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PubMed2003

Synthesis of 18F-fluoroalkyl-beta-D-glucosides and their evaluation as tracers for sodium-dependent glucose transporters.

UNLABELLED: Three omega-(18)F-fluoro-n-alkyl-beta-D-glucosides (alkyl = ethyl (5a)), n-butyl (5b), and n-octyl (5c)) were synthesized and evaluated as potential substrates for the sodium/D-glucose cotransporter SGLT1. METHODS: The ligands were prepared by (18)F-fluoride displacement of the corresponding tetraacetyl-protected tosylate alkylglucoside precursors in CH(3)CN, followed by hydrolysis of the protective acetate esters with NaOMe/MeOH. Transport of the nonradioactive analogs 5a, 5b, and 5c by the human sodium-D-glucose cotransporter hSGLT1 was characterized in vitro in oocytes of Xenopus laevis that expressed hSGLT1. The biodistribution of the tracers was determined in mice and the presence of metabolites in the blood was investigated. Compound 5a was also evaluated in mice pretreated with phlorizin. The intrarenal distribution of 5a in mice kidney was visualized using autoradiography. RESULTS: The radiochemical yield of 5a, 5b, and 5c was in the range of 8%-15% (end of bombardment) with a total synthesis time of 90 min. The in vitro evaluation after expression of the hSGLT1 showed that 2'-fluoroethyl-beta-D-glucoside (5a) was transported with similar Michaelis-Menten K(m) and V(max) (maximum velocity) values as compared with methyl-alpha-D-glucopyranoside (alpha MDG). The more lipophilic compounds 5b and 5c were not transported but inhibited transport of alpha MDG. In vivo tissue distribution in mice revealed that 5a, 5b, and 5c were cleared mainly by the renal pathway and that 5a showed a significantly higher accumulation in the kidneys and a slower renal excretion as compared with 5b and 5c. Compound 5a was retained mainly in the renal outer medulla containing S3 segments of proximal tubules and the accumulation could be blocked by phlorizin pretreatment. Compound 5c passed the blood-brain barrier to some extent. CONCLUSION: The data indicate that 2'-(18)F-fluoroethyl-beta-D-glucoside (5a) is a specific tracer of Na(+)-dependent glucose transport that may be used to visualize this transport activity in the S3 segments of renal proximal tubules.

Animals↗

PubMed1992

The glucosidic pathways and glucose production by frog muscle.

Resting muscle is generally perceived as a glucose-utilizing organ; however, we show that resting well-oxygenated frog muscle recovering from strenuous exercise can release significant amounts of glucose. The metabolic pathway responsible for this process does not involve glucose-6-phosphatase because this enzyme is undetectable in frog muscle. The participation of amylo-1,6-glucosidase in the production of glucose is also ruled out since neither marked net phosphorolytic breakdown of glycogen nor considerable cycling between glycogen and glucose 6-phosphate occur. The glucosidic pathways of glycogen breakdown are the likely source of glucose as they are the only metabolic avenues with sufficient capacity to account for the rate at which glucose is released from post-exercised muscle. This rate of glucose production is high enough to be of physiological importance. Our results clearly indicate that to measure lactate glycogenesis in muscle, the simultaneous hydrolysis of muscle glycogen by the glucosidic pathways must be taken into account to prevent marked underestimation of the rate of glycogen synthesis. The glucosidic pathways seem the predominant avenues of glycogen breakdown in post-exercised resting frog muscle and are active enough to account for the rate of glycogen breakdown in resting muscle, suggesting that these rather than the phosphorolytic pathways are the chief routes of glycogen breakdown in resting muscle.

Animals↗

PubMed1991

Characterization of acyllipid: sterol glucoside acyltransferase from oat (Avena sativa L.) seedlings.

Membranous fractions from leaves of oat seedlings readily convert cholesterol beta-D-glucoside into its 6'-O-acyl derivative using endogenous acyllipids as acyl sources. Experiments with delipidated enzyme preparations showed that among acyllipids present in oat leaves digalactosyldiacylglycerols are evidently the best acyl donors in this reaction. Beside of sterol glucosides, the enzyme can acylate beta-D-glucosides of several other steroids, although at very different rates.

Acylation↗

PubMed2002

Bioactivity studies on beta-sitosterol and its glucoside.

Beta-sitosterol and beta-sitosteryl-beta-D-glucoside were isolated as analgesic constituents from the leaves of Mentha cordifolia Opiz. The acetic acid-induced writhing test showed that beta-sitosterol and beta-sitosteryl-beta-D-glucoside decreased the number of squirms induced by acetic acid by 70.0% and 73.0%, respectively, at a dose of 100 mg / kg mouse. Statistical analysis using the Kruskall Wallis one-way analysis of variance by ranks showed that these isolates approximate the analgesic activity of mefenamic acid at a 0.001 level of significance. The hot plate method confirmed their analgesic activities, as beta-sitosterol and beta-sitosteryl-beta-D-glucoside exhibited a 300% and 157% increase in pain tolerance, respectively, while mefenamic acid, a known analgesic, showed a 171% increase. Neither isolate exhibited antiinflammatory activity using the carrageenan-induced mouse paw oedema assay. Beta-sitosterol also exhibited anthelminthic and antimutagenic activities. In vitro tests using live Ascaris suum as test animals showed that the behaviour of worms treated with beta-sitosterol approximated that of the positive controls, Combantrin and Antiox. An in vivo micronucleus test showed that beta-sitosterol inhibited the mutagenicity of tetracycline by 65.3% at a dose of 0.5 mg /kg mouse. At the same dose, it did not exhibit chromosome-breaking activity.

Acetic Acid↗

PubMed2001

Identification of a novel fluorophore, xanthurenic acid 8- O -beta-D-glucoside in human brunescent cataract.

We have identified the chemical structure of a novel protein-unbound fluorescent glucoside (Fl-Glc), found to be far more abundant in the human brunescent cataractous lens nuclei than in non-brunescent ones. Our earlier experiments showed that long-term incubation of the protein-free filtrate of non-brunescent cataractous nuclei generated increasing amounts of a particular yet to be characterized fluorophore (Fl-X). High performance liquid chromatography (HPLC) analyses revealed Fl-X and Fl-Glc to be identical. HPLC-electrospray ionization-mass spectrometry (HPLC-ESI-MS) disclosed the molecular weights (MW) of Fl-X and its beta-glucosidase-digest (Fl-X-aglycon) to be 367 and 205, respectively. Fl-X-aglycon and authentic xanthurenic acid (MW = 205) not only eluted at exactly the same retention time on HPLC but also revealed their protonated ions at the same m/z of 206.1 by positive ion analysis on HPLC-ESI-MS. These results suggest that Fl-X ( = Fl-Glc) is a beta-glucoside of xanthurenic acid. Fl-Glc was finally identified as xanthurenic acid 8- O -beta- D -glucoside because the retention times of both completely agreed with three kinds of HPLC conditions.

Cataract↗

PubMed2000

Purification and characterization of a hydroxamic acid glucoside beta-glucosidase from wheat (Triticum aestivum L.) seedlings.

A beta-glucosidase (EC 3.2.1.21) with a high affinity for cyclic hydroxamic acid beta-D-glucosides was purified from 48-h-old wheat (Triticum aestivum L.) seedlings. The activity occurred transiently at a high level during the non-autotrophic stage of growth, and the nature of the transient occurrence was correlated with that of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one glucoside (DIMBOA-Glc). The glucosidase had maximum activity at an acidic pH (pH 5.5) and the purified enzyme showed a high affinity for DIMBOA-Glc, Vmax and Km being 4100 nkat/mg protein and 0.27 mM, respectively. It also hydrolyzed p-nitrophenol beta-glycosides, as well as flavone and isoflavone glucosides, but to a lesser extent. The results indicated that the primary natural substrate for the glucosidase is DIMBOA-Glc and that the enzyme is involved in defense against pathogens and herbivores in non-autotrophic wheat. The glucosidase was found to be present as oligomeric forms with a molecular mass of 260-300 kDa comprising 60- and 58-kDa monomers. The N-terminal 12-amino-acid sequences of the two monomers were identical (Gly-Thr-Pro-(Ser?)-Lys-Pro-Ala-Glu-Pro-Ile-Gly-Pro), and showed no similarity to those of other plant glucosidases. Polyacrylamide gel electrophoresis under nondenaturing condition indicated the existence of at least eight isozymes. Three cultivars of Triticum aestivum had the same zone of glucosidase activity on zymograms, but the activity zones of the Triticum species, T. aestivum L., T. spelta L. and T. turgidum L., had different mobilities.

Amino Acid Sequence↗

PubMed1986

Purfication and properties of a specific isoflavone 7-O-glucoside-6''-malonate malonyestrase from roots of chickpea (Cicer arietinum L.).

Protein extracts from roots of chickpea (Cicer arietinum L.) plants contained high esterase activity hydrolyzing malonate hemiesters of isoflavone 7-O-glucosides. Using 5,7-dihydroxy-4'-methoxyisoflavone (biochanin A) 7-O-glucoside-6"-malonate as a substrate, a specific malonylesterase was purified about 700-fold to near homogeneity. The purified enzyme possesses an extremely low enzyme activity with synthetic esterase substrates. Various putative nonspecific esterases, as tested with alpha-naphthylacetate, were removed during enzyme purification. The malonylesterase demonstrated a very high molecular mass in gel chromatography and in sedimentation analyses with sucrose gradients (greater than or equal to 2 X 10(6)). Analytical sodium dodecyl sulfate-polyacrylamide gel electrophoresis pointed to a single subunit of 32,000. The catalyzed reaction showed a pH optimum at 7.5 and a temperature optimum between 30 and 35 degrees C. The apparent Km for biochanin A 7-O-glucoside-6"-malonate was (4.2 +/- 1.2) X 10(-4) M. The malonylesterase was insensitive to the esterase inhibitors eserine and neostigmine (10(-3) M) as well as phenylmethylsulfonyl fluoride, paraoxon, and diisopropylfluorophosphate (10(-4) M). On the other hand enzyme activity was totally inhibited by Hg2+ ions (10(-5) M) and p-hydroxymercuribenzoate (10(-4) M), whereas iodoacetamide (10(-6)-10(-4) M) inhibited only partially. Di- and tricarboxylic acids strongly stimulated enzyme activity at 10(-2) M. These properties indicate that the malonylesterase from chickpea roots greatly differs from other known esterases. The possible biological function of the specific malonylesterase is discussed in relation to isoflavone conjugate metabolism in chickpea.

Carboxylic Acids↗

PubMed1975

The effect of diamide and glutathione on the uptake of alpha-methyl-D-glucoside by slices of rat kidney cortex.

The uptake of alpha-methyl-D-glucoside was stimulated in slices of rat kidney cortex by pretreatment with reduced glutathione. Diamide, an oxidizind agent with high specificity for GSH, caused an inhibition of alpha-methyl-D-glucoside uptake. These effects appeared to be related specifically to GSH, since dithiothreitol and mercaptoethanol did not increase alpha-methyl-D-glucoside uptake, and were not as effective as GSH in reversing the effects of diamide. GSH and diamide had no effect on the uptake of another sugar analog, 3-O-methylglucose, which is not actively transported. Kinetic studies indicated that GSH increased the apparent V without affecting K-m. The results are discussed in terms of the possible role of GSH in the process of sugar transport.

Amides↗

PubMed1979

Effects of dibutyryl cyclic AMP on the transport of alpha-methyl-D-glucoside and alpha-aminoisobutyric acid in separated tubules and brush border membranes from rabbit kidney.

The effect of dibutyryl cyclic AMP on the transport of alpha-methyl-D-glucoside and alpha-aminoisobutyric acid in separated tubules and purified brush border membranes from rabbit kidney was investigated using a rapid filtration procedure. Dibutyryl cyclic AMP stimulated the uptake of alpha-methyl-D-glucoside and alpha-aminoisobutyric acid by separated renal tubules in agreement iwth prior studies utilizing renal slices (Rea, C. and Segal, S. (1973) Biochim. Biophys. Acta 311, 615--624; Weiss, I.W., Morgan, K. and Phang, J.M. (1972) J. Biol. Chem. 247, 760--764). However, in contrast to previous reports, no preincubation of the tissue with dibutyryl cyclic AMP was required for stimulation of transport to be manifest. Dibutyryl cyclic AMP stimulated oxygen consumption by separated tubules suggesting that stimulation of transport may occur by a linkage with renal oxidative metabolism. Dibutyryl cyclic AMP increased the uptake of alpha-aminoisobutyric acid into purified renal brush border membranes. However the uptakes of alpha-methyl-D-glucoside, proline, leucine and phosphate into brush border membranes were significantly inhibited.

Aminoisobutyric Acids↗

PubMed1989

In-vivo inhibition by polycations of small intestinal absorption of methyl alpha-D-glucoside and leucine in the rat.

Polycations are able to inhibit active transport processes in rat small intestine in vitro. Whether this effect can also be confirmed in vivo is the concern of this study. Therefore, the effect of various polycations, e.g., protamine and polylysine, on the absorption of methyl alpha-D-glucoside and leucine was investigated in vivo by single-pass perfusion of rat jejunum. The inhibition of absorption of methyl alpha-D-glucoside and leucine by the polycations was strongly dose dependent. At a substrate concentration of 1 mmol/l a 50% inhibition was achieved with a protamine concentration of 3.2 mg/ml. The inhibition increased as the chain length of the polycation increased. In the presence of protamine the concentration-dependent leucine absorption was reduced at leucine concentrations below 60 mmol/l, but was increased at 100 mmol/l. Absorption of mannitol and 2-deoxy-D-glucose was significantly enhanced by the polycations. These results demonstrate that polycations inhibit active transport and increase passive diffusion processes in the rat small intestine in vivo. In addition, pretreatment of rats with a polycation added to the drinking water impaired the small intestinal absorption of methyl alpha-D-glucoside as subsequently measured by the tissue accumulation technique in vitro. Since polycations are hardly absorbed in the intestine, but do attach to negatively charged groups at the mucosal surface, polycations may be useful to study the influence of these negative groups on the absorption of nutrients and drugs.

Animals↗

PubMed1991

Evidence for the in vivo formation of ascorbic acid 2-O-alpha-glucoside in guinea pigs and rats.

In vivo formation of ascorbic acid 2-O-alpha-glucoside (AA-2G) in guinea pigs and rats given ascorbic acid (AA) orally in combination with maltose was examined. A metabolite of AA which has the same HPLC retention characteristics as authentic AA-2G was detected in the blood, urine and liver of guinea pigs 1-2 hr after their administration. The metabolite was isolated from the urine by chromatographic procedures and identified as AA-2G by its UV spectrum, non-reducibility, susceptibility to alpha-glucosidase hydrolysis, HPLC profile and elementary analysis. The same glucoside was also synthesized by rats and found in the urine, although it could not be determined qualitatively in the blood. AA-2G-forming activities of tissue homogenates from both animals were apparently correlated with their alpha-glucosidase activities and, moreover, both activities were completely inhibited by a specific neutral alpha-glucosidase inhibitor. Thus, we conclude that AA-2G is a possible metabolite produced by enzymatic alpha-glucosidation after a combined administration of AA and maltose to guinea pigs and rats.

Animals↗

PubMed1996

Dhurrin-6'-glucoside, a cyanogenic diglucoside from Sorghum bicolor.

A novel cyanogenic diglucoside has been isolated from methanolic extracts of young seedlings of Sorghum bicolor. Its structure was established as dhurrin-6-glucoside from NMR, mass spectrometry and enzymatic hydrolysis data. Compared with dhurrin, which is the major cyanogenic glucoside in sorghum leaves, dhurrin-6-glucoside occurs only in low concentrations. In contrast, however, the diglucoside is present in significant amounts in guttation droplets of young Sorghum seedlings. The presence of the diglucoside and its occurrence in apoplasmic exudates supports the hypothesis that diglucosides represent metabolites of cyanogenic monoglucosides which can be translocated within the plant.

Hydrolysis↗

PubMed2003

Anthocyanins with 4'-glucosidation from red onion, Allium cepa.

The anthocyanins, cyanidin 3-O-(3"-O-beta-glucopyranosyl-6"-O-malonyl-beta-glucopyranoside)-4'-O-beta-glucopyranoside, cyanidin 7-O-(3"-O-beta-glucopyranosyl-6"-O-malonyl-beta-glucopyranoside)-4'-O-beta-glucopyranoside, cyanidin 3,4'-di-O-beta-glucopyranoside, cyanidin 4'-O-beta-glucoside, peonidin 3-O-(6"-O-malonyl-beta-glucopyranoside)-5-O-beta-glucopyranoside and peonidin 3-O-(6"-O-malonyl-beta-glucopyranoside) have been isolated in minor amounts from pigmented scales of red onion, Allium cepa, in addition to six known anthocyanins. The structures were established mainly by extensive use of 2D NMR spectroscopy and electrospray LC-MS. With exception of cyanidin 4'-glucoside and cyanidin 3,4'-diglucoside reported from Hibiscus esculentus with inadequate documentation, this is the first identification of anthocyanins with 4'-glycosidation. Compared to cyanidin 3-glycosides the cyanidin 4'-glucoside derivatives showed hypsochromic shifts of visible lambda(max) and hyperchromic effects on wavelengths around 440 nm, similar to pelargonidin 3-glycosides.

Anthocyanins↗

PubMed2004

Iridoid glucosides of Paederota lutea and the relationships between Paederota and Veronica.

In a chemical investigation of the water soluble compounds in Paederota lutea eight known iridoids were isolated together with a new one with a 8,9-double bond, namely paederotoside (10-O-benzoyl-6'-O-alpha-arabino(1-->6)-beta-glucopyranosyl arborescosidic acid) and the 6-hydroxy-flavone glucoside 4'-O-methylscutellarein 7-O-beta-glucopyranoside. The known iridoid glucosides were 8-epiloganic acid, gardoside, aucubin, catalpol and the 6-O-esters of catalpol: veronicoside, catalposide, amphicoside and verproside. The compounds isolated show that Paederota has a glycoside content almost identical to that of a general Veronica species, and this is in good agreement with the results from recent investigations of the phylogeny of Veronica and its closest relatives, where Paederota is placed as a sister-group next to Veronica. In an analysis of the iridoid glucosides from some of these relatives, it is shown that Veronica, Paederota, Picrorhiza and Veronicastrum are all characterized by containing 6-O-esters of catalpol. Some less closely related taxa namely: Lagotis, Wulfenia, Plantago, Aragoa and Globularia instead contain 10-O-esters of catalpol or aucubin.

Iridoids↗

PubMed2003

Determination of five major iridoid glucosides in Flos Lonicerae by high-performance liquid chromatography coupled with evaporative light scattering detection.

This study presents a new HPLC method using evaporative light scattering detection for the simultaneous determination of live major iridoid glucosides, namely 7-epi-loganin, sweroside, loganin, 7-epi-vogeloside, and secoxyloganin in Flos Lonicerae, an important traditional Chinese medicinal herb. The optimal conditions of separation and detection were achieved on a C18 analytical column with an isocratic mobile phase consisting of methanol-water (30:70, v/v) containing 0.5% acetic acid at the flow-rate of 1.0 ml/min, temperature for the detector drift tube set at 90 degrees C and the nitrogen flow-rate of 2.6 l/min. The limit of detection (S/N = 3) is less than 35.1 microg/ml and the limit of quantification (S/N = 10) is less than 140.1 microg/ml. All calibration curves show good linear regression (r2>0.996) within test ranges. This method provides good reproducibility for the quantification of the major iridoid glucosides in four Lonicera species with overall intra- and inter-day variation of less than 5% and 9%, respectively. The assay was successfully applied to quantify the main iridoid glucosides in the herb and to identify the botanical origin of Flos Lonicerae.

Chromatography, High Pressure Liquid↗

PubMed2003

High-performance liquid chromatographic analysis of secoisolariciresinol diglucoside and hydroxycinnamic acid glucosides in flaxseed by alkaline extraction.

A HPLC method was developed for the analysis of secoisolariciresinol diglucoside (SDG) and hydroxycinnamic acid glucosides in milled defatted flaxseed flour. Direct extraction by 1 M NaOH for 1 h at 20 degrees C resulted in a higher yield than that obtained by hydrolysis of alcoholic extracts. An internal standard, o-coumaric acid, was used and the method was found to be easy, fast, and with good repeatability. On dry matter basis, different samples of flaxseeds varied considerably in their content of (+)-SDG (11.9-25.9 mg/g), (-)-SDG (2.2-5.0 mg/g), p-coumaric acid glucoside (1.2-8.5 mg/g), and ferulic acid glucoside (1.6-5.0 mg/g).

Alkalies↗

PubMed1998

Optimization of the enzymatic synthesis of butyl glucoside using response surface methodology

Enzymatic synthesis of butyl glucoside by beta-glucosidase from bitter almonds was optimized using response surface methodology (RSM). Empirical models were developed to describe relationships between the operating variables (temperature, water/butanol volume ratio, glucose concentration, enzyme concentration) and responses (butyl glucoside concentration, conversion yield). Statistical analysis indicated that the four factors had significant effects on the butyl glucoside synthesis. Optimal concentration (41.6 g/L) was reached when the operating conditions were temperature (44.7 degreesC), water/butanol volume ratio (17.6%), glucose concentration (199.2 g/L), and enzyme concentration (2.5 g/L). Good agreement between predicted and measured data at the predicted optimal conditions confirmed the usefulness of the model. Synthesis at a laboratory pilot scale was successful.

Journal Article↗

PubMed2002

Determination of flavonol metabolites in plasma and tissues of rats by HPLC-radiocounting and tandem mass spectrometry following oral ingestion of [2-(14)C]quercetin-4'-glucoside.

Epidemiological studies suggest that consumption of flavonol-rich diets decreases the risk of developing heart disease and certain cancers. Recent studies have detected flavonol conjugates in blood and urine following various dietary interventions. To assess to what extent flavonols also accumulate in tissues, where they might be expected to exert anti-carcinogenic and anti-atherogenic effects, [2-(14)C]quercetin-4'-glucoside was synthesized and fed to rats. After 60 min, 93.6% of the ingested radioactivity was recovered from the intestine, incorporated into 18 metabolites that had undergone deglycosylation followed by varying degrees of glucuronidation, methylation, and/or sulfation. [(14)C]Quercetin, the aglycon of the radiolabeled substrate, was present in the intestine and in trace amounts in the liver but was not detected in the plasma and kidneys. The original [2-(14)C]quercetin-4'-glucoside was detected exclusively in the intestine, where it accounted for only 26.2% of the radioactivity. The remainder of the recovered radioactivity was located mainly in the plasma, liver, and kidneys as (14)C-labeled metabolites. However, compared to the quantities in the gastrointestinal tract, the levels of metabolites in plasma and body tissues were very low, indicating only limited absorption into the blood stream. The data demonstrate that quercetin-4'-glucoside, which is a major flavonol in onions, undergoes rapid and extensive metabolism in the intestine, and this appears not to be associated to any extent with transport across the gut wall into the blood stream.

Animals↗