Showing papers on "Xanthone published in 2005"
TL;DR: It is proposed that P450-mediated aryl epoxidation (AflN) initially disrupts the aromatic A-ring of versicolorin A, which leads inescapably to a more subtle reaction sequence of oxidation-reduction-oxidation.
Abstract: The biosynthesis of the potent environmental carcinogen aflatoxin B1 involves ca. 15 steps beyond the first polyketide intermediate. Central among these is the rearrangement of the anthraqinone versicolorin A to the xanthone demethylsterigmatocystin. Genetic evidence strongly suggests that two enzymes are required for this process, a cytochrome P450, AflN, and a probable NADPH-dependent oxidoreductase, AflM. Given the overall redox change evident in this skeletal rearrangement, two rounds of oxidation and a reduction necessarily occur. Earlier experiments indicated that reductive deoxygenation of versicolorin A is not the first step. In the present report we consider a mechanistic alternative that AflM-mediated reduction is instead the last of these three reactions prior to formation of the xanthone intermediate. To this end, 9-hydroxydihydrodemethylsterigmatocystin was prepared by total synthesis as was its 9-deoxy analogue, an established aflatoxin precursor. During the final isolation of the "angular" synthetic xanthone targets it was found that acid catalysis promoted their isomerization to thermodynamically favored "linear" xanthones. Whole-cell and ground-cell incubations of the 9-hydroxy- and 9-deoxyxanthones were conducted with a mutant strain of Aspergillus parasiticus blocked at the first step of the pathway and examined for their ability to support aflatoxin production. The 9-deoxyxanthone gave dramatically enhanced levels of the mycotoxin. The 9-hydroxyxanthone, on the other hand, afforded no detectable increase in aflatoxins above controls, indicating that reductive deoxygenation at C-9 of a xanthone precursor does not take place in aflatoxin biosynthesis. Constraints imposed by earlier studies and the experiments in this paper serve to eliminate simple and intuitive conversions of versicolorin A to demethylsterigmatocystin and lead inescapably to a more subtle reaction sequence of oxidation-reduction-oxidation. Previous puzzling observations of extensive A-ring hydrogen exchange in the course of the rearrangement of versicolorin A to demethylsterigmatocystin have now been explained by a new mechanism that is consistent with all extant data. We propose that P450-mediated aryl epoxidation (AflN) initially disrupts the aromatic A-ring of versicolorin A. Oxirane opening enables A-ring proton exchange, as does the subsequent AflM-mediated reductive step. A second cycle of P450 oxidation (AflN), this time a Baeyer-Villiger cleavage, enables decarboxylation and the formation of demethylsterigmatocystin. Mechanistic and stereoelectronic principles that underlie this proposal are described and may prove general as illustrated in biogenetic hypotheses for four other fungal anthraquinone --> xanthone transformations.
85 citations
TL;DR: It was deduced that the alpha,beta-unsaturated carbonyl moiety at C-10 contributed to the cytotoxicity of gambogic acid.
Abstract: In this study, the stability of gambogic acid (GA), a polyprenylated xanthone with potent cytotoxicities against various cancer cell lines, was evaluated under several experimental conditions including addition of acids, alkalis and organic solvents. GA was stable when dissolved in acetone, acetonitrile, and chloroform, even when acids were added. However, a new derivative was produced after GA was stored in the methanol solution for a week at room temperature. The addition of alkalis could increase the rate of this chemical transformation. This derivative was determined to be gambogoic acid (GOA) by the HPLC-MS comparison with the known compound. GOA was proposed to be the product of neuclophilic addition of methanol to the olefinic bond at C-10 of GA. Furthermore, when these two compounds were tested for their cytotoxicity, GOA showed significantly weaker inhibitory effects than GA. It was therefore deduced that the alpha,beta-unsaturated carbonyl moiety at C-10 contributed to the cytotoxicity of gambogic acid.
53 citations
TL;DR: The xanthone natural product psorospermin was synthesized in 13 steps with an overall yield of 1.7% as mentioned in this paper, which shows potent antineoplastic activity in a variety of cancer cell lines.
48 citations
TL;DR: A new caged-tetraprenylated xanthone was isolated from the fresh fruits of Garcinia hanburyi and showed moderately antibacterial activity against methicillin-resistant Staphylococcus aureus with a MIC value of 25 microg/ml.
Abstract: A new caged-tetraprenylated xanthone, hanburinone (1), was isolated from the fresh fruits of Garcinia hanburyi together with four known caged-tetraprenylated xanthones; isomoreollin B (2), morellin (3), moreollic acid (4) and morellic acid (5). Their structures were elucidated by analysis of spectroscopic data and comparison of the NMR data with those reported previously. Compounds 4 and 5 showed moderately antibacterial activity against methicillin-resistant Staphylococcus aureus with a MIC value of 25 microg/ml.
45 citations
TL;DR: Ascherxanthone A (1), a novel symmetrical tetrahydroxanthone dimer, was isolated from the entomopathogenic fungus Aschersonia sp.
Abstract: Ascherxanthone A (1), a novel symmetrical tetrahydroxanthone dimer, was isolated from the entomopathogenic fungus Aschersonia sp. BCC 8401. The structure of 1 was elucidated by spectroscopic analysis, especially 2D-NMR. Compound 1 exhibited activity against Plasmodium falciparum K1 with an IC(50) value of 0.20 microg/mL, but it also showed cytotoxic activities against Vero cells and three tumor cell lines.
42 citations
TL;DR: Seven xanthone glycosides were isolated from the cortexes of Polygala tenuifolia, and their structures were identified as polygalaxanthones VIII-XI, sibiricoxanthone B, 7-O-methylmangiferin (6), and lancerin (7), on the basis of spectroscopic analyses.
Abstract: Seven xanthone glycosides were isolated from the cortexes of Polygala tenuifolia, and their structures were identified as polygalaxanthones VIII-XI (1-4), sibiricoxanthone B (5), 7-O-methylmangiferin (6), and lancerin (7), on the basis of spectroscopic analyses. Compounds 1-4 are new xanthone glycosides, and compounds 4 and 5 exist as rotamers. To explain this phenomenon, conformational analyses were performed on compounds 4 and 5 and other compounds with similar skeletons that were isolated from P. tenuifolia.
41 citations
TL;DR: The fruits of Garcinia scortechinii afforded 10 new compounds, including four caged-tetraprenylated xanthones, which were elucidated by analysis of spectroscopic data and comparison of the NMR data with those reported previously.
Abstract: The fruits of Garcinia scortechinii afforded 10 new compounds: four caged-tetraprenylated xanthones (scortechinones Q-T, 1-4), four rearranged xanthones (scortechinones U-X, 5-8), and two sesquiterpene derivatives (scortechterpenes A, B, 9, 10), together with 14 known compounds: one sesquiterpene, two biflavonoids, and 11 caged-polyprenylated xanthones. Their structures were elucidated by analysis of spectroscopic data and comparison of the NMR data with those reported previously. All xanthone derivatives were evaluated for antibacterial activity against methicillin-resistant Staphylococcus aureus.
41 citations
TL;DR: These potential biosynthetic intermediates were examined for their ability to support aflatoxin formation in the blocked mutant DIS-1, defective in its ability to synthesize the first intermediate in the pathway, norsolorinic acid.
Abstract: o-Carboxybenzophenones have long been postulated to be intermediates in the oxidative rearrangement of anthraquinone natural products to xanthones in vivo. Many of these Baeyer−Villiger-like cleavages are believed to be carried out by cytochrome P450 enzymes. In the biosynthesis of the fungal carcinogen, aflatoxin, six cytochromes P450 are encoded by the biosynthetic gene cluster. One of these, AflN, is known to be involved in the conversion of the anthraquinone versicolorin A (3) to the xanthone demethylsterigmatocystin (5) en route to the mycotoxin. An aryl deoxygenation, however, also takes place in this overall transformation and is proposed to be due to the requirement that an NADPH-dependent oxidoreductase, AflM, be active for this process to take place. What is known about other fungal anthraquinone → xanthone conversions is reviewed, notably, the role of the o-carboxybenzophenone sulochrin (25) in geodin (26) biosynthesis. On the basis of mutagenesis experiments in the aflatoxin pathway and these ...
40 citations
TL;DR: Three pentacyclic triterpenoids, friedelin, oleanolic acid and lupeol were isolated from the chloroform extract of the stem bark of Garcinia polyantha and showed antioxidant DPPH radical scavenging activities.
39 citations
TL;DR: In this article, a bioactivity-guided fractionation of methanol extract from the leaves of Santolina insularis led to the isolation of one new xanthone, (E)-3-(6]-(E)- 3-hydroxy-3-oxo-1-propenyl]-9-oxosynthetic acid, together with six known flavonoids: hispidulin, nepetin, cirsimaritin, rhamnocitrin, luteolin, 7-O-beta-D-glucopyr
Abstract: Bioactivity-guided fractionation of the methanol extract from the leaves of Santolina insularis led to the isolation of one new xanthone, (E)-3-(6-[(E)-3-hydroxy-3-oxo-1-propenyl]-9-oxo-9H-xanthen-2-yl)-2-propenoic acid, together with six known flavonoids: hispidulin, nepetin, cirsimaritin, rhamnocitrin, luteolin and luteolin 7-O-beta-D-glucopyranoside. The structures were elucidated by means of 1D-, 2D-NMR spectroscopy and mass spectrometry. The topical anti-inflammatory activity of all isolated compounds and extracts was investigated employing the croton oil-induced dermatitis in mouse ear. The most active compound, luteolin, showed an ID50 of 0.3 micromol/cm(2) and prevented ear oedema more effectively than an equimolar dose of indomethacin within 24 h.
39 citations
TL;DR: Cudratricusxanthone H, macluraxanthone B, two xanthones previously isolated from this plant, and 5, showed significant inhibitory effects on four kinds of human digestive apparatus tumor cell lines with IC50 values of 2.70–12.66 μM.
Abstract: Further phytochemical investigation on the roots of Cudrania tricuspidata afforded a new isoprenylated xanthone, cudratricusxanthone I (1), two new isoprenylated flavanones, cudraflavanones C and D (2 and 3, resp.), and seven known compounds, 1,7-dihydroxy-3,6-dimethoxyxanthone (4), macluraxanthone C (5), cudraxanthones E, K, and L (6, 7, and 8, resp.), cudraflavanone A (9), and cudraflavone C (10). Their structures were identified by spectroscopic methods. Cudratricusxanthone H (12), macluraxanthone B (13), two xanthones previously isolated from this plant, and 5, showed significant inhibitory effects on four kinds of human digestive apparatus tumor cell lines (HCT-116, SMMC-7721, SGC-7901, and BGC-823) with IC50 values of 2.70-12.66 microM.
TL;DR: The antibacterial activity of all caged-polyprenylated xanthones, isolated from the latex and stem bark of G. scortechinii, was evaluated and some structure-antibacterial activity relationships were established.
Abstract: Five new caged-tetraprenylated xanthones, scortechinones L - P (1-5), together with six known scortechinones (A, B, D, F, I and J) and one known xanthone, 4 '',5 ''-dihydro-1,5-dihydroxy-6 ',6 '-dimethylpyrano(2 ',3 ':6,7)-4 '',4 '',5 ''-trimethylfurano(2 '',3 '':3,4)- xanthone, were isolated from the crude methanol extract of the stem bark of Garcinia scortechinii. The structures were elucidated by analysis of spectroscopic data and comparison of the NMR data with those reported previously. The antibacterial activity of all caged-polyprenylated xanthones, isolated from the latex and stem bark of G. scortechinii, was evaluated. Scortechinone B (6) exhibited significant antibacterial activity against a methicillin-resistant Staphylococcus aureus strain with an MIC value of 2 microg/mL. From the MIC values, some structure-antibacterial activity relationships were established.
TL;DR: A new isoprenylated xanthone, cudrafrutixanthone A, was isolated from the roots of Cudrania fruticosa, together with 18 known compounds, and their structures were elucidated by spectroscopic methods.
Abstract: A new isoprenylated xanthone, cudrafrutixanthone A, was isolated from the roots of Cudrania fruticosa, together with 18 known compounds. Their structures were elucidated by spectroscopic methods. Most isoprenylated xanthones exhibited cytotoxicity against HCT-116, SMMC-7721, SGC-7901, and BGC-823 cell lines with IC50 values of 1-5 mu g/mL. Toxyloxanthone C and wighteone showed antifungal activity against Candida albicans with MICs of 25 and 12.5 mu g/mL, respectively.
TL;DR: Molecular docking simulations show that the flexible tail of the prenylated xanthone could allow favorable molecular interactions and may be explored for the design of new ligands for thyroxine metabolism and/or over the pathogenic process associated with the amyloid disease.
TL;DR: A new xanthone derivative was isolated together with other 13 known constituents from a Chinese natural medicine, Swertia pseudochinensis HARA and exhibited significant hepatoprotective activities at a dose showing no hepatoxicity.
Abstract: A new xanthone derivative was isolated together with other 13 known constituents from a Chinese natural medicine, Swertia pseudochinensis HARA. Their structures were determined based on the spectral and chemical evidences. Furthermore, respective hexane, ethyl acetate, 1-BuOH, MeOH and water extracts of S. pseudochinensis, and purified compounds were respectively evaluated for their hepatoprotective activities against hepatocyte injury induced by CCl4. All the extracts and isolated compounds exhibited significant hepatoprotective activities at a dose showing no hepatoxicity.
TL;DR: Five new xanthone O-glycosides, tricornosides B-F, were isolated from the roots of Polygala tricORNis together with three known glycosides.
Abstract: A new benzophenone O-glycoside, tricornoside A, and five new xanthone O-glycosides, tricornosides B-F, were isolated from the roots of Polygala tricornis together with three known glycosides. The structures of new compounds were elucidated on the basis of chemical and spectroscopic evidence.
TL;DR: In this article, the equilibrium solubility of two pesticides (xanthone and xanthene) in supercritical carbon dioxide was determined with a flow-type method with measurements performed at pressures ranging from 80 to 300 bar and temperatures from 308.15 to 328.15 K.
Abstract: The equilibrium solubility of the two pesticides – xanthone and xanthene – in supercritical carbon dioxide was determined with a flow-type method. Measurements were performed at pressures ranging from 80 to 300 bar and temperatures from 308.15 to 328.15 K. The results show that xanthene was much more soluble in supercritical carbon dioxide than xanthone with its solubility being over 10-fold higher than that of xanthone due to their different volatility related to their chemical structures. The determined solubility data were well correlated by the Peng–Robinson equation of state and the empirical density-based Chrastil model with the average absolute relative deviation (AARD) less than 11.5% for two solutes investigated.
TL;DR: A new natural xanthone, 1,3-dihydroxy-6,7-dimethoxy-2,8-diprenylxanthone with moderate activity against the human small cell lung cancer NCI-H187 cell line with the IC50 values of 3.69 +/- 1.27 microg/mL and 3.08 +/- 0.73 microg /mL, respectively.
Abstract: A new natural xanthone, 1,3-dihydroxy-6,7-dimethoxy-2,8-diprenylxanthone, together with four known compounds, fuscaxanthone C, 1,7-dihydroxyxanthone, 3-geranyloxy-6-methyl-1,8-dihydroxyanthraquinone and 2-geranylemodin were isolated from the stem bark of Cratoxylum arborescens (Vahl) Blume. The structure elucidations were achieved through spectroscopic analyses. Compounds 1 and 5 showed moderate activity against the human small cell lung cancer NCI-H187 cell line with the IC50 values of 3.69 +/- 1.27 microg/mL and 3.08 +/- 0.73 microg/mL, respectively.
TL;DR: The electronic transitions involved in the photoluminescent process, and the relation between the energy levels of host and guest and emission quenching of the guest in the supramolecular solid have been investigated by means of time-dependent density functional theory (TDDFT) calculations.
Abstract: Two new crystalline resorcinarene-based xanthone inclusion complexes, CECRxanthoneMeOH (1), and HECR2 xanthone6 MeOH (2) (CECR = C-ethylcalix[4]resorcinarene, HECR = hexaethylresorcin[6]arene) have been prepared to study the relation between photophysical properties and solid-state structure. Compared with the neat crystals, the xanthone phosphorescence is severely quenched in both solids, but the lifetime is an order of magnitude larger in 2, in which xanthone occurs as a dimer, than in 1, in which it occurs as a monomer. The electronic transitions involved in the photoluminescent process, and the relation between the energy levels of host and guest and emission quenching of the guest in the supramolecular solid have been investigated by means of time-dependent density functional theory (TDDFT) calculations.
TL;DR: From the rhizomes of Swertia speciosa, a traditional medicinal plant from the Himalayan region of Uttaranchal (North India), a new constituent, 6‐hydroxy‐3,5‐dimethoxy‐1‐ was isolated, together with nine known compounds, and exhibited potent antioxidant activities in different biological assays.
Abstract: From the rhizomes of Swertia speciosa, a traditional medicinal plant from the Himalayan region of Uttaranchal (North India), a new constituent, 6-hydroxy-3,5-dimethoxy-1-[(6-O-beta-D-xylopyranosyl-beta-D-glucopyranosyl)oxy]-9H-xanthen-9-one (8), was isolated, together with nine known compounds. Their structures were elucidated on the basis of chemical, physical, and spectroscopic evidence. Both the acetone and MeOH extracts, as well as the known constituents ursolic acid (5) and 1,5,8-trihydroxy-3-methoxy-9H-xanthen-9-one (6) exhibited potent antioxidant activities in different biological assays (Table 2).
TL;DR: A prenylated xanthone has been isolated from the seeds of Symphonia globulifera together with the known compounds sitosterol and oleanolic acid.
TL;DR: Compounds 4 and 5 were moderately effective in influencing the mitogenic response to human lymphocytes to hemoagglutinin, with IC values of 26.1 +/- 3.6 and 40.8 +/- 4.9, respectively.
Abstract: 5-Hydroxy-2-methoxyxanthone (1), 2-hydroxy-3-methoxyxanthone (2), trans-kielcorin (3), 4-hydroxy-3-methoxyphenyl ferulate (4) and 3beta-O-caffeoylbetulinic acid (5) were isolated from Hypericum hookerianum. Compounds 1-5 were tested against the growth of three human tumor cell lines, MCF-7, NCI-H460 and SF-268. Compounds 4 and 5 exhibited significant inhibitory activity effects against all three; GI50 values for 4 were 15.1 +/- 1.6, 18.7 +/- 2.3 and 15.9 +/- 2.7 and for 5 12.2 +/- 2.4, 19.6 +/- 2.3 and 24.3 +/- 2.5. Compound 3 was less active with GI50 values of 55.1 +/- 2.3, 49.7 +/- 3.0 and 40.5 +/- 1.5, while 1 and 2 exhibited only weak effects. Compounds 4 and 5 were moderately effective in influencing the mitogenic response to human lymphocytes to hemoagglutinin, with IC values of 26.1 +/- 3.6 and 40.8 +/- 4.9, respectively.
TL;DR: Fluorescence microscopy analysis confirmed that a phagocytic process was involved in the macrophage uptake of xanthone- and 3-methoxyxanth one-loaded PLGA nanocapsules, which might be the main mechanism responsible for the enhancement of the intracellular delivery of both compounds and consequently for the improvement of their biological effect.
Abstract: For the first time the inhibitory effect of xanthone and 3-methoxyxanthone on nitric oxide (NO) production by IFN-gamma/LPS activated J774 macrophage cell line is reported A remarkable improvement of this effect promoted by encapsulation of these compounds in nanocapsules of poly (DL-lactide-co-glycolide) (PLGA) is also demonstrated A weak inhibitory effect of 36% on NO production by activated macrophages was observed for xanthone at the highest studied concentration (100 microM) This effect was slightly higher for 3-methoxyxanthone at the same concentration, producing a reduction of 165% on NO production In contrast, equivalent concentrations of xanthone and 3-methoxyxanthone incorporated in nanocapsules produced a significant decrease on NO production of 918 and 800%, respectively Empty nanocapsules also exhibited a slight NO inhibitory activity, which may be due to the presence of soybean lecithin in the composition of the nanosystems The viability of the macrophages was not affected either by free or nanoencapsulated xanthones Fluorescence microscopy analysis confirmed that a phagocytic process was involved in the macrophage uptake of xanthone- and 3-methoxyxanthone-loaded PLGA nanocapsules Phagocytosis might be the main mechanism responsible for the enhancement of the intracellular delivery of both compounds and consequently for the improvement of their biological effect
TL;DR: In this paper, the equilibrium solubilities of the two pesticides xanthone and xanthene in supercritical CO2 have been measured by using a dynamic flow method combined with gravimetric analysis.
TL;DR: In vitro anticancer assay indicated that compound 1 seems to be a promising lead, since it was not only the most‐potent aggregation inhibitor, but was also found to be noncytotoxic at a concentration of 100 μM.
Abstract: A series of oxime- and methyloxime-containing flavone, isoflavone, and xanthone derivatives (1-12) were synthesized (Scheme) and evaluated for their cytotoxic (Table 1) and antiplatelet activities (Table 2). The in vitro anticancer assay indicated that the cytotoxicity of structurally related compounds decreases in the order isoflavones (7a-7c) > flavones (8a-8c) > xanthones (9a-9c), electron-releasing substituents (R) on the Ph ring being favorable (mean GI50 values of 2.84, 12.3, and 20.9 microM for 7c, 8c, and 9c, resp.). The inhibition of platelet aggregation induced by arachidonic acid (AA) similarly decreased from the isoflavone 1 (IC50 = 2.97 microM) to the flavone 2 (7.70 microM) to the xanthone 3 (inactive). Thereby, compound 1 seems to be a promising lead, since it was not only the most-potent aggregation inhibitor (IC50 = 2.97 microM), but was also found to be noncytotoxic at a concentration of 100 microM.
TL;DR: A new xanthone glycoside has been isolated from Swertia franchetiana together with five known xanthones and their structures were elucidated on the basis of spectroscopic evidence.
TL;DR: A new caged-tetraprenylated xanthone, hanburinone (1), was isolated from the fresh fruits of Garcinia hanburyi together with four known Caged-Tetramerylated Xanthones; isomoreollin B (2), morellin (3), moreollic acid (4), and morellic acid(5), which showed moderately antibacterial activity against methicillin-resistant Staphylococcus aureus as discussed by the authors.
Abstract: A new caged-tetraprenylated xanthone, hanburinone (1), was isolated from the fresh fruits of Garcinia hanburyi together with four known caged-tetraprenylated xanthones; isomoreollin B (2), morellin (3), moreollic acid (4) and morellic acid (5). Their structures were elucidated by analysis of spectroscopic data and comparison of the NMR data with those reported previously. Compounds 4 and 5 showed moderately antibacterial activity against methicillin-resistant Staphylococcus aureus with a MIC value of 25 microg/ml.
TL;DR: In this paper, a series of tri-, tetra-oxygenated xanthones including 1-hydroxyl-2,3,4,7-tetramethoxy xanthone, 1,1.5,8-trihydroxymethyl-3-methoxy Xanthone 5 has been isolated from Swertia chirayita.
Abstract: In order to study the relationship between biological and pharmacological activities with their structures, a series of tri-, tetra-oxygenated xanthones including 1-hydroxyl-2,3,4,7-tetramethoxy xanthone 1, 1-hydroxyl-2,3,4,5-tetramethoxyl xanthone 2, 1-hydroxyl-3,5-dimethoxy xanthone 3, 1,8-dihydroxyl-3,5-dimethoxyl xanthone 4, 1,5,8-trihydroxyl-3-methoxy xanthone 5 has been isolated from Swertia chirayita. Their structures were established on the basis of spectral and chemical evidence. The crystal structure of 5 was also investigated by single crystal X-ray diffraction analysis. It crystallizes in the triclinic system, space group P
$$\bar{1}$$
, with a = 7.1540(10) A, b = 7.520(2)
A, c = 10.671(2) A, V = 562.7(2) A3, α = 86.50(3)∘, β = 80.06(3)∘, γ = 85.00(3)∘, Z = 2, D
c
= 1.618 g m−3, R
int = 0.0230, w
R(F
2) = 0.1028, F(000) = 284. The molecular structure is nearly plane and four substituents are much closer to the plane of the molecule. Compound 5 also shows three intermolecular hydrogen bonds. A recent study shows that phenolic hydroxyls in xanthones are the main active groups capable of scavenging •OH and O2•.
TL;DR: A xanthone derivative, 3,6,7-trihydroxy-1-methoxyxanthone has been isolated from the stem bark of Allanblackia monticola and the structure was elucidated by spectroscopic methods.
TL;DR: This is the first report describing a C-glucosyl-cleaving enzyme from human intestinal bacterium that seems to involve a novel enzyme mechanism.
Abstract: 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.