Malonylated flavonol glycosides from the petals of Clitoria ternatea

Three flavonol glycosides, kaempferol 3-O-(2"-O-alpha-rhamnosyl-6"-O-malonyl)-beta-glucoside, quercetin 3-O-(2"-O-alpha-rhamnosyl-6"-O-malonyl)-beta-glucoside, and myricetin 3-O-(2",6"-di-O-alpha-rhamnosyl)-beta-glucoside were isolated from the petals of Clitoria ternatea cv. Double Blue, together with eleven known flavonol glycosides. Their structures were identified using UV, MS, and NMR spectroscopy. They were characterized as kaempferol and quercetin 3-(2(G)- rhamnosylrutinoside)s, kaempferol, quercetin, and myricetin 3-neohesperidosides, 3-rutinosides, and 3-glucosides in the same tissue. In addition, the presence of myricetin 3-O-(2"-O-alpha-rhamnosyl-6"-O-malonyl)-beta-glucoside was inferred from LC/MS/MS data for crude petal extracts. The flavonol compounds identified in the petals of C. ternatea differed from those reported in previous studies.     

Anthocyanin 3-galactosides from Cornus alba 'Sibirica' with glucosidation of the B-ring

The three anthocyanins, delphinidin 3-O-beta-galactopyranoside-3',5'-di-O-beta-glucopyranoside (1), delphinidin 3-O-beta-galactopyranoside-3'-O-beta-glucopyranoside (2) and cyanidin 3-O-beta-galactopyranoside-3'-O-beta-glucopyranoside (3), and the 3-O-beta-galactopyranosides of delphinidin (4) and cyanidin (5) were isolated from the bluish white berries and compound umbel of Siberian dogwood, Cornus alba 'Sibirica'. The ornamental autumn leaves and the characteristic purplish red bark of this variety were found to contain only pigment 5.     

Semisynthetic lysogalactolipids of plant origin

Starting from the natural mono- and digalactosyl diglycerides, 1′-O-acyl-3′-O-β-d-galactopyranosyl-sn-glycerol and 1′-O-acyl-3′-O-(6-O-α-d-galactopyranosyl-β-d-galactopyranosyl)-sn-glycerol were synthesized. In an attempt to prepare the 2′-O-acyl-isomer, only a mixture of the 1′-and 2′-O-acyl-isomers was obtained.     

Secondary metabolites from Opuntia ficus-indica var. saboten

A butanol fraction, from the methanolic extract of Opuntia ficus-indica var. saboten, on purification either by preparative TLC or reversed phase HPLC, yielded three chemical components: isorhamnetin 3-O-(6'-O-E-feruloyl)neohesperidoside (1), (6R)-9,10-dihydroxy-4,7-megastigmadien-3-one-9-O-beta-D-glucopyranoside (2) and (6S)-9,10-dihydroxy-4,7-megastigmadien-3-one-9-O-beta-D-glucopyranoside (3) along with 15 known compounds. Structures of compounds (1-3) were elucidated by aid of spectroscopic analyses. The absolute stereochemistry in compounds 2 and 3 was established with the help of CD data analysis and comparison with the literature data. In a DPPH radical scavenging assay, compound 1 showed moderate inhibitory activity (IC50 = 45.58 microg/ml).     

Biosynthetic studies on the alpha-glucosidase inhibitor acarbose: the chemical synthesis of isotopically labeled 2-epi-5-epi-valiolone analogs

2-epi-5-epi-valiolone is a cyclization product of the C(7) sugar phosphate, sedoheptulose 7-phosphate, involved in the biosynthesis of the aminocyclitol moieties of acarbose, validamycin, and pyralomicin. As part of our investigation into the pathway from 2-epi-5-epi-valiolone to the valienamine moiety of acarbose, we prepared 1-epi-5-epi-(6-(2)H(2))valiolol [(6-(2)H(2))-6], 5-epi-(6-(2)H(2))valiolol [(6-(2)H(2))-17], 1-epi-2-epi-5-epi-(6-(2)H(2))valiolol [(6-(2)H(2))-12] and 2-epi-5-epi-(6-(2)H(2))valiolamine [(6-(2)H(2))-11]. Compounds (6-(2)H(2))-6 and (6-(2)H(2))-17 were synthesized from 2,3,4,6-tetra-O-benzyl-D-glucopyranose in 10 and seven steps, respectively, whereas (6-(2)H(2))-12 and (6-(2)H(2))-11 were synthesized from 2,3,4,6-tetra-O-benzyl-D-mannopyranose in eight and 10 steps, respectively.     

Distribution of reaction products in phospholipase A2 hydrolysis

We have monitored the composition of supported phospholipid bilayers during phospholipase A₂ hydrolysis using specular neutron reflection and ellipsometry. Porcine pancreatic PLA₂ shows a long lag phase of several hours during which the enzyme binds to the bilayer surface, but only 5 ± 3% of the lipids react before the onset of rapid hydrolysis. The amount of PLA₂, which resides in a 21 ± 1 Å thick layer at the water-bilayer interface, as well as its depth of penetration into the membrane, increase during the lag phase, the length of which is also proportional to the enzyme concentration. Hydrolysis of a single-chain deuterium labelled d₃₁-POPC reveals for the first time that there is a significant asymmetry in the distribution of the reaction products between the membrane and the aqueous environment. The lyso-lipid leaves the membrane while the number of PLA₂ molecules bound to the interface increases with increasing fatty acid content. These results constitute the first direct measurement of the membrane structure and composition, including the location and amount of the enzyme during hydrolysis. These are discussed in terms of a model of fatty-acid mediated activation of PLA₂.     

Flavonoid glycosides from Centaurea pseudoscabiosa subsp. pseudoscabiosa from Turkey

Three flavonoid glycosides were isolated and characterized, together with a further 13 substances belonging to various classes of compounds, in particular two phenolic acids, a coumarin, a sugar and nine flavonoids from the flowered aerial parts of Centaurea pseudoscabiosa subsp. pseudoscabiosa Boiss. et Buhse (Asteraceae). Some considerations about their evolutionary meaning are provided.     

Sablacaurin A and B, two 19-nor-3,4-seco-lanostane-type triterpenoids from Sabal causiarum and Sabal blackburniana, respectively

In search for bioactive compounds from Sabal species, sablacaurin A [25-ethyl,23-methyl-19-nor-24-methylene-3,4-seco-4(28)-lanosten-10,3-olide] and sablacaurin B [24-ethyl,24-methyl-19-nor-3,4-seco-4(28),25(26)-lanostadiene-10,3-olide], the first 19-nor lanostane derivatives of the 3,4-seco type with a spiro element, have been isolated from the leaves of Sabal causiarum and Sabal blackburniana respectively, together with the known squalene (S. blackburniana) and ss-sitosterol (S. causiarum). From leaves of Sabal peregrina, the known triterpenes 3-oxo-24-methylenecycloartane and 24-methylcycloart-25(26)-en-3-one were isolated. The structures of these compounds were established from spectroscopic studies.     

Ent-3,4-seco-labdane and ent-labdane diterpenoids from Croton stipuliformis (Euphorbiaceae)

From a methanolic extract of the leaves of Croton stipuliformis, three ent-3,4-seco-labdanes (1-3) and an ent-labdane (4) together with the known compounds 6-hydroxynidorellol (5), maravuic acid, and sitosterol were isolated and identified from their spectroscopic data. The absolute stereochemistry of compound 4 was determined by application of Mosher's method in the NMR tube.     

Bioconversion of ginsenosides Rb(1), Rb(2), Rc and Rd by novel β-glucosidase hydrolyzing outer 3-O glycoside from Sphingomonas sp. 2F2: cloning, expression, and enzyme characterization

A new β-glucosidase gene (bglSp) was cloned from the ginsenoside converting Sphingomonas sp. strain 2F2 isolated from the ginseng cultivating filed. The bglSp consisted of 1344 bp (447 amino acid residues) with a predicted molecular mass of 49,399 Da. A BLAST search using the bglSp sequence revealed significant homology to that of glycoside hydrolase superfamily 1. This enzyme was overexpressed in Escherichia coli BL21 (DE3) using a pET21-MBP (TEV) vector system. Overexpressed recombinant enzymes which could convert the ginsenosides Rb₁, Rb₂, Rc and Rd to the more pharmacological active rare ginsenosides gypenoside XVII, ginsenoside C-O, ginsenoside C-Mc₁ and ginsenoside F₂, respectively, were purified by two steps with Amylose-affinity and DEAE-Cellulose chromatography and characterized. The kinetic parameters for β-glucosidase showed the apparent K_m and V_max values of 2.9 ± 0.3 mM and 515.4 ± 38.3 μmol min⁻¹ mg of protein⁻¹ against p-nitrophenyl-β-d-glucopyranoside. The enzyme could hydrolyze the outer C3 glucose moieties of ginsenosides Rb₁, Rb₂, Rc and Rd into the rare ginsenosides Gyp XVII, C-O, C-Mc₁ and F₂ quickly at optimal conditions of pH 5.0 and 37 °C. A little ginsenoside F₂ production from ginsenosides Gyp XVII, C-O, and C-Mc₁ was observed for the lengthy enzyme reaction caused by the side ability of the enzyme.     

Six naphthylisoquinoline alkaloids and a related benzopyranone from a Congolese Ancistrocladus species related to Ancistrocladus congolensis

From the roots of a recently discovered Ancistrocladus taxon, with close affinities to Ancistrocladus congolensis regarding molecular ITS sequence data, six naphthylisoquinoline alkaloids, 5'-O-demethylhamatine (2), 5'-O-demethylhamatinine (3), 6-O-demethylancistroealaine A (4), 6,5'-O,O-didemethylancistroealaine A (5), 5-epi-6-O-methylancistrobertsonine A (6), and 5-epi-4'-O-demethylancistrobertsonine C (7), have been isolated, along with a likewise benzopyranone carboxylic acid, 8. The structural elucidation succeeded by chemical, spectroscopic, and chiroptical methods. Their bioactivities were tested against protozoan parasites causing severe tropical diseases. Furthermore, eight known related alkaloids were identified.     

Alkaloids from Galanthus nivalis

Phytochemical studies on Galanthus nivalis of Bulgarian origin resulted in the isolation of five compounds: 11-O-(3'-hydroxybutanoyl)hamayne, 3,11-O-(3',3'-dihydroxybutanoyl)hamayne, 3-O-(2'-butenoyl)-11-O-(3'-hydroxybutanoyl)hamayne, 3,11,3'-O-(3',3',3'-trihydroxybutanoyl)hamayne, and 2-O-(3'-acetoxybutanoyl)lycorine, together with five known alkaloids: ungeremine, lycorine, tazettine, hamayne, and ismine. Their structures were determined by (1)H and (13)C NMR spectroscopy and two-dimensional (1)H-(1)H and (1)H-(13)C chemical shift correlation experiments.     

New cyclomaltoheptaose (beta-cyclodextrin) derivative 2-O-(2-hydroxybutyl)cyclomaltoheptaose: preparation and its application for the separation of enantiomers of drugs by capillary electrophoresis

A new soluble cyclomaltoheptaose (cyclodextrin) derivative, 2-O-(2-hydroxybutyl)cyclomaltoheptaose [2-O-(2-hydroxybutyl)-beta-cyclodextrin, 2-HB-beta-CD], was prepared and studied as an efficient chiral selector in the separation of racemic mixtures of drugs by capillary electrophoresis (CE). Results showed that 2-HB-beta-CD could provide higher separating capability than that of beta-CD and the similarly substituted 2-HP-beta-CD.     

Au(III)-complexes of the alanyl-containing peptides glycylalanine and glycylalanylalanine - Synthesis, spectroscopic and structural characterization

As part of an investigation on the coordination ability of peptides, the dipeptide glycylalanine (H-Gly-Ala-OH), tripeptide glycylalanylalanine (H-Gly-Ala-Ala-OH) and their Au(III)-complexes have been characterized structurally. The quantum chemical calculations and linear-dichroic infrared (IR-LD) spectroscopy predict structures of the compound studied, which are compared with a single crystal X-ray diffraction of H-Gly-Ala-OH. The coordination processes with Au(III) are supported by data for ¹H NMR, ESI-MS, HPLC-MS-MS, TGV and DSC methods. The [Au(Gly-Ala)H₋₁Cl] and [Au(Gly-Ala-Ala)H₋₂] · 2H₂O complexes are formed via -NH₂, N⁻amide/s and groups of the peptides. One Cl⁻ ion is attached to the metal center as terminal ligand in the first complex. In both cases a near to square-planar geometry of the chromophors AuN₂OCl and AuN₃O is yielded.     

Glycosylation of l,4:3,6-dianhydro-D-glucitol (isosorbide)

Condensation of 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl-, 2,3,4-tri-O-acetyl-alpha-D-xylopyranosyl- and of 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromides with l,4:3,6-dianhydro-D-glucitol under Koenigs-Knorr conditions, and using the Helferich modification of the reaction showed regioselectivity in glysosylation at C-5 of isosorbide.     

Isolation and structure elucidation of 5′-O-β-d-glucopyranosyl-dihydroascorbigen from Cardamine diphylla rhizome

From the methanol extract of Cardamine diphylla rhizome, 5′-O-β-d-glucopyranosyl-dihydroascorbigen (1) and 6-hydroxyindole-3-carboxylic acid 6-O-β-d-glucopyranoside (2) were isolated. The structures of the compounds were elucidated using spectroscopic methods. This is the second report on the presence of a glucosylated indole ascorbigen in plants.     

Glycosylamines of 4,6-O-butylidene-alpha-D-glucopyranose: synthesis and characterization of glycosylamines, and the crystal structure of 4,6-O-butylidene-N-(o-chlorophenyl)-beta-D-glucopyranosylamine

A total of nine glycosylamines of 4,6-O-butylidene-alpha-D-glucopyranose were synthesized using primary amines having various groups in their ortho- or para-positions. Among these, six are monoglycosylamines, including one primary glycosylamine, and three are bis-glycosylamines. All these compounds were characterized by 1H, 1H-1H COSY, 1H-13C COSY and 13C NMR spectroscopy and FTIR spectra. The FAB mass spectra provided the molecular weights of the products by exhibiting the corresponding molecular ion peaks. The crystal structure of 4,6-O-butylidene-N-(o-chlorophenyl)-beta-D-glucopyranosylamine revealed the C-1 glycosylation, the beta-anomeric nature, and the 4C1 chair conformation of the saccharide unit in the product. In the lattice two types of dimers exist. While one type of dimer is formed through O-H...O type of interactions, the other type is formed via C-H...O type of interactions. In the direction of these C-H...O type of interactions, the dimeric units are connected to form a chain.     

Anthocyanins in Caprifoliaceae

The qualitative and relative quantitative anthocyanin content of 19 species belonging to the genera Sambucus, Lonicera and Viburnum in the family Caprifoliaceae has been determined. Altogether 12 anthocyanins were identified; the 3-O-glucoside (2), 3-O-galactoside (5), 3-O-(6″-O-arabinosylglucoside) (7), 3-O-(6″-O-rhamnosylglucoside) (9), 3-O-(2″-O-xylosyl-6″-O-rhamnosylglucoside) (10), 3-O-(2″-O-xylosylgalactoside) (11), 3-O-(2″-O-xylosylglucoside) (12), 3-O-(2″-O-xylosylglucoside)-5-O-glucoside (14), 3-O-(2″-O-xylosyl-6″-O-Z-p-coumaroylglucoside)-5-O-glucoside (15) and 3-O-(2″-O-xylosyl-6″-O-E-p-coumaroylglucoside)-5-O-glucoside (16) of cyanidin, in addition to the 3-O-glucosides of pelargonidin and delphinidin (1 and 3). Pigment 7 is the first complete identification of the disaccharide vicianose, 6″-O-α-arabinopyranosyl-β-glucopyranose, linked to an anthocyanidin.     

Theoretical study of the experimental coordination behavior of N-(2-aminophenyl)-D-glycero-D-gulo-heptonamide to Hg(II) ion

The reactivity of N-(2-aminophenyl)-d-glycero-d-gulo-heptonamide (adgha), with the group 12 cations, Zn(II), Cd(II), and Hg(II), was studied in DMSO-d₆ solution. The studied system showed a selective coordination to Hg(II), and the products formed were characterized by ¹H and ¹³C NMR in DMSO-d₆ solution and fast atom bombardment (FAB⁺) mass spectra. The expected coordination compounds, [Hg(adgha)](NO₃)₂ and [Hg(adgha)₂](NO₃)₂, were observed as unstable intermediates that decompose to bis-[2-(d-glycero-d-gulo-hexahydroxyhexyl)-benzimidazole-κN]mercury(II) dinitrate, [Hg(ghbz)₂](NO₃)₂. The chemical transformation of the complexes was followed by NMR experiments, and the nature of the species formed is sustained by a theoretical study done using DFT methodology. From this study, we propose the structure of the complexes formed in solution, the relative stability of the species formed, and the possible role of the solvent in the observed transformations.