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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A simple, accurate and highly sensitive spectrophotometric method is proposed for the rapid determination of pipazethate hydrochloride, dextromethorphan hydrobromide and drotaverine hydrochloride using chromotrope 2B (C2B) and chromotrope 2R (C2R). The method consists of extracting the formed ion-associates into chloroform in the case of pipazethate HCl and dextromethorphan HBr or into methylene chloride in the case of drotaverine HCl. The ion-associates exhibit absorption maxima at 528, 540 and 532 nm with C2B and at 526, 517 and 522 nm with C2R for pipazethate HCl, dextromethorphan HBr and drotaverine HCl, respectively. The calibration curves resulting from the measurements of absorbance-concentration relations (at the optimum reaction conditions) of the extracted ion-pairs are linear over the concentration range 4.36-52.32 microg mL(-1) for pipazethate, 3.7-48.15 microg mL(-1) for dextromethorphan and 4.34-60.76 microg mL(-1) for drotaverine, respectively. The effect of acidity, reagent concentration, time, solvent and stoichiometric ratio of the ion-associates were estimated. The molar absorptivity and Sandell sensitivity of the reaction products were calculated. Statistical treatment of the results reflects that the procedure is precise, accurate and easily applied for the determination of the drugs under investigation in pure form and in their pharmaceutical preparations.
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PMID:Spectrophotometric determination of pipazethate HCl, dextromethorphan HBr and drotaverine HCl in their pharmaceutical preparations. 1709 67

Novel di-ionizable p-tert-butylcalix[4]arene-1,2-crown-3 ligands in cone and 1,2-alternate conformations were prepared as potential metal ion extractants. Selective bridging of proximal hydroxyl groups of the calix[4]arene platform by a crown-3 polyether unit was achieved under Mitsunobu reaction conditions. In addition to the carboxylic acid group, the acidity tunable N-(X)sulfonyl oxyacetamide functions [OCH(2)C(O)NHSO(2)X] with X group variation from methyl to phenyl to p-nitrophenyl to trifluomethyl were used as the proton-ionizable groups. Conformations and regioselectivities of the new ligands were established by (1)H and (13)C NMR spectroscopy. Competitive solvent extractions of alkali metal cations and of alkaline earth metal cations from aqueous solutions into chloroform were performed, as were single species extractions of lead(ii) and mercury(ii).
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PMID:Di-ionizable p-tert-butylcalix[4]arene-1,2-crown-3 ligands in cone and 1,2-alternate conformations: synthesis and metal ion extraction. 1740 24

The guaianolide type sesquiterpene lactones chlorojanerin, 13-acetyl solstitialin A and solstitialin A were identified as the anti-ulcerogenic components of the chloroform extract of the aerial parts of Centaurea solstitialis ssp. solstitialis (Asteraceae). In this study, these compounds were investigated by using various in vivo ulcer models in rats and mice. Chlorojanerin was shown to be significantly effective in preventing the induction of lesions by ethanol- (EtOH-) (both oral and subcutaneous administration), indomethacin-, indomethacin plus HCl/EtOH-, N(G)-nitro-l-arginine methyl ester plus EtOH-, N-ethylmaleimide plus EtOH-, water immersion and restraint stress, and serotonin, as well as inhibiting titratable gastric acidity and acid output, and increasing gastric pH, but was ineffective in the prevention of ulcers induced by pyloric ligation, diethyldithiocarbamate, and cysteamine, and had no effect on gastric secretion volume or peptic activity. A mixture of 13-acetyl solstitialin A (95%) and solstitialin A (5%) was found to be significantly effective against EtOH-induced lesions on oral administration but was ineffective when administered subcutaneously. This mixture was also found to be effective in preventing lesions induced by EtOH, indomethacin, indomethacin plus HCl/EtOH, N(G)-nitro-l-arginine methyl ester plus EtOH, N-ethylmaleimide plus EtOH, water immersion and restraint stress, serotonin and cysteamine, as well as inhibiting titratable gastric acidity and titratable acid output, and gastric pH, but was found ineffective against the pyloric ligation-induced and diethyldithiocarbamate-induced ulcerogenesis models, as well as gastric secretion volume and peptic activity. On the other hand, active compounds did not show any toxic effect on acute toxicity (3 days administration) evaluation tests in mice.
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PMID:Evaluation of the anti-ulcerogenic effect of sesquiterpene lactones from Centaurea solstitialis L. ssp. solstitialis by using various in vivo and biochemical techniques. 1741 88

Partition coefficients for 86 varied compounds were determined for the chloroform-methanol-water (8:4:3 v/v) biphasic partition system and used to derive a model for the distribution of neutral compounds between the water-rich and chloroform-rich layers. The partition coefficients, log K(p), were correlated through the solvation parameter model giving log K(p) = 1.336 - 0.014E + 0.413S + 1.583A + 1.344B - 1.378V with a multiple correlation coefficient of 0.973, standard error of the estimate 0.151, and Fischer statistic 286. In the model the solute descriptors are excess molar refraction, E, dipolarity/polarizability, S, overall hydrogen-bond acidity, A, overall hydrogen-bond basicity, B, and McGowan's characteristic volume, V. The model is expected to be able to estimate further values of the partition coefficient to about 0.13 log units. The chloroform-methanol-water partition system is shown to have different selectivities to 44 common water-organic solvent and totally organic biphasic partition systems.
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PMID:Distribution model for Folch partition. 1766 9

Arctium lappa L. is used in folk medicine as a diuretic, depurative and digestive stimulant and in dermatological conditions. The objective of this study was to evaluate the effect and the possible mechanisms involved in the gastroprotective effects of a chloroform extract (CE) of the roots from A. lappa and its fractions. Oral pretreatment with CE (10, 30 and 100 mg kg(-1)) significantly reduced gastric lesions induced by ethanol by 61%, 70% and 76%, respectively. Oral administration of CE (100 mg kg(-1) per day for 7 days) reduced the chronic gastric ulceration induced by acetic acid by 52%. Intraduodenal CE (100, 300 and 600 mg kg(-1)) reduced the total acidity of gastric secretion by 22%, 22% and 33%, respectively, while i.p. administration (10, 30 and 100 mg kg(-1)) inhibited total acidity by 50%, 60% and 67%, respectively. In-vitro, CE inhibited H+, K+ -ATPase activity with an EC50 of 53 microgmL(-1) and fraction A (30 and 100 microgmL(-1)) reduced this by 48% and 89%, respectively. CE had no effect on gastrointestinal motility. CE (250 microgmL(-1)) and fraction B (100 and 250 microgmL(-1)) had free-radical scavenging ability, inhibiting 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical activity by 50%, 20% and 55%, respectively. Collectively, the results show that the CE protects animals from gastric lesions by reducing gastric acid secretion via inhibition of gastric H+, K+ -ATPase.
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PMID:Gastroprotective activity of the chloroform extract of the roots from Arctium lappa L. 1849 17

Baccharis illinita DC (Compositae) is used in folk medicine to treat gastric disturbances. Preliminary studies with other extracts of B. Illinita showed gastric protection against ethanol-, indometacin- and stress-induced ulcers and the inhibition of gastric secretion. Based on these data, the aim of this study was to verify the pathways involved in the inhibition of gastric secretion. The chloroform extract (CE) of flowers from B. illinita (3, 10, 30 and 100 mg kg(-1) i.p.) tested on rats with pylorus ligature reduced the volume and the total acidity of gastric content by approximately 50% (ED50 = 69 mg kg(-1)). Treatment with CE (100 mg kg(-1) i.p.) reduced the gastric total acidity stimulated by histamine, bethanechol and pentagastrin to 42%, 27% and 57% of that in the stimulated control group, respectively. The CE (10, 30 and 100 microM) inhibited H+/K+ ATPase activity in-vitro, with an IC50 of 37 microM. The isolated flavonoid luteolin (1, 3, 10 and 30 microM) also inhibited H+/K+ ATPase activity by 50%, at a dose of 30 microM. Our results suggest that the reduction in gastric secretion occurs through inhibition of H+/K+ ATPase, which is the final step in acid secretion and therefore one of the most important steps.
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PMID:Inhibition of H+/K+ ATPase in the gastroprotective effect of Baccharis illinita DC. 1864 3

The terdentate ligand 3 (LH, 2-formylpyridine 4-thiosemicarbazone) forms with FeII and NiII 2:1 complexes of octahedral geometry of formula [MII(LH)2]2+. X-ray diffraction studies have shown that in both complexes the thiourea moieties of the coordinated thiosemicarbazones are exposed to the outside and are prone to establish hydrogen-bonding bifurcate interactions with oxoanions. However, spectrophotometric studies in CHCl3 solution have shown that only the poorly basic NO3 - ion is able to form authentic hydrogen-bond complexes with thiourea subunits, whereas all the other investigated anions (CH3COO-, NO2 -, F-) induce deprotonation of the N-H fragment. The extreme enhancement of the thiourea acidity is based on the coordinative interaction of the sulphur atom with the metal, which stabilises the thiolate form, and it is much higher than that exerted by any other covalently linked electron-withdrawing substituent, for example, --NO2.
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PMID:Metal-controlled anion-binding tendencies of the thiourea unit of thiosemicarbazones. 1879 40

The extraction of tungsten by chloroform solutions of 8-hydroxyquinoline(I), 2-methyl-8-hydroxyquinoline(II), 5,7-dibromo-8-hydroxyquinoline(III) and 8-mercaptoquinoline(IV), as a function of the concentration of tungsten and reagent and the acidity of the aqueous phase, has been studied. Evidence was obtained for the quantitative extraction of tungsten over a wide range of acidity. The degree of extraction of tungsten at 10(-5)M concentration with I,III and IV gives two maxima when plotted against acidity. The extraction maximum for the more acidic solutions lies in the region where the reagents exist in the protonated form and its position depends on the reagent used. It is suggested that different tungsten complexes are extracted, depending on the acidity of the aqueous phase.
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PMID:Extraction of tungsten with 8-hydroxyquinoline and some of its derivatives. 1896 Aug 84

A sensitive and selective method for the extraction of trace rhenium is based on extraction of a Re-thiocyanate complex with hexamethylphosphoramide and chloroform at an acidity of 2-3 M hydrochloric acid. Hydrazine sulphate is used as the reducing agent. The system obeys Beer's law at 430 nm, the optimum concentration range is 1.7-8 ppm. The molar absorptivity is calculated to be 2.23 x 10(4) 1.mole(-1) .cm(-1). The colour is stable for at least 48 hr. The method is simple and rapid and is generally free from interference by most of the metals commonly associated with rhenium.
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PMID:Liquid%liquid extraction of a rhenium%thiocyanate complex with hexamethylphosphoramide and direct spectrophotometric determination in the organic phase. 1896 33

Anionic surfactants, S(-) [where S(-) is dodecyl sulphate (DS) or dodecylbenzenesulphonate (DBS)] were extracted with a series of copper (II)-ethylenediamine derivative complexes, CU(R-en)(2)(2+), where R-en is ethylenediamine (en), N,N'-dimethylethylenediainine (NN'Me(2)en), N,N-dimethylethylenediamine (NNMe(2)en), N,N-diethylethylenediamine (NNE(2)en) or 1,2-cyclohexanediamine (Cyen). The extraction constant of the ion-pair is K(ex) = [Cu(R-en)(2)(2+) . 2S(-)](0)/[Cu(R-en)(2)(2+)][S(-)](2). The constants for extraction of the DS complexes with en, NN'Me(2)en, NNMe(2)en, NNEt(2)en and Cyen into chloroform were found to be log K(ex) = 7.93, 9,19, 8.88, 8.74 and 11.45 (+/- 0.05 at 25 degrees C), respectively. The extractability of the ion-pair Cu(en)(2)(2+) . 2S(-) gave a linear correlation with the acidity of the solvent. The Cu(Cyen)(2)(2+) extraction system was applied to the determination of some anionic surfactants. With use of graphitefurnace atomic-absorption spectrophotometry, a limit of detection of 5mug l . was obtained with a 20-ml sample of river water or sea-water.
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PMID:Extraction and determination of anionic surfactants with copper (II)-ethylenediamine derivative complexes. 1896 38


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