PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “alpha-Cyclodextrins”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources
PubMed1992

Preparation of di-O-triphenylmethyl-(trityl-) cyclomaltohexaoses and -cyclomaltoheptaoses and characterization of three positional isomers of each by the "hex-5-enose degradation".

Regioisomeric 6(1),6n-di-O-trityl-cyclomaltohexaoses (cG6s) or -cyclomaltoheptaoses (cG7s) were prepared by the reaction of cyclomaltohexaose (1, cG6) or cylomaltoheptaose (5, cG7) with chlorotriphenyl-methane in pyridine and isolation by h.p.l.c. The regiochemical determination of each three ditrityl-substituted derivatives has been accomplished by the "hex-5-enose degradation", followed by measurement of their f.a.b.-mass spectra.

Carbohydrate Conformation↗
PubMed1991

The utility of 2-hydroxypropyl-beta-cyclodextrin as a vehicle for the intracerebral and intrathecal administration of drugs.

The substituted glucopyranose ring structure 2-hydroxypropyl-beta-cyclodextrin (CDEX) increases the solubility of molecules by inclusion of the agent in the lipophilic interior of the ring. This property is of particular use for the administration of molecules by the intracerebral (ICV) or intrathecal (IT) routes. In concentrations up to 40% w/v (isotonic), this agent (10 microliters) effect upon nociceptive or motor function after IT injection or on EEG and general behavior after ICV injection in rats. Using 20% CDEX, there is no change in the ED50 as compared to saline on the hot plate (HP) after IT injection of morphine, D-Ala2-D-Leu5 enkephalin or Tyr-Aib-Gly-gPhe-mAib-NH2, (Aib: alpha-aminoisobutyric acid) although there is an increase in their respective durations of effect. Cyclic peptide opioids: Tyr-c[D-A2bu-Gly-D-beta Nal(1)-D-Leu] (A2bu: alpha, gamma-diaminobutyric acid; beta-Nal(1): beta-naphthylalanine(1)) or Tyr-c[DA2bu-Gly-beta Nal(1)-D-Leu] are insoluble in saline but are readily dissolved in CDEX, and display a naloxone-sensitive antinociception following spinal administration. In other studies, saline insoluble capsaicin is administered in 25% dimethylsulfoxide (DMSO) or 20% CDEX (15 microliters; 5 mg/ml) which result in a significant reduction in the spinal levels of substance P and calcitonin gene related peptide and an increase in the HP latency. DMSO alone, but not CDEX alone, reduces the levels of the two peptides. These data emphasize the utility of complexation with CDEX for intracerebral drug delivery and compatibility with brain and spinal tissue.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed1991

Structural effects on the binding of amine drugs with the diphenylmethyl functionality to cyclodextrins. II. A molecular modeling study.

Molecular modeling has been used to study the complexation between alpha, beta, or gamma-cyclodextrin (CD) and a group of amine compounds having the diphenylmethyl functionality. The computer program SYBYL 5.3 and the Tripos force field (version 5.2) were used for all the calculations. Three-dimensional structures of 13 amine compounds were built individually from their atoms, and CDs were built based on the X-ray crystallographic coordinates. The diphenylmethyl derivative-CD complexes were constructed and optimized. Based on the calculated binding energies accompanying the inclusion process, the preferred method of approach of the compounds to the cavities of the CD molecules, and the structural effects on the binding between amine compounds and three CDs were explored. The calculated binding energies exhibited a good correlation with the stability constants obtained from solution calorimetric titrations. The present study shows that for similar ligand molecules, the molecular modeling technique should enable us to visualize the structure of the inclusion complexes and will also assist us in determining the ability of a potential drug molecule to form a stable complex with CDs.

Amines↗
PubMed1988

Purification and characterization of a novel thermostable beta-amylase from Clostridium thermosulphurogenes.

An extracellular beta-amylase from Clostridium thermosulphurogenes was purified 811-fold to homogeneity, and its general molecular, physico-chemical and catalytic properties were determined. The native enzyme was a tetramer of 210 kDa composed of a single type subunit; its 20 amino acid N-terminus displayed 45% homology with Bacillus polymyxa beta-amylase. The beta-amylase was enriched in both acidic and hydrophobic amino acids. The pure enzyme displayed an isoelectric point of 5.1 and a pH activity optimum of 5.5. The optimum temperature for beta-amylase activity was 75 degrees C, and enzyme thermostability at 80 degrees C was enhanced by substrate and Ca2+ addition. The beta-amylase hydrolysed amylose to maltose and amylopectin and glycogen to maltose and limit dextrins, and it was inhibited by alpha- and beta-cyclodextrins. The enzyme displayed kcat. and Km values for boiled soluble starch of 400,000 min-1 per mol and 1.68 mg/ml, respectively. The enzyme was antigenically distinct from plant beta-amylases.

Amino Acid Sequence↗
PubMed1991

Rapid smooth muscle cell growth and endogenous prostaglandin system in spontaneously hypertensive rats.

Vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) exhibit rapid cell growth. In this study, to reveal the mechanisms of the quick VSMC growth, we analyzed the alterations in the respective periods of the proliferating cell cycle, and investigated the role of the endogenous prostaglandin system in this rapid cell growth. The VSMC from SHR showed increased [3H]thymidine uptake and shortened doubling time, compared with Wistar-Kyoto rats (WKY). These properties were mainly due to both shortened transition time from G0/G1 to S and shortened G2 duration. There was a difference neither in the DNA-replication rate nor in the mitotic period. Generating capacity for vasodepressor prostaglandins was significantly reduced in the VSMC from SHR, particularly in the G0/G1 period. When the endogenous prostaglandin synthesis was inhibited by 10(-5) mol/L indomethacin, the transition from G0/G1 to S was shortened. This alteration was eliminated by supplementation with OP41483, a stable prostacyclin analog. In contrast, the alteration in the G2 duration was unaffected by indomethacin. These data indicate that the rapid VSMC growth in SHR is mainly due to the shortening of both the G0/G1 and G2 period, and that the impaired prostaglandin system is responsible, at least in part, for the shortened G0/G1 duration.

Animals↗
PubMed1986

Interaction of soybean beta-amylase with glucose.

The interaction of soybean beta-amylase with glucose was investigated by inhibition kinetics studies and spectroscopic measurements. The inhibition type, inhibitor constant (Ki) and dissociation constant (Kd) of beta-amylase-glucose complex were dependent on pH. At pH 8.0, glucose behaved as a competitive inhibitor (Ki = 34 mM). Binding of glucose produced a characteristic difference spectrum and a change of circular dichroism (CD) at pH 8.1. By using difference absorbance at 292 nm and difference ellipticity at 290 nm, Kd values for beta-amylase-glucose complex were determined to be 45 and 46 mM, respectively. In contrast to pH 8.0, glucose behaved as a mixed-type inhibitor (Ki = 320 mM) at pH 5.4. The Kd values obtained from the difference spectrum were increased by lowering the pH from 8. The pH dependence of the Ki and Kd values suggested that one ionizable group of pK = 8.0, which is shifted to 6.9 by the binding of glucose, controls the binding affinity of glucose. The binding of glucose competed with the binding of cyclohexaamylose and maltose at pH 8.0. The modification of SH groups of the enzyme affected the binding of glucose but did not affect the binding of maltose or cyclohexaamylose at pH 8.0. It was concluded from these results that the binding site of glucose is different from that of maltose and cyclohexaamylose. Presumably, glucose may bind to the subsite 1 of soybean beta-amylase.

Amylases↗
PubMed1989

Differential effects of alpha-, beta- and gamma-cyclodextrins on human erythrocytes.

Alpha-, beta- and gamma-cyclodextrins are cyclic hexamers, heptamers, and octamers of glucose, respectively, and thus are hydrophilic; nevertheless, they have the ability to solubilize lipids through the formation of molecular inclusion complexes. The volume of lipophilic space involved in the solubilization process increases with the number of glucose units in the cyclodextrin molecule and, consequently, cyclodextrins were found to have different effects on human erythrocytes: (a) in the induction of shape change from discocyte to spherocyte the potency was observed to be alpha greater than gamma, but with beta-cyclodextrin hemolysis occurred before the change was complete; (b) in the increase of fluorescence intensity of 1-anilinonaphthalene-8-sulfonate in cyclodextrin-pretreated membranes, the observed potency was beta much greater than gamma greater than alpha; (c) in the release of potassium and hemoglobin, the potency was beta greater than alpha greater than gamma. The potencies of cyclodextrin for solubilizing various components of erythrocytes were alpha greater than beta much greater than gamma for phospholipids, beta much greater than gamma greater than alpha for cholesterol and beta much greater than gamma greater than alpha for proteins. The solubilization potencies were derived from concentration/final-effect curves. The above processes occurred without entry of solubilizer into the membrane, since (a) beta-[14C]cyclodextrin did not bind to erythrocytes and (b) cyclodextrins did not enter the cholesterol monolayer. A study of the [3H]cholesterol in erythrocytes indicated that beta-cyclodextrin extracted this lipid from membrane into a new compartment located in the aqueous phase which could equilibrate rapidly with additional erythrocytes. Therefore, the effects of cyclodextrins differ from those of detergents which first incorporate themselves into membranes then extract membrane components into supramolecular micelles.

Cyclodextrins↗
PubMed1992

Preparation of three positional isomers of diglucosyl-cyclomaltohexaose.

Three positional isomers of diglucosyl-cyclomaltohexaose (diglucosyl-cG6) were chemically synthesized via 6(1),6(2)-, 6(1),6(3)-, and 6(1),6(4)-di-O-(TERT-butyldimethylsilyl)-cG6S (1, 2, and 3) prepared regiospecifically. Glucosylation of bis(2,3-di-O-acetyl)tetrakis(2,3,6-tri-O-acetyl)-CG6S obtained from the three regioisomeric compounds 1, 2, and 3 with 2,3,4,6-tetra-O-benzyl-1-O-trichloroacetimidoyl-alpha-D-glucopyran ose, followed by debenzylation and then deacetylation, afforded 6(1),6(2)-, 6(1),6(3)-, and 6(1),6(4)-di-O-(alpha-D-glucopyranosyl)-cG6S (10, 11, and 12) together with configurational isomers. The desired compounds 10, 11, and 12 containing two (1----6)-alpha-linkages were isolated from the mixtures of their configurational isomers by high performance liquid chromatography. The three diglucosyl-cG6S synthesized chemically were used as authentic samples to identify the components in a mixture of diglucosyl-cG6S produced by an enzymatic process.

Carbohydrate Sequence↗
PubMed1992

Bile acid and sterol solubilization in 2-hydroxypropyl-beta-cyclodextrin.

The use of 2-hydroxypropyl-beta-cyclodextrin has made it possible to prepare stable aqueous solutions of cholesterol, 26-hydroxycholesterol, 7 alpha-hydroxycholesterol, and monohydroxy bile acids such as lithocholic and 3 beta-hydroxy-5-cholenoic acids. These solutions are suitable for cell culture studies and for parenteral administration to animals.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed1989

[Preventive effect of OP-41483-alpha-CD on cyclosporine A-induced renal tubular and arterial damages].

The aim of this study is to test whether a stable analogue prostaglandin I2 (OP-41483-alpha-CD) (OP) is effective to prevent Cyclosporine A (CsA)-induced nephrotoxicity. Male Lewis rats were administrated with CsA (50 or 100 mg/kg/day, per os) and treated with OP (25 micrograms/kg/day, subcutaneously). For the quantitativeness of qualitative changes, percent area of tubular vacuolization and the grade of renal arteriolar changes were evaluated at light microscopic level, then further examined under electron microscopy. CsA trough levels in the whole blood were also analyzed with HPLC and prostaglandin I2 was assayed by radioimmunoassay of its stable degeneration product 6-keto-PGF1-alpha. As a result, 1) ultrastructurally, perinuclear vacuoles in arteriolar media consisted of cellular intervaginated cytoplasmic processes of neighboring cells, suggesting spastic vasoconstriction induced by CsA, 2) survival rate of OP-treated rats were significantly high compared to that of rats with CsA alone, 3) pathologically, tubular and arterial damages were reduced in OP-treated models, 4) pharmacokinetic studies revealed that CsA trough levels were not different from those of CsA-received alone and OP-treated models, and 5) mean blood 6-keto-PGF1-alpha excretion in rats given CsA was higher than in normal rats.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

The effect on the cornea of alpha cyclodextrin vehicle for cyclosporin eye drops.

We tested four different combinations of alpha-CD and CYA: 0.075% and 80 mg/mL alpha-CD, 0.025% CYA and 40 mg/mL alpha-CD, 0.009% CYA and 20 mg/mL alpha-CD, and 0.003% CYA and 10 mg/mL alpha-CD. We found that 0.025% CYA (alpha-CD[40 mg/mL]) resulted in the least corneal toxicity and penetrated in the cornea 5 to 10 times more than did lipophilic vehicle with CYA.

Administration, Topical↗