Hydroxycinnamic acids (HCAs) are important phytochemicals possessing significant biological properties. Several investigators have studied in vitro antioxidant activity of HCAs in detail. In this review, we have gathered the studies focused on the structure-activity relationships (SARs) of these compounds that have used medicinal chemistry to generate more potent antioxidant molecules. Most of the reports indicated that the presence of an unsaturated bond on the side chain of HCAs is vital to their activity. The structural features that were reported to be of importance to the antioxi-dant activity were categorized as follows: modifications of the aromatic ring, which include alterations in the number and position of hydroxy groups and insertion of electron donating or withdrawing moieties as well as modifications of the car-boxylic function that include esterification and amidation process. Furthermore, reports that have addressed the influence of physicochemical properties including redox potential, lipid solubility and dissociation constant on the antioxidant activ-ity were also summarized. Finally, the pro-oxidant effect of HCAs in some test systems was addressed. Most of the investigations concluded that the presence of ortho-dihydroxy phenyl group (catechol moiety) is of significant importance to the antioxidant activity, while, the presence of three hydroxy groups does not necessarily improve the activity. Optimiza-tion of the structure of molecular leads is an important task of modern medicinal chemistry and its accomplishment relies on the careful assessment of SARs. SAR studies on HCAs can identify the most successful antioxidants that could be use-ful for management of oxidative stress-related diseases.Keywords: Antioxidant, hydroxycinnamic acids, in vitro, ROS, structure-activity relationships. OXIDATIVE STRESS AND ANTIOXIDANTSReactive oxygen species (ROS) are oxygen derived molecules that readily react with other compounds and macromolecules and oxidize them. Some representative exam-ples of these species include superoxide (O2•-), hydroxy (HO • ) and peroxy (ROO • ) radicals, hydrogen peroxide (H2O2) and singletROS are involved in important physiological processes such as immune response, gene expression, signal transduc-tion and growth regulation [5,6]; however if they are not kept under tight control by physiological antioxidant systems they will be able to oxidize and damage various biological molecules leading to a condition called oxidative stress [1,7,8]. In this regard, oxidative stress has been reported to be in-volved in the pathogenesis of diseases such as cancer [9], neurodegenerative diseases [10], stroke [11], and others [12,13].Since an important source of ROS comes from environment [14], with the industrial development and the change in life style, oxidative stress related diseases need a special attention [15].Antioxidants operate by preventing or slowing the progression of oxidative damage reactions [16,17]. An antioxidant has been defined as "any substance that delays, p...

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Isatin is an important compound from the biological aspect of view. It is an endogenous substance and moreover; various pharmacological activities have been reported for isatin and its derivatives. In-vitro cytotoxic effects of the prepared isatin Schiff bases toward HeLa, LS180 and Raji human cancer cell lines has been reported in our previous work. 3-(2-(4-nitrophenyl)hydrazono) indolin-2-one was found to be the most potent one among the studied compounds (IC(30) =12.2 and 21.8 μM in HeLa and LS-180 cell lines, respectively). Obtained biological data could be well interpreted using docking binding energies toward vascular endothelial growth factor receptor (VEGFR-2); a key anticancer target being biologically investigated against various isatin derivatives. In the present work, quantum mechanical (QM) method including functional B3LYP in association with split valence basis set using polarization functions (Def2-SVP) was used to estimate individual ligand-residue interaction energies for the docked 3-(2-(4-nitrophenyl)hydrazono) indolin-2-one into VEGFR-2 active site. Results were further interpreted via calculated polarization effects induced by individual amino acids of the receptor active site. A fairly good correlation could be found between polarization effects and estimated binding energies (R(2) =0.7227). Conformational analysis revealed that 3-(2-(4-nitrophenyl) hydrazono) indolin-2-one might not necessarily interact with the VEGFR-2 active site in its minimum energy conformation.

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Considering lack of validated therapeutic drugs or vaccines against contagious SARS-CoV2, various efforts have been focused on repurposing of existing drugs or identifying new agents. In an attempt to identify new and potential SARS-CoV2 inhibitors targeting specific enzyme of the pathogen, a few induced fit models of SARS-CoV2 main protease (Mpro) including N-aryl amide and aryl sulfonamide based fragments were subjected to a multi-step in silico strategy. Sub-structure query of co-crystallographic fragments provided numerous ZINC15 driven commercially available compounds that entered molecular docking stage to find binding interactions/modes inside Mpro active site. Docking results were reevaluated through time dependent stability of top-ranked ligand-protease complexes by molecular dynamics (MD) simulations within 50 ns. Relative contribution of interacted residues in binding to the most probable binding pose was estimated through amino acid decomposition analysis in B3LYP level of theory with Def2-TZVPP split basis set. In confirmation of docking results, MD simulations revealed less perceptible torsional distortions (more stable binding mode) in binding of ZINC_252512772 (DG b À9.18 kcal/mol) into Mpro active site. H-bond interactions and hydrophobic contacts were determinant forces in binding interactions of in silico hit. Quantum chemical calculations confirmed MD results and proved the pivotal role of a conserved residue (Glu166) in making permanent hydrogen bond (98% of MD simulations time) with ZINC_252512772. Drug-like physicochemical properties as well as desirable target binding interactions nominated ZINC_252512772 as a desirable in silico hit for further development toward SARS-CoV2 inhibitors. HIGHLIGHTS A few N-aryl amide/aryl sulfonamide based fragments were subjected to a multi-step in silico strategy to afford potential SARS-CoV2 Mpro inhibitors. MD simulations revealed less perceptible torsional distortions (more stable binding mode) in binding of ZINC_252512772 (DG b-9.18 kcal/mol) into Mpro active site. H-bond interactions and hydrophobic contacts were determinant forces in binding interactions of in silico hit. Quantum chemical calculations confirmed MD results and proved pivotal role of a conserved residue (Glu166) in making permanent hydrogen bond (98% of MD simulations time) with ZINC_252512772.

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The currently available therapies for type 2 diabetes have been unable to achieve normoglycemic status in the majority of patients. The reason may be attributed to the limitations of the drug itself or its side effects. In an effort to develop potent and safe oral antidiabetic agents, we evaluated the in vitro and in vivo hypoglycemic effects of 10 synthetic polyphenolic curcumin analogues on alloxan-induced male diabetic albino rats. In vitro studies showed 7-bis(3,4-dimethoxyphenyl)hepta-1,6-diene-3,5-dione (4) to be the most potential hypoglycemic agent followed by 1,5-bis(4-hydroxy-3-methoxyphenyl)penta-1,4-dien-3-one (10). Structure activity relationship (SAR) of the tested compounds was elucidated and the results were interpreted in terms of in vitro hypoglycemic activities. Furthermore, oral glucose tolerance test (OGTT) with compounds 4, 10 and reference hypoglycemic drug glipizide showed that compound 4 and glipizide had relatively similar effects on the reduction of blood glucose levels within 2 h. Thus, compound 4 might be regarded as a potential hypoglycemic agent being able to reduce glucose concentration both in vitro and in vivo.