Classical chemical sciences
A spectrofluorimetric method has been developed for the determination of tetracycline hydrochloride and terbutaline sulphate in different dosage forms. The method is based on the quantitative quenching effect of tetracycline hydrochloride and terbutaline sulphate on the native fluorescence of Eosin Y at the pH 6.4 and 3.5 respectively. The quenching of the fluorescence of Eosin Y was measured at 545 nm after excitation at 350 nm. The fluorescence-concentration plots are rectilinear over the range 0.5–18 and 0.05-5.0 μg mL-1 with LOD of 0.531 and 0.241 μg mL-1 and LOQ of 1.77 and 0.806 μg mL-1 for above drugs respectively. The proposed method has been successfully applied to the analysis of commercial tablets and capsules containing the drug. Statistical comparison of the results with those of the reference method revealed good agreement and proved that there were no significant differences in the accuracy and precision between the two methods.
Keywords: Tetracycline; terbutaline sulphate; Eosin Y; fluorimetry
A simple, rapid and sensitive method has been applied on three amino acids viz., methionine, cystine and cysteine, to estimate the ionization constant. Spectrophotometric measurements were carried out on the absorbance of each amino acid at different pH values. The results showed that the cystine and cysteine have one pKa, while the methionine gave two different pKa values by using this method.
Keywords: amino acids, ionization constant, spectrophotometry, cystine, cysteine, methionine
Materials and environmental chemistry
Rifaximin, an oral antibiotic marketed as tablets, does not have dissolution method described either in official compendiums or literature. This lack of knowledge blinds the real rate of drug availability. Thus, all potentialities of the active principle are not enough if it is trapped in its formulation or it is released erroneously. The absence of dissolution method can reduce the drug to the level of an adjuvant. Therefore, the objective of this study was to develop and validate a successful dissolution method for the evaluation of rifaximin tablets. The method contemplated the parameters for linearity, selectivity, precision, accuracy and robustness. It was found that for the dissolution of the tablets of rifaximin of 200 mg, paddle apparatus at 50 rpm and 900 mL of acetate buffer of pH 5.0 + 0.2 % SLS as dissolution medium are optimum conditions. The method presented is useful and can be applied for the routine quality control of tablets of rifaximin.
Keywords: Antibiotic, dissolution, quality control, rifaximin, tablets
Chemical and biological aspects of life
Cancer is heterogeneous disorders characterized by cellular different genetic alterations and diverse clinical behaviours results from uncontrolled division leads to loss of control of the cells growth. Neuron Specific Enolase(NSE) is considered as a marker of many diseases such as brain damage (traumatic brain injury), stroke and anoxic encephalopathy after cardiac arrest. Generally, in adults NSE accepted as a marker protein in the brain. Serotonin exhibits a growth stimulatory effect on several types of carcinoma, carcinoid and other tumor cells. In contrast, a few data are available on serotonin involvement in cancer cell migration and metastatic processes. Serum serotonin level was found to be suitable for prognosis evaluation of urothelial carcinoma in the urinary bladder, adenocarcinoma of the prostate and renal cell carcinoma. 201 patients with malignant tumors, 74 patients with different benign tumors and, 83 healthy individuals were enrolled in the present study. Our results show a significant increase (p = 0.011, and 0.043) of serum serotonin levels in malignant tumors group when compared with those of benign tumors (as a pathological control) group, and healthy individuals groups; respectively. No such results were shown when the two control (benign tumors and healthy individuals) groups were compared together. While evaluation of the NSE concentrations revealed a significant decrease in patients with malignant tumors when compared with those of benign tumors (p = 0.028), and healthy individuals (p 0.000). According to ANOVA test, Same variations (p 0.000) were obtained when benign tumors and healthy controls groups were compared together. Results shows a significant decrease in the serotonin concentration as well as the NSE levels, correlation between the levels of the two examined parameters has been negative and statically acceptable at malignant tumor patients group after treatment by chemotherapy or radiotherapy. Before treatment with chemotherapy or radiotherapy, negatively significant correlation was observed for the concentrations of Serotonin to the NSE in the sera of malignant tumor patients group, while no such correlations were noted at this relation examined in the benign tumor patients. Serotonin and NSE correlations together can be used as primary diagnostic tools for distinguishing between cancerous and benign tumors, this correlation increases the sensitivity of the two biomarkers together comparing to measure everyone alone.
Keywords: Cancer; Neuron-Specific Enolase (NSE); Serotonin; Chemotherapy; Radiotherapy
Antioxidants were used to prevent oxidation process in foods which lead to rancidity and browning, DNA oxidation and have many positive physiological effects in human. The concentration and the absorption mechanism of natural antioxidants are important in obtaining the maximum beneficial effect. The sources of antioxidants must be carefully considered to maximize absorption and avoid the toxicity of higher concentration of synthetic groups. A general lack of information about antioxidants indicates by a survey of the general public. An organized effort to educate individuals about foods rich in natural antioxidants and the ability to recognize the major synthetic antioxidants on food labels would be highly beneficial, though more research needs to be done to fully understand their physiological effects.
Keywords: Oxidants, antioxidants, definition, natural and synthetic types, assay methods
Theoretical and computational chemistry
A theoretical study was conducted to determine the ionization constants of N-substituted amino acid derivatives using HF, DFT, and MP2 calculation methods. The extent of compatibility of these methods was determined by discussing the theoretical variables calculated in the three methods mentioned above, the relationship between the calculated physical variables have been found to be theoretical and to determine their nature. These variables were then correlated with the known chemical values of amino acids as pKa ionization parameters. The results obtained by this relationship were found to be good. This is indicated by the results of the statistical analysis across the correlation coefficient values. The theory that gave the best agreement between the values of the theoretical and the experimental ionization parameters were the MP2 method with good correlation coefficient (0.997) and standard error (0.162). As well as the large overlap between pKa values calculated theoretically with practical values where the difference (0.008) gives the opportunity to apply these variables in other studies.
Keywords: amino acids derivates, computational chemistry, ionization constant
To investigate the energy bands structure of α-Hg3S2Cl2, first-principles calculations were performed within the density functional theory (DFT) formalism using the SIESTA software package. Using the local density approximation the atomic positions are relaxed so as to minimize the forces acting on the atoms. The analysis of band energy dispersion shows that the VBM and CBM are located at Г symmetry point, resulting in a direct energy band gap of 3.198 eV. It is established that the nature of interatomic interactions has complex character and includes covalent and ionic parts. The inclusion of spin-orbit coupling does not strongly modifies the structure of energy bands.
Keywords: corderoite structure; DFT; energy dispersion; band gap