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At least 55 records · Page 3Linked to original sources
PubMed1999

The cyanogenic glucoside, prunasin (D-mandelonitrile-beta-D-glucoside), is a novel inhibitor of DNA polymerase beta.

A DNA polymerase beta (pol. beta) inhibitor has been isolated independently from two organisms; a red perilla, Perilla frutescens, and a mugwort, Artemisia vulgaris. These molecules were determined by spectroscopic analyses to be the cyanogenic glucoside, D-mandelonitrile-beta-D-glucoside, prunasin. The compound inhibited the activity of rat pol. beta at 150 microM, but did not influence the activities of calf DNA polymerase alpha and plant DNA polymerases, human immunodefficiency virus type 1 reverse transcriptase, calf terminal deoxynucleotidyl transferase, or any prokaryotic DNA polymerases, or DNA and RNA metabolic enzymes examined. The compound dose-dependently inhibited pol. beta activity, the IC(50) value being 98 microM with poly dA/oligo dT(12-18) and dTTP as the DNA template and substrate, respectively. Inhibition of pol. beta by the compound was competitive with the substrate, dTTP. The inhibition was enhanced in the presence of fatty acid, and the IC(50) value decreased to approximately 40 microM. In the presence of C(10)-decanoic acid, the K(i) value for substrate dTTP decreased by 28-fold, suggesting that the fatty acid allowed easier access of the compound to the substrate-binding site.

Amygdalin↗
PubMed2002

Modulation of proton pumping across proteoliposome membranes reconstituted with tonoplast H(+)-ATPase from cultured rice (Oryza sativa L. var. Boro) cells by acyl steryl glucoside and steryl glucoside.

Tonoplast H(+)-ATPase purified from cultured rice cells (Oryza sativa L. var. Boro) was reconstituted into asolectin liposomes containing steryl glucoside (SG) or acyl steryl glucoside (ASG), and the effects of SG and ASG on proton pumping, ATP-hydrolysis activity and proton permeability of the proteoliposome membranes were investigated. In the proteoliposomes containing 10 mol% SG, proton pumping and ATP-hydrolysis activity were increased to around 140% of those in SG-free proteoliposomes. In the proteoliposomes containing ASG, proton pumping and ATP-hydrolysis activity were decreased to one-tenth of those in ASG-free proteoliposomes at 15 mol% ASG; however, activity increased again slightly in the range between 20 and 40 mol% ASG. The change in proton pumping across the proteoliposome membrane is not due to a change of proteoliposome size nor to the location of the catalytic site of the tonoplast H(+)-ATPase in the proteoliposomes. SG and ASG also reduced the passive proton permeability of the proteoliposomes. These results show that SG and ASG modulate proton pumping across the tonoplast toward stimulation and depression, respectively, and they reduce the passive proton permeability of the tonoplast.

Biological Transport↗
PubMed2004

Regioselective enzymatic acetylation of the aglycone moiety of a secoiridoid glucoside. Two new secoiridoid glucoside acetates.

Candida antarctica lipase (CAL) catalyses the regioselective acetylation of the 10-hydroxyl group of 10-hydroxyoleoside dimethyl ester, a secoiridoid glucoside, using THF as a solvent and ethyl acetate or vinyl acetate as acetyl group suppliers. Two acetyl derivatives at 3'- and 6'-sites of the glucosidic ring of 10-acetoxyoleoside dimethylester, not previously described, were obtained by acetylation in the same conditions.

Acetylation↗
PubMed2006

The flavonol quercetin-3-glucoside inhibits cyanidin-3-glucoside absorption in vitro.

At present, little is known about the mechanisms responsible for intestinal absorption of anthocyanins (ACNs). For example, it has not yet been established if ACNs are absorbed through an active transport mechanism, such as the sodium-dependent glucose transporter (SGLT1), or by passive diffusion. Previously, we found that the absorption of ACNs differs between regions of the digestive tract and is maximal in the jejunum, suggesting that an active transport mechanism is involved. In the present study, we examined the effect of d-glucose (main substrate of SGLT1), phloridzin (inhibitor of SGLT1), and quercetin-3-glucose (Q3G, a flavonol) on the absorption of cyanidin-3-glucoside (C3G; approximately 5 micromol/L) by mouse jejunum mounted in Ussing chambers. We found that the presence of either D-glucose (10, 20, and 40 mmol/L) or phloridzin (50, 100, and 200 micromol/L) resulted in a small but insignificant inhibition of C3G disappearance from the mucosal solution (decrease of disappearance with glucose, 33%; with phloridzin, 18%; NS). However, when the flavonol Q3G (50 micromol/L) was added to the mucosal solution together with the C3G, the disappearance of C3G was significantly decreased (74%; p < 0.001), and Q3G disappeared instead. In addition, we found phloretin and quercetin, the aglycones of phloridzin and Q3G, respectively, present in the mucosal solution and tissue extracts, indicating hydrolysis of these compounds by the enterocytes of the jejunum. In contrast, the aglycone cyanidin was not detected at all. Our results show that in the mouse small intestine, ACN absorption is not solely dependent on the activity of the SGLT1 transporter, as d-glucose and phloridzin had only a slight effect on uptake. Q3G, however, clearly inhibited C3G disappearance. These results suggest that there might be a competitive inhibition between C3G and Q3G absorption. It is possible that an absorption mechanism other than the SGLT1 is involved, which has a structural preference toward flavonols.

Animals↗
PubMed1999

Intestinal absorption of acyclovir beta-glucoside: comparative study with acyclovir, guanosine, and kinetin beta-glucoside.

PURPOSE: To characterize the intestinal absorption of a beta-glucose conjugate of acyclovir (9-[(2-hydroxyethoxy) methyl] guanine, ACV) and compare it to ACV and its analogues in terms of stability and transport by Na+/glucose cotransporter (SGLTI). METHODS: ACVbeta(glc) was enzymatically synthesized using cellulase. Intestinal absorption experiments were performed with rat everted small intestine. Conformation of the glucose moiety was analyzed by NMR spectroscopy. RESULTS: The ACVbeta(glc) was stable on the mucosal side, and was transported to the serosal side in all regions of the small intestine. However, significant contribution of SGLTI to the transport of ACVbetaglc was not observed. NMR spectroscopic analysis indicated that the glucose conformation of ACVbeta(glc) was the 4C1 chair form, identical to beta-glucose or SGLT1-transportable beta-glucosides reported previously. Therefore, other factors such as molecular size and charge due to aglycone may cause no transport of ACVbeta(glc) by SGLT1. On the other hand, the hydrophilicity of ACVbeta(glc) was much higher than of ACV, suggesting water solubility-derived improvement of intestinal absorption of ACV. CONCLUSIONS: ACVbeta(glc) is stable and absorbable, but it is not transported by SGLT1. No involvement of SGLT1 in the ACVbeta(glc) transport is not due to glucose conformation.

Acyclovir↗
PubMed2002

Intestinal brush border membrane catalyzes hydrolysis of pyridoxine-5'-beta-D-glucoside and exhibits parallel developmental changes of hydrolytic activities toward pyridoxine-5'-beta-D-glucoside and lactose in rats.

Pyridoxine-5'-beta-D-glucoside (PNG) is a major form of vitamin B-6 in plant foods that exhibits partial bioavailability as vitamin B-6 in humans. We previously identified an intestinal mucosal cytosolic PNG hydrolase that catalyzes the partial hydrolysis of PNG absorbed without prior deglycosylation. Recent observations that the brush border membrane also catalyzes PNG hydrolysis led to the hypothesis that PNG hydrolysis may be another function of the beta-glucosidase lactase-phlorizin hydrolase (LPH) and, thus, brush border PNG hydrolysis would undergo a developmental decline similar to that of lactose hydrolysis. In this study, the relationships among hydrolytic activities in small intestinal cytosolic and brush border fractions in rats (n = 9 per group) of various ages (1-2 d and 2, 4, 8, 12 and 24 wk) were examined. In vitro specific activities toward PNG and lactose were greater in brush border than cytosol, and these were greater in newborn rats than in all other age groups (P < 0.01). Brush border activities toward PNG and lactose and were closely correlated (r = 0.84; P < 0.0001). These findings suggest that the hydrolysis of PNG is catalyzed at least partially at the brush border and that the bioavailability of PNG may be influenced by the residual LPH activity in children and adults.

Animals↗
PubMed2004

beta-Sitosterol, beta-Sitosterol Glucoside, and a Mixture of beta-Sitosterol and beta-Sitosterol Glucoside Modulate the Growth of Estrogen-Responsive Breast Cancer Cells In Vitro and in Ovariectomized Athymic Mice.

We hypothesized that the phytosterols beta-sitosterol (BSS), beta-sitosterol glucoside (BSSG), and Moducare (MC; BSS:BSSG = 99:1) could modulate the growth of estrogen-dependent human breast cancer cells in vitro and in vivo. The present study evaluated the estrogenic and antiestrogenic effects of BSS, BSSG, and MC (0.001 to 150 micromol/L) on the proliferation of Michigan Cancer Foundation 7 (MCF-7) cells in vitro. Both BSS (>1 micromol/L) and MC (>50 micromol/L) increased MCF-7 cell proliferation. Treatment with 150 micro mol/L of BSS and MC increased cell growth by 2.4 and 1.5 times, respectively, compared to the negative control (NC) group. However, BSSG had no effect at the concentrations tested. The effects of dietary BSS, BSSG, and MC on the growth of MCF-7 cells implanted in ovariectomized athymic mice were also evaluated. Estrogenic effects of the phytosterols were evaluated in the NC, BSS, BSSG, and MC treatment groups, and antiestrogenic effects were evaluated in the 17 beta-estradiol (E(2)), E(2) + BSS, E(2) + BSSG, and E(2) + MC treatment groups. Mice were treated with dietary BSS (9.8 g/kg AIN93G diet), BSSG (0.2 g/kg diet), or MC (10.0 g/kg diet) for 11 wk. Dietary BSS, BSSG, and MC did not stimulate MCF-7 tumor growth. However, dietary BSS, BSSG, and MC reduced E(2)-induced MCF-7 tumor growth by 38.9% (P < 0.05), 31.6% (P = 0.08), and 42.13% (P < 0.05), respectively. The dietary phytosterols lowered serum E(2) levels by 35.1, 30.2, and 36.5% in the E(2) + BSS, E(2) + BSSG, and E(2) + MC groups, respectively (P < 0.05), compared to that of the E(2) treatment group. Estrogen-responsive pS2 mRNA expression in tumors did not differ among groups, but expression of the antiapoptotic marker B-cell lymphoma/leukemia-2 (bcl-2) in tumors from the E(2) + MC group was downregulated, compared to that of the E(2) treatment group. In summary, BSS and MC stimulated MCF-7 cell growth in vitro. Although BSSG comprises only 1% of MC, BSSG made MC less estrogenic than BSS alone in vitro. However, dietary BSS and MC protected against E(2)-stimulated MCF-7 tumor growth and lowered circulating E(2) levels.

Animals↗
PubMed2004

Acetophenone C-glucosides and stilbene O-glucosides in Upuna borneensis.

Three acetophenone C-glycosides; 2,4,6-trihydroxyacetophenone 3-C-beta-(2'-O-p-hydroxybenzoyl)-glucopyranoside, 2,4,6-trihydroxyacetophenone 3-C-beta-(2'-O-E-coumaroyl)-glucopyranoside, 2,4,6-trihydroxyacetophenone 3-C-beta-(2'-O-E-cinnamoyl)-glucopyranoside, and two resveratrol O-glycosides; piceid 2'-O-p-hydroxybenzoate and, piceid 2'-O-E-ferulate, together with three known compounds were isolated from the acetone soluble part of stem of Upuna borneensis (Dipterocarpaceae). The structures of isolates were determined by spectral analysis including extensive 2D-NMR spectral analyses.

Acetophenones↗
PubMed2002

Synthesis of an ether-linked alkyl 5a-carba-beta-D-glucoside, a 5a-carba-beta-D-galactoside, a 2-acetamido-2-deoxy-5a-carba-beta-D-glucoside, and an alkyl 5a'-carba-beta-lactoside.

For the purpose of providing biologically stable building blocks for the biocombinatorial synthesis using a living cell, some ether-linked alkyl 5a-carba-beta-D-glycoside primers were prepared. The key step of the synthesis was coupling of 1-bromo-n-alkanes with the 1-OH unprotected derivatives of 5a-carba-sugar analogues of D-glucose, D-galactose, and 2-acetamido-2-deoxy-D-glucose (N-acetyl-D-glucosamine), in DMF in the presence of sodium hydride. Alternatively, alkyl carba-lactoside was synthesized by incorporation of a 5a-carba-beta-D-galactose residue into the 4-position of dodecyl beta-D-glucopyranoside. A strong and specific inhibition of beta-galactosidase (K(i) 0.67 microM, bovine liver) was found for dodecyl 5a-carba-beta-D-galactopyranoside.

Animals↗
PubMedDate not supplied

Effects of naturally occurring glucosides, solasodine glucosides, ginsenosides and parishin derivatives on multidrug resistance of lymphoma cells and leukocyte functions.

Solamargine, solasonine, ginsenosides and parishin-related compounds were investigated for their effects on mdr efflux pump of lymphoma cells, and their effects on T cell proliferative assays and cell mediated immune functions, antibody-dependent cellular cytotoxicity (ADCC) and natural killer (NK) cell activity of human peripheral mononuclear cells. Solamargine and solasonine were the only drugs which inhibited all of the tested immune functions; however, ginsenoside Rc and Rd enhanced T cell proliferative assays and marginally increased the NK cell activity. The majority of the compounds were not able to reverse the multidrug resistance of mouse lymphoma cells. However, ginsenosides Rc, Rd and parishin C were able to moderately reduce the activity of the efflux pump. Parishin, parishin C and crude extract significantly enhanced the ADCC reaction.

Animals↗