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BahceçI, K.S. & Acar, J. (2007): Determination of guaiacol produced by Alicyclobacillus acidoterrestris in apple juice by using HPLC and spectrophotometric methods, and mathematical modeling of

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This research article describes a simple and sensitive thin-layer chromatographic (TLC)-densitometric method for simultaneous determination of guaifenesin (GUF) and pseudoephedrine HCl (PSH) in their binary mixtures and in the presence of guaifenesin impurity and related substance, guaiacol. The proposed chromatographic method has been developed using silica gel plates 60 F254 as a stationary phase with hexane-acetone-ethyl acetate-triethylamine-water (3:4:3:0.1:0.3, by volume) as a developing system followed by densitometric measurements at 208 (for pseudoephedrine HCl and guaifenesin) and 278 nm (for guaiacol). Experimental conditions have been optimized to get the desired separation and sensitivity. Calibration curves for the three studied components were constructed using polynomial equation which was superior to linear equation with respect to correlation coefficients and quantified ranges (14–25, 2–12, and 0.1–1.1 μg band−1) for pseudoephedrine HCl, guaifenesin and guaiacol, respectively. The developed method has been successfully applied for determination of pseudoephedrine HCl and guaifenesin in Triaminic® Chest Congestion syrup where no interference from syrup additives has been found. The data obtained from method validation confirm the specificity, sensitivity and accuracy of the method. Statistical comparison of the results obtained by the proposed chromatographic method and of those obtained by the reported chemometric technique showed no significant difference at 95% confidence limit.

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Nitration of acetyl guaiacol, one typical aromatic nitration, is highly exothermic and extremely fast. Better control and high efficiency can be achieved in the microreactor due to its enhanced mixing and heat transfer rates. In this study, nitration of acetyl guaiacol was carried out in a microreactor using nitric acid—acetic acid as nitrating agent. The nitration kinetics was first investigated, and a kinetic model was established and revealed good prediction of experimental results at higher temperatures. Effects of molar ratio of nitric acid—acetyl guaiacol, residence time, temperature, and nitric acid concentration on the reaction were studied in detail. Under optimized condition, 90.7% yield of desired product, 5-nitroguaiacol, was achieved with 40% of nitric acid concentration, nitric acid—acetyl guaiacol molar ratio of 2.6, reaction temperature of 120 °C, and residence time of 2 min. Compared to traditional batch reactor, microreactor showed the advantages of higher yield and selectivity, much shorter reaction time, and less use of nitric acid.

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Abstract  

Guiacol, i.e. o-hydroxyanisole, gives a distinct color reaction with U(VI) suitable for spectrophotometric determination of the metal. The complex formed in the reaction has an absorption maximum at 352 nm. Optimum pH for the color development ranges from 6.5 to 8.5. The molar absorptivity and Sandell's sensitivity of the method were found to be 3.75×103 l·mol–1·cm–1 and 0.063 g·cm–2, respectively. Many anions and cations do not interfere up to 100 ppm. The method has been made very specific by selective extraction of U(VI) with TBP from a mixture of different cations and anions in the presence of 60% NH4NO3 as salting out agent followed by developing the color in the non-aqueous phase by adding quaiacol in methanol at pH 6.5 to 8.5 An amount as low as 30 g of uranium (VI) per 10 ml of the solution could be satisfactorily determined with an RSD of ±2.0%. The method was applied to rock samples after U(VI) had been extracted from a sample solution into 25% TBP in hexane. Results obtained by the new method compare very well with those of conventional fluorimetric and radiometric assays. The features of the method include excellent precision, rapidity, good selectivity, and ease of performance.

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Kubis, J. (2003) Polyamines and “scavenging system”: Influence of exogenous spermidine on catalase and guaiacol peroxidase activities, and free polyamine level in Barley leaves under water deficit. Acta Physiol. Plant. 25, 337

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Abstract  

Eugenol is an allyl chain-substituted guaiacol in the biosynthesized phenylpropanoid compound class derived from Syzygium aromaticum L. and widely used in folk medicine. Nonetheless, its pharmacological use is limited by some problems, such as instability when exposed to light and high temperature. In order to enhance stability, the eugenol molecule was structurally modified, resulting in eugenyl acetate. The eugenyl acetate’s thermal behavior and crystal structure was then characterized by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) and compared to a commercial sample.

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Cereal Research Communications
Authors:
Tibor Janda
,
Eszter Kósa
,
János Pintér
,
Gabriella Szalai
,
Csaba Marton
, and
Emil Páldi

Six maize hybrids and their parental inbred lines, grown under controlled conditions, were tested for chilling tolerance using the chlorophyll fluorescence induction technique. The genotypes were ranked based on the decrease in the F v /F m parameter after chilling stress at 5°C. The activities of enzymes playing a role in stress defence mechanisms (catalase, glutathione reductase, ascorbate peroxidase, guaiacol peroxidase and glutathione-S-transferase) were determined in control plants and after 1 day of cold treatment. The results suggest that although there are differences between the genotypes in the activities of almost all the antioxidant enzymes, these differences do not reflect the differences in the chilling tolerance.

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Abstract  

Thermogravimetry-mass spectrometry (TG-MS) was used to study the effect of the inorganic salts (NH4)2SO4 and (NH4)2HPO4, active substances of many commercial forest fire retardants, on the pyrolysis of Pinus halepensis needles and their main components (cellulose, lignin and extractives). These salts seemed to affect the pyrolysis of cellulose by increasing significantly the char residue, decreasing the pyrolysis temperature and changing the composition of the evolved gases, that is, increasing levoglucosenone and decreasing oxygen containing volatile products. (NH4)2SO4 seemed to have negligible effect on the pyrolysis of lignin, while (NH4)2HPO4 increased the char residue and decrease the relative contribution of guaiacols in the evolved gases. No effects of the inorganic salts on the extractives were observed. Finally, the inorganic salts seemed to affect the pyrolysis of pine-needles, mainly the cellulose component, but the effects were not as intense as in the pyrolysis of cellulose.

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Volatile constituents of four red pepper (called paprika in Hungarian) cultivars of the famous Szeged paprika growing region were analysed by GC-MS measurements subsequent to Likens-Nickerson simultaneous distillation extraction (LN-SDE) sample preparation. Of the compounds, 107 common constituents were managed to be identified. The examination detected the presence of terpenes, esters, hydrocarbons, acids, alcohols, aldehydes, and ketones. Several sulphur, cyclic nitrogen, and oxygen containing compounds were found as well, which usually present fairly high odour activities. The most abundant components in the examined cultivars were the hexadecanoic acid, tetradecanoic acid, dodecanoic acid, 4-vinyl-2-methoxy-phenol (4-vinyl guaiacol), and a compound of unknown structure. Though many pyrazines and relative substances occurred in the samples, 2-methoxy-3-isobutylpyrazine, responsible for the fresh red bell pepper note, could not be detected.

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Hydrogen sulfide (H2S) has been recently found to be a gaseous signaling molecule in plants. In this work, we studied the role of H2S in alleviating salinity stress during wheat grain germination (Triticum aestivum L. Yangmai 158). Pretreatment with NaHS, a H2S donor, during wheat grain imbibition, could significantly attenuate the inhibitory effect of salinity stress on wheat germination. NaHS-pretreated grain showed higher amylase and esterase activities than water control. NaHS pretreatment differentially stimulated the activities of catalase (CAT), guaiacol peroxidase (POD) and ascorbate peroxidase (APX), decreased the level of malondialdehyde (MDA) and reduced NaCl-induced changes in plasma membrane integrity in the radicle tips of seedlings compared with water control. We conclude that H2S plays an important role in protecting wheat grain from oxidative damage induced by salinity stress.

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