Complexes of iron(III) and chromium(III) salen and salophen Schiff bases with bridging 1,3,5-triazine derived multidirectional ligands

Elucidation of the Microwave-Assisted Synthesis and Characterization of Heteronuclear Complexes of Bisbenzimidazole Derivatives and Their Biological Activities by In Vitro and In Silico Assays

A novel and efficient protocol for the microwave-assisted synthesis of diversely substituted 2,2'-bisbenzimidazol-5,6'-dicarboxylic acid (BIMCA) from the reaction of 3,4-diaminobenzoic acid with oxalic acid has been developed, which proceeds through sequential nucleophilic addition and electrophilic substitution in accordance with the Philips method. The synthetic utility of this strategy was demonstrated by the concise, one-pot synthesis of (BIMCA) and metal complexes. (BIMCA) with a [{Fe(salen)}2O] Schiff base ligand complex and new benzimidazole coordination compounds with double oxygen [(BIMCA){Fe(salen)}2] ligand complexes were obtained. The resulting [(BIMCA){Fe(salen)}2] ligand complex was then synthesized from Co(CH3COO)2.4H2O, Ni(CH3COO)2.4H2O and Cu(CH3COO)2.H2O heteronuclear complexes. The condensations proceed with good yield to give products that, in certain instances, are not readily attainable by conventional condensation techniques. The structures of the compounds were identified by Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), elemental analysis and magnetic susceptibility. The mutagenic potential of the synthesized chemicals was evaluated by the Ames test towards mutant Salmonella typhimurium strains TA98 and TA100. It was recorded that these chemicals had no mutagenic action. Also, antimicrobial activities were screened by broth microdilution test. It was seen that the minimum inhibitory concentration (MIC) against Klebsiella pneumoniae, Staphylococcus aureus and Staphylococcus epidermidis was 0.195 mg/mL, followed by a MIC value of 0.390 mg/mL against Escherichia coli and Salmonella typhimurium. [(BIMCA){Fe(salen)}2Co(II)] demonstrated significant antimicrobial activity against Proteus mirabilis and Staphylococcus aureus, with an MIC of 0.195 mg/mL, followed by an MIC of 0.390 mg/mL against Pseudomonas aeruginosa, K. pneumonia and Salmonella typhimurium. The antioxidant properties were examined using various chemical assays, and [(BIMCA){Fe(salen)}2O] and (BIMCA) exhibited greater 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability, when compared with other compounds. Enzyme inhibitory effects were tested against acetylcholinesterase (AChE), amylase, butyrylcholinesterase (BChE) and tyrosinase. [(BIMCA){Fe(salen)}2Cu(II)] displayed the best AChE (IC50 0.51 mg/mL), BChE (IC50 0.51 mg/mL) and tyrosinase (IC50 1.52 mg/mL) inhibitory effects. Furthermore, molecular docking calculations were performed to gain insights into the interaction between [(BIMCA){Fe(salen)}2] and AChE, and between [(BIMCA){Fe(salen)}2Cu(II)] and amylase. Both compounds showed the potential inhibition of the protein targets.

Sequential nucleophilic aromatic substitutions on cyanuric chloride: synthesis of BODIPY derivatives and mechanistic insights

Herein we report a study on the sequential substitution of different nucleophiles on cyanuric chloride to obtain potential candidates for metal sensors (5a-c). The set of nucleophiles on the 1,3,5-triazine ring includes a phenolic BODIPY, an aminoalkyl pyridine and aminoalkyl phosphoramidates, each one designed to play a specific role in the final fluoroionophore. Three new triazine triads were synthesized in similar yields: 5a (45%), 5b (43%) and 5c (52%) after a methodical sequential combination of the nucleophiles via thermodependent nucleophilic aromatic substitution of the three chlorine atoms of cyanuric chloride. To ratify the synthetic results we simulated the reaction mechanisms for the different nucleophiles, aiming to address the distinctive orthogonality and temperature control inherent in this process, identifying and providing a sound rationale for any preferential sequence of nucleophiles inserted into the triazine core. According to our experimental and computational analysis (thermo- and kinetic preferences), we have identified the following preferential order for the sequential substitution: p-hydroxybenzaldehyde > 2-(pyridin-2-yl)ethanamine > aminoalkyl phosphoramidate, indicating that all steps follow a single-step process (concerted) in two stages, where nucleophilic addition precedes leaving group dissociation. The Meisenheimer σ-complex was identified as a transition state structure, with insufficient stability to exist as an intermediate. We observed a consistent and progressive increase in barrier height: 2-8 kcal mol-1 for the first step, 9-15 kcal mol-1 for the second step, and >15 kcal mol-1 for the third substitution. These findings align with the experimental observation of thermodependency in the sequential substitution.

First-in-Class Star-Shaped Triazine Dendrimers Endowed with MMP-9 Inhibition and VEGF Suppression Capacity: Design, Synthesis, and Anticancer Evaluation

Off-target side effects are major challenges hindering the clinical success of matrix metalloproteinase (MMP) inhibitors. Various targeting strategies revitalized MMP research to eliminate this drawback. Herein, we developed s-triazine-based dendrimeric architecture not only amenable to tumor targeting but also decorated with pharmacophoric entities to endow MMP-9 inhibition for halting cancer progression. The design rationale utilized hydrazide branching chains as well as carboxylic and hydroxamic acid termini as Zn-binding groups to confer substantial MMP inhibitory potential. The carboxylic acids are tetherable to tumor targeting ligands and other cargo payloads as synergistic drugs via biodegradable linkages. The synthesized series were screened for cytotoxicity against normal fibroblasts (Wi-38) and two selected cancers (MDA-MB 231 and Caco-2) via MTT assay. The most active hexacarboxylic acid dendrimer 8a was more potent and safer than Dox against MDA-MB 231 and Caco-2 cells. It intrinsically inhibited MMP-9 with selectivity over MMP-2. Docking simulations demonstrated that the extended carboxylic acid termini of 8a could possibly chelate the active site Zn of MMP-9 and form hydrogen-bonding interactions with the ligand essential backbone Tyr423. In addition, it suppressed the correlated oncogenic mediators VEGF and cyclin D, upregulated p21 expression, induced apoptosis (>75%), and inhibited the tumor cell migration (∼84%) in the treated cancer cells. Thus, up to our knowledge, it is the first triazine-based MMP-9 inhibitor dendrimer endowed with VEGF suppression potential that can be employed as a bioactive carrier.

Orto-hydroxy bioactive schiff base compounds: Design, comprehensive characterization, photophysical properties and elucidation of antimicrobial and mutagenic potentials

Preparation and comprehensive characterization of three Schiff base ligands; with trimethoxy substitution (1E,1'E)-N,N'-(naphthalene-1,5-diyl)bis(1-(3,4,5-trimethoxyphenyl)methanimine, 1, with ortho-hydroxy substitution 6,6'-((1E,1'E)-(naphthalene-1,5-diylbis(azaneylylidene))bis(methaneylylidene))bis(2-methoxyphenol), 2 and 3,4-bis(((E)-2-hydroxy-3-methoxy benzylidene)amino)benzoicacid, 3 and their Ni(II), Cu(II), Co(II), Zn(II), Fe(II), Mn(II) complexes have been reported. Their spectral properties were studied in solution and solid-state by a combination of different analytical techniques; FT-IR spectroscopy, ¹H NMR and ¹³C NMR spectroscopy, elemental analysis and thermal analysis. Diamagnetic and paramagnetic natures of the complexes were also determined by magnetic susceptibility measurements in solid-state. Promising photophysical properties were observed as; A_max. were recorded at 226 nm for 2; at 795 nm for 2-Ni, at 782 nm for 2-Cu, at 784 nm for 2-Co, at 702 nm for 2-Zn, at 784 nm for 2-Fe, at 702 nm for 2-Mn and at 289 nm for 3, at 786 nm for 3-Ni, at 797 nm for 3-Cu, at 746 nm for 3-Co, at 794 nm for 3-Zn, at 699 nm for 3-Fe, at 781 nm for 3-Mn ; and I_max were also recorded at; 380, 490, 725 nm for 2 and 2-Metal; 375 nm, 510 nm, 725 nm for 3 and 3-Metal when excitated at 220 nm. Antibacterial activities against different microorganisms; Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae ATCC 70603, Staphylococcus aureus ATCC 43,300 (MRSA), Salmonella enteritidis ATTC 13076, Sarcina lutea ATCC 9341, Bacillus cereus ATTC 11778, and antifungal activities against Candida albicans NRRL Y-417 of the compounds 1, 2, 3, 2-Cu, 2-Fe, 3-Zn, 3-Fe were determined. Mutagenic properties of the compounds were also studied and according to the results 2-Cu and 3 have been found non-mutagenic in Ames test but also they have strong antimicrobial potential against pathogen microorganisms. For 2-Cu MIC values were ranging between 0.39 and 0.024 mg/ml and the lowest minimum inhibitory concentration (0.024 mg/ml) was determined against E. coli. The 3 numbered compound revealed strong antimicrobial activity at doses of ranging between 0.39 and 0.097 mg/ml and E. coli was the most sensitive bacterium against this chemical.

Synthesis, characterization and evaluation of 1,3,5-triazine aminobenzoic acid derivatives for their antimicrobial activity

Background

Replacement of chloride ions in cyanuric chloride give several variants of 1,3,5-triazine derivatives which were investigated as biologically active small molecules. These compounds exhibit antimalarial, antimicrobial, anti-cancer and anti-viral activities, among other beneficial properties. On the other hand, treatment of bacterial infections remains a challenging therapeutic problem because of the emerging infectious diseases and the increasing number of multidrug-resistant microbial pathogens. As multidrug-resistant bacterial strains proliferate, the necessity for effective therapy has stimulated research into the design and synthesis of novel antimicrobial molecules.

Results

1,3,5-Triazine 4-aminobenzoic acid derivatives were prepared by conventional method or by using microwave irradiation. Using microwave irradiation gave the desired products in less time, good yield and higher purity. Esterification of the 4-aminobenzoic acid moiety afforded methyl ester analogues. The s-triazine derivatives and their methyl ester analogues were fully characterized by FT-IR, NMR (¹H-NMR and ¹³C-NMR), mass spectra and elemental analysis. All the synthesized compounds were evaluated for their antimicrobial activity. Some tested compounds showed promising activity against Staphylococcus aureus and Escherichia coli.

Conclusions

Three series of mono-, di- and trisubstituted s-triazine derivatives and their methyl ester analogues were synthesized and fully characterized. All the synthesized compounds were evaluated for their antimicrobial activity. Compounds (10), (16), (25) and (30) have antimicrobial activity against S. aureus comparable to that of ampicillin, while the activity of compound (13) is about 50% of that of ampicillin. Compounds (13) and (14) have antimicrobial activity against E. coli comparable to that of ampicillin, while the activity of compounds (9–12) and (15) is about 50% of that of ampicillin. Furthermore, minimum inhibitory concentrations values for clinical isolates of compounds (10), (13), (14), (16), (25) and (30) were measured. Compounds (10) and (13) were more active against MRSA and E. coli than ampicillin. Invitro cytotoxicity results revealed that compounds (10) and (13) were nontoxic up to 250 µg/mL (with SI = 10) and 125 µg/mL (with SI = 5), respectively.Graphical abstract