Synthesis and Antioxidant Studies of 2,4-Dioxothiazolidine-5-acetic Acid Based Organic Salts: SC-XRD and DFT Approach

In the current study, two organic salts (1 and 2) are synthesized, and then crystalline structures are characterized by FTIR, UV spectroscopy, and X-ray crystallographic studies. The organic salts 1 and 2 are optimized at the M06/6-311G(d,p)level of theory and further utilized for analysis of natural bond orbitals (NBOs), natural population, frontier molecular orbitals (FMOs), and global reactivity parameters, which confirmed the stability of the studied compounds and charge transfer phenomenon in the studied compounds. The studies further revealed that 1 and 2 are more stable than 3. The lowest energy merged monomer-coformer conformations were docked as flexible ligands with rigid fungal proteins and DNA receptors. The stagnant binding of the monomer through two H bonds with protein was observed for ligands 1 and 3 while different pattern was found with 2. The coformers formed a single H bond with the active site in 2 and 3 and a single pi-arene H interaction in 1. The two-point ligand-receptor interactions hooked the monomer between DNA base pairs for partial intercalation; pi stacking with additive hydrogen bonding with the base pair led to a strong benzimidazole interaction in 1 and 2, whereas ethylene diamine formed weak H bonding. Thus, the molecular docking predicted that the coformer exhibited DNA intercalation reinforced by its salt formation with benzimidazole 1 and methyl benzimidazole 2. Antioxidant studies depicted that 3 has a higher IC50 value than that of 2,4-D and also the largest value among the studied compounds, whereas 2 showed the lowest value among the studied compounds.

Investigation of redox mechanism and DNA binding of novel 2-(x-nitrophenyl)-5-nitrobenzimidazole (x = 2, 3 and 4)

The present study describes the investigation of the binding modes of potential anti-cancerous nitrophenyl derivatives of 2-(x-nitrophenyl)-5-nitrobenzimidazole with calf thymus DNA. The -2-(x-nitrophenyl)-5-nitrobenzimidazoles under investigation differ only in position x of nitro group in nitrophenyl substituent relative to benzimidazole moiety leading to 1-NPNB (x = 2), 2-NPNB (x = 3) and 3-NPNB (x = 4). The DFT calculations predicted that derivatives were electrochemically reducible which was then confirmed by cyclic voltammetry. In cyclic voltammetry, the second reversible peak was dependent on first irreversible reduction. This revealed that electrochemical irreversible process was governed by some other process which was then followed by reversible second electron transfer. Thus, ECE (electron transfer leading to coupled chemical reaction followed by another electron transfer process) mechanism was attributed for electrochemical reduction. Experimental results based on UV-Vis spectroscopy vaguely showed intercalation of 1-NPNB, 2-NPNB and 3-NPNB into DNA which was assisted by cyclic voltammetry. However, thermal melting and florescence spectroscopy unambiguously established intercalation for all three compounds. Molecular docking analysis ascertained in pocket stacking of 5-nitrobenzimidazole moiety in 1-NPNB and 2-NPNB while nitro phenyl substitution in 3-NPNB stacks between DNA base pair during intercalation which was in agreement with DFT computed molecular geometry. Therefore, the relative positions of nitro group and 5-nitrobenzimidazole moieties in 2-(x-nitrophenyl)- 5-nitrobenzimidazole influenced the DNA binding pattern of compounds during intercalation. The cytotoxicity of these compounds was comparable to standard drug doxorubicin against both cancerous (MCF-7) and normal (MCF-10A) breast cells which depicts their anti-cancerous potential.

Radical scavenging propensity of Cu2+, Fe3+ complexes of flavonoids and in-vivo radical scavenging by Fe3+-primuletin

Cu²⁺ and Fe³⁺ complexes of three flavonoids (morin or mo, quercetin or quer and primuletin or prim) were synthesized with the objective of improving antioxidant capacities of flavonoids. The radical scavenging activities of pure flavonoids and their metal complexes were assayed to monitor their tendencies towards sequestering of radicals at physiological conditions. The scavenger potencies of metal-flavonoid complexes were significantly higher than those of the parent flavonoids. Further, influence of the solvent polarity on the radical capturing by flavonoids and their metal complexes was in favor for the polar solvent. Fe³⁺-prim displayed its radical scavenging ability via up gradation of CAT and SOD activities in in-vivo antioxidant assays.

β-Cyclodextrin assisted solubilization of Cu and Cr complexes of flavonoids in aqueous medium: a DNA-interaction study

Cu and Cr complexes of three flavonoids (morin, quercetin and 6-hydroxyflavone) were synthesized and included in beta-cyclodextrin (βCD) with the objective of improving their pharmacokinetic profiles. Then binding with ds.DNA was studied to monitor their interactive tendencies at physiological conditions. The binding constants and other thermodynamic data from UV-vis spectroscopy and cyclic voltammetry revealed Cr-flavonoid-βCD to interact with ds.DNA at pH-7.4 through electrostatic mode of binding while Cu-flavonoid-βCD can intercalate into DNA. The strong binding propensity of Cu-flavonoid-βCD with ds.DNA encourages their application as anticancerous agent.