Simultaneous determination of potassium clavulanate and cefixime in synthetic mixtures by high-performance liquid chromatography

A simple, precise, and sensitive high-performance liquid chromatographic method was developed and validated for the simultaneous determination of potassium clavulanate and cefixime in synthetic mixture form. The analytes were separated on a C18 column by using 0.03 M disodium hydrogen phosphate buffer (pH 6.5)-methanol (84 + 16, v/v) as the mobile phase with detection at 220 nm. The method exhibited high sensitivity and good linearity in the concentration ranges of 12.5-62.5 and 20-100 microg/mL for potassium clavulanate and cefixime, respectively. The total run time for the 2 components was <8 min, and the average recovery was >101.5% with a relative standard deviation of <1.0%. The proposed method was validated according to guidelines of the International Conference on Harmonization by evaluation of linearity, recovery, selectivity, robustness, limits of detection and quantitation, and within- and between-day precision. The results obtained for the synthetic mixture show that the method is highly precise and accurate for the simultaneous determination of potassium clavulanate and cefixime.     

Optimisation and characterisation of various extraction conditions of phenolic compounds and antioxidant activity in olive seeds

This study was conducted to optimise the extraction conditions of phenolic compounds to evaluate antioxidant extraction parameters and to identify the major free and bound phenolic compounds in olive seeds. The results obtained using methanol as an extraction solvent for olive seeds indicated that the optimised total phenolic content and antioxidant activity were obtained at an extraction time of 12 h, an extraction temperature of 70°C and an extraction cycle of three stages. The correlation coefficient between total phenolic compounds and antioxidant activities was positive (R2 = 0.83). The major finding is that the predominant phenolic compounds in olive seeds were present in free form. However, a small percentage of the bound phenolic compounds was found in olive seeds compared to that of the free phenolic compounds. This study recommends that olive seeds with optimised extraction conditions (i.e. optimised correlation between phenolic compound contents and antioxidant activities) can be used as potential food additive candidates in functional, nutraceutical and pharmaceutical industries.     

Syntheses, Spectral Studies and Bioanalyses of Some Triorganotin(Ⅳ) Complexes of Cephlaxine

Five novel triorganotin(Ⅳ) complexes have been synthesized by refluxing trimethyl, triethyl, tributyl, triphenyl and tribenzyltin chloride with Cephlaxine.These compounds were characterized by spectroscopic (IR,1H, 13C, 119Sn NMR) techniques and elemental analysis.The results obtained through these techniques are in full agreement with the proposed 1:1 stoichiometry.The synthesized compounds were than tested against various microorganisms and fungi.The results of new products obtained showed that the triphenyltin(IV) complex displayed promising activity against all types of bacteria and fungi used while all other compounds showed significant antibacterial and antifungal activity.     

Synthesis of functionalized diaryl sulfides based on regioselective one-pot cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes

Functionalized diaryl sulfides were prepared based on one-pot cyclizations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes.     

Some aromatic polyimides based on diamines containing hydrazo group and ether linkages

Three new hydrazo-bridged diamines, 4,4′-bis [4-(4-aminophenyloxy) phenylhydrazyl] biphenyl (BPD-2), 4,4′-bis [4-(4-aminophenyloxy) phenylhydrazyl] biphenyl ether (SPD-2) and 4,4-bis [4-(4-aminophenyloxy) phenyl] hydrazine (APD-2), were synthesized by the reduction of three azo-diols, 4,4′-bis (4-azo-1-hydroxyphenyl) biphenyl (BPD), 4,4′-bis (4-azo-1-hydroxyphenyl) biphenyl ether (SPD) and azo-4-hydroxybenzene (APD), and polymerized with pyromellitic dianhydride (PM), 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride (BP) and 3,4,9,10-perylenetetracarboxylic acid dianhydride (PR) either by one-step solution polymerization or by two-step procedure which includes ring-opening polyaddition to give poly(amic acid) followed by cyclic dehydration to polyimide. The monomers and polyimides were characterized by their elemental analyses, FTIR and ¹H NMR spectroscopy. Glass transition temperatures of the polymers are quite high (175-310 °C), characteristic of polyimides. The decomposition temperatures for 10% weight loss fall in the range of 280-575 °C in nitrogen. Activation energies of pyrolysis for each of the polymers calculated from Horowitz and Metzger's method are also high (52.54-95.28 kJ mol⁻¹). The inherent viscosities of the polyimides at a concentration of 0.5 g/dl in DMF range from 0.94 to 1.93 dl/g.     

An isocratic reversed-phase high-performance liquid chromatographic method for the simultaneous determination of benzoyl peroxide and the related compounds benzoic acid, benzaldehyde, ethyl benzoate, methylparaben, and propylparaben in dermal preparations

A reversed-phase high-performance liquid chromatographic method was developed for the simultaneous determination of benzoyl peroxide and the related compounds benzoic acid (BA), methylparaben, benzaldehyde, propylparaben, and ethyl benzoate. The compounds are separated on a column containing octadecyl silane chemically bonded to porous silica particles. The mobile phase is acetonitrile-buffer (45 + 55, v/v). Solutions are injected into the chromatographic system under isocratic conditions at a constant flow rate of 1.5 mL/min with UV detection at 235 nm. Analysis of stability samples showed rapid accumulation of BA by thermal degradation. A rationale has been established for the acceptable limit of BA in the formulation, which already contains BA (0.2%) as a preservative. The proposed method is efficient and determines the active compound and 5 related compounds in a run time of 20 min. The method was validated according to the guidelines of the International Conference on Harmonization and demonstrated good agreement with the validation requirements.     

Identification of low molecular weight carbohydrates employing new binary mixtures for matrix-assisted laser desorption/ionisation mass spectrometry

Various energy-absorbing substances, aminopyrazine (AP), 4,4'-azodianiline (ADA), and 1-chloro-4-hydroxyisoquinoline (CHIQ), together with their binary mixtures with existing acidic MALDI matrices were subjected to matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) and evaluated for the analysis of low molecular weight carbohydrates. The newly introduced systems, especially AP and the combination of 2,5-dihydroxybenzoic acid and aminopyrazine (DHB-AP), have solved almost all the existing problems of the generally low sensitivity of carbohydrate analysis and of the strong background noise produced from single acidic matrices. In fact, especially at a mixing ratio of 3:1 (DHB/AP), outstanding results could be achieved, enabling the detection of analytes down to a concentration of 4 fmol/microL with mass accuracy of 37 ppm. The performance of the system was finally proven by analysing dextrins and biological samples each of which showed excellent signal intensity and signal-to-noise ratio.     

A renewable, chemoselective, and quantitative ligand density microarray for the study of biospecific interactions

Novel renewable microarray technology has been developed to immobilize and release carbohydrates and proteins from self-assembled monolayers (SAMs) of electroactive quinone-terminated alkanethiolates on gold surfaces. This method may be applied to a variety of research fields for use in biosensor technology and the generation of renewable and tailored microarrays for biospecific cell-based assays.     

Flavonoid-DNA binding studies and thermodynamic parameters

Interactional studies of new flavonoid derivatives (Fl) with chicken blood ds.DNA were investigated spectrophotometrically in DMSO-H2O (9:1 v/v) at various temperatures. Spectral parameters suggest considerable binding between the flavonoid derivatives studied and ds.DNA. The binding constant values lie in the enhanced-binding range. Thermodynamic parameters obtained from UV studies also point to strong spontaneous binding of Fl with ds.DNA. Viscometric studies complimented the UV results where a small linear increase in relative viscosity of the DNA solution was observed with added optimal flavonoid concentration. An overall mixed mode of interaction (intercalative plus groove binding) is proposed between DNA and flavonoids. Conclusively, investigated flavonoid derivatives are found to be strong DNA binders and seem to be promising drug candidates like their natural analogues.