Vijisha K. Rajan

A computational investigation on the structure, global parameters and antioxidant capacity of a polyphenol, Gallic acid

A computational DFT-B3LYP structural analysis of a poly phenol, Gallic acid (GA) has been performed by using 6-311++ G (df, p) basis set. The GA is a relatively stable molecule with considerable radical scavenging capacity. It is a well known antioxidant. The NBO analysis shows that the aromatic system is delocalized. The results reveal that the most stable radical is formed at O3-atom upon scavenging the free radicals. Global descriptive parameters show that GA acts as an acceptor center in charge transfer complex formation which is supported by ESP and contour diagrams and also by Qmax value. The GA is a good antioxidant and it can be better understood by HAT and TMC mechanisms as it has low BDE, ΔHacidity and ΔGacidity values. The ΔBDE and ΔAIP values also confirm that the antioxidant capacity of GA can be explained through HAT rather than the SET-PT mechanism.

Green synthesis of pure and doped semiconductor nanoparticles of ZnS and CdS

Abstract Nanoparticles of pure and Cu/Ag-doped CdS and ZnS have been synthesized via chemical bath deposition without using any capping or toxic reagents. The synthesis was carried out through a simple and less expensive green method. The XRD result shows that both pure CdS and ZnS and their doped derivatives are of high crystalline with hexagonal packing structure. The average crystalline size of all nanoparticles was calculated using Debye–Scherrer formula. The crystalline size of nanoparticles of pure samples varied with that of the doped sample. The average crystalline sizes of all nanoparticles are found to be in the range of 5.5–2.2 nm for CdS (from pure to doped) and 4.3–3.4 nm for ZnS, respectively. The band gap values obtained from UV-visible spectra are in the range of 3.5–2.1 eV for CdS and 3.3–2.7 eV for ZnS derivatives, respectively. The FTIR spectral data give characteristic peaks for Cd—S, Cu—S, Ag—S and Zn—S bonds and confirm the formation of respective nanoparticles. The peaks corresponding to the microstructural formation are also observed. The FE-SEM images show the granular morphological structure for all the samples. The agglomeration size of the samples in the range of 10–50 nm for CdS:Cu and 50–100 nm for ZnS:Cu is observed.

A DFT based analysis of adsorption of Hg2+ ion on chitosan monomer and its citralidene and salicylidene derivatives: Prior to the removal of Hg toxicity

A Density functional theory based study of adsorption of the toxic metal Hg (II) ion by chitosan monomer and two of its derivatives; citralidene and salicylidene chitosan, has been performed. The effect of structural features on the stability of studied complexes has been analyzed by using Gaussian03 software package. All the possible conformations of these adsorbents were studied using the global minimum geometries. All the adsorbing sites were studied by placing the metal ion on the centroid of the atoms and the stable conformer of the adsorbent-metal ion complex was identified. Interaction between Hg (II) and the adsorbents is found to be electrostatic. Metal ion binding with nitrogen atom is stronger than that with oxygen atoms in all the cases as the charge density of nitrogen is enhanced on Schiff base formation. The advantage of derivatives over chitosan monomer is their stability in acidic media. ΔE value of the complexes are in the order SC-Hg (II)>chitosan-Hg (II)>CC-Hg (II) which indicates that the stability of complexes increases with increase in energy gap. The study reveals that aromatic Schiff base derivatives of chitosan is better for Hg(II) intake than aliphatic derivatives.

Experimental and density functional theory studies on benzalkonium ibuprofenate, a double active pharmaceutical ingredient

Molecular aspects of a double active pharmaceutical ingredient in ionic liquid form, benzalkonium ibuprofenate (BaIb), were studied using density functional theory (DFT/B3LYP/6-31+G (d, p)). A detailed discussion on optimized geometry, energy, heat and the enthalpy of BaIb was carried out. The computed vibrational results agree well with the experimental results. The stability and biological activity were compared to the parent drugs on the basis of global descriptive parameters. The electrophilic and nucleophilic sites were pointed out in the MESP structures well evidently. NBO analysis was also done to predict the relative aromaticity, delocalization effects and the contribution towards stabilization energy of the title compound. The information about non-covalent, non-ionic weak interaction between the cation and anion was obtained from the list of Mulliken charges and NBO analysis.

The natural food colorant Peonidin from cranberries as a potential radical scavenger – A DFT based mechanistic analysis

A theoretical evaluation of the antioxidant property of a natural food colorant Peonidin has been performed. The most suitable mechanism for explaining the radical scavenging capacity of Peonidin is the Hydrogen Atom Transfer and the most active site for radical formation is position 3 and is confirmed through Mulliken charge analysis, pKa value evaluation, Bond Dissociation Energy values, and Natural Bond Orbital analysis. Position 3 and 5 in Peonidin exists in blood as deprotonated as their pKa values are lower than the pH of blood. Peonidin is highly reactive than Quercetin and less stable than flavan-3-ols due to the small band gap. Global descriptor analysis shows that PN prefers to accept electrons than to donate. The effect of number of OH groups and the nature of substituents are well explained through this work.

A comparative study on the druggability of Schiff bases and dithiocarbamate derivatives of chitosan

The druggability of the Schiff bases and dithiocarbamate derivatives of chitosan was examined; the oral bioavailability and bioactivity of all these molecules against selected drug targets were investigated, as well as ADME/Tox studies were conducted. It was observed that the Lipinski’s rule of five was satisfied by all the molecules. The Schiff bases and dithiocarbamate derivatives of chitosan also show good bioactivity score for protease and enzyme inhibition. The ADME/Tox studies conducted show that almost all the derivatives are free from toxicity risks, except citral- and sulfur-containing derivatives. Substitution of the –SH group by –NH2 gives better positive results in toxicology studies. From this study, it has been observed that these molecules exhibit fairly good drug score and are orally viable molecules. The mechanism driving their bioactivity might be chelation of chitosan and its derivatives with essential metal ions. Chitosan and the derivatives studied can serve as good lead molecules for further research.

Data on the UV filtering and radical scavenging capacity of the bitter masking flavanone Eriodictyol

A computational analysis of UV filtering and radical scavenging capacity of a flavanone, Eriodictyol has been performed under DFT-B3LYP/6–31+ G (d, p). Eriodictyol is nontoxic and nonirritant bitter masker used in wine and can be used for photo protection due to its potential UV filtering and radical scavenging capacity. The compound has an absorbance in the UV-A and UV-B region of electromagnetic spectrum, it can be used as a potential UV filter in sunscreen lotions and other cosmetic products. Eriodictyol is a potent antioxidant than the most commonly studied Quercetin. The most active site in the compound is 3׳ position and is confirmed by NPA, NBO and pKa value analysis. The BDE values follow the order 3′<4′<7<5. The major transitions in the UV–visible spectrum of Eriodictyol are between HOMO and HOMO-1 with LUMO level and are well explained by NBO–NLMO tool in G09.