Biotransformation of a C-glycosylflavone, abrusin 2''-O-beta-D-apioside, by human intestinal bacteria

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.

In Vitro Gastrointestinal Digestion and Colonic Catabolism of Mango (Mangifera indica L.) Pulp Polyphenols

Mango (Mangifera indica L.), a fruit with sensorial attractiveness and extraordinary nutritional and phytochemical composition, is one of the most consumed tropical varieties in the world. A growing body of evidence suggests that their bioactive composition differentiates them from other fruits, with mango pulp being an especially rich and diverse source of polyphenols. In this study, mango pulp polyphenols were submitted to in vitro gastrointestinal digestion and colonic fermentation, and aliquots were analyzed by HPLC-HRMS. The main phenolic compounds identified in the mango pulp were hydroxybenzoic acid-hexoside, two mono-galloyl-glucoside isomers and vanillic acid. The release of total polyphenols increased after the in vitro digestion, with an overall bioaccessibility of 206.3%. Specifically, the most bioaccessible mango polyphenols were gallic acid, 3-O-methylgallic acid, two hydroxybenzoic acid hexosides, methyl gallate, 3,4-dihydroxybenzoic acid and benzoic acid, which potentially cross the small intestine reaching the colon for fermentation by the resident microbiota. After 48 h of fecal fermentation, the main resultant mango catabolites were pyrogallol, gallic and 3,4-dihydroxybenzoic acids. This highlighted the extensive transformation of mango pulp polyphenols through the gastrointestinal tract and by the resident gut microbiota, with the resultant formation of mainly simple phenolics, which can be considered as biomarkers of the colonic metabolism of mango.

Transformation of Mangiferin to Norathyriol by Human Fecal Matrix in Anaerobic Conditions: Comprehensive NMR of the Xanthone Metabolites, Antioxidant Capacity, and Comparative Cytotoxicity Against Cancer Cell Lines

Several natural drugs (termed prodrugs) when administered orally undergo transformation by intestinal bacteria, producing metabolites, which may be more active than the parent compound. Mangiferin (I) is reported to have very low bioavailability in the upper gastrointestinal tract and reaches the large intestine, where it may be metabolized by the indigenous bacteria. Therefore, the aim of this study was to conduct pilot anaerobic fermentation studies with fecal inocula from human volunteers ( n = 3) to identify possible metabolic end products of mangiferin by the gastrointestinal metabolome. The major metabolite identified was deglycosylated mangiferin, namely, norathyriol (II) with an increase in homomangiferin (III) which was a minor contaminant of I. Mangiferin metabolites were identified and quantitated in the fermentation broths by high performance liquid chromatography (HPLC)–diode array detection–electrospray ionization-mass spectrometry, and structures confirmed unequivocally by nuclear magnetic resonance, after purification by semipreparative HPLC. Cell culture assays with 2 human cancer cell lines Caco-2 (colon cancer) and A240286S (non-small lung adenocarcinoma) showed that while the substrate mangiferin (I) and homomangiferin (III), a minor metabolite, are non-cytotoxic (half-maximal inhibitory concentration [IC50] ≥ 100 µM), the major metabolite norathyriol (II) is cytotoxic against Caco-2 cells (IC50 = 51.0 µM), whereas it is cytostatic against A240286S cells with a similar IC50 (51.1 µM).

Discovery and mechanism of intestinal bacteria in enzymatic cleavage of C-C glycosidic bonds

C-Glycosides, a special type of glycoside, are frequently distributed in many kinds of medicinal plants, such as puerarin and mangiferin, showing various and significant bioactivities. C-Glycosides are usually characterized by the C-C bond that forms between the anomeric carbon of sugar moieties and the carbon atom of aglycon, which is usually resistant against acidic hydrolysis and enzymatic treatments. Interestingly, C-glycosides could be cleaved by several intestinal bacteria, but whether the enzymatic cleavage of C-C glycosidic bond is reduction or hydrolysis has been controversial; furthermore, whether existence of a "C-glycosidase" directly catalyzing the cleavage is not clear. Here we review research advances about the discovery and mechanism of intestinal bacteria in enzymatic cleavage of C-C glycosidic bond with an emphasis on the identification of enzymes manipulation the deglycosylation. Finally, we give a brief conclusion about the mechanism of C-glycoside deglycosylation and perspectives for future study in this field.

Chemical constituents from the stems of Machilus philippinensis Merr. and the neuroprotective activity of cinnamophilin

The Machilus genus (Lauraceae) had been extensively utilized in folk medicine due to its broad range of bioactivities. In the present study, a series of chromatographic separations of the methanol extract of stems of M. philippinensis led to the identification of thirty eight compounds totally. Among these, biscinnamophilin (1), machilupins A–C (2–4), machilutone A (5), and machilusoxide A (6) were new compounds reported for the first time. In addition, 5 was characterized with a unprecedented carbon skeleton. Other known compounds, including the major compounds cinnamophilin (7) and meso-dihydroguaiaretic acid (8), are identified by comparison of their physical and spectroscopic data with reported values. One of the reported compounds, cinnamophilin A (10), should be revised as dehydroguaiaretic acid (9) after careful comparison of all the ¹H and ¹³C NMR data. Moreover, the neuroprotective activity of cinnamophilin (7) was examined in a primary cortical neuron culture and the results indicated that 7 was effective against glutamate induced excitotoxicity.

The Machilus genus (Lauraceae) had been extensively utilized in folk medicine due to its broad range of bioactivities.

A comprehensive in vitro and in vivo metabolism study of hydroxysafflor yellow A

As the most important marker component in Carthamus tinctorius L., hydroxysafflor yellow A (HSYA) was widely used in the prevention and treatment of cardiovascular diseases, due to its effect of improving blood supply, suppressing oxidative stress, and protecting against ischemia/reperfusion. In this paper, both an in vitro microsomal incubation and an in vivo animal experiment were conducted, along with an LC-Q-TOF/MS instrument and a 3-step protocol, to further explore the metabolism of HSYA. As a result, a total of 10 metabolites were searched and tentatively identified in plasma, urine, and feces after intravenous administration of HSYA to male rats, although no obvious biotransformation was found in the simulated rat liver microsomal system. The metabolites detected involving both phase I and phase II metabolism including dehydration, deglycosylation, methylation, and glucuronic acid conjugation. A few of the metabolites underwent more than one-step metabolic reactions, and some have not been reported before. The study would contribute to a further understanding of the metabolism of HSYA and provide scientific evidence for its pharmacodynamic mechanism research and clinical use.

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.

Leguminous Plants in the Indonesian Archipelago: Traditional Uses and Secondary Metabolites

Indonesia is one of the richest countries with respect to plants resources. People from various ethnic, language, and religious groups have used the plants as alternative medicines, health foods and beverages for hundreds of years. To establish modern application for these understudied plant resources, ethnopharmacological data from more than 40 leguminous plants in Indonesia, spanning the western to the eastern parts of the Indonesian archipelago, were reviewed. In particular, bioactive secondary metabolites, including flavonoids, were described in detail to promote research into these plants as functional foods, nutraceuticals, and medicines.

Enzymatic cleavage of the C-glucosidic bond of puerarin by three proteins, Mn(2+), and oxidized form of nicotinamide adenine dinucleotide

We previously isolated the human intestinal bacterium, strain PUE, which can cleave the C-glucosidic bond of puerarin to yield its aglycone daidzein and glucose. In this study, we partially purified puerarin C-glucosidic bond cleaving enzyme from the cell-free extract of strain PUE and demonstrated that the reaction was catalyzed by at least three proteins, Mn(2+), and oxidized form of nicotinamide adenine dinucleotide (NAD(+)). We completely purified one of the proteins, called protein C, by chromatographic separation in three steps. The molecular mass of protein C was approximately 40 kDa and the amino acid sequence of its N-terminal region shows high homology to those of two putative proteins which belong to Gfo/Idh/MocA family oxidoreductase. Protein C catalyzed hydrogen-deuterium exchange reaction of puerarin to 2"-deuterated puerarin in D(2)O condition, which closely resembles those of glycoside hydrolase family 4 and 109.

Deglycosylation of puerarin and other aromatic C-glucosides by a newly isolated human intestinal bacterium

The human intestinal microbiota may influence the fate of bioactive polyphenols, such as the isoflavone puerarin (daidzein 8-C-glucoside), following their oral intake. Faecal suspensions from 19 healthy subjects were tested for their ability to C-deglycosylate puerarin. Only one of these catalysed this reaction. A rod-shaped Gram-positive bacterium, strain CG19-1, capable of deglycosylating puerarin to daidzein was isolated from the corresponding suspension. However, the strictly anaerobic isolate was unable to utilize puerarin as sole carbon and energy source nor any of the tested carbohydrates. Comparative 16S rRNA gene sequence analysis indicated that strain CG19-1 is a new species of the Lachnospiraceae. Strain CG19-1 also converted other aromatic C-glucosides in addition to puerarin. The xanthone C-glucoside mangiferin was deglycosylated to norathyriol. The flavone C-glucosides homoorientin and vitexin were degraded to 3-(3,4-dihydroxyphenyl)propionic acid via luteolin and 3-(4-hydroxyphenyl)propionic acid respectively. In addition, strain CG19-1 converted flavonoid O-glucosides, but at rates that were lower than those of the C-glucosides tested. The isolate deglycosylated the isoflavone O-glucosides daidzin and genistin to daidzein and genistein respectively. Several O-glucosides of the flavones luteolin and apigenin undergoing deglycosylation were subsequently cleaved to 3-(3,4-dihydroxyphenyl)propionic acid and 3-(4-hydroxyphenyl)propionic acid respectively. Moreover, strain CG19-1 cleaved both O-desmethylangolensin and 6'-hydroxy-O-desmethylangolensin to yield 2-(4-dihydroxyphenyl)propionic acid. The corresponding cleavage product, resorcinol, was only observed for O-desmethylangolensin.

Neolignans and glycosides from the stem bark of Illicium difengpi

Five new neolignans (1-4 and 9), two pairs of neolignan epimers (5-8), and two new aromatic glycosides (10 and 11) have been isolated from the stem bark of Illicium difengpi. Their structures were determined by spectroscopic methods, including 1D and 2D NMR, HRESIMS, CD experiments, and chemical methods. The absolute configurations of the 3,4-diol moiety in 1 and 1,3-diol moiety in 2 were confirmed by Snatzke's method, observing the induced circular dichroism after addition of dimolybdenum tetraacetate in DMSO. Compounds 3, 4, and 11 exhibited moderate anti-inflammatory activities with IC(50) values ranging from 1.62 to 24.4 microM, while compound 3 displayed antioxidant activity with an IC(50) value of 42.3 microM.

Isolation of a human intestinal bacterium that transforms mangiferin to norathyriol and inducibility of the enzyme that cleaves a C-glucosyl bond

The C-glucosyl bond of C-glucosides generally tolerates acid and enzymatic hydrolysis. Many C-glucosides are cleaved by human intestinal bacteria. We isolated the specific bacterium involved in the metabolism of mangiferin (2-beta-D-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone), C-glucosyl xanthone, from a mixture of human fecal bacteria. The anaerobic Bacteroides species named MANG, transformed mangiferin to the aglycone, norathyriol, suggesting cleavage of a C-glucosyl bond. However, B. sp. MANG cleaved C-glucosyl in a dose- and time-dependent manner only when cultivated in the presence of mangiferin. Cleavage was abolished by inhibitors of RNA and protein syntheses, such as rifampicin and chloramphenicol, respectively, indicating that the enzyme that cleaves C-glucosyl is induced by mangiferin. In contrast, mangiferin did not affect bacterial alpha- and beta-glucosidase activities under any conditions. The C-glucosyl-cleavage in cell-free extracts was not altered by potent glucosidase inhibitors such as 1-deoxynojirimycin and gluconolactone. Therefore, the C-glucosyl-cleaving enzyme substantially differs from known glucosidases that cleave O-glucosides. This is the first description of a specific intestinal bacterium that is involved in the metabolism of mangiferin and which produces a novel and inducible C-glucosyl-cleaving enzyme.

Two Proteins, Mn2+, and Low Molecular Cofactor Are Required for C-Glucosyl-Cleavage of Mangiferin

C-Glucosides, in which sugars are attached to the aglycone by carbon-carbon bonds, are generally resistant to acid and enzyme hydrolysis. The C-glucosyl bond of mangiferin, a xanthone C-glucoside, was cleaved by anaerobic incubation with a human intestinal bacterium, Bacteroides sp. MANG, to give norathyriol. A cell-free extract obtained by sonication of B. sp. MANG demonstrated cleaving activity for mangiferin to norathyriol by adding NADH, diaphorase, and dithiothreitol. Both high molecular weight (>10 k) and low molecular weight (<10 k) fractions obtained from the cell-free extract were required for the activity. MnCl2 was necessary for the activity, but other metal ions were not. By purification of the high molecular weight fraction using DEAE-cellulose and Phenyl Sepharose column chromatography, two fractions, designated as proteins A and B, were separated and required for the activity. Neither protein A nor protein B alone showed any activity. This is the first report describing a C-glucosyl-cleaving enzyme from human intestinal bacterium that seems to involve a novel enzyme mechanism.

The pig caecum model: A suitable tool to study the intestinal metabolism of flavonoids

Pig caecum was used under anaerobic conditions to metabolize flavonoids from several classes, i.e., chrysin 1, naringenin 2, quercetin 3, and hesperetin 4. Whereas chrysin 1 was not converted by the pig intestinal flora under the experimental conditions used, naringenin 2 was transformed to 3-(4-hydroxyphenyl)-propionic acid and 3-phenylpropionic acid. Quercetin 3 was metabolized to phloroglucinol, 3,4-dihydroxyphenylacetic acid, and 3,4-dihydroxytoluene. Hesperetin 4 was degraded via eriodictyol to 3-(3-hydroxyphenyl)-propionic acid and phloroglucinol. Structural elucidation of the formed metabolites was performed by high-performance liquid chromatography--diode array detection (HPLC-DAD) as well as HPLC-electrospray ionization--mass spectrometry (ESI-MS (MS)) and high resolution gas chromatography-mass spectrometry (HRGC-MS) analyses. The time course of microbial conversion of 2-4 was determined by HPLC-DAD analysis, revealing slow degradation of 2 and rapid transformation of 3 and 4. The results lead to the conclusion that the pig caecum model is a suitable ex vivo model for studying the intestinal degradation of flavonoids.

Cleavage of the C-C linkage between the sugar and the aglycon in C-glycosylphloroacetophenone, and the NMR spectral characteristics of the resulting di-C-glycosyl compound

The treatment of unprotected mono-C-beta-D-glucopyranosylphloroacetophenone with a cation-exchange resin in anhydrous acetonitrile afforded both a phloroacetophenone and a di-C-beta-D-glucopyranosylphloroacetophenone. Treatment of an unprotected mono-C-(2-deoxy-beta-D-arabino-hexopyranosyl)phloroacetophenone (mono-C-2-deoxy-beta-D-glucopyranosylphloroacetophenone) also afforded both the aglycon and di-C-(2-deoxy-beta-D-arabino-hexopyranosyl)phloroacetophenone. The reaction mixtures were acetylated, and the structures of the isolated products were determined by NMR spectroscopy. This is the first demonstration of the formation of a di-C-glycosyl compound during the chemical cleavage of the C-C linkage between the sugar and the aglycon in an aryl C-glycosyl derivative.