Synthesis of novel amides with antiradical capacity from 2-mercaptobenzimidazole and cinnamic acids: Evaluation through donor-acceptor maps and QSAR

Determining Antiradical Capacity of Medicinal Plant Extract Individual Constituents Using Post-Column Reaction Method

The post-column reaction method enables the evaluation of the antiradical capacity of individual components in a mixture by separating the components using HPLC and measuring stable free radical (e.g., DPPH●) scavenging that occurs after the chromatography column. The equipment typically consists of two detectors. The first records signals of the analytes leaving the column. The second records radical scavenging by the analytes, which appears as a negative band. The recorded signals are found on two separate chromatograms, which must be combined to interpret the results. In this study, a single DAD detector was used behind the post-column reactor, enabling the simultaneous recording of the analyte bands and negative signals, indicating radical scavenging. The objective of this study was to evaluate the antiradical capacity of key compounds found in two herbal raw materials used in traditional Chinese medicine. Saposhnikovia divaricata roots contain phenolic acids, chromones, and furanocoumarins. Chlorogenic acid, rosmarinic acid, and imperatorin demonstrated strong radical scavenging, while prim-O-glucoslocimifugin showed a weaker response, both in standards and in root extracts. However, scavenging was not observed for cimifugin and 4'-O-β-D-glucosyl-5-O-methylvisamminol. Astragalus mongholicus roots contain astragalosides I-IV (triterpene saponins). None of these showed DPPH● scavenging. Furthermore, additional signals were observed, indicating the presence of unidentified radical scavenging compounds.

New cyclic arylguanidine scaffolds as a platform for development of antimicrobial and antiviral agents

According to WHO, infectious diseases are still a significant threat to public health. The combine effects of antibiotic resistance, immunopressure, and mutations within the bacterial and viral genomes necessitates the search for new molecules exhibiting antimicrobial and antiviral activities. Such molecules often contain cyclic guanidine moiety. As part of this work, we investigated the selected antimicrobial and antiviral activity of compounds from the cyclic arylguanidine group. Molecules were designed using molecular modeling and obtained using microwave radiation (MW) and sonochemical ()))) methods, in accordance with the previously developed pathways. The obtained compounds were screened for the ability to inhibit the growth of Escherichia coli, Acinetobacter baumannii, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, and Cryptococcus neoformans. The capacity to block the entry of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) into the host cell was probed using a bioluminescence immunoassay. The cytotoxicity and hemolytic properties of the most active molecules were also evaluated. The N-[2-(naphthalen-1-yl)ethyl]-5-phenyl-1,4,5,6-tetrahydro-1,3,5-triazin-2-amine 12j showed a high inhibition of Staphylococcus aureus and Cryptococcus neoformans (MIC ≤ 0.25 µg/mL), with no cytotoxic nor hemolytic effect (CC50, HC10 > 32 µm/mL). The CO-ADD platform identified many potentially useful molecules. A particularly rich population was examined in the database of the N.D. Zelinsky Institute of Organic Chemistry, in which 2517 active molecules (MIC ≤ 32 mg/mL) were found, of which about 10% are active at very low concentrations (MIC ≤ 1 mg/mL).

Eco-friendly methods of synthesis and preliminary biological evaluation of sulfonamide derivatives of cyclic arylguanidines

The chemotype of arylsulfonamide derivatives of cyclic arylguanidines is a source of molecules with valuable biological activities, including antimicrobial and antitumor properties. The methods of the synthesis presented in the literature are characterized with low selectivity and high environmental nuisance. In this publication, we present a developed alternative and earlier undescribed pathway C, for the synthesis of arylsulfonamide derivatives of cyclic arylguanidines (N-(1H-arylimidazol-2-yl)arylsulfonamides and N-(1,4-dihydroquinazolin-2-yl)arylsulfonamides), including reaction between 2-(methylsulfanyl)-benzimidazole or 2-(methylsulfanyl)-3,4-dihydroquinazoline with arylsulfonamides. We also optimized previously reported methods; A (reaction of 2-aminobenzimidazole or 2-amino-3,4-dihydroquinazoline with arylsulfonyl chlorides) and B (reaction of dimethyl-(arylsulfonyl)carbonodithioimidate with aryldiamines). The conducted research allowed achieving two independent ecological and quick methods of obtaining the desired products. We used ecological methods of ultrasound-assisted or microwave synthesis, solvent-free reactions and a"green" reaction environment. In both pathways, it has proven advantageous to use H₂O as the solvent and K₂CO₃ (1 or 3 equivalent) as the basic agent. In the sonochemical variant, the efficiency reached B: 37-89 %, C: 90 % in 60 min (P = 80 W and f = 40 kHz), while in the microwave synthesis it was B: 38-74 %, C: 63-85 % in 0.5-4 min (P = 50 W). Path A led to a complementary substitution product (i.e. 1-(arylsulfonyl)-1H-benzimidazol-2-amine or 1-(arylsulfonyl)-1,4-dihydroquinazolin-2-amine). We obtained a small group of compounds that were tested for cytotoxicity. The 10f (N-(1,4-dihydroquinazolin-2-yl)naphthalene-1-sulfonamide) showed cytotoxic activity towards human astrocytoma cell line 1321 N1. The calculated IC₅₀ value was 8.22 µM at 24 h timepoint (doxorubicin suppressed 1321 N1 cell viability with IC₅₀ of 1.1 µM). The viability of the cells exposed to 10f for 24 h dropped to 48.0 % compared to vehicle control, while the cells treated with doxorubicin experienced decline to 47.5 %. We assessed its potential usefulness in pharmacotherapy in the ADMET study, confirming its ability to cross the blood-brain barrier (Pe = 5.0 ± 1.5 × 10^-6 cm/s) and the safety of its potential use in terms of DDI and hepatotoxicity.

13C-NMR Chemical Shifts in 1,3-Benzazoles as a Tautomeric Ratio Criterion

Benzimidazole is an important heterocyclic fragment, present in many biologically active compounds with a great variety of therapeutic purposes. Most of the benzimidazole activities are explained through the existence of 1,3-tautomeric equilibrium. As the binding affinity of each tautomer to a protein target depends on an established bioactive conformation, the effect of tautomers on the ligand protein binding mechanism is determinant. In this work, we searched and analyzed a series of reported ¹³C-NMR spectra of benzazoles and benzazolidine-2-thiones with the purpose of estimating their tautomeric equilibrium. Herein, several approaches to determine this problem are presented, which makes it a good initial introduction to the non-expert reader. This chemical shift difference and C4/C7 signals of benzimidazolidine-2-thione and 1-methyl-2-thiomethylbenzimidazole as references were used in this work to quantitatively calculate, in solution, the pyrrole–pyridine tautomeric ratio in equilibrium. The analysis will help researchers to correctly assign the chemical shifts of benzimidazoles and to calculate their intracyclic or exocyclic tautomeric ratio as well as mesomeric proportion in benzimidazoles.