Tyrosinase inhibitory constituents from the bark of Peltophorum dasyrachis (yellow batai)

Tyrosinase inhibitory activity-guided fractionation of the bark of Peltophorum dasyrachis (yellow batai) led to the isolation of the six active compounds which were characterised as six flavonoids: apigenin (1), (+)-2,3-trans-dihydrokaempferol (2), (+)-2,3-trans-dihydrokaempferol-3-O-α-L-rhamnoside (3), (+)-4',7-dimethoxy-2,3-trans-dihydroquercetin (4), (+)-2,3-trans-dihydroquercetin (5) and (-)-2,3-trans-dihydroquercetin-3-O-α-L-rhamnoside (6). All compounds were isolated for the first time from the bark of P. dasyrachis. Moreover, all compounds were evaluated for tyrosinase activities towards L-DOPA as the substrate. We observed that compounds 2 and 5 showed potent inhibitory effects (IC?? values were 126?±?3.2 and 210?±?5.8?μM, respectively). In general, for flavonoids the 3',4'-dihydroxy group's substituent is a more potent inhibitor than the 4'-hydroxy group substituent, i.e. quercetin?>?kaempferol. Interestingly, our result in the oxidation of L-DOPA showed that the 4'-hydroxy group substituent (compound 2) is a more potent inhibitor than the 3',4'-dihydroxy group substituent (compound 5). This result showed a new relationship between tyrosinase inhibitory activities and flavonoids. The kinetic analyses by Lineweaver-Burk plots showed that both the compounds 2 and 5 behaved as competitive inhibitors of L-DOPA oxidation.     

Two new 5-deoxyflavonoids from Calliandra inermis

Two new 5-deoxyflavonoids, 7,2',3',4'-tetramethoxyflavone (1) and 7,2',3',4'-tetramethoxyflavanone (2) together with a known flavone 7,4'-dimethoxy-3'-hydroxyflavone (3) were isolated from the whole plant of Calliandra inermis. The structures of these new compounds were elucidated by high resolution electron impact mass spectrometry (HR-EI-MS) and 1D and 2D-NMR spectral studies including 1H-1H correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond connectivity (HMBC) and nuclear Overhauser enhancement spectroscopy (NOESY).     

A new chalcone and a flavone from Andrographis neesiana

Two new flavonoids, 2',4',6',2,3,4-hexamethoxychalcone (1) and 5-hydroxy-7,2',5'-trimethoxyflavone (2) together with a known flavone glycoside, echioidinin 5-O-beta-D-glucopyranoside (3) were isolated from the whole plant of Andrographis neesiana, and the structures were elucidated by electrospray ionization tandem mass spectrometry (ESI-MS/MS) and one- and two-dimensional (1D- and 2D)-NMR spectral studies including 1H-1H correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond connectivity (HMBC) and nuclear Overhauser enhancement spectroscopy (NOESY) experiments.     

Glycosylated constituents of iris fulva and Iris brevicaulis

The major constituents of leaf extracts of Iris fulva KER GAWL. comprised a known flavone C-glycoside, 5,4'-dihydroxy-7-methoxyflavone-6-C-(6?-O-(E)-p-coumaroyl-β-glucopyranosyl)(1?→2″)-β-glucopyranoside (1) and the new monoterpene glycoside, linalyl-6'-O-(3″-hydroxy-3″-methylglutaroyl)-β-D-glucopyranoside (2), both of which were prominent components of Iris brevicaulis RAF. leaf extracts. The structure of a new polyacylated sucrose derivative (3a) obtained from the rhizomes of I. fulva was elucidated as 3-O-(E)-p-coumaroyl-β-D-fructofuranosyl-(2?1')-[2″,4″,6″-tri-O-acetyl-β-D-glucopyranosyl-(1″→3')-(2',6'-di-O-acetyl-4'-O-(E)-p-coumaroyl-α-D-glucopyranoside)]. Selective hydrolysis of the 4″-O-acetyl moiety of the terminal β-glucopyranosyl residue of 3a occurred after several hours in solution giving 3-O-(E)-p-coumaroyl-β-D-fructofuranosyl-(2?1')-[2″,6″-di-O-acetyl-β-D-glucopyranosyl-(1″→3')-(2',6'-di-O-acetyl-4'-O-(E)-p-coumaroyl-α-D-glucopyranoside)] (3b), which subsequently underwent further deacetylation.     

Two new 5-deoxyflavones from Albizia odoratissima

Two new 5-deoxyflavones, 7,8-dimethoxy-3',4'-methylenedioxyflavone (1) and 7,2',4'-trimethoxyflavone (2) together with a known flavone, 7,4'-dimethoxy-3'-hydroxyflavone (3) were isolated from the rootbark of Albizia odoratissima. The structures of these new compounds were elucidated by electrospray ionization mass spectrometry (ESI-MS) and 1D and 2D-NMR spectral studies including (1)H-(1)H correlation spectroscopy (COSY), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond connectivity (HMBC) and nuclear Overhauser enhancement spectroscopy (NOESY).     

Reactive oxygen species scavenging activity of flavone glycosides from Melilotus neapolitana

One new and six known flavone glycosides were isolated from the MeOH extract of Melilotus neapolitana Ten. The new compound, identified as 7-O-beta-D-glucopyranosyloxy-4',5-dihydroxy-3-[O-alpha-L-rhamnopyranosyl-(1-->6)-3-O-beta-D-glucopyranosyloxy]flavone (1) by 1D and 2D NMR techniques and mass spectra, was isolated along with kaempferol-3-O-rutinoside (2), kaempferol-3-O-glucoside (3), rutin (4), quercetin-3-O-glucoside (5), isorhamnetin-3-O-rutinoside (6), and isorhamnetin-3-O-glucoside (7). The antioxidant and radical scavenging activities of these compounds and the whole crude methanol extract were evaluated. The organic extract can inhibit MDA marker's synthesis by 57%. All the metabolites displayed good reducing power, with the kaempferol (2,3) and isorhamnetin derivatives (6,7) being less active than the corresponding quercetin derivatives 4,5.     

Studies on the conformational flexibility of α-L-rhamnose-containing oligosaccharides using 13C-site-specific labeling, NMR spectroscopy and molecular simulations: implications for the three-dimensional structure of bacterial rhamnan polysaccharides

Bacterial polysaccharides are comprised of a variety of monosaccharides, L-rhamnose (6-deoxy-L-mannose) being one of them. This sugar is often part of α-(1 → 2)- and/or α-(1 → 3)-linkages and we have therefore studied the disaccharide α-L-Rhap-(1 → 2)-α-L-Rhap-OMe to obtain information on conformational preferences at this glycosidic linkage. The target disaccharide was synthesized with (13)C site-specific labeling at C1' and at C2', i.e., in the terminal group. 2D (1)H,(13)C-HSQC-HECADE and (1)H,(13)C-J-HMBC NMR experiments, 1D (13)C and (1)H NMR spectra together with total line-shape analysis were used to extract conformationally dependent hetero- and homonuclear spin-spin coupling constants. This resulted in the determination of (2)J(C2',H1'), (3)J(C1',C1), (3)J(C1',C3), (3)J(C2',C2), (2)J(C1',C2), (1)J(C1',C2'), and (1)J(C1',H1'). These data together with previously determined J(CH) and (1)H,(1)H NOEs result in fourteen conformationally dependent NMR parameters that are available for analysis of glycosidic linkage flexibility and conformational preferences. A 100 ns molecular dynamics (MD) simulation of the disaccharide with explicit water molecules as solvent showed a major conformational state at φ(H)≈ 40° and ψ(H)≈-35°, consistent with experimental NMR data. In addition, MD simulations were carried out also for α-L-Rhap-(1 → 3)-α-L-Rhap-OMe and a rhamnan hexasaccharide. The gathered information on the oligosaccharides was used to address conformational preferences for a larger structure, a 2- and 3-linked nonasaccharide, with implications for the 3D structure of rhamnan polysaccharides, which should be regarded as flexible polymers.     

Cytotoxic compounds from the leaves of Gaillardia aristata Pursh. growing in Egypt

Ten compounds, neopulchellin (1), 6α- hydroxyneopulchellin (2), β-sitosterol-3-O-β-D-glucoside (3), apigenin (4), quercitin (5), eupafolin (6), kaempferol-3-methoxy-7-O-α-L-rhamnoside (7), apigenin-7-O-β-D-glucopyranoside (8), α-amyrin (9) and β-sitosterol (10), were isolated from the leaves of Gaillardia aristata by applying bioassay guided fractionation. The cytotoxicity was traced against two human cancer cell lines (breast (MCF7) and colon (HCT116)). The highest cytotoxicity was revealed by compounds 1 and 2 (isolated from chloroform extract); with IC(50) values of 0.43, 0.32?μg?mL(-1) against MCF7 and 0.46, 0.34?μg?mL(-1) against HCT116, respectively. Compounds 9 and 10 (isolated from the n-hexane extract) exhibited lower IC(50) values of 3.05, 2.35?μg?mL(-1) against MCF7 and 3.05, 2.35?μg?mL(-1) against HCT116, respectively, while compounds 4-7 obtained from the ethyl acetate extract revealed the lowest cytotoxicity. Identification of the aforementioned compounds was carried out on the basis of their physico-chemical properties and spectral analysis (UV, EI/MS, 1D and 2D).     

A predictive tool for assessing (13)C NMR chemical shifts of flavonoids

Herein are presented the (1)H and (13)C NMR data for seven monohydroxyflavones (3-, 5-, 6-, 7-, 2'-, 3'-, and 4'-hydroxyflavone), five dihydroxyflavones (3,2'-, 3,3'-, 3,4'-, 3,6-, 2',3'-dihydroxyflavone), a trihydroxyflavone (apigenin; 5,7,4'-trihydroxyflavone), a tetrahydroxyflavone (luteolin; 5,7,3',4'-tetrahydroxyflavone), and three glycosylated hydroxyflavones (orientin; luteolin-6C-beta-D-glucoside, homoorientin; luteolin-8C-beta-D-glucoside, vitexin; apigenin-8C-beta-D-glucoside). When these NMR spectra are compared, it is possible to assess the impact of flavone modification and to elucidate detailed structural and electronic information for these flavonoids. A simple predictive tool for assigning flavonoid (13)C chemical shifts, which is based on the cumulative differences between the monohydroxyflavones and flavone (13)C chemical shifts, is demonstrated. The tool can be used to accurately predict (13)C flavonoid chemical shifts and it is expected to be useful for rapid assessment of flavonoid (13)C NMR spectra and for assigning substitution patterns in newly isolated flavonoids.     

Isolation and structure determination of a new flavone glycoside from seed residues of seabuckthorn (Hippophae rhamnoides L.)

In this study, a valid method was established for the isolation and purification of flavone glycosides from Hippophae rhamnoides L. seed residues using high-speed counter-current chromatography in one step, with a solvent system of ethyl acetate-methanol-n-butyl alcohol-water (9:1:0.5:9, v/v/v/v). A total of 28.8 mg compound I and 57.3 mg compound II were obtained from 200 mg of flavone H-glycosides rich extract, with purities of 98.3 and 96.4%, respectively. The structures of two compounds were identified by MS and NMR. 3-O-β-D-Sophorosylkaempferol-7-O-{3-O-[2(E)-2,6-dimethyl-6-hydroxyocta-2,7-dienoyl]}-α-L-rhamnoside is compound I and compound II named hippophanone is a new compound were identified by MS and NMR. The method was efficient and convenient, which could be used for the preparative separation of flavone glycosides from H. rhamnoides L. seed residues.     

Chemical and biological study of the seeds of Eragrostis tef (Zucc.) Trotter

A chemical study of the red type of the seeds of Eragrostis tef (Zucc.) Trotter (Poaceae) led to the isolation of seven compounds from its ethanol extract, namely β-sitosterol (1), β-amyrin-3-O-(2'-acetyl(glucoside (2), β-sitosterol-3-O-β-D-glucoside (3), naringenin (4), naringenin-4'-methoxy-7-O-α-L-rhamnoside (5), eriodictyol-3',7-dimethoxy-4'-O-β-D-glucoside (6) and isorhamnetin-3-O-rhamnoglucoside (7), which are reported for the first time in the genus Eragrostis. This is the first report for the isolation of compounds (2) and (6) in nature. The isolated compounds were identified using different spectroscopic methods (EIMS, UV, 1H NMR, 13C NMR, HMQC and HMBC). A proximate analysis revealed the high nutritive value of the seeds: carbohydrates (57.27%), protein (20.9%), essential amino acids (8.15%) with major leucine and lysine (1.71 and 1.35%, respectively), vitamin B? (1.56?mg/100?g) and potassium and calcium (32.4 and 9.63%, respectively). The seeds yielded 22% w/w of fixed oil rich in unsaturated fatty acids (72.46%), among which oleic acid, was predominant (32.41%), followed by linolenic acid (23.83%). The ethanolic extract and fixed oil of the seeds exhibited anti-hyperlipedaemic and anti-hyperglycaemic activities. Oral administration of the fixed oil for 10 days resulted in a rise in serum calcium levels in rats.     

Three new steroidal glycosides from the roots of Cynanchum auriculatum

Three new steroidal glycosides, cyanoauriculosides F, G and H (1-3), were isolated from the roots of Cynanchum auriculatum (Asclepiadaceae) along with two known steroidal derivatives. On the basis of spectroscopic analysis and chemical methods, their structures were identified as 20-O-acetyl-8,14-seco-penupogenin-8-one 3-O-α-L-cymaropyranosyl-(1→4)-β-D-cymaropyranosyl-(1→4)-α-L-diginopyranosyl-(1→4)-β-D-cymaropyranoside (1), 2',3'-Z-gagaminine 3-O-α-L-cymaropyranosyl-(1→4)-β-D-cymaro-pyranosyl-(1→4)-α-L-diginopyranosyl-(1→4)-β-D-cymaropyranoside (2), 17-O-acetyl-kidjoranin 3-O-α-L-cymaropyranosyl-(1→4)-β-D-cymaropyranosyl-(1→4)-α-L-cymaro-pyranosyl-(1→4)-β-D-digitoxopyranosyl-(1→4)-β-D-digitoxopyranoside (3), gagaminine 3-O-α-L-cymaropyranosyl-(1→4)-β-D-cymaropyranosyl-(1→4)-α-L-digino-pyranosyl-(1→4)-β-D-cymaropyranoside (4) and wilfoside D1N (5).     

Two new C-glycosylflavones from Mimosa pudica

Two new C-glycosylflavones were isolated from the whole plant of Mimosa pudica,and their structures were determined as 6,7,3′,4′-tetrahydroxyl-8-C-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranosyl flavone(1),5,7,3′,4′-tetrahydroxy-8-C[β-D- apiose-(1→4)]-β-D-glycopyranosyl flavone (2).Their structures elucidated by chemical and spectroscopic analysis including IR,MS,1D and 2D NMR spectra.     

Polar Chemical Constituents from Phoebe formosana

A chemical investigation on the H₂O-soluble constituents from the leaf of Phoebe formosana. led to the characterization often compounds including two C-glycosylflavone — vitexin ( 1 ), isovitexin ( 2 ); six O-glycosylflavonol — quercetin 3-O-galactoside ( 3 ), quercetin 3-O-α-L-arabinopyranoside ( 4 ), kaempferol 3-O-α-L-arabinofuranoside ( 5 ), kaempferol 3-O-α-L-rhamnoside ( 6 ), kaempferol 3-O-β-D-xylopyranoside ( 7 ); one dihydroflavonol -(+)-dihydroquercetin ( 8 ) and two nucleosides -adenosine ( 9 ), and adenine ( 10 ). Their structures were determined on the basis of spectral analysis.     

九子参中三个糖链上带乙酰基的新三萜皂苷-九子参苷B,C, D

从石竹科植物九子参(Silene rubicunda)根中得到四个糖链上带乙酰基的新的三萜皂苷-九子参苷A, B, C, D(rubicunosides A~D, 1~4)。前文已详细报道了九子参苷A的结构研究, 本文报道九子参苷B, C, D的结构。通过FAB-MS和NMR,分别确定九子参苷B, C, D为糖链上带单乙酰基的三萜九糖苷、七糖苷和糖链上带双乙酰基的三萜八糖苷, 分别命名为皂树酸-3-O-β-D-吡喃半乳糖-(1→2)-[β-D-吡喃木糖-(1→3)]-β-D-吡喃葡萄糖醛酸-28-O-β-D-吡喃木糖-(1→3)-β-D-吡喃木糖-(1→4)-α-L-吡喃鼠李糖-(1→4)-[β-D-吡喃葡萄糖-(1→4')-β-D-吡喃鸡纳糖-(1→2)]-[3'-O-乙酰基]-β-D-吡喃夫糖苷(九子参苷B, 2), 皂树酸-3-O-β-D-吡喃半乳糖-(1→2)-[β-D-吡喃木糖-(1→3)]-β-D-吡喃萄淘糖醛酸-28-O-β-D-吡喃木糖-(1→4)-α-L-吡喃鼠李糖-(1→4)-[4"-O-乙酰基-β-D-吡喃葡萄糖-(1→2)]-β-D-吡喃夫糖苷(九子参苷C, 3), 皂树酸-3-O-β-D－吡喃半乳糖-(1→2)-[β-D-吡喃半乳糖-(1→2)-[β-D-吡喃木糖-(1→3)]-[6'-O-正丁基]-β-D-吡喃葡萄糖醛酸-28-O-β-D-吡喃木糖-(1→3)-β-D-吡喃木糖-(1→4)-α-L-吡喃鼠李糖-(1→4)-[2"-O-乙酰基-β-D-吡喃鸡纳糖-(3'-O-乙酰基]-β-D-吡喃夫糖苷(九子参苷D, 4)。     

Isolation of Six New Flavonoids from Melicope triphylla

Six new flavonoids-5-hydroxy-3,8-dimethoxy-3',4':6,7-bismethylenedioxyflavone (1), 3,3',4',5-tetramethoxy-7-(3-methylbut-2-enyloxy)flavone (2), 7-(2-hydroxy-3-methylbut-3-enyloxy)-3,3',4',5-tetramethoxyflavone (3), 7-(2-hydroxy-3-methylbut-3-enyloxy)-3,5-dimethoxy-3',4'-methylenedioxyflavone (4), 7-(2-hydroxy-3-methylbut-3-enyloxy)-3,3',4',5,8-pentamethoxyflavone (5), and 7-(2-hydroxy-3-methylbut-3-enyloxy)-3,5,8-trimethoxy-3',4'-methylenedioxyflavone (6)-were isolated from the leaves of Melicope triphylla. In addition, six already known flavonoids were also detected: 5-hydroxy-3,6,7-trimethoxy-3',4'-methylenedioxyflavone (7), 5,7-dihydroxy-3,3',4',8-tetramethoxyflavone (8), 4',5-dihydroxy-3,3',7,8-tetramethoxyflavone (9), 3,5,6,7,8-pentamethoxy-3',4'-methylenedioxyflavone (10), 3,5,6,7-tetramethoxy-3',4'-methylenedioxyflavone (11), and 3,3',4',5,6,7,8-heptamethoxyflavone (12). The structures of the new compounds were established by spectroscopic methods. Compound 2 displayed ichthyotoxic activity against Japanese killifish (medaka in Japanese) (Oryzias latipes var.) at 10?ppm.     

Isolation, Crystal Structure and Inhibitory Activity against Magnaporthe Grisea of （2R,3R）-3,5,7-trihydroxyflavanone 3-Acetate from Myoporum Bontioides A. Gray

The title compound, (2R,3R)-3,5,7-trihydroxyflavanone 3-acetate, is a flavanonol derivative which was first isolated from Myoporum bontioides A. Gray and characterized by MS, NMR and CD spectra. In addition, the structure was determined by X-ray single-crystal diffraction analysis. It crystallizes in the triclinic lattice, space group P21 with a = 10.686(3), b = 6.862(2), c = 11.267(3) , β = 107.46(1), V = 788.3(4) 3, Z = 2, C17H16O7, Mr = 332.30, Dc = 1.400 g/cm3, μ(MoKα) = 0.110 mm-1, F(000) = 348, the final R = 0.0283 and wR = 0.0826 for 3428 independent reflections (Rint = 0.017) and 1500 observed ones (I > 2σ(I)). The structure consists of one flavone and one water molecule. The flavone molecules form a 1D column by the p…π stacking interactions and C–H…O hydrogen bonds. The weak intermolecular/intermolecular O–H…O hydrogen bonds observed in the crystal give further rise to a complicated network structure. Primary bioassay showed that the title compound has high inhibitory activity against Magnaporthe grisea with the EC50 values of 199.41 μg/mL.     

Three-dimensional open-frameworks based on Ln(III) ions and open-/closed-shell PTM ligands: synthesis, structure, luminescence, and magnetic properties

A series of isostructural open-framework coordination polymers formulated as [Ln(dmf)(3)(ptmtc)] (Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5); PTMTC = polychlorotriphenylmethyl tricarboxylate) and [Ln(dmf)(2)H(2)O(αH-ptmtc)] (Ln = Sm (1'), Eu (2'), Gd (3'), Tb (4'), Dy (5')) have been obtained by treating Ln(III) ions with PTMTC ligands with a radical (PTMTC(3-)) or a closed-shell character (αH-PTMTC(3-)). X-ray diffraction analyses reveal that these coordination polymers possess 3D architectures that combine large channels and fairly rare lattice complex T connectivity. In addition, these compounds show selective framework dynamic sorption properties. For both classes of ligands, the ability to act as an antenna in Ln sensitization processes has been investigated. No luminescence was observed for compounds 1-5, and 3' because of the PTMTC(3-) ligand and/or Gd(III) ion characteristics. Conversely, photoluminescence measurements show that 1', 2', 4', and 5' emit dark orange, red, green, and dark cyan metal-centered luminescence. The magnetic properties of all of these compounds have been investigated. The nature of the {Ln-radical} exchange interaction in these compounds has been assessed by comparing the behavior of the radical-based coordination polymers 1-5 with those of the compounds with the diamagnetic ligand set. While antiferromagnetic {Sm-radical} interactions are found in 1, ferromagnetic {Ln-radical} interactions propagate in the 3D architectures of 3, 4, and 5 (Ln = Gd, Tb, and Dy, respectively). This procedure also provided access to information on the {Ln-Ln} exchange existing in these magnetic systems.     

新疆雪莲化学成分的研究(Ⅰ)

从新疆雪莲中首次得到五种结晶,经鉴定晶Ⅰ为槲皮素,晶Ⅱ为4′,5,7,-三羟基-3′,6-二甲氧基黄酮,晶Ⅲ为高车前素,晶Ⅳ结构待定,晶Ⅴ为芦丁。     

A Density Functional Study on the Geometries of Compounds Fe(HCN)n+(n = 1～6)

The possible geometries of Fe(HCN)n+ (n = 1～6) compounds were studied by using DFT/UB3LYP/6-31G(2df) method. The structure and ground state of each fragmental ion are C∞v (4∑+ or 6∑+), D∞h(4∑g+), D3h (4A1'), C2v or Td or C3v (4A1), and D3h (4A1') or C4v( (2A1') sequentially with n = 1～5. For the compound Fe(HCN)6+, the possible geometry was not obtained. The sequential incremental interaction energy (-△(△E)), dissociation energy (△D0), enthalpy (-△(△H)) and Gibbs free energy (-△(△G)), and frequencies for HCN-Fe(HCN)n-1+ were also calculated, and the results are all in good agreement with the experiments. The bond length of Fe-N is lengthened with the increase of cluster size, and the strength of Fe+-N coordination bond varies nonmon- tonically as increasing the number of ligands. The Fe+-N bond of Fe(HCN)2+ is the strongest in all compounds.