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The effects of 9 saccharides on the crystallization of sucrose have been comparatively studied with analytical purposes. A sensitive (detection limit 0.1 μg mL−1) and simple kinetic turbidimetric procedure is used for determination of stachyose, based on its inhibitory action on the crystallization of sucrose. The supersaturated solutions of sucrose were prepared by addition of acetone to stable water sucrose solutions. The induction period of the crystallization process was turbidimetrically measured. Controlled constant stirring and temperature are convenient in order to obtain reproducible results. The method was applied to the determination of stachyose in synthetic mixtures.

The influence of oxalic acid, malonic acid, malic acid, tartaric acid, succinic acid and glycolic acid on the growth of calcium fluoride has been studied and interpreted in terms of Langmuir-type adsorption isotherms. Oxalic acid was the most active inhibitor of calcium fluoride growth, followed by tartaric, malic and malonic acids. Succinic acid caused a very slight effect and mono-carboxylic acids caused no inhibitory effects under the conditions studied. An attempt to relate the chemical structure of the studied carboxylic acids with their inhibitory capacity using molecular models and MNDO calculation has been described. The presence of a sequence constituted by a carboxylic group and an hydroxy group in the α position, in addition to another carboxylic group demonstrated a special efficacy to inhibit crystal growth of calcium fluoride crystals due to structural features. Interactions between inhibitors and the crystal surface were found to be mainly electrostatic in nature.

Ischemic stroke (IS) is a multifactorial disease caused by the interaction of genetic and environmental factors. The question of whether mild hyperhomocysteiemia (Hcy) is a risk factor for CVD has been debated and is still unclear. Common single nucleotide polymorphisms (C677T and A1298C) in the methylenetetrahydrofolate reductase gene (MTHFR) decrease the activity of the enzyme, leading to hyperhomocysteinemia, particularly in folate-deficient states. We investigated whether there is a link between MTHFR gene C677T and A1298C polymorphisms or plasma homocysteine and IS. Patients and methods: Genotypic analyses were performed on 308 consecutive unrelated patients diagnosed with IS, 147 women and 161 men, mean age 700.8 years, who were diagnosed according to the Trial of Org 10172 in Acute Stroke Treatment. All included cases were age and sex matched to a control from the same geographic area who had no history of vascular disease. Patients and controls completed a questionnaires including blood pressure, diabetes status, total serum cholesterol level and smoking history. Genetic tests were performed by RFLP-PCR and homocysteine levels in plasma were measured by ELISA method. The strength of the association of the polymorphisms with the occurrence of IS was estimated by calculation of the OR and its 95%CI by exact method. P values less than 0.05 were considered significant. Logistic regression analysis was applied to estimate the risk in a multivariable predictive model with dependent variable (case/control) and all independent variables significant in the bivariate analysis. SPSS 9.0 was used for the statistical analysis. Results: The distribution of MTHFR gene C677T genotypes in patients (or controls) was: CC-genotype in 134 cases, 44.1% (155 controls, 50.5%); CT-genotype in 131 cases, 43.1% (138 controls, 44.9%); and TT-genotype in 39 cases, 12.8% (14 controls, 4.6%). The distribution of MTHFR gene A1298C genotypes in patients (or controls) was: AA-genotype in 164 cases, 55.6% (127 controls, 41.2%); AC-genotype in 113 cases, 38.3% (149 controls, 48.4%); and CC-genotype in 18 cases, 6.1% (32 controls, 10.4%). Genotype analysis showed a significant higher prevalence of the TT-genotype of MTHFR C677T in patients (p= 0.001;OR= 3.08;95%CI= 1.63–5.79). Nevertheless, genotype analysis showed a lower prevalence of the CC genotype of MTHFR A1298C in patients (p= 0.056;OR= 0.56;95%CI= 0.3–1.02). The genetic analysis was similar for the different subtypes of IS. Homocysteine plasma level was significantly higher in homozygosity for 677T allele than wild type (20.2±9.3 mmol/l and 17.4±6.5 mmol/l; p=0.029) and was lower in homozygosity for 1298C allele than wild type (16.2±5.7 mmol/l and 18.7±9.0 mmol/l; p=0.029). Homocysteine plasma levels in doubly heterozygous for C677T and A1298C mutations in the MTHFR gene were higher than the other genotypes (20.6±8.4 mmol/l and 18.6±8.3 mmol/l; p= 0.133). Logistic regression analysis showed a independent association of 677T allele of MTHFRwith CVD. Also hypertension, diabetes mellitus and current smoking status were statistically associated with CVD. Conclusions: Our findings suggest that the T allele of 677 MTHFR polymorphism is a genetic risk factor for IS in Spanish population. The unexpected protective effect of the 1298C allele of 1298 MTHFR polymorphism for IS needs further study. Supported by Grant FIS 03/0176. Oa R: Fundacion Conchita Rabago Grant. Santos AB: Fundacion LAIR 2004 Grant.

Preliminary studies of the mechanism of Michael addition of ethyl acetoacetate to chalcone are presented. Different products may be obtained with good yields (≧80%) and selectivities (≃100%), under different reaction conditions. A mechanism based on the geometric characteristics of the active site of activated barium hydroxide (C-200) is proposed.

The hydrogen transfer reduction of benzylideneacetone derivatives p-X-C6H4—CH=CH—CO—R (X = —OCH3, H; R = C6H5, alkyl, OR, OH) using cyclohexene as hydrogen donor has been studied. The selective reduction of the C=C bond is observed and the effects of the nature of X and R, solvent, catalyst, and reaction temperature on the initial reaction rate are analyzed. In all cases, and for any substrate or catalyst, the reaction is first-order with respect to the hydrogen donor and acceptor.

The kinetics of crystal growth of calcium oxalate monohydrate seed crystals were investigated potentiometrically in the presence of several polyhydroxycarboxylic acids; etylenediaminetetraacetic acid, citric acid, isocitric acid, malic acid and succinic acid, and it was found that they inhibited crystal growth, except in the case of isocitric acid manifested no-effects. An apparent rate order of 2 in the presence of all the inhibitors, suggested a spiral growth mechanism. Application to a kinetic Langmuir-type model suggested that adsorption of the polyhydroxycarboxylic acids, at the active growth sites, is the cause of the reduction in the crystal growth rates. The inhibitory action of the different substances assayed was comparatively evaluated. Relations between chemical structure and inhibitory capacity were established.

Par lithiation de dimethylaminomethyl-4, -hydroxymethyl-4 et -methoxymethyl-4 phenols, obtention regioselective de benzoquinones-1,4

A detailed study of the regioselectivity of the Fremy's salt oxidation of phenols, including a series of MNDO calculations of the intermediate phenoxy radicals, has been carried out. The analysis of these results has led us to establish a new rule for the para vs. ortho regioselectivity, namely: “C-4 unsubstituted phenols, as well as phenols substituted at C-4 with easy-to-displace groups, undergo oxidation (or oxidative degradation) by the action of Fremy's salt, thus eventually providing the corresponding p-quinones”. A similar rule for the ortho vs. ortho' regioselectivity could not be so precisely formulated since now steric effects play a significant major role.

Relationships between gas-chromatographic retention indices of aromatic hydrocarbons and several parameters were considered. Van der Waals volume was proposed to distinguish the basic skeleton of polycyclic aromatic hydrocarbons. The influence on retention of the stationary phase polarity (p) and column temperature (t) were considered. General equations, I versus tB and t (tB =boiling point) and I versus tB , t and p with high correlation coefficient were obtained. These expressions could be used for analytical purposes.

The heat of solution (ΔH s ) of several homologous series of linear and monofunctional organic compounds (n-alkanes,n-alcohols,n-aldehyds and esters) in polar stationary phase (Carbowax 1540) can be expressed by ΔH s =a+b·n R +c·C G , wherea is a constant,n R is the number of carbon atoms not belonging to the functional group in the molecule andC G represents the contribution of each functional group to the ΔH s value. The accuracy of the ΔH s values calculated by this equation is sufficient for all the compounds tested (average relative error=1.92%).C G can be calculated from the plots ΔH s versusn R .

Preparation de phenyl-1 alcene-1ones-3 et de diphenyl-1,5 pentadiene-1,4 one-3 et dibenzylidene cyclanones

The contents of hemicellulose, cellulose and lignin in neutral-detergent fibre, and acid-detergent fibre in hulls of hazelnuts, peanuts, coconuts, sunflower seeds, pumpkin seeds, acorns and chestnuts were determined. Similar cell-wall characteristics for sunflower-acorn, peanut-pumpkin and hazelnut-chestnut pairs can be deduced from their similar composition. High amounts of hemicellulose and lower ones of cellulose and lignin are dissolved in the process of determining crude fibre. The results are discussed.

Par lithiation de dimethylaminomethyl-4, -hydroxymethyl-4 et -methoxymethyl-4 phenols, obtention regioselective de benzoquinones-1,4

Conjugate addition of the lithium dienediolate derived from crotonic acid to several α,β-unsaturated ketones gave 7-oxocarboxylic acids. Styrl ketones (2a–g) afforded mixtures of 1,4-α- and 1,4-γ-adducts, in proportions depending on the bulk of the substituents attached to the carbonyl group. The reaction with the styryl ketones occurs through a tandem 1,2-addition–oxy-Cope rearrangement mechanism. On the other hand, α- and β-methyl styryl phenones (2h and i) afforded 1,4-γ-products through 1,2-addition with subsequent retro-aldol and Michael-type addition.