Ankit Mittal

Bio: Ankit Mittal is an academic researcher from University of Delhi. The author has contributed to research in topics: Electron transfer & Natural bond orbital. The author has an hindex of 2, co-authored 8 publications receiving 18 citations.

The effect of solvent polarity on the antioxidant potential of echinatin, a retrochalcone, towards various ROS: a DFT thermodynamic study.

Abstract: The antioxidant properties of echinatin (Ech), isolated from liquorice, have recently been reported. It is well known that the free radical species can be deactivated by phenolic antioxidants via different mechanistic pathways. In this work, the scavenging of eighteen different reactive oxygen species (ROS) has been considered, focussing on three main working mechanisms, namely hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET). The investigations have been performed in different dielectric media, viz. gas phase, benzene, methanol and aqueous solution, using density functional theory (DFT) calculations at the M05-2X/6-311++G** level. Various molecular descriptors have been elucidated for Ech as well as the ROS and compared with the reference antioxidant molecule, trolox. In addition, the redox potentials and the equilibrium constants have been calculated to discuss the feasibility of the overall scavenging process. The results demonstrate that the 4-OH group is the first site for H-atom donation, followed by 4'-OH. Further, it has been found that HAT would be the most favourable mechanism in the gas phase. The SPLET mechanism is thermodynamically favoured in polar media like water and methanol, while in the case of non-polar solvents like benzene, the two mechanisms are observed to be competitive.

A DFT study of the conformational and electronic properties of echinatin, a retrochalcone, and its anion in the gas phase and aqueous solution

Abstract: Echinatin (Ech), a characteristic retrochalcone isolated from liquorice, a widely used herbal medicine, has been investigated in detail in terms of its conformational and electronic properties in different dielectric media using density functional calculations. Natural bond orbital (NBO) analysis suggests an extended conjugation in the molecule, including a keto-ethylenic group (–CO–CH=CH–) connecting both the rings. The aromaticity of Ech has been studied using the nucleus-independent chemical shift (NICS) method. The acidity constants (pKa) have been simulated for both the hydroxyl groups in the molecule. Molecular electrostatic potentials (MEPs) have been computed to predict the reactivity of Ech toward both electrophiles and nucleophiles. Further, the electronic spectra of the neutral and deprotonated states have been computed in different solvents using an implicit solvation model, SMD. The vibrational spectra of both the neutral and anionic forms have also been simulated. Besides these, 1H-NMR and 13C-NMR spectra have been computed and compared with the experimental values. In addition, the frontier molecular orbital (FMO) energies, a number of global reactivity descriptors, viz., chemical hardness (η), chemical potential (μ), global softness (S), global electrophilicity (ω), and nucleophilicity (N) indices and various thermodynamic parameters have also been calculated in order to get a better insight into the molecular properties.

Synthetic methods and biological applications of retrochalcones isolated from the root of Glycyrrhiza species: A review

Abstract: In the search for novel drugs for health preservation, the active ingredients of medicinal herbs have been used since time immemorial. Liquorice, a potent medicinal herb derived from the root and rhizomes of Glycyrrhiza species, has been used worldwide for the treatment of various diseases. A number of compounds have been isolated from the liquorice root, including retrochalcones, viz. echinatin, licochalcone A, B, C, D and E, having a diverse range of pharmacological applications such as antioxidant, anti-inflammatory, anti-cancer, anti-bacterial, anti-diabetic, anti-obesity, anti-parasitic, to name a few. This review highlights the different synthetic procedures for retrochalcones and their in vitro, in vivo, ex vivo and in silico studies, along with the underlying molecular mechanisms. In addition, the total syntheses of licochalcone F and H, the regioisomers of licochalcone E and C, respectively, have also been included. Herein, the maximum possible biological applications of retrochalcones cited so far in the literature have been reviewed. The insights from this review will further advance the role and application of retrochalcones in the field of medicinal chemistry.

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

The effect of solvent polarity on the antioxidant potential of echinatin, a retrochalcone, towards various ROS: a DFT thermodynamic study.

Abstract: The antioxidant properties of echinatin (Ech), isolated from liquorice, have recently been reported. It is well known that the free radical species can be deactivated by phenolic antioxidants via different mechanistic pathways. In this work, the scavenging of eighteen different reactive oxygen species (ROS) has been considered, focussing on three main working mechanisms, namely hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET). The investigations have been performed in different dielectric media, viz. gas phase, benzene, methanol and aqueous solution, using density functional theory (DFT) calculations at the M05-2X/6-311++G** level. Various molecular descriptors have been elucidated for Ech as well as the ROS and compared with the reference antioxidant molecule, trolox. In addition, the redox potentials and the equilibrium constants have been calculated to discuss the feasibility of the overall scavenging process. The results demonstrate that the 4-OH group is the first site for H-atom donation, followed by 4'-OH. Further, it has been found that HAT would be the most favourable mechanism in the gas phase. The SPLET mechanism is thermodynamically favoured in polar media like water and methanol, while in the case of non-polar solvents like benzene, the two mechanisms are observed to be competitive.