Succinate Ester Research Articles

Stimulation of Biosynthetic Activity by Novel Succinate Esters in Rat Pancreatic Islets

Selected esters of succinic acid are currently under investigation as possible insulinotropic agents for the treatment of noninsulin-dependent diabetes mellitus. The aim of the present study was to investigate the effects of ten novel esters of succinic acid upon biosynthetic activity in rat pancreatic islets. In the absence of any other exogenous nutrient, glycerol-3-hydroxy-1,2-dimethyl succinate (0.5 mM), d-arabitol-5-hydroxy-1,2,3,4-tetramethylsuccinate (0.5 mM), and 4-tert-butylsuccinate (2.5 mM) exerted little or no effect upon l-[4- 3H]phenylalanine incorporation into trichloroacetic acid-precipitable material. A modest but significant increase in biosynthetic activity to approximately 150% of basal value was found in the presence of l-threitol-1,2,4-trimethylsuccinate (2.0 mM) and ethanediol-1,2-diethylsuccinate (2.5 mM). A two- to five-fold increase in protein biosynthesis was observed in islets exposed to propanediol-1,2-dimethylsuccinate, glycerol-1,2-dimethylsuccinate-3-hydrogenosuccinate, l-threitol-3-succinoyl-1,2,4-trimethylsuccinate, glycerol-1,2-dimethylsuccinate or ethanediol-1,2-dimethylsuccinate (2.5 mM each), these esters being mentioned in order of increasing biological efficiency. There was a significant correlation between these results and the insulinotropic action of the same esters. The present findings thus reinforce the view that such esters act as nutrients in islet cells and, therefore, offer the advantage over pharmacological agents currently used for the treatment of type-2 diabetes in stimulating both the biosynthetic and secretory activity of insulin-producing B-cells.

The myelotoxicity of chloramphenicol: in vitro and in vivo studies: II: in vivo myelotoxicity in the B6C3F mouse

1. Chloramphenicol continues to be widely used in many parts of the world despite its known haematotoxicity. Until now, elucidation of the mechanisms involved and any attempt at amelioration of the toxic effects have been hampered by the lack of an animal model. 2. In this study neither acute nor chronic administration of chloramphenicol as its succinate ester in the drinking water produced anaemia in mice as assessed by changes in peripheral blood parameters. 3. Chloramphenicol could not be detected in the bone marrow when the antibiotic was administered either in the drinking water or by gavage, although it was detected in the serum. 4. In marrow taken from mice after chloramphenicol succinate administration and cultured in vitro, depression of the differentiation of immature committed erythroid progenitors occurred 15 min after administration of the antibiotic by gavage. However, recovery was beginning to occur at 48 h after administration of chloramphenicol succinate at 50 and 200 mg/kg and this was then followed by an 'overshoot' response at the higher dose. A toxic effect was therefore achieved in the bone marrow but this was probably masked in the peripheral blood by enhanced proliferation. 5. Morphological evidence of apoptosis was seen in erythroid and myeloid precursors in mice treated with 200 mg/kg. 6. The data suggest that the effect of chloramphenicol was at the differentiation stage of the committed marrow progenitor cells rather than at the replication stage of the stem cells and therefore this response appears to mimic the reversible bone marrow depression seen in the treated patient.

Investigation of far red dyes for use in peroxyoxalate chemiluminescence detection and analysis of the cy5 derivative of amantadine hydrochloride in human plasma.

Peroxyloxalate chemiluminescence is well established as a tool for improvement of selectivity and sensitivity for chemiluminophores and their derivations in HPLC eluates. Chemiluminescence in the far-red spectral region was investigated in this work to further enhance the sensitivity of chemiluminescence through more efficient singlet excitation energy transfer and to enhance the selectivity of the approach through a reduction in matrix and scatter interference. A number of fluorescent compounds that can be excited in the UV, visible and far red spectral regions were investigated for chemiluminescence yield using the bis(2,4,6-trichlorphenyl) oxylate reaction. It was found that a trend of increasing chemiluminescence with increasing excitation wavelength could be observed with cy5 providing the most efficient chemiluminescence. The succinate ester of cy5 was used to derivatize amantadine hydrochloride, an antiparkinsons drug, to form the derivative. The derivative was separated from reaction by products by C18 reversed phase HPLC and detected using a Soma S-3400 chemiluminescence detector. The detection limit for the diluted derivative was 200 femtomoles on column and sufficient for plasma analysis. Selectivity in plasma was demonstrated through derivatization of extracts of plasma that had been spiked with amantadine hydrochloride.

Haemolysis of Human Erythrocytes by alpha -Tocopheryl Succinate

Alpha-tocopheryl acid succinate. when incubated at concentrations above 100 mg l - 1 with human red blood cells in a phosphate buffer pH 7.5, caused significant haemolysis of the cells. This effect appears to be unique to the succinate ester of alpha -tocopherol, since no haemolysis was observed under equivalent conditions with alpha -tocopherol itself, succinic acid or a range of other tocopherol compounds. Haemolysis was considerably reduced when the test solutions were deaerated before adding the tocopheryl succinate, which suggests the involvement of activated oxygen species in the lysis of the red blood cells. However, no activated oxygen species could be detected in the test solutions. When used as a dietary supplement, alpha -tocopheryl succinate should not cause haemolysis, since the ester is dissociated in the gut before absorption into the blood stream, and concentrations of alpha -tocopherol in the blood normally do not exceed 15 mg l- 1. Also, calcium and magnesium in blood serum were found to...

Synergistic insulinotropic action of succinate, acetate, and glucose esters in islets from normal and diabetic rats.

Succinic acid esters are currently under investigation as possible insulinotropic tools in the treatment of noninsulin-dependent diabetes mellitus. The present article introduces three novel nutrient esters and aims mainly to explore, in both normal and GK rats, the secretory response to such esters when tested alone or in combination. It documents that in pancreatic islets from normal rats, methyl acetate (10 mM), which fails to augment basal insulin output, potentiates the secretory response to succinate dimethyl ester (also 10 mM). It also reveals that alpha-D-glucose pentaacetate (alpha GPA) (1.7 mM) stimulates insulin release in the absence of any other exogenous nutrient and even more so in the presence of succinate methyl ester. Moreover, the methyl esters of succinic acid (10 mM), when used together with either methyl acetate or alpha GPA, provoked insulin secretion in islets from diabetic GK rats incubated in the absence of D-glucose, although no significant secretory response of such islets could be detected when each of these agents was tested separately. These findings thus draw attention to the insulinotropic potential in type 2 diabetes of selected combinations of nutrient esters, including a D-glucose ester presumably able to enter into islet cells without requiring the intervention of a hexose carrier.

Anionic Synthesis of Polymers Functionalized with a Terminal Anhydride Group

Polymers bearing a single succinic anhydride at the chain end were synthesized using anionic polymerization techniques. Specifically, the living anions of poly(methyl methacrylate) (PMMA), polystyrene (PS), polyisoprene (PI), and poly(vinylpyridine) (PVP) were found to exclusively undergo a 1,4-conjugate addition reaction with di-tert-butyl maleate. Only a single maleate adds. The gel permeation chromatograms for the synthesized polymers were found to have very narrow molecular weight distributions (Mw/Mn < 1.15) after the end-capping reaction. Pyrolysis (235 °C, 2−12 h) of the resulting substituted di-tert-butyl succinate ester efficiently produced the related succinic anhydride functional polymers in the case of PMMA and PS. The functionality of these polymers (f ≥ 0.81) was determined following derivatization reactions with various amines. Nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC) of the resulting amides permits quantification of the extent of functionalization. Upon melt blending (200 °C) an anhydride terminal PMMA (29 kg/mol) with an amino terminal PS (18.5 kg/mol) all of the monofunctional homopolymers were converted to PS−PMMA diblock within 20 min (GPC and transmission electron microscopy, TEM). A lamellar morphology (TEM) was obtained after further annealing of this sample (72 h).

Alpha-Tocopheryl succinate inhibits monocytic cell adhesion to endothelial cells by suppressing NF-kappa B mobilization.

The adherence of monocytes to activated endothelium is an early event in atherogenesis. Because antioxidants have been considered to be of antiatherosclerotic potential, we investigated the effects of alpha-tocopherol (TCP) and its acetate and succinate esters on monocyte adhesion to cytokine-stimulated human umbilical vein endothelial cells (HUVEC). Endothelial cells were treated with TCP, alpha-tocopherol acetate (TCP acetate), or alpha-tocopheryl succinate (TCP succinate) before stimulation with tumor necrosis factor-alpha (TNF-alpha; 10 U/ml, 6 h) or interleukin-1 beta (IL-1 beta; 10 U/ml, 6 h). Cytokine-stimulated cell surface expression of vascular cell adhesion molecule-1 (VCAM-1, CD106) and E-selectin (ELAM-1, CD62E), but not of intercellular adhesion molecule-1 (ICAM-1, CD54), was time- and dose-dependently inhibited by TCP succinate but not by TCP or TCP acetate. TCP succinate (200 microM, 24 h) reduced TNF-induced VCAM-1 and E-selectin expression from a specific mean fluorescence intensity of 151 +/- 28 to 12 +/- 4 channels and from 225 +/- 38 to 79 +/- 21 channels, respectively. Succinate alone had no effect. Decreased adhesion molecule expression was associated with a reduction of monocytic cell adhesion. TCP succinate (20 microM, 72 h), but not TCP (200 microM, 72 h), reduced U-937 cell adhesion to TNF-alpha-stimulated (10 U/ml, 6 h) HUVEC by 30% (P < 0.025) and to IL-1 beta-stimulated HUVEC by 56% (P < 0.010). Electrophoretic mobility-shift assays of HUVEC nuclear proteins revealed a decrease in TNF-alpha-stimulated nuclear factor-kappa B (NF-kappa B) activation after pretreatment of HUVEC with TCP succinate but not with TCP, TCP acetate, or succinate alone. In conclusion, we demonstrate that the vitamin E derivative TCP succinate prevents monocytic cell adhesion to cytokine-stimulated endothelial cells by inhibiting the activation of NF-kappa B, further emphasizing the antiatherosclerotic potential of lipid soluble antioxidants.

Alkoxide-Induced Succinate Ester Formation from Alcohols and Bis(trimethylsilyl) 1,2-Bisketene

Reaction of the 1,2-bisketene (Me(3)SiC=C=O)(2) (1) with alcohols (ROH) catalyzed by LiOR gives rapid and efficient conversion to mixtures of the meso and dl succinates (Me(3)SiCHCO(2)R)(2) (4). There is a change in selectivity with the dl/meso ratio varying from 18/82 with MeOH to 92/8 for t-BuOH. This procedure occurs with minimal desilylation, which is the predominant path in the uncatalyzed reaction. Preferential attack of lithium alkoxides on the carbonyl carbon of ketenes induced by lithium coordination to the ketenyl oxygen is proposed to account for the low extent of desilylation. The stereochemical assignments of the meso and dl configurations are based upon vicinal H,H coupling constants both from a mixed succinate ester and also from (13)C,(1)H satellite spectra and are confirmed by X-ray structure determinations. Reaction of 1 with catechols 10-12 catalyzed by n-BuLi leads to ortho esters 15-18, while reaction with the perhalo catechols 13 and 14 gives isolable hydroxaryl ketenyl esters 19 and 20.

Nutritional value of succinic acid monoethyl ester in starvation.

Rats were fasted for 48 h, but infused with either NaCl or the sodium salt of monoethyl succinic acid (EMS), both delivered at a rate of 80 mumol/g body weight per day. The infusion of EMS, as compared to NaCl, failed to affect paraovarian adipose tissue or liver weight, liver or muscle glycogen, and insulinemia. It accentuated the starvation-induced fall in body weight, and decreased both liver and muscle protein content. Nevertheless, the succinate ester increased plasma D-glucose concentration, delayed the rise in ketonemia, maintained a higher glucokinase/hexokinase activity ratio in liver and pancreatic islets, and allowed for a more efficient stimulation of insulin release by D-glucose or 2-ketoisocaproate in isolated pancreatic islets. These findings indicate that monoethyl succinate displays a significant nutritional value when infused in starved rats.

Growth inhibition of MCF-7 and MCF-10A human breast cells by alpha-tocopheryl hemisuccinate, cholesteryl hemisuccinate and their ether analogs.

The growth inhibitory properties of alpha-tocopheryl hemisuccinate (vitamin E succinate) and related compounds were examined in MCF-7 human breast tumor cells and MCF-10A normal-like human breast cells since they have been suggested to be an effective antitumor compound. The data showed that both alpha-tocopherol hemisuccinate and a structurally-similar compound, cholesteryl hemisuccinate, inhibited the growth of MCF-7 and MCF-10A cells, while alpha-tocopherol, cholesterol, cholesteryl sulfate and Tris succinate had little effect on cell growth. The ether analogs of the succinate esters, alpha-tocopheryloxybutyric acid and cholesteryloxybutyric acid, also inhibited growth of MCF-7 and MCF-10A cells, indicating that hydrolysis of the succinate esters by esterases is not required for the antiproliferative effects. The antiproliferative effects of these succinate esters and ethers may be related to their physiochemical properties that allow incorporation into cell membranes.

Reactivity of tixocortol pivalate-positive patients in intradermal and oral provocation tests.

Pivalone/tixocortol pivalate commonly yields positive reactions in the patch test series. The clinical relevance of these positive reactions was investigated in more detail. In the standard patch test series 5.6% (73 of 1306) of the patients were positive to corticosteroids, 5.2% to 0.1% tixocortol pivalate in ethanol (Pivalone nasal spray diluted 1:10) and 2.3% to 1% hydrocortisone butyrate in ethanol. Some of the patients were tested in parallel with Pivalone and 1% tixocortol pivalate in petrolatum. The former test reagent yielded some false-positive reactions, whereas with the latter, some allergic responses were missed. Intradermal tests with the succinate esters of hydrocortisone, methylprednisolone and prednisolone were performed with 52 patients positive to Pivalone. Of these 76.9% (40 of 52) were positive in the intradermal tests; 38 to hydrocortisone, 35 to methylprednisolone and 30 to prednisolone. Twelve patients who had been positive in the intradermal tests were challenged orally with corticosteroids and they all showed positive reactions to hydrocortisone, methylprednisolone or prednisolone. The patients developed localized reactions at the sites of previous eczema or positive skin tests or diffuse erythema or exanthema. The oral doses of hydrocortisone eliciting positive delayed skin reactions ranged from 20 to 200 mg. Reactivity to tixocortol pivalate is closely related to sensitivity to hydrocortisone, methylprednisolone and prednisolone, but high oral doses of these corticosteroids may be required to produce allergic symptoms.

Selective spectrophotometric method for the determination of erythromycin and its esters in pharmaceutical formulations using gentiana violet

A simple and selective method for the determination of erythromycin and its stearate and succinate esters in their pure forms and in pharmaceutical formulations is described. The procedure is based on the formation of a blue-coloured ({ce:inline-formula}λ max = 633nm{/ce:inline-formula}) complex with gentiana violet in alkaline medium. Different variables affecting the colour development were studied and optimized. The method was used to determine 2.5–25 μg ml −1 of erythromycin in the final measured solution. The simplicity of the method permits rapid analysis and it is thus suitable for routine control. The method is highly specific for the determination of stearate and succinate esters in pharmaceutical formulations. The reliability of the method was established by parallel determinations against the official British Pharmacopoeial method.

Transport of alpha-tocopherol and its derivatives through erythrocyte membranes.

To investigate the transport of alpha-tocopherol (T), tocopherol succinate (TS) and tocopherol succinate-3-glucose (a newly synthetized, less hydrophobic T ester; TSG) through bovine erythrocyte membranes. Our experiments were carried out on erythrocytes (obtained from heparinized fresh bovine blood), because they represent a suitable model for investigations of membrane transport. T was shown to reside almost completely in the suspension medium, while the greater part of TS disappeared from the suspension medium and was mainly incorporated into erythrocyte membranes. In comparison with T, a larger amount of TSG was incorporated into erythrocyte membranes and taken up by cells; however the TSG intracellular accumulation was significantly lower than that observed with TS. Furthermore, the transport of TS and TSG was partially inhibited by p-chloromercuribenzenesulfonate (which inhibits monocarboxylate uptake; PCMBS) and by maltose (a competitive inhibitor of glucose transport) respectively, with a concomitant increase in drug membrane incorporation. No significant change in drug transport was observed in the presence of 4,4'-diisothiocyanostilbene-2,2'-disulfonate, a selective and irreversible blocker of band 3 protein (DIDS). Our results show 1) the existence of large differences in membrane incorporation of T, TS and TSG (very likely caused by differing abilities to fill spaces in the lipid bilayer) and 2) a specific contribution of the monocarboxylate transport protein and of the glucose transport protein in the cellular uptake of TS and TSG, respectively. A tempting suggestion is that the unique cytoprotective properties of TS may be related to the differences in the transmembrane mobility observed between T and its succinate ester. Furthermore, T conjugation to a monocarboxylate or glycoside moiety could provide suitable substrates for active membrane transport, thus appearing as a promising pharmaceutical strategy for the improved delivery of tocopherol derivatives.

Biokinetics in humans of RRR-α-tocopherol: The free phenol, acetate ester, and succinate ester forms of vitamin E

The bioavailability of RRR-α-tocopherol from the oral administration of RRR-α-tocopherol itself and its acetate and succinate esters was determined in healthy human subjects. Venous blood samples were withdrawn periodically over a 51-h period following oral administration of a gelatin capsule containing an equimolar mixture of RRR-α-tocopherol and RRR-α-tocopheryl acetate. In a second study, subjects received a capsule containing an equimolar mixture of RRR-α-tocopheryl acetate and RRR-α-tocopheryl succinate. In Study 1, RRR-α-tocopherol was absorbed at similar rates from both the free phenol, and the acetate ester and maximum plasma levels occurred at 12 h in most subjects. The extent of absorption of RRR-α-tocopherol varied considerably between subjects in absolute terms, but the relative absorption from the two forms was remarkably consistent, and a ratio of 1.0 was found for parameters of relative bioavailability in plasma. The concentration of RRR-α-tocopherol from each form was maximal at approximately 27 h in red blood cells and, as seen with the plasma data, there was a large inter-individual variability. In Study 2, there was no significant difference in the extent of absorption of RRR-α-tocopherol from the acetate ester and the succinate ester, although there was an apparently higher initial rate of absorption from the acetate ester.

Discrimination of two methylene groups in non‐symmetric succinate esters in sesquiterpene dimers by heteronuclear 13C{1H}NOE spectroscopy

AbstractIn the assignment of the non‐equivalent methylene group of an asymmetric succinate residue in the macrocyclic lactone ring of shizukaols B and F, isolated from Chloranthus japonicus, distinction of two‐bond C—H and three‐bond C—H was needed. The steady state and transient 13C{1H}NOE was used to detect two‐bond C‐H. One pair of non‐equivalent methylene protons was saturated simultaneously by quasi‐simultaneous irradiation. Inversion of two protons whose chemical shifts were close was carried out by a squared pulse, and inversion of two protons whose chemical shifts were far from each other was performed using a double DANTE pulse train.

O-Chlorobenzoyl Protected Nucleoside Succinates for Functionalization of the Solid Support Used in Oligoribonucleotide Synthesis

Abstract In the final stages of automated oligonucleotide synthesis the oligomer has to be cleaved from the solid support. This is usually carried out using ammonolysis since the 3′-end of the oligomer is most commonly attached to the support via a succinate ester linkage. The t-butyldimethylsilyl (TBDMS) group is currently the most widely used 2′-hydroxyl in RNA-synthesis and is used together with phosphoroamidites1 as well as with H-phosphonates2. The nucleoside directly attached to the support, often carries the same TBDMS-protection on the secondary hydroxyl next to the succinate linker. The use of more labile acyl groups for N-protection in RNA-synthesis was suggested in reports where partial loss of the TBDMS groups during ammonolysis was detected3,4. This has since been introduced5,6 and is now general practice. However, one can question if all oligomer will be released from the support under the milder ammonolytic conditions used to remove these more labile N-protecting groups.

Effects of the ester moiety on stereoselective hydrolysis of several propranolol prodrugs in rat tissues.

The stereochemical characteristics of the hydrolysis of several ester-type prodrugs of propranolol, O-acetyl, O-propionyl, O-butyryl, O-pivaloyl and succinyl esters, were studied in phosphate buffer (pH 7.4), rat plasma and rat tissue homogenates. In phosphate buffer, no differences were observed in the hydrolysis rate between the esters of (R)- and (S)-propranolol. The effects of the ester moieties on the hydrolysis rate in phosphate buffer were in the following order: acetate > propionate > butyrate > succinate > pivalate. In rat plasma and tissue homogenates, the hydrolysis of the esters was accelerated, and stereoselective hydrolysis was observed. In plasma, the hydrolysis of the (R)-isomer was faster than that of the (S)-isomer except for the succinate ester. On the other hand, in the liver and intestine homogenates, the (S)-isomer was hydrolyzed faster than the (R)-isomer except for the succinate and pivalate esters in the liver homogenate. Also, the ratio of the hydrolysis rates (S/R) changed with the type of prodrug. As the length of the alkyl chain of the ester increased, the S/R ratio approached unity in liver and intestine homogenates but stayed almost constant in plasma. For the pivalate ester, stereoselective hydrolysis was observed in plasma and intestine homogenate but not in liver homogenate. The stereoselective hydrolysis of the succinate ester was observed only in intestine homogenate, but the S/R ratio was almost 1 in plasma, liver and intestine homogenates. No interconversion between (R)- and (S)-isomer was observed during the hydrolysis of any of the ester prodrugs. These results indicate that hydrolysis of ester-type prodrugs of propranolol occurs stereoselectively in rat tissues, and that its selectivity is dependent on the kind of tissue and prodrug.

Reaction of C60 with Benzocyclobutenol: Expeditious Route to Fullerene Adducts

Reaction of C 60 with benzocyclobutenol (2a) and its methoxy ether (2b) in refluxing toluene gave 1,9-dihydrofullerene cycloadducts (3a) and (3b) in 59% and 50% yields, respectively. The alcohol was converted to pyranyl ether (4), acrylate (5), p-vinylbenzoate (6) and acid succinate esters (7) in good yields under very mild conditions. The adducts exist as two interconverting boat conformers. Acrylate (5) and p-vinylbenzoate (6) should be used for polymerization studies. Acid (7) shows enhanced solubility in polar solvents

The Pharmacokinetics and Pharmacodynamics of Methylprednisolone in Chronic Renal Failure.

Methylprednisolone (MP) pharmacokinetics and its directly suppressive effects on cortisol secretion, circulating T-cells, and basophils in blood were compared in six chronic renal failure (CRF) subjects and six healthy controls after an IV administration of MP 0.6 mg kg(minus sign1) as the sodium succinate ester. The CRF subjects were studied between hemodialysis treatments. The total clearance of methylprednisolone sodium succinate (the prodrug) was reduced by 40% in CRF; however, the pharmacokinetics of methylprednisolone remained unchanged. Methylprednisolone clearance was approximately 280 ml h(minus sign1) kg(minus sign1) and volume of distribution was about 1.1 L kg(minus sign1). Physiological pharmacodynamic models were applied for the immediate effects of MP, based on the premise that receptor binding is followed by rapid suppression of the secretion of cortisol and recirculation of basophils, T-helper cells, and T-suppressor cells, which persist until inhibitory concentrations (IC(50)) of methylprednisolone disappear. The difference in IC(50) for each pharmacodynamic parameter was not statistically significant, suggesting no difference in the responsiveness of these factors to methylprednisolone in CRF. As the pharmacokinetics of other corticosteroids are altered in CRF, the lack of pharmacokinetic and pharmacodynamic changes of methylprednisolone may engender a therapeutic advantage for this corticosteroid in CRF.

Fulgenates. A New Class of Fulgide-Related Thermally Irreversible Photochromic System

Abstract Thermally irreversible photochromic properties of indolylfulgenates, i.e. 2-alkylidene-3-[1-(1,2-dimethyl-3-indolyl)alkylidene]succinate esters were examined. A large indolylalkylidene group reduced the relative ratio of the colored species at the photostationary state of UV irradiation. Introduction of an adamantylidene group increased the bleaching quantum yield. The absorption maximum wavelengths of the colorless and colored species were shorter than those of the corresponding indolylfulgide.