.23 µg/mL in the DPPH assay and 32.49/72.01 mg GAE/100 g fresh material in the TPC assay, for edible pulp and peel, respectively) than Tommy Atkins fruits (127.22/46.39 µg/mL in the DPPH assay and 25.03/72.01 mg GAE/100 g fresh material in the TPC assay for pulp and peel, respectively). The peel of Pica mangoes showed also the highest content of phenolics (66.02 mg/100 g FW) measured by HPLC-PDA. The HPLC generated fingerprint can be used to authenticate Pica mango fruits and Pica mango food products.

High-performance liquid chromatography-electrospray ionization tandem mass spectrometry for metabolism study of timosaponin AIII

A sensitive method based on high-performance liquid chromatography-electrospray ionization tandem mass spectrometry was developed for the determination of timosaponin AIII (TA3) and its in vivo and in vitro metabolites. The rat plasma, urine, feces and tissue samples were collected after oral administration of TA3 at a single dose of 300 mg/kg. TA3 was incubated into artificial gastric juice and artificial intestinal juice. The in vivo and in vitro samples were purified by using liquid-liquid extraction. The structures of metabolites were elucidated by comparing their molecular weights, retention times and tandem mass spectrometric spectra with those of the parent drug. As a result, four metabolites (deglycosylated TA3, two hydroxylated TA3 and timosaponin BII) and the parent drug were found in in vivo and in vitro samples. In addition to the parent drug, one, one and two metabolites were identified in heart, urine and feces, respectively. Only the parent drug was detected in plasma, liver and kidney. One hydroxylation metabolite and TA3 were identified from incubation samples with AGJ, whereas two hydroxylation metabolites and TA3 were detected from the incubation with AIJ. This is the first systematic metabolism study of TA3. The biotransformation pathways of TA3 primarily included deglycosylation, hydroxylation and glycosylation.

Metabolism and pharmacokinetics of mangiferin in conventional rats, pseudo-germ-free rats, and streptozotocin-induced diabetic rats

To clarify the role of the intestinal flora in the absorption and metabolism of mangiferin and to elucidate its metabolic fate and pharmacokinetic profile in diabetic rats, a systematic and comparative investigation of the metabolism and pharmacokinetics of mangiferin in conventional rats, pseudo-germ-free rats, and streptozotocin (STZ)-induced diabetic rats was conducted. Forty-eight metabolites of mangiferin were detected and identified in the urine, plasma, and feces after oral administration (400 mg/kg). Mangiferin underwent extensive metabolism in conventional rats and diabetic rats, but the diabetic rats exhibited a greater number of metabolites compared with that of conventional rats. When the intestinal flora were inhibited, deglycosylation of mangiferin and sequential biotransformations would not occur. Pharmacokinetic studies indicated a 2.79- and 2.35-fold increase in the plasma maximum concentration and the area under the concentration-time curve from 0 to 24 h of mangiferin in diabetic rats compared with those for conventional rats, whereas no significant differences were observed between conventional rats and pseudo-germ-free rats. Further real-time quantitative reverse transcription-polymerase chain reaction results indicated that the multidrug resistance (mdr) 1a level in the ileum increased, whereas its level in the duodenum and the mdr1b mRNA levels in the duodenum, jejunum, and ileum decreased in diabetic rats compared with those in conventional rats. With regard to the pseudo-germ-free rats, up-regulated mdr1a mRNA levels and down-regulated mdr1b mRNA levels in the small intestines were observed. The diabetic status induced increased UDP-glucuronosyltransferase (UGT) 1A3, UGT1A8, UGT2B8, and sulfotransferase (SULT) 1A1 mRNA levels and decreased catechol-O-methyltransferase (COMT), UGT2B6, UGT2B12, and SULT1C1 mRNA levels. These results might partially explain the different pharmacokinetic and metabolic disposition of mangiferin among conventional and model rats.

In vivo metabolism study of vaccarin in rat using HPLC-LTQ-MSn

In order to illustrate the main biotransformation pathways of vaccarin in vivo, metabolites of vaccarin in rats were identified using a specific and sensitive high-performance liquid chromatography-electrospray ionization linear ion trap mass spectrometry (LTQ XL™) method. The rats were administered a single dose (200 mg/kg) of vaccarin by oral gavage. By comparing their changes in molecular masses (ΔM), retention times and spectral patterns with those of the parent drug, the parent compound and six metabolites were found in rat urine after oral administration of vaccarin. The parent compound and five metabolites were detected in rat plasma. In heart, liver and kidney samples, respectively, one, four and three metabolites were identified, in addition to the parent compound. Three metabolites, but no trace of parent drug, were found in the rat feces. This is the first systematic metabolism study of vaccarin in vivo. The biotransformation pathways of vaccarin involved methylation, hydroxylation, glycosylation and deglycosylation.

Mangiferin glucuronidation: important hepatic modulation of antioxidant activity

Mangiferin displays an extensive spectrum of pharmacological properties, including antioxidant activity. Its phase II metabolism in the presence of Aroclor 1254-induced and un-induced microsomal and cytosolic fractions from rat liver and the antioxidant potency of the glucuronidated conjugates were investigated. Mangiferin was not a substrate for the cytosolic sulphotransferases. Glucuronidation led to the formation of two monoglucuronidated metabolites of mangiferin and a monoglucuronidated metabolite of homomangiferin (a minor constituent of the mangiferin standard). Deconjugation utilising glucuronidase resulted in the disappearance of the metabolites, with the concomitant formation of the two parent compounds. Considering steric hinderance caused by the C-2 glucosyl moiety and the relative acidity of the xanthone OH groups, the 6-OH of mangiferin and, to a lesser degree the 7-OH, are likely to be the primary glucuronidation targets. The ferric iron reducing ability of the glucuronidated reaction mixture was reduced, while the free radical scavenging abilities of mangiferin, utilising on-line post-column HPLC-DAD-DPPH· and HPLC-DAD-ABTS·+ assays, were eliminated, providing further evidence that the catechol arrangement at C-6 and C-7 was the preferred site of conjugation. This paper provides the first evidence that the glucuronidated metabolites of mangiferin resulted in a loss in free radical scavenging and ferric iron reducing ability.