A series of mesoionic pyrimidinium betaines were synthesized and tested in vitro for their antioxidant activity using three tests: 2,2-diphenyl-1-picrylhydrazil (DPPH) free radical scavenging, Ferric Reducing Antioxidant Power (FRAP) and bleaching of β-carotene. The results indicated that pyrimidinium betaines possess antioxidant properties with three methods. In the DPPH assay, the monocyclic pyrimidinium betaine showed the highest activity with an IC 50 value of 300 µg/mL. The pyrimidinium betaines also revealed a reducing power lower than that of the control antioxidants, and the monocyclic pyrimidinium betaine was the most active one. In the β-carotene bleaching test, the oxidation of linoleic acid was inhibited by all the betaines. The bicyclic one showed the greatest inhibitory activity of the oxidation of linoleic acid with a relative antioxidant activity (RAA) of 90%, an activity higher than that of the reference antioxidant α-tocopherol (41%). It was found that the antioxidant efficacy increased with increasing concentration of betaine and depended on the nature of the substituent on the pyrimidine ring.

The aim of this study was to evaluate the antioxidant activities of five amides: benzanilide 1, dodecanilide 2, N-cyclohexyloctamide 3, acetanilide 4, and acetaminophen (paracetamol) 5, and to compare them to those of standard antioxidants, i.e. butylated hydroxyanisole (BHA), butylated hydroxy toluene (BHT), ascorbic acid (vitamin C) and α-tocopherol (vitamin E). Three common experimental tests were used to assess their antioxidant properties: 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, ferric ions reducing antioxidant power (FRAP) and β-carotene/linoleic acid assays. The amides 1-3 proved to be antioxidant as per three methods; the fatty anilide 2 showed the highest radical scavenging activity, whereas the fatty amide 3 showed the lowest one. Increasing the concentration resulted in an increased ferric reducing antioxidant power for all the examined amides; the reducing power of fatty anilide 2 was relatively higher than those of benzanilide 1 and fatty amide 3. Oxidation of the linoleic acid was strongly inhibited by all amides. The obtained results were comparable to antioxidant properties of the standard antioxidants.

Objective: Linezolid is a significant antibiotic used against severe infections initiated by multi-resistant bacterial pathogens. Method: Linezolid extraction from plasma is obtained using methanol. Chromatographic separation is achieved isocratically on a C18 column [Zorbax C18, 5 µm particle size, 150 mm ˟ 4.6 mm] making use of a mobile phase of acetonitrile / 0.05 M phosphate buffer, pH = 4.5 (30 : 70 v/v) at a flow rate of 1.2 mL/min with photodiode array detector DAD, at a wavelength of 256 nm. Method: Linezolid extraction from plasma is obtained using methanol. Chromatographic separation is achieved isocratically on a C18 column [Zorbax C18, 5 µm particle size, 150 mm ˟ 4.6 mm] making use of a mobile phase of acetonitrile / 0.05 M phosphate buffer, pH = 4.5 (30 : 70 v/v) at a flow rate of 1.2 mL/min with photodiode array detector DAD, at a wavelength of 256 nm. Results : The retention time of linezolid was 2.5 min. The analytical method was linear (r2 > 0.998) over the calibration range of 0.30 to 50.0 µg/mL. The extraction recoveries of linezolid range from 71.03 to 91.93 %. The limit of quantification and the limit of detection were 0.112 µg and 0.037 µg, respectively. The RSDs for intraday and interday assays were < 7.77 and 4.32 %, respectively. The intraday and interday accuracies were in the range 80.6-112 % and 77.44-104.85 %, respectively. Conclusion: The applied method is precise, accurate and appropriate for pharmacokinetic studies and therapeutic drug monitoring of linezolid in routine clinical practice.

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Betaine derivatives are widely used in cosmetic, industrial uses, biology and other scientific fields. Pyrimidinium betaine is a special class of bioactive heterocyclics. They have interesting antioxidant and free radical scavenging activities. This work aims to examine the influence of some parameters on the antioxidant activity of some synthesized betaines containing pyrimidine ring. Four pyrimidinium betaines: monocyclic, bicyclics, and one with a fatty alkyl chain were synthesized from condensation of 2-aminopyrimidine or amidine derivatives with malonic esters, and their antioxidant capacity was evaluated. The effects of concentration, reaction time and temperature on their antioxidant activities were investigated by three common methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging, ferric reducing antioxidant power (FRAP) and β-carotene bleaching. The results showed that all pyrimidinium betaines exhibited antioxidant activities in different assays. In the DPPH and reducing power assays, antioxidant activity increased with concentration, whereas in the β-carotene/linoleic acid system, it increased with temperature. On the other hand, the DPPH assay showed an increase in antioxidant capacity over time, while the β-carotene bleaching assay showed a decrease. These results indicate that the antioxidant activity differs depending on the method used and that the various factors affect the antioxidant activity in a different order.