Computational and spectral studies of 3,3'-(propane-1,3-diyl)bis(7,8-dimethoxy-1,3,4,5-tetrahydro-2H-benzo[d]azepin-2-one)

A new stability indicating HPLC method with QDa and PDA detectors for the determination of process and degradation impurities of ivabradine including separation of diastereomeric N-oxides

In this study, a new reversed phase high performance liquid chromatography method using two detectors was developed for the analysis of degradation and process impurities of ivabradine in pharmaceutical preparations. A PDA detector set to 285 nm wavelength and a QDa detector set to positive scan mode were used in the method. In the developed method, the separation process was carried out in a Zorbax phenyl column with a gradient application of a 0.075% trifluoroacetic acid, acetonitrile, and methanol mixture at a flow rate of 1.5 ml min-1. During the degradation studies, the samples were exposed to acidic, alkaline, oxidative, thermal, and photolytic conditions. Process-related impurities were separated not only without interfering with each other but also with the degradation product and ivabradine peaks, and thanks to QDa, all impurities could be identified with their molecular weights. This method, in addition to providing stability data, was also able to separate two diastereomeric N-oxide impurities which are major oxidative degradation impurities of ivabradine having a chiral center. Some additional measurements such as solubility, specific rotation, melting point and differential scanning calorimetry analysis proved the formation of the two diastereomeric N-oxide impurities under oxidative conditions. Method validation was performed according to the International Council for Harmonization guidelines and the analysis of ivabradine, its process related impurities (dehydro ivabradine, acetyl ivabradine, and hydroxy ivabradine) and a major oxidative degradation product (ivabradine N-oxide) was successfully performed by this method.

Differentiation of puerarin chelate from salt by phase solubility test

Different from salt, metal chelate is a novel state of drug constructed by more separate coordinate bonds to form a chelating circle. Due to their composition similarity, it is hard to distinguish them except identifying ionic bond (i.e., salt) or coordinate bond (i.e., chelate) in the single crystal structure. In this study, sodium chelate (CDCC No: 1865670) and lithium salt (CDCC No: 2161617) of puerarin (PUE) was prepared. In addition to difference in single crystal structure, it was found that they showed totally different phase solubility behaviors: lithium salt demonstrated a typical inverse proportion curve as other common salts, while sodium chelate exhibited disordered scatters. However, when incorporating the unit PUE-Na complex in solution state and complexation constant K11 in chemical equation, the scatters in phase solubility diagram of chelate could be well fitted and the value of K11 was dramatically higher with orders of magnitude than the dissociation constant Kc; while processing phase solubility curve of lithium salt by incorporating complex item, it could not well match the curve at all. PUE sodium chelate is more likely to be a weak electrolyte with partial dissociation, while PUE lithium salt acted as a strong electrolyte with complete dissociation. The phase solubility test would be served as a surrogate tool for differentiation of chelates from salts when single crystal was not available.

Computational Investigation of Ligand Binding of Flavonoids in Cytochrome P450 Receptors

AIM

The cytochrome P450 enzymes play a significant role in regulating cellular and physiological processes by activating endogenous compounds. They also play an essential role in the detoxification process of xenobiotics. Flavonoids belong to a class of polyphenols found in food, such as vegetables, red wine, beer, and fruits, which modulate biological functions in the body.

METHODS

The inhibition of CYP1A1 and CYP1B1 using nutritional sources has been reported as a strategy for cancer prevention. This study investigated the interactions of selected flavonoids binding to the cytochrome P450 enzymes (CYP1A1 and CYP1B1) and their ADMET properties in silico. From docking studies, our findings showed flavonoids, isorhamnetin and pedalitin, to have the strongest binding energies in the crystal structures 6DWM and 6IQ5.

RESULTS

The amino acid residues Asp 313 and Phe 224 in 6DWM interacted with all the ligands investigated, and Ala 330 in 6IQ5 interacted with all the ligands examined. The ligands did not violate any drug-likeness parameters.

CONCLUSION

These data suggest roles for isorhamnetin and pedalitin as potential precursors for natural product- derived therapies.

Synthesis, biological evaluation and in silico studies of new pyrazoline derivatives bearing benzo[d]thiazol-2(3H)-one moiety as potential urease inhibitors

Novel pyrazoline derivatives containing benzo[d]thiazol-2(3H)-one moiety were synthesized and screened for their inhibitory properties against to urease, a clinically important metabolic enzyme. In vitro enzyme inhibition studies revealed that all pyrazolines (7.21-87.77 µM) were more potent than the standard inhibitor acetohydroxamic acid (251.74 µM) against the urease enzyme. Most notably, compound 2m , which is more active than the other compounds in in vitro and molecular docking studies, showed a significant inhibition potential and efficient IC 50 values (7.21±0.09 µM) and in silico inhibition constant (0.11 µM). Furthermore, molecular dynamics (MD) simulation analysis suggests that the binding stability of urease enzyme and compound 2m were stably maintained during the 100 ns simulation time. Compound 2m also exhibited good physicochemical and pharmacokinetic parameters. The overall results of urease inhibition have indicated that these pyrazoline derivative compounds can be further optimized and developed for the discovery of novel urease inhibitors.

Preliminary investigation of drug impurities associated with the anti-influenza drug Favipiravir - An insilico approach

The role of repurposed or modified antiviral drugs has become more significant during the current global pandemic of SARS Covid-19. In the present study, four structurally analogous impurity molecules of antiviral drug Favipiravir are selected for preliminary computational investigation for assessing the structure-activity relationship. The optimized geometry and the electronic structures of the compounds are computed using Density Functional Theory as a precursor to evaluating their physical, chemical and spectral properties. The frontier orbitals analysis is performed to obtain global reactivity parameters namely, the chemical potential, absolute electronegativity, global softness, global hardness, electrophilicity, etc. The natural Bond Orbital (NBO) analysis and Mulliken analysis provided an understanding of the charge-transfer interactions of molecules. The possibilities of intermolecular interactions of the drug systems with the receptors are also visualized using the electrostatic potential maps (MEP) derived from the DFT computations. The physiochemical properties are assessed computationally using SwissADME webtool to correlate the structural aspects of the compounds with their biological responses. Useful parameters namely flexibility, lipophilicity, size, polarity, solubility and saturation were also computed to evaluate the therapeutic activity or drug-likeness.

From Infection Clusters to Metal Clusters: Significance of the Lowest Occupied Molecular Orbital (LOMO)

In this paper, the nature of the lowest-energy electrons is detailed. The orbital occupied by such electrons can be termed the lowest occupied molecular orbital (LOMO). There is a good correspondence between the Hückel method in chemistry and graph theory in mathematics; the molecular orbital, which chemists view as the distribution of an electron with a specific energy, is to mathematicians an algebraic entity, an eigenvector. The mathematical counterpart of LOMO is known as eigenvector centrality, a centrality measure characterizing nodes in networks. It may be instrumental in solving some problems in chemistry, and also it has implications for the challenge facing humanity today. This paper starts with a demonstration of the transmission of infectious disease in social networks, although it is unusual for a chemistry paper but may be a suitable example for understanding what the centrality (LOMO) is all about. The converged distribution of infected patients on the network coincides with the distribution of the LOMO of a molecule that shares the same network structure or topology. This is because the mathematical structures behind graph theory and quantum mechanics are common. Furthermore, the LOMO coefficient can be regarded as a manifestation of the centrality of atoms in an atomic assembly, indicating which atom plays the most important role in the assembly or which one has the greatest influence on the network of these atoms. Therefore, it is proposed that one can predict the binding energy of a metal atom to its cluster based on its LOMO coefficient. A possible improvement of the descriptor using a more sophisticated centrality measure is also discussed.