Synchronous spectrofluorimetric study of the supramolecular host-guest interaction of β-cyclodextrin with propranolol: A comparative study

The Binding Mechanism Between Cyclodextrins and Anticancer Drug Noscapine: A Spectroscopic and Molecular Docking Study

In this paper the binding of noscapine (NOS) as an anticancer drug with poor bioavailability and low solubility with beta and methyl-beta cyclodextrins (β-CD and M-β-CD) as the biocompatible drug carriers were discussed using ultraviolet-visible, fluorescence and nuclear magnetic resonance spectroscopy, as well as molecular docking. The absorption of NOS changed when it was bound to both cyclodextrins, resulting in a hyperchromic shift. It formed a 1:1 stoichiometry inclusion complex with both cyclodextrins according to the Benesi-Hildebrand equation. The binding affinity was larger in NOS-M-β-CD (5.9 (± 0.66) × 103 M- 1) than NOS-β-CD (3.7 (± 0.22) × 103 M- 1) complex. The fluorescence emission band of NOS at 408 nm was quenched when NOS was complexed with β-CD, and enhanced in the presence of M-β-CD, while the shoulder at 350 nm was enhanced selectively when NOS was complexed with M-β-CD. The fluorescence quenching of NOS with β-CD showed a negative deviation from the Stern-Volmer. The thermodynamic parameters have been estimated with the help of the Van't Hoff equation in different temperatures, and a dynamic mechanism was proposed for quenching. Also, both ΔH and ΔS have positive values thus the main interactions result in hydrophobic forces. Moreover, the negative value of ΔG indicates that the bonding process is spontaneous. 1H NMR chemical shift changes were observable for NOS and both CDs protons due to the chemical environment changes of some nuclei upon complexation. The molecular docking results revealed that the 1:1 inclusion complex possesses a good molecular shape complementarity score for their most probable structures, and indicated that the M-β-CD inclusion system gave the higher complexation efficiency. The binding energy values for β-CD and M-β-CD were determined to be -6.7 and - 9.5 kcal/mol, respectively. These findings suggest the same as the result of experimental tests that the NOS-M-β-CD complex is more stable than the NOS-β-CD complex.

Computational Study on the Mechanism of the Photouncaging Reaction of Vemurafenib: Toward an Enhanced Photoprotection Approach for Photosensitive Drugs

The photochemical behavior of the photosensitive first-line anticancer drug vemurafenib (VFB) is of great interest due to the impact of such behavior on its pharmacological activity. In this work, we computationally elucidated the mechanism of the photoinduced release of VFB from the 4,5-dimethoxy-2-nitrobenzene (DMNB) photoprotecting group by employing various density functional theory (DFT)/time-dependent DFT (TD-DFT) approaches. The computational investigations included a comparative assessment of the influence of the position of the photoprotecting group as a substituent on the thermodynamics and kinetics of the photouncaging reactions of two VFB-DMNB prodrugs, namely pyrrole (N_P) and sulfonamide (N_S). With the aid of the DFT calculations concerning the activation energy barrier (∆G^‡), the obtained results suggest that the step of the photoinduced intramolecular proton transfer of the DMNB moiety is not detrimental concerning the overall reaction profile of the photouncaging reaction of both prodrugs. However, the obtained results suggested that the position of the substitution position of the DMNB photoprotecting group within the prodrug structure has a substantial impact on the photouncaging reaction. In particular, the DMNB-N_s-VFB prodrug exhibited a notable increase in ∆G^‡ for the key step of ring opining within the DMNB moiety indicative of potentially hindered kinetics of the photouncaging process compared with DMNB-N_p-VFB. Such an increase in ∆G^‡ may be attributed to the electronic influence of the N_P fragment of the prodrug. The results reported herein elaborate on the mechanism of the photoinduced release of an important anticancer drug from photoprotecting groups with the aim of enhancing our understanding of the photochemical behavior of such photosensitive pharmaceutical materials at the molecular level.

Second-derivative synchronous spectrofluorimetric assay of dapagliflozin: Application to stability study and pharmaceutical preparation

A highly accurate, simple and sensitive spectrofluorimetric analytical method for dapagliflozin (DGF) quantitation was developed. The proposed method was successively applied to DGF analysis in both its pure and pharmaceutical dosage forms. This method was developed to investigate DGF stability in its degradation products, as laid out in International Council for Harmonisation (ICH) rules. Kinetics of alkaline degradation of DGF was also calculated. The half-life time (t_1/2 ) of the reaction was 75.32 min. An alkaline degradation pathway was described. The present study involved measurement of the second-derivative synchronous fluorescence intensity of DGF at Δλ = 30 nm. Peak amplitude was measured at 322 nm. Linear range of the calibration curve was 0.1-1.0 μg ml^-1 . Lower detection and quantitation limits were 0.023 and 0.071 μg ml^-1 , respectively, and indicated good sensitivity of the proposed method. Mean per cent recovery was 99.78 ± 1.78%. The proposed analytical approach was successfully applied to DGF in the quality control laboratory and would be suitable as a stability-indicating assay.

On the encapsulation of Olsalazine by β-cyclodextrin: A DFT-based computational and spectroscopic investigations

In this work, the supramolecular host-guest interaction of the prodrug Olsalazine (OLZ) and β-Cyclodextrin (β-CD) was examined experimentally and computationally. Experimentally, employing the UV-Vis spectroscopic method in aqueous media at various pH's, results obtained using the Benesi-Hilderbrand approach demonstrated that OLZ can form supramolecular inclusion complex with β-CD with stoichiometric ratio of 1:1. Furthermore, these results revealed that the formation of OLZ: β-CD complexes exhibited insignificant pH dependency in the range 5-8 with an average binding constant (K_b) of approximately 1×10³M^-1. Computationally, geometry optimization of 1:1 OLZ: β-CD complexes was performed employing the ONIOM (DFT((ωB97XB)/6-31+G(d)),SQM(PM3)) approach. Obtained results demonstrated that OLZ: β-CD complex is stabilized by the formation of intermolecular hydrogen bonds with an average length of approximately 1.8Å. Additionally, the stability of OLZ: β-CD complex was demonstrated employing ADMP molecular dynamic simulations over a timeframe of 500fs. The molecularity of the supramolecular host-guest interaction between OLZ and β-CD is presented and interpreted in the essence of TD-DFT and molecular orbitals analyses.

Liquid chromatographic and spectrofluorimetric assays of empagliflozin: Applied to degradation kinetic study and content uniformity testing

Stability-indicating high-performance liquid chromatography (HPLC) and spectrofluorimetric methods were developed for determination of empagliflozin (EGF). EGF was subjected to oxidation, wet heat, photo-degradation, acid hydrolysis and alkali hydrolysis. The alkaline degradation pathway was subjected to a kinetics study as the major product obtained after stress conditions. Arrhenius plots were constructed and the activation energies of the degradation process were calculated. HPLC was used for the kinetic study as it enabled simultaneous determination of EGF and the degradation product while the spectrofluorimetric assay was applied to content uniformity testing due to its higher sensitivity and lower limit of detection (LOD). Isocratic chromatographic elution was attained for HPLC on a Intersil® C₁₈ column (150 mm × 4 mm, 5 μm), using a mobile phase of acetonitrile-potassium dihydrogen phosphate buffer pH 4, (50:50, v/v) at a flow rate of 1 ml/min with ultraviolet (UV) detection at 225 nm. The relative fluorescence intensity was recorded by spectrofluorimeter applying synchronous mode using ∆λ = 70 nm at 297.6 nm. Linearity ranges were found to be 5-50 μg/ml and 50-1000 ng/ml for HPLC and spectrofluorimetric methods, respectively.

Effects of RAMEB and/or mechanical mixing on the bioavailability and biodegradation of PCBs in soil/slurry

Microbial remediation is preferred as a clean and cost-effective method for restoring environments polluted by organics. But the biodegradation rates of hydrophobic organic contaminants (HOCs) are usually extremely restricted by their low bioavailability, especially in soil. Here, a physical method (mechanical mixing) and a chemical method (randomly methylated-β-cyclodextrins, RAMEB) were adopted to improve the bioavailability and biodegradation of polychlorinated biphenyls (PCBs) of an aged soil. The bioavailability of tri-CBs was increased by adding RAMEB in soil/slurry or assisting mechanical mixing in slurry, but these methods had no effects on the bioavailability of tetra-CBs and high chlorinated PCBs (Cl > 4). The degradation rate of tri-CBs could be obviously enhanced by adding RAMEB in soil or assisting mechanical mixing in slurry. The highest removal amount of tri-CBs reached 43.8% in 100 d with a first-order decay kinetics constant of 0.0059 d(-1). But the removal of tetra-CBs and high chlorinated PCBs (Cl > 4) were not significant in all mesocosms, possibly due to the lack or weakness of the native degrading microflora. Based on the analysis of the richness and diversity of bacterial communities, the characteristics of the heatmap and the variation of bphC copy numbers in the soil/slurry mesocosms, it could be inferred that there was no obvious corresponding relationship between the variation of the bacterial communities and the physical/chemical measures.

Phenylcarboxyl-decorated tetraphenylethene with diverse molecular RIM-induced emission from host–guest inclusion and aggregation formation

Basing on an amphiphilic TPE molecule, host–guest complexation with α-CD could be obtained. For the cavity restrict the motions of AIE molecules the RIM induced fluorescence could be confirmed which clarified the slightly difference from AIE process.