Glycosyl Moiety Research Articles

13,28-Epoxy triterpenoid saponins from Ardisia japonica selectively inhibit proliferation of liver cancer cells without affecting normal liver cells

Twenty 13,28-epoxy and related triterpenoid saponins from Ardisia japonica were evaluated for their anti-proliferative activity on human liver cancer cells and normal liver cells. Eight saponins selectively inhibited the growth of liver cancer Bel-7402 and HepG-2 cells without affecting the survival of normal liver HL-7702 cells. The structure–activity relationship analyses indicated that the 13,28-epoxy, 16α-hydroxy, and C-30 methyl moieties in the sapogenin parts and the glycosyl moiety consisting from tetra- to hepta-saccharide units are important for this activity. Among the active saponins, ardisianoside B (2) and 3β-O-β-d-glucopyranosyl-(1→2)-[α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyl-(1→4)]-α-l-arabinopyranosyl-13β,28-epoxy-16α-hydroxyoleanane (3) showed the most potent anti-proliferative activity against Bel-7402 cells in a dose- and time-dependent manner. The selective anti-proliferative activity is attributed to the different cellular responses (CDKs and cyclins levels, cell cycle arrest and apoptosis) between tumor and normal liver cells. Exposure to 2 and 3 selectively led to cell cycle arrest and apoptosis in Bel-7402 cells together with the increased pro-apoptotic caspase-8 and the decreased anti-apoptotic Cdc25A levels.

A novel sucrose phosphorylase from the metagenomes of sucrose-rich environment: isolation and characterization

Sucrose phosphorylase, an important enzyme mainly involved in the generic starch and sucrose pathways, has now caught the attention of researchers due to its transglycosylation activity. A novel sucrose phosphorylase, unspase, has been isolated, and its transglycosylation properties were characterized. Compared with Bisp, the sucrose phosphorylase from Bifidobacterium adolescentis, unspase had two deleted regions in its C: -terminal. These deleted regions were probably equivalent to the important five-stranded anti-parallel β-sheet domain in sucrose phosphorylase. Unspase has a k(m) of 21.12 mM, a V(max) of 69.24 μmol min(-1) mg(-1) and a k(cat) of 31.19 s(-1) with sucrose as substrate. In 3-(N-morpholino) propanesulfonic acid (MOPS) buffer, unspase transferred the glycosyl moiety to L-arabinose, D-fructose and L-sorbose. Much to our surprise, unspase can catalyze the transglycosylation in which a glycosyl moiety was transferred to L-arabinose in the presence of phosphate, which is an interesting exception to the generally accepted fact that transglycosylation can only occur under the condition of phosphate absence. The final yield of the transglycosylation product (37.9 %) in phosphate buffer was even higher than that (5.8 %) in MOPS buffer. This is a novel phenomenon that a sucrose phosphorylase can catalyze a transglycosylation reaction in the presence of phosphate.

Identification of metabolites in Withania sominfera fruits by liquid chromatography and high‐resolution mass spectrometry

Withania somnifera is a rich source of biologically active secondary metabolites. Our earlier investigations on the fruits of this plant have yielded novel compounds, withanamides, with potent antioxidant activity and protective effect on β-amyloid-induced cytotoxicity in vitro. However, several minor compounds present in the fruits have not been characterized previously which may contribute to the observed biological activities. Liquid chromatography (LC) coupled with high-resolution mass spectrometry (HRMS) with data-dependent and targeted MS/MS experiments were conducted to elucidate the structure of observed metabolites. A total of 62 metabolites identified included 32 withanamides, 22 withanolides, 3 steroidal saponins, 2 lignanamides, feruloyl tyramine, methoxy feruloyl tyramine and a diglucoside of hydroxyl palmitic acid. The structures of these compounds were proposed based on accurate masses of the molecular and fragment ions. Several of these new compounds identified from the profile were derived from withanamides with variations in aliphatic and/or glycosyl moieties. In addition, six new withanolides, a new hydroxy fatty acid diglucoside and several known compounds in the extract were identified. The current study revealed the presence of several new and known compounds in Withania somnifera fruits. High-resolution MS and MS/MS experiments provide an extremely effective approach to derive the structures of plant secondary metabolites including isomeric compounds.

A Focus on Glucose-Mediated Drug Delivery to the Central Nervous System

Drug delivery to the central nervous system (CNS) is a timely and challenging issue: 95 percent; of the pharmacological drugs cannot be delivered to the brain. This is mainly due to the blood-brain barrier (BBB), a highly selective boundary that hampers the passage of most compounds into the CNS. To overcome this problem, several approaches exist to deliver a therapeutic drug to the brain that takes into account not only the chemical properties of the drug but also the type of transport used at the BBB. One of those strategies is the glucose-mediated drug delivery which will be the focus of the present review. Glucose-mediated drug delivery requires the attachment of glycosyl moieties to a drug and the use of endogenous glucose transporters as a way to circumvent the blood-brain barrier. Glycosylated drugs display improved cell penetrability, enhanced biodistribution, stability and low toxicity. Examples such as glycosylation of ibuprofen and different opioids result in an enhanced central effect and will be discussed.

Streptocarbazoles A and B, Two Novel Indolocarbazoles from the Marine-Derived Actinomycete Strain Streptomyces sp. FMA

Streptocarbazoles A (1) and B (2), two novel indolocarbazoles featuring unprecedented cyclic N-glycosidic linkages between 1,3-carbon atoms of the glycosyl moiety and two indole nitrogen atoms of the indolocarbazole core, were isolated from the marine-derived actinomycetes strain Streptomyces sp. FMA. Their structures were established by spectroscopic methods, CD spectra, and ECD quantum mechanical calculations. Compound 1 was cytotoxic on HL-60 and A-549 cell lines and could arrest the cell cycle of Hela cells at the G(2)/M phase.

Characterization of Steroidal Saponins in Crude Extracts from Dioscorea Species using Liquid Chromatography/Electrospray Ionization Time-of-Flight Mass Spectrometry

Yam (Dioscorea spp.) is an important tuber plant for edible and medicinal use to promote health and longevity in Chinese traditional medicne [1]. Steroidal saponins were reported to be the major physiologically active constituents in yam [2]. Furostanol and spirostanol glycosides, two main steroidal saponins, have been found in many types of yams (Dioscorea species) [3]. A steroidal saponin molecule consists of an aglycone and any of several glycosyl moieties. The common sugars present in steroidal saponins from Dioscoreaceae are hexose (glucose) and 6-deoxyhexose (rhamnose), and generally, glucosyls are connected with the hydroxyl groups at C-3 and/or C-26 positions of steroidal aglycones [3].

Characterization and identification of baccharane glycosides in Impatientis Semen by rapid-resolution liquid chromatography with electrospray ionization quadrupole time-of-flight tandem mass spectrometry

Baccharane glycosides represent a group of rare saponins in plant kingdom and have been regarded as chemical marker for quality control of Impatientis Semen. Based on the structural skeleton, the baccharane glycosides were classified into three types: hosenkol A, hosenkol B and hosenkol C type. In this study, a rapid-resolution liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (RRLC/ESI-Q-TOF MS/MS) was performed to investigate the fragmentation behaviours of baccharane glycosides from Impatientis Semen. In full scan mass spectrum, the accurate determination of molecular formula was obtained by the predominant ion [M+COO](-) in negative mode. In the MS/MS spectrum, fragmentation reactions of the [M+H](+) acquired in positive mode were recorded to provide abundant structural information on the aglycone and glycosyl moieties. The characteristic ion for hosenkol A and hosenkol B type glycosides was at m/z 399, while for hosenkol C type glycosides the diagnostic ion was at m/z 381. Neutral losses of monosaccharide, disaccharide, H(2)O and C(3)H(4) were observed for stepwise structural characterization. As a result, 19 compounds including 9 target saponins and 10 non-target saponins were rapidly screened out in ethanol extract of Impatientis Semen, and 5 of them were found to be novel baccharane glycosides.

Study on the noncovalent interactions of saikosaponins and cytochrome c by electrospray ionization mass spectrometry

The study of interactions between protein and pharmaceutical molecules including natural extracts has become of increasing interest in biological and biomedical research. An investigation of the interaction between saikosaponins and cytochrome c (Cyt c) by electrospray ionization mass spectrometry (ESI-MS) is described in this study. Saikosaponins are found in Bupleurum falcatum (a flowering plant), and they are glycosides that consist of saccharides and the sapogenins of triterpenoids. Seven model molecules of saccharides and triterpenes, namely maltose (Mal II), maltotriose (Mal III), raffinose (Raf), and stachyose (Sta), glycyrrhetinic acid (Gly), ursolic acid (Urs) and oleanic acid (Ole), were chosen to perform a series of ESI-MS control experiments for the exploration of the interaction groups in saikosaponins with Cyt c. The dissociation constants of detected noncovalent complexes were determined by using a direct ESI-MS assay. We have observed in the ESI mass spectra the formation of Cyt c complexes with saikosaponins a and c, and these saccharides, with 1:1 and 1:2 stoichiometry. Our results showed that no complex ions of triterpenes and Cyt c were detected in the ESI-MS and similar Kd values were obtained for the Cyt c complexes of saikosaponins and saccharides. This demonstrates that the glycosyl moiety in the saikosaponins is the effective interaction group with Cyt c. We propose that saikosaponins and saccharides interact with Cyt c by hydrogen bonds. The binding affinity of these six ligands with Cyt c is shown to be in the order Ssa > Ssc > Raf, Mal III > Sta ≥ Mal II. The ESI-MS methodology presented in this study enables us to investigate the interactions of saikosaponins with Cyt c, and allows the direct determination of binding constants. These results could guide further research for providing insights into the structure-binding relationship of ligands with Cyt c.

Screening of glycoside isomers in P. scrophulariiflora using ionic liquid‐based ultrasonic‐assisted extraction and ultra‐performance liquid chromatography/electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry

A powerful ionic liquid-based ultrasonic-assisted extraction (ILUAE) method combined with ultra-performance liquid chromatography coupled to electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC/ESI-QTOFMS(n) ) was employed in the rapid simultaneous screening of iridoid glycosides, phenylethanoid glycosides, and cucurbitacin glycosides from P. scrophulariiflora. The ILUAE procedure was optimized over several ultrasonic parameters, including the ultrasonic power, concentration of the ionic liquid, and solid-liquid ratio. A comparison with conventional heat-reflux extraction and regular UAE demonstrated that the optimized approach yielded a high extraction efficiency (Picroside I, 2.84%; Picroside II, 3.57%; 6-O-E-feruloyl catalpol, 2.20%) within a short extraction time of 30 min. Negative ion mode ESI-QTOFMS(2) analysis of the fragmentation reactions of the [M-H](-) ions was conducted to characterize the diagnostic ions related to the glycosyl moieties, aglycone units, and the type and substituted position of the ester groups. Interestingly, the positional isomers of the iridoid glycosides could be easily discriminated based on the characteristic ions. A total of 15 glycosides, including three groups of iridoid glycoside isomers and two groups of phenylethanoid glycoside isomers, were conveniently identified within 13.5 min. Moreover, 6'-O-vanilloyl catalpol was identified in P. scrophulariiflora for the first time. The method developed here was further validated by measuring the recovery, correlation coefficient (R(2) ), and reproducibility (RSD, n = 5) of three iridoid glycosides: 89.60%-109.02%, 0.9991-0.9998, and 0.93%-1.44%, respectively. This study demonstrated the capabilities of ILUAE combined with UPLC/ESI-QTOFMS(n) for the rapid screening of glycosides in P. scrophulariiflora. This method offers an approach to similar studies on other natural plants.

Synthesis of 2-Deoxy-2-C-alkyl Glycal and Glycopyranosides from 2-Hydroxy Glycal Ester

A method to convert 2-hydroxy glycal ester to the corresponding 2-deoxy-2-C-alkyl glycal in a facile manner, through key reactions including (i) C-allylation at C-1, (ii) Wittig reaction, and (iii) Cope rearrangement of a 1,5-diene derivative, is reported. The α-anomer of the 1,5-diene derivative underwent Cope rearrangement to afford 2-deoxy-2-C-glycal derivative, whereas the β-anomer was found to be unreactive. Employing this sequence, 3,4,6-tri-O-benzyl-2-O-acetyl-1,5-anhydro-d-arabino-hex-1-enitol was transformed to 3,4,6-tri-O-benzyl-2-deoxy-2-C-alkyl-1,5-anhydro-D-arabino-hex-1-enitol. 2-Deoxy-2-C-alkyl glycal derivative is a suitable glycosyl donor to prepare 2-deoxy-2-C-alkyl glycosides, mediated through haloglycosylation and a subsequent dehalogenation. A number of 2-deoxy-2-C-alkyl glycosides, with both glycosyl and nonglycosyl moieties at the reducing end, are thus prepared from the glycal.

Dual Carbamoylations on the Polyketide and Glycosyl Moiety by Asm21 Result in Extended Ansamitocin Biosynthesis

Carbamoylation is one of the post-PKS modifications in ansamitocin biosynthesis. A novel ansamitocinoside with carbamoyl substitution at the C-4 hydroxyl group of the N-β-D-glucosyl moiety was identified from the ansamitocin producer, Actinosynnema pretiosum. Through biotransformation, the carbamoyltransferase gene asm21 was suggested to be responsible for the carbamoylation of the glucosyl moiety. Three new derivatives without the backbone carbamoyl group were isolated from an asm21 mutant and characterized by NMR spectroscopy. Among them, 18-O-methyl-19-chloroproansamitocin was the major product and the preferred substrate for macrolactam C-7 carbamoylation by Asm21. However, Asm21 exhibited higher catalytic efficiency toward the glucosyl moiety. Furthermore, the dual carbamoylations and N-glycosylation were precisely demonstrated invivo. This work represents the first biochemical characterization of an O-carbamoyltransferase performing dual actions on both a polyketide backbone and a glycosyl moiety during ansamitocin biosynthesis.

Glycosyl Coumarin Carbonic Anhydrase IX and XII Inhibitors Strongly Attenuate the Growth of Primary Breast Tumors

A series of 7-substituted coumarins incorporating various glycosyl moieties were synthesized and investigated for the inhibition of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1). These coumarins were very weak or ineffective as inhibitors of the housekeeping, off target isoforms CA I and II, but some of them inhibited tumor-associated CA IX and XII in the low nanomolar range. They also significantly inhibited the growth of primary tumors by the highly aggressive 4T1 syngeneic mouse mammary tumor cells at 30 mg/kg, constituting interesting candidates for the development of conceptually novel anticancer drugs. Because CA IX is overexpressed in hypoxic tumors and exhibits very limited expression in normal tissues, such compounds may be useful for treating cancers not responsive to classic chemo- and radiotherapy.

Glycopeptide Antibiotics and their Novel Semi-Synthetic Derivatives

Glycopeptide antibiotics, vancomycin and teicoplanin, inhibit cell wall synthesis in Gram-positive bacteria by interacting with peptidoglycan D-Ala-D-Ala peptide stem termini of the pentapeptide side chains of the peptidoglycan precursors. In glycopeptide-resistant bacteria, multiresistance poses major therapeutic problems. New potent antibacterial agents are needed to combat these resistance problems, resulting in the explosion of novel glycopeptides in recent years. The glycosylation patterns of glycopeptides and the chemical modifications of the glycosyl moieties greatly influence their antibiotic activity, and certain combinations have resulted in highly active new compounds. Considerable efforts have been made to produce semisynthetic glycopeptides with improved pharmacokinetic and pharmacodynamic properties and activity towards resistant strains. This review provides an overview of the chemistry, the antimicrobial activity, the pharmacokinetics and the toxicology of teicoplanin and other glycopeptide antibiotic derivatives.

Response surface analysis of nano-ureases from Canavalia ensiformis and Cajanus cajan

Ureases isolated from leguminous sources, Canavalia ensiformis and Cajanus cajan were immobilized onto gold nanoparticles (nano-ureases). Optimization of the urease immobilization was carried using response surface methodology based on Central Composite Design. Immobilization efficiency of nano-urease from C. ensiformis and C. cajan were found to be 215.10% and 255.92%, respectively. The methodology adopted has deviation of 2.56% and 3.01% with respect to experimental values in case of C. ensiformis and C. cajan, respectively. Nano-urease from C. cajan has broad physico-chemical parameters with pH optimum from 7.1 to 7.3 and temperature optimum from 50 to 70°C. Nano-urease from C. ensiformis has sharp pH and temperature optima at 7.3 and 70°C, respectively. Fourier transform infra-red spectroscopy has revealed involvement of groups viz. amino, glycosyl moiety, etc. in urease immobilization onto gold nano-particles. Transmission and scanning electron micrographs revealed that arrangement of urease onto gold nano-particles from C. ensiformis was uniform while it was localized in case of C. cajan. Nano-urease from C. ensiformis has higher specificity and catalysis toward urea as compared to nano-urease from C. cajan. Nano-ureases from both sources are equally stable for 6 months under dried conditions and can be used for 10 washes.

Synthesis of novel 6-triazologlycolipids via click chemistry and their preliminary cytotoxicity assessments

Series of novel 6-triazole-linked galacto- or glucolipids were efficiently synthesized from O-benzylated sugar azides and various lipid alkynes via Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (click chemistry) followed by hydrogenolysis with PdCl(2)/H(2). Subsequent MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay toward a panel of human cancer cell lines revealed that these triazologlycolipids possess low-to-modest toxicity on A549 (lung), MCF-7 (breast), HeLa (cervix), and HepG2 (liver). Furthermore, both the carbon chain length at the lipid end and the epimeric identity of the glycosyl moiety were determined to impact their corresponding bioactivity.

Nanodisc-based Co-immunoprecipitation for Mass Spectrometric Identification of Membrane-interacting Proteins

Proteomic identification of protein interactions with membrane associated molecules in their native membrane environment pose a challenge because of technical problems of membrane handling. We investigate the possibility of employing membrane nanodiscs for harboring the membrane associated molecule to tackle the challenges. Nanodiscs are stable, homogenous pieces of membrane with a discoidal shape. They are stabilized by an encircling amphipatic protein with an engineered epitope tag. In the present study we employ the epitope tag of the nanodiscs for detection and co-immunoprecipitation of interaction partners of the glycolipid ganglioside GM1 harbored by nanodiscs. Highly specific binding activity for nanodisc-GM1 immobilized on sensorchips was observed by surface plasmon resonance in culture media from enterotoxigenic Escherischia coli. To isolate the interaction partner(s) from enterotoxigenic Escherischia coli, GM1-nanodiscs were employed for co-immunoprecipitation. The B subunit of heat labile enterotoxin was identified as a specific interaction partner by mass spectrometry, thus demonstrating that nanodisc technology is useful for highly specific detection and identification of interaction partners to specific lipids embedded in a membrane bilayer.

Anti-complementary Ginsenosides Isolated from Processed Ginseng

As part of an ongoing search for immunomodulatory components aimed at the anti-complementary effect, ginsenosides isolated from processed ginseng were found to have inhibitory activity on complement activation through classical pathways. Activity-guided fractionation was used to isolate four ginsenosides, namely ginsenoside Rg₆, F₄, Rk₃, and Rh₄. Ginsenoside Rk₃ and Rh₄ had a 3 fold higher inhibition activity than rosmarinic acid which was used as a positive control while ginsenoside Rg₆ and F₄ showed only mild effects similar to that of the positive control. The results suggest that the activity of the corresponding ginsenosides may be increased by the glycosyl moiety at the C₆ position rather than the double bond conformation at C₂₀, and ginsenoside Rk₃ and Rh₄ could have a role in treating inflammatory diseases.

Regioselective synthesis of di-C-glycosylflavones possessing anti-inflammation activities

Three methods are utilized to synthesize a variety of 6,8-di-C-glycosylflavones bearing identical or distinct glycosyl moieties. Some C-glycosylation compounds are found to have better anti-inflammation activities than the parent flavones. Among them, 6,8-di-C-glucosylapigenin (known as vicenin-2) shows inhibition of TNF-alpha expression and NO production with IC(50) values of 6.8 and 5.2 muM, respectively.

Analysis of supercooling-facilitating (anti-ice nucleation) activity of flavonol glycosides

Deep supercooling xylem parenchyma cells (XPCs) of katsura tree ( Cercidiphyllum japonicum) contain four kinds of flavonol glycosides with high supercooling-facilitating (anti-ice nucleation) activities. These flavonol glycosides have very similar structures, but their supercooling-facilitating activities are very different. In this study, we analyzed the supercooling-facilitating activities of 12 kinds of flavonol glycosides in order to determine the chemical structures that might affect supercooling-facilitating activity. All of the flavonol glycosides tested showed supercooling-facilitating activity, although the magnitudes of activity differed among the compounds. It was clear that the combination of the position of attachment of the glycosyl moiety, the kind of attached glycosyl moiety and the structure of aglycone determined the magnitude of anti-ice nucleation activity. However, there is still some ambiguity preventing the exact identification of features that affect the magnitude of supercooling-facilitating activity.

Structural characterization of pregnane glycosides from Cynanchum auriculatum by liquid chromatography on a hybrid ion trap time‐of‐flight mass spectrometer

A method coupling high-performance liquid chromatography with hybrid ion trap time-of-flight mass spectrometry (TOFMS) using an electrospray ionization source was firstly used to characterize ten major pregnane glycosides including one novel compound auriculoside IV from the roots of Cynanchum auriculatum Royle ex Wight. In the MS/MS spectra, fragmentation reactions of the [M+Na]+ were recorded to provide abundant structural information on the aglycone and glycosyl moieties. Experiments using TOFMS allowed us to obtain precise elemental compositions of molecular ions and subsequent product ions with errors less than 6 ppm. The pregnane glycosides in C. auriculatum were classified into two major core groups: one is caudatin characterized by the neutral loss of one ikemamic acid molecule (128 Da) from the precursor ion, and the other is kidjoranin characterized by the neutral loss of cinnamic acid (148 Da) from the precursor ion. Meanwhile, a series of sugar-chain fragment ions provided valuable information about the compositions of the sugar residues and the sequences of the sugar chain. Logical fragmentation pathways for pregnane glycosides have been proposed and are useful for the identification of these compounds in natural products especially when there are no reference compounds available.