Mass spectrometric investigation of buspirone drug in comparison with thermal analyses and MO-calculations

Thermal Analysis Investigation of Dapoxetine and Vardenafil Hydrochlorides using Molecular Orbital Calculations

PURPOSE

Thermal analysis techniques have been used to study the thermal behavior of dapoxetine and vardenafil hydrochlorides and confirmed using semi-empirical molecular orbital calculations.

METHODS

Thermogravimetric analysis, derivative thermogravimetry, differential thermal analysis and differential scanning calorimetry were used to determine the thermal behavior and purity of the drugs under investigation. Thermodynamic parameters such as activation energy, enthalpy, entropy and Gibbs free energy were calculated.

RESULTS

Thermal behavior of DAP and VAR were confirmed using by semi-empirical molecular orbital calculations. The purity values were found to be 99.97% and 99.95% for dapoxetine and vardenafil hydrochlorides, respectively. The purity of dapoxetine and vardenafil hydrochlorides is similar to that found by reported methods according to DSC data.

CONCLUSION

Thermal analysis justifies its application in quality control of pharmaceutical compounds due to its simplicity, sensitivity and low operational costs.

Synthesis, structure investigation, spectral characteristics and biological activities of some novel azodyes

Four novel azo compounds were synthesized; o-phenylazo- (C(14)H(13)N(3)O(2)) (I), p-bromo-o-phenylazo- (C(14)H(13)BrN(3)O(2)) (II), p-methoxy-o-phenaylazo- (C(15)H(16)N(3)O(3)) (III) and p-nitro-o-phenylazo-p-acetamidophenol (C(14)H(13)N(4)O(4)) (IV). These compounds were carefully investigated using elemental analyses, UV-vis, FT-IR, (1)H NMR and mass spectra. Also, the effects of p-substituents such as bromo, methoxy and nitro groups on the mass fragmentation pathways of these dyes were studied using Hammet's effects. This research aimed chiefly to threw lights on the structures-stability relationship of four novel newly prepared azo derivatives of p-acetoamidophenol. The data obtained referred to the variation of mass fragmentation pathways with the variation of p-substituent of these dyes which can be used in industry for various dyeing purposes. This variation is also correlated and verified by molecular orbital calculations which were done on ionic forms of these dyes using semi empirical PM3 program. The biological activities of these dyes were also investigated and its structure relationship was correlated.

Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometric and semi-empirical calculations study of five isoflavone aglycones

Five isoflavones, daidzein, genistein, formononetin, prunetin and biochanin A, known for their biological properties, are investigated by electrospray ionization mass spectrometry in the positive ion mode. The most probable protonation sites are determined taking into account semi-empirical calculations using the PM6 Hamiltonian. Fragmentation mechanisms are proposed based on accurate mass measurements, MS(3) experiments and supported by the semi-empirical calculations. Some of the fragmentation pathways were found to be dependent on the substitution pattern of the B-ring and the ions afforded by these fragmentations can be considered as diagnostic. It was possible to distinguish between prunetin and biochanin A, two isobaric isoflavone aglycones included in this study. Furthermore, a comparison of the fragmentation patterns of genistein and biochanin A, two isoflavones, with those of their flavone counterparts, apigenin and acacetin, enabled us to identify some key ions mainly due to structural features, allowing distinction to be made between these two classes of compounds.

Furanose C-C-linked γ-lactones: a combined ESI FTICR MS and semi-empirical calculations study

Sugars that incorporate the unsaturated carbonyl motif have become important synthetic targets not only as a result of their potential biological properties but also as precursors in the synthesis of many bioactive products. Moreover, little is known about the influence of the γ-lactone moiety in the fragmentation pattern of furanose rings. Therefore, two α,β-unsaturated γ-lactones (butenolides) and two β-hydroxy γ-lactones, C-C linked to a furanose ring were studied using electrospray ionization FTICR mass spectrometry. The behaviour of the protonated and sodiated forms of the compounds under study has been compared considering their structural features. Fragmentation mechanisms were established and ion structures were proposed taking into account the MS(2) and MS(3) experiments, accurate mass measurements and semi-empirical calculations. These inexpensive methods proved to be a valuable resource for proposing protonation sites and for the establishment of fragmentation pathways.

Spectroscopic study of structure of diphenhydramine drug and its products obtained via reactions with tetracynoethylene and iodine reagents and applications

The reactions between diphrenhydramine drug (diphen) in the base form and the iodine amphoteric reagent (n-donor and/or σ-acceptor) and tetracyanoethylene as a π-acceptor reagent (TCNE) have been spectrophotometrically studied at different conditions of reactant concentrations, time intervals, temperatures, solvents, and different wavelengths aiming to shed light on the nature of these reactions. Consequently, it is possible to select the proper conditions for spectrophotometric determination of this biologically active drug in its formulations. The reaction mechanism between iodine and diphen involves the formation of diphen-I₂ outer-and inner-sphere complexes, whereas diphen-TCNE reaction involves the formation of charge transfer (CT) complex. The analytical parameters of the suggested spectrphometric procedures have been calculated. The values of the Sandell sensitivity, standard deviation (SD), relative standard deviation (RSD) and recovery % refer to the high sensitivity of these procedures applied in analysis of diphen in its formulations. This research also presents a new diphen-I₂ promising drug derivative that can be used for the same purpose as its parent. Both diphen-drug and diphen-I₂ separated solid product are critically investigated by elemental analyses, FT-IR, ¹HNMR, electron ionization mass spectrometry (EI-MS) and thermal analyses (TA). Practical investigation (TA and MS) data of diphen-drug and its reaction product are confirmed by MO calculations. This research gives a clear idea about the possible metabolites and metabolic pathways of diphen and its derivative in vitro system that may occur in vivo system. The importance of this drug stems from its use as an antihistamine with anticholinergic (drying) and sedative side effects.

Stability studies of double-base propellants with centralite and malonanilide stabilizers using MO calculations in comparison to thermal studies

Propellants containing nitrate esters need stabilizers to avoid early decomposition or even explosion during storage. Newly prepared malonanilides M1-M5 were tested in stabilizing double-base propellants (DBPs). Their stabilization was compared with the effect of classical stabilizer N,N'-diethyldiphenyl urea (C1) using both practical thermal stability tests (qualitative and quantitative tests) and theoretical molecular orbital calculations. This research shows that the new stabilizers (malonanilides) have good stabilizing effects. Some of malonanilides e.g. (M5) and (M2) have higher stability effects. Different mechanisms were suggested to explain the role of different stabilizers. Molecular orbital calculations using the semi-empirical program AM1 are performed on the new and classical stabilizers. Correlation was made between the volume (ml) of NO(x), weight loss (wt%), other thermal analyses data, calculated thermodynamic parameters like activation energy (E(a), kJ mol(-1)) of the decomposed propellant samples containing different stabilizers and some of their calculated properties such as HOMO, LUMO energies, the charge distribution and the pi-bond order. The stabilization effect decreases with the increase in HOMO energy. The correlation between the net charge and parameters measured for the stabilization effect shows good accordance. Comparison of the results obtained show that the high electron charge on N atom of the stabilizers and on its benzene ring is the most important factor, but not the only factor governing the stabilization effect of the stabilizers.

Electrospray ionization mass spectrometric analysis of newly synthesized alpha,beta-unsaturated gamma-lactones fused to sugars

Knowledge of the fragmentation mechanisms of lactones and their behaviour under electrospray ionization (ESI) conditions can be extended to larger and more complex natural products that contain an alpha,beta-unsaturated gamma-lactone moiety in their structure. Moreover, little is known about the gas-phase behaviour of alpha,beta-unsaturated gamma-lactones linked or fused to sugars. Therefore, five alpha,beta-unsaturated gamma-lactones (butenolides) fused to a pyranose ring, recently synthesized compounds with potential relevance regarding their biological properties, were investigated using ESI-MS and ESI-MS/MS in both positive and negative ion modes. Their fragmentation mechanisms and product ion structures were compared. It was observed that two isomers could be unambiguously distinguished in the negative ion mode by the fragmentation pathways of their deprotonated molecules as well as in the positive ion mode by the fragmentation pathways of either the protonated or the sodiated molecule. Fragmentation mechanisms are proposed taking into account the MS/MS data and semi-empirical calculations using the PM6 Hamiltonean. The semi-empirical calculations were also very useful in determining the most probable protonation and cationization sites.