Hyaluronic Acid Hydrogels Crosslinked in Physiological Conditions: Synthesis and Biomedical Applications

Hyaluronic acid (HA) hydrogels display a wide variety of biomedical applications ranging from tissue engineering to drug vehiculization and controlled release. To date, most of the commercially available hyaluronic acid hydrogel formulations are produced under conditions that are not compatible with physiological ones. This review compiles the currently used approaches for the development of hyaluronic acid hydrogels under physiological/mild conditions. These methods include dynamic covalent processes such as boronic ester and Schiff-base formation and click chemistry mediated reactions such as thiol chemistry processes, azide-alkyne, or Diels Alder cycloaddition. Thermoreversible gelation of HA hydrogels at physiological temperature is also discussed. Finally, the most outstanding biomedical applications are indicated for each of the HA hydrogel generation approaches.

Review Article on Metal Complexes derived from 2’-hydroxyacetophenone based Schiff Base

In this review article, we try to cover various studies have been done on 2’-hydroxyacetophenone based schiff bases and formed metal complexes such as Formation with diamine, amino acids etc., antibacterial, antifungal, cytotoxicity, larvicidal, oxidation-reduction and schiff base Formation with different amine group containing compounds etc.

Design and Characterization of New Dinuclear Macrocyclic Dithiocarbamate Complexes by the Preparation of a Free Ligand Derived from Isopropylamine

The synthesis and structural characterization of new dithiocarbamate (DTC) ligand and some of its dinuclear transition metal complexes are described. The free dithiocarbamate ligand was prepared through several synthetic routes, including Schiff-base formation. The reaction of 2-aminopropane with terephthaldehyde leads to the formation of Schiff_base which is reduced by methanolic NaBH4 to the corresponding secondary diamine. Diamine( N,N'_ (1,4 phenylenebis (methylene)) bis(propan-2 amine)) reacts with (CS2) in a basic solution of (KOH) to provide the corresponding bis(dithiocarbamate) free_ligand, which undergoes complexation with the appropriate metal (II) chloride to constitute macrocyclic complexes. Characterization of the ligand and its complexes was achieved by FTIR, UV-Vis, melting points, conductance, magnetic susceptibility, and 1H, 13C NMR spectroscopy. The analytical and spectroscopic data were employed to obtain the suggested geometries around metal centres. These studies revealed the formation of dinuclear macrocyclic complexes of the general formula [M(L)]2 (where M= Mn(II) , Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)), with tetrahedral. geometries for Mn(II) , Fe(II), Co(II) and Zn(II), and square. planar geometry with Ni(II) and Cu(II) complexes.

Immobilization of Chondroitin Sulfate A onto Monolithic Epoxy Silica Column as a New Chiral Stationary Phase for High-Performance Liquid Chromatographic Enantioseparation

Chondroitin sulfate A was covalently immobilized onto a monolithic silica epoxy column involving a Schiff base formation in the presence of ethylenediamine as a spacer and evaluated in terms of its selectivity in enantioseparation. The obtained column was utilized as a chiral stationary phase in enantioseparation of amlodipine and verapamil using a mobile phase consisting of 50 mM phosphate buffer pH 3.5 and UV detection. Sample dilution by organic solvents (preferably 25% v/v acetonitrile-aqueous solution) was applied to achieve baseline enantioresolution (Rs > 3.0) of the individual drug models within 7 min, an excellent linearity (R2 = 0.999) and an interday repeatability of 1.1% to 1.8% RSD. The performance of the immobilized column for quantification of racemate in commercial tablets showed a recovery of 86–98% from tablet matrices. Computational modeling by molecular docking was employed to investigate the feasible complexes between enantiomers and the chiral selector.

Oxidation Assisted Fabrication of Sterculia Gum/Protein Hybrid Hydrogel Networks through Schiff Base Formation: Characterization and Swelling Kinetic Studies

Polysaccharide/protein hybrid conjugate system becomes an emerging system with integrated characteristics of protein as well as polysaccharide to be exploited for recent advancements in biomedical sectors. Present study is an attempt to fabricate a sterculia gum/gelatin hybrid hydrophilic network system via Schiff base formation using oxidative route at ambient conditions. This route transforms hydrogel synthesis through green mode without employing any crosslinking systems so as to minimize the toxicity issues associated. Fabricated Schiff base based gel systems have been characterized by FT-IR, powdered XRD, FESEM and EDX to confirm the inclusion of new characteristics, morphological changes and functionalization. Oxidation of natural gum drastically alter the physico-chemical behaviour of the gum as confirmed by powdered XRD by incorporating crystalline nature of oxidized sterculia gum as compared to the native sterculia gum and the Schiff base formed. The changes observed are due to the chemical modification of sterculia gum during Schiff base formation. Further the swelling capacity of oxidized sterculia gum and crosslinked network formed is also modulated and was less as compared to native sterculia gum and gelatin. This article also elaborates the mechanistic changes which take place during oxidative route of hydrogel formation in various segments of sterculia gum during oxidation and Schiff base formation.

SYNTHESIS AND ANTITUMOR ACTIVITY OF NEW MULTIFUNCTIONAL COUMARINS

Cancer constitutes one of the most severe public health menaces worldwide. It is imperative to synthesize new compounds and explore their antitumor activity to find a potential resolution to this health problem. Synthesis of new scaffolds and evaluating their antitumor activity is a relevant approach for combating cancer development. Coumarins can exhibit diverse biological activities, and one of these is the antitumor activity. This study aimed to synthesize new coumarins by grafting their precursors to the aromatic amines via Schiff base formation and evaluating their introductory antitumor activity. New multifunctional coumarins (MC1-MC9) were prepared by integrating a functionalized coumarin with different toluidine derivatives via a Schiff-base linkage. Spectral characterization inspired by FTIR, 1H- and 13C- NMR spectroscopies has established the chemical structures of the synthesized products. The antitumor activity was explored in vitro versus four dominant human cancer lines, including HeLa, SKG, MCF-7, and AMN3. The outcomes acquired from the cell viability assay inspected by applying MTT dye have revealed that the synthesized multifunctional coumarins, particularly MC3, have a hopeful activity. It can be concluded that a similar trend of activity against the test cell lines was observed for the synthesized coumarins, with the best action being versus MCF-7 and the least one versus AMN3. This study not only affords a new scaffold of a significant antitumor activity but also provides some insights into its structureactivity relationship.

Glycation With Fructose: The Bitter Side of Nature’s Own Sweetener

: Fructose is a ketohexose and sweetest among all the natural sugars. Like other reducing sugars, it reacts readily with the amino- and nucleophilic groups of proteins, nucleic acids and other biomolecules resulting in glycation reactions. The non-enzymatic glycation reactions comprise Schiff base formation, their Amadori rearrangement followed by complex and partly incompletely understood reactions culminating in the formation of Advance Glycation End products (AGEs). The AGEs are implicated in complications associated with diabetes, cardiovascular disorders, Parkinson’s disease, etc. : Fructose is highly reactive and forms glycation products that differ both in structure and reactivity as compared to those formed from glucose. Nearly all tissues of higher organisms utilize fructose but only a few like the ocular lens, peripheral nerves erythrocytes and testis have polyol pathway active for the synthesis of fructose. Fructose levels rarely exceed those of glucose but, in tissues that operate the polyol pathway, its concentration may rise remarkably during diabetes and related disorders. Diet contributes significantly to the body fructose levels however, availability of technologies for the large scale and inexpensive production of fructose, popularity of high fructose syrups as well as the promotion of vegetarianism have resulted in a remarkable increase in the consumption of fructose. In vivo glycation reactions by fructose, therefore, assume remarkable significance. The review, therefore, aims to highlight the uniqueness of glycation reactions with fructose and its role in some pathophysiological situations.