Inhibition of secretory phospholipase A2. 2-Synthesis and structure–activity relationship studies of 4,5-dihydro-3-(4-tetradecyloxybenzyl)-1,2,4-4H-oxadiazol-5-one (PMS1062) derivatives specific for group II enzyme

The Synthesis and Evaluation of Amidoximes as Cytotoxic Agents on Model Bacterial E. coli Strains

The biological research on newly synthesized amidoximes, Boc-protected amidoximes and Boc-derived amidines, obtained by a reduction of the parent amidoximes is reported, herein. Due to the presence of a free amino group in both amidines and amidoximes, these compounds can undergo various chemical reactions such as N-alkylation and N-acylation. One such reaction is Boc-protection, often used in organic synthesis to protect the amino and imino groups. Until now, Boc-protected amidoximes have not been tested for biological activity. Amidoxime derivatives were tested on bacterial E. coli strains. Initial cellular studies tests and digestion with Fpg after the modification of bacterial DNA, suggest that these compounds may have greater potential as antibacterial agents compared to antibiotics such as ciprofloxacin (ci), bleomycin (b) and cloxacillin (cl). The described compounds are highly specific for pathogenic E. coli strains on the basis of the model strains used and may be used in the future as new substitutes for commonly used antibiotics in clinical and hospital infections in the pandemic era.

Investigation of Masked N-Acyl-N-isocyanates: Support for Oxadiazolones as Blocked N-Isocyanate Precursors

In contrast to carbon-substituted isocyanates that are common building blocks, N-substituted isocyanates remain underdeveloped and reports on their N-acyl derivatives (i. e. amido-isocyanates) are exceedingly rare. Herein, amido-isocyanates were investigated in the context of syntheses of aza-tripeptide and hydantoins subunits starting from simple bench-stable precursors. A key finding is that the amido-isocyanate formed in situ cyclized to yield an oxadiazolone, and that under suitable reaction conditions this heterocycle is a traceless blocked (masked) N-isocyanate. Using organic bases as catalysts and upon heating, oxadiazolone formation is observed, and various nucleophiles to provide the desired aza-dipeptides or hydantoins in moderate to high yields. Further support for an amido-isocyanate intermediate was obtained using carboxylic acids as nucleophiles, affording N-acylhydrazide products.

A one-pot route to N-acyl ureas: a formal four-component hydrolytic reaction involving aminonitrones and isocyanide dibromides

A one-pot route to N-acyl ureas proceeds via generation of electrophilically activated 2-substituted 1,2,4-oxadiazolium salts. The conformation of the N-acyl ureas is stabilized via moderate strength (6.2–7.8 kcal mol⁻¹) resonance-assisted hydrogen bonds.

Aminonitrones as highly reactive bifunctional synthons. An expedient one-pot route to 5-amino-1,2,4-triazoles and 5-amino-1,2,4-oxadiazoles – potential antimicrobials targeting multi-drug resistant bacteria

A four-component one-pot reaction proceeds very rapidly under mild conditions and gives the heterocyclic systems in good yields.

Formal reductive addition of acetonitrile to aldehydes and ketones

An efficient and highly productive rhodium-catalyzed method for the synthesis of nitriles employing aldehydes or ketones, methyl cyanoacetate, water and carbon monoxide as starting materials has been developed. Simple rhodium chloride without any ligands can be used. The fine tuning of the substrate can lead to the activity higher than 5000 TON.

Facile selective synthesis of 2-methyl-5-amino-1,2,4-oxadiazolium bromides as further targets for nucleophilic additions

The reaction of aminonitrones with isocyanides and Br₂ gives 2-methyl-5-amino-1,2,4-oxadiazolium bromides, which are convenient precursors for other heterocycles and ureides.

In vitro study of the PLA2 inhibition and antioxidant activities of Aloe vera leaf skin extracts

Background

In the present work we determined the total phenolic content of Aloe vera leaf skin (AVLS) extracts by using various solvents (hexane, chloroform-ethanol (1/1), ethyl acetate, butanol and water). We have also evaluated the antioxidant and the anti-PLA2 properties of these extracts by measuring their inhibition potency on the human pro-inflammatory phospholipase A2 (group IIA).

Results

The water extract exhibits the highest inhibitory effect with an IC₅₀ = 0.22 mg/ml and interestingly no effect was observed on the digestive phospholipase A2 (group IB) even at a concentration of 5 mg/ml. Antioxidant activities were also analyzed and the most active extracts were observed when using chloroform ethanol (1/1) and ethyl acetate (IC₅₀ = 0.274 and 0.326 mg/ml, respectively). Analysis of the total phenolic content reveals that the water extract, with the best anti-PLA2 effect, was poor in phenolic molecules (2 mg GAE/g). This latter value has to be compared with the chloroform-ethanol and the ethyl acetate extracts (40 and 23.8 mg GAE/g, respectively), mostly responsible for the antioxidant activity.

Conclusion

A significant correlation was established between the total phenolic content and the antioxidant capacity but not with the anti PLA2 activity. Results from phytochemical screening suggest that the anti PLA2 molecules were probably catechin tannins compounds.

Design of 1-arylsulfamido-2-alkylpiperazine derivatives as secreted PLA2 inhibitors

Structure and analog based analysis of 3D-QSAR, CoMFA and CoMSIA, along with different docking protocols were used to evaluate the structure activity relationship of 26 analogues of 1-aryl sulfamido-2-alkyl piperazines to model the activities of group I and II secreted phospholipases A(2) (sPLA(2)s) and probe into the chemical space and nature of receptor--ligand interactions. The best CoMFA model yields cross-validated (q(2)) and conventional correlation coefficients (r(2)) of 0.703 and 0.962 respectively whereas CoMSIA model yields q(2) and r(2) values of 0.408 and 0.922 respectively, followed by docking analysis using FlexX and GOLD methodologies on the X-ray structure of human and bovine PLA(2)s. A comparative study was made to find out the differences in the active site residues of both PLA(2)s. The information enunciated from the analysis of CoMFA and CoMSIA maps and docking results were analyzed and employed in the design of 29 new ligands using molecules 4, 21, 22 from the initial set as templates. New ligands for group I and II secreted phospholipases A(2) (sPLA(2)s) have been thus designed based on the 32 analogues of 1-aryl sulfamido-2-alkyl piperazine with a cursory note on its synthetic feasibility. Molecular modeling studies indicate that the newly designed ligands are expected to show high affinity and experimental efforts in this direction is highly rewarding.

Design of group IIA secreted/synovial phospholipase A(2) inhibitors: an oxadiazolone derivative suppresses chondrocyte prostaglandin E(2) secretion

Group IIA secreted/synovial phospholipase A₂ (GIIAPLA₂) is an enzyme involved in the synthesis of eicosanoids such as prostaglandin E₂ (PGE₂), the main eicosanoid contributing to pain and inflammation in rheumatic diseases. We designed, by molecular modeling, 7 novel analogs of 3-{4-[5(indol-1-yl)pentoxy]benzyl}-4H-1,2,4-oxadiazol-5-one, denoted C1, an inhibitor of the GIIAPLA₂ enzyme. We report the results of molecular dynamics studies of the complexes between these derivatives and GIIAPLA₂, along with their chemical synthesis and results from PLA₂ inhibition tests. Modeling predicted some derivatives to display greater GIIAPLA₂ affinities than did C1, and such predictions were confirmed by in vitro PLA₂ enzymatic tests. Compound C8, endowed with the most favorable energy balance, was shown experimentally to be the strongest GIIAPLA₂ inhibitor. Moreover, it displayed an anti-inflammatory activity on rabbit articular chondrocytes, as shown by its capacity to inhibit IL-1β-stimulated PGE₂ secretion in these cells. Interestingly, it did not modify the COX-1 to COX-2 ratio. C8 is therefore a potential candidate for anti-inflammatory therapy in joints.