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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
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.
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.
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.
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
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.
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.
The effect of copper excess on growth, H 2 O 2 level and peroxidase activities were studied in maize shoots. Ten-day-old seedlings were cultured in nutrient solution that contained Cu 2+ ions at various concentrations (50 and 100 μM) for seven days. High concentrations of Cu 2+ ions caused significant decrease both in matter production and elongation of maize shoots. In addition, treatment with CuSO 4 increased levels of H 2 O 2 and induced changes in several peroxidase activities. Moreover, the disturbance of the physiological parameters was accompanied by the modulation of the peroxidase activities: GPX (Guaiacol peroxidase, EC 1.11.1.7), CAPX (Coniferyl alcohol peroxidase, EC 1.11.1.4) and APX (Ascorbate peroxidase, EC.1.11.1.11). Furthermore, this modulation becomes highly significant, especially, in the presence of 100 μM of CuSO 4 .
We studied oxidative stress and peroxidase activity resulting from application of excess copper in the nutrient medium on the roots of young bean seedlings. The change in H 2 O 2 content, lipid peroxidation and antioxidant enzymes activities were quantified and located. Excess of copper caused a loss of membrane integrity and the formation of hydrogen peroxide (H 2 O 2 ) as visualized in the transmission electron microscopy and measured using spectrophotometry. H 2 O 2 accumulated in the intercellular spaces and in the cell wall. The production of H 2 O 2 was accompanied by an increase in the activity of soluble and ionic GPX (guaiacol peroxidase, EC 1.11.17), CAPX (coniferyl alcohol peroxidase) and NADH oxidase.
S-methylmethionine (SMM) is an important intermediary compound in the sulphur metabolism and has been shown to play a possible role in moderating the damaging effects of low temperature stress. The present work investigated the extent to which SMM is capable of influencing the activity of antioxidant enzymes when the subtropical species maize is exposed to chilling temperatures during the early developmental phase. SMM was found to contribute to the protection of maize seedlings against low (<14°C) temperature stress by enhancing the activity of certain antioxidant enzymes to varying extents, and thus helping to neutralise the reactive oxygen species (ROS) formed at this temperature. Results obtained in a gradient plant growth chamber revealed that, with the exception of catalase, SMM increased the activity of all the antioxidants studied (glutathione reductase, glutathione-S-transferase, guaiacol peroxidase, ascorbate peroxidase), particularly in the lower ranges of the temperature gradient (6–14°C).
