Imidazo[1,2-c]quinazolines as a novel and potent scaffold of α-glucosidase inhibitors: design, synthesis, biological evaluations, and in silico studies

α-Glucosidase inhibition is an approved treatment for type 2 diabetes mellitus (T2DM). In an attempt to develop novel anti-α-glucosidase agents, two series of substituted imidazo[1,2-c]quinazolines, namely 6a-c and 11a-o, were synthesized using a simple, straightforward synthetic routes. These compounds were thoroughly characterized by IR, 1H and 13C NMR spectroscopy, as well as mass spectrometry and elemental analysis. Subsequently, the inhibitory activities of these compounds were evaluated against Saccharomyces cerevisiae α-glucosidase. In present study, acarbose was utilized as a positive control. These imidazoquinazolines exhibited excellent to great inhibitory potencies with IC50 values ranging from 12.44 ± 0.38 μM to 308.33 ± 0.06 μM, which were several times more potent than standard drug with IC50 value of 750.0 ± 1.5 μM. Representatively, compound 11j showed remarkable anti-α-glucosidase potency with IC50 = 12.44 ± 0.38 μM, which was 60.3 times more potent than positive control acarbose. To explore the potential inhibition mechanism, further evaluations including kinetic analysis, circular dichroism, fluorescence spectroscopy, and thermodynamic profile were carried out for the most potent compound 11j. Moreover, molecular docking studies and in silico ADME prediction for all imidazoquinazolines 6a-c and 11a-o were performed to reveal their important binding interactions, as well as their physicochemical and drug-likeness properties, respectively.

Synthesis and tyrosinase inhibitory activities of novel isopropylquinazolinones

To find new anti-browning and whitening agents in this study, new series of isopropylquinazolinone derivatives were designed and synthesized. All derivatives were evaluated as possible tyrosinase inhibitors and compound 9q bearing 4-fluorobenzyl moieties at the R position exhibited the best potencies with an IC₅₀ value of 34.67 ± 3.68 µM. The kinetic evaluations of 9q as the most potent derivatives recorded mix-type inhibition. Compounds 9o and 9q also exhibited potent antioxidant capacity with IC₅₀ values of 38.81 and 40.73 µM, respectively confirming their antioxidant potential. Molecular docking studies of 9q as the most potent derivative were exacuated and it was shown that quinazolinone and acetamide moieties of compound 9q participated in interaction with critical His residues of the binding site. The obtained results demonstrated that the 9q can be considered a suitable pharmacophore to develop potent tyrosinase inhibitors.

Synthesis, in vitro inhibitor screening, structure-activity relationship, and molecular dynamic simulation studies of novel thioquinoline derivatives as potent α-glucosidase inhibitors

New series of thioquinoline structures bearing phenylacetamide 9a-p were designed, synthesized and the structure of all derivatives was confirmed using different spectroscopic techniques including FTIR, ¹H-NMR, ¹³C-NMR, ESI-MS and elemental analysis. Next, the α-glucosidase inhibitory activities of derivatives were also determined and all the synthesized compounds (IC₅₀ = 14.0 ± 0.6-373.85 ± 0.8 μM) were more potent than standard inhibitors acarbose (IC₅₀ = 752.0 ± 2.0 μM) against α-glucosidase. Structure-activity relationships (SARs) were rationalized by analyzing the substituents effects and it was shown that mostly, electron-donating groups at the R position are more favorable compared to the electron-withdrawing group. Kinetic studies of the most potent derivative, 9m, carrying 2,6-dimethylphenyl exhibited a competitive mode of inhibition with K_i value of 18.0 µM. Furthermore, based on the molecular dynamic studies, compound 9m depicted noticeable interactions with the α-glucosidase active site via several H-bound, hydrophobic and hydrophilic interactions. These interactions cause interfering catalytic potential which significantly decreased the α-glucosidase activity.

Synthesis and bioactivities evaluation of quinazolin-4(3H)-one derivatives as α-glucosidase inhibitors

The development of new antidiabetes agents is necessary to obtain optimal glycemic control and overcome its complications. Different quinazolin-4(3H)-one bearing phenoxy-acetamide derivatives (7a–r) were designed and synthesized to develop α-glucosidase inhibitors. All the synthesized derivatives were evaluated against α-glucosidase in vitro and among them, compound 7b showed the highest α-glucosidase inhibition with an IC50 of 14.4 µM, which was ∼53 times stronger than that of acarbose. The inhibition kinetic studies showed that the inhibitory mechanism of compound 7b was a competitive type towards α-glucosidase. Also, molecular docking studies analyzed the interaction between the most potent derivative and α-glucosidase. Current findings indicate the new potential of quinazolin-4(3H)-ones that could be used for the development of novel agents against diabetes mellitus.

Increased stability and lifetime of the complex formed between DNA and meta-phenyl-substituted Hoechst dyes as studied by fluorescence titrations and stopped-flow kinetics

The large increase in fluorescence upon binding of five para- and meta-phenyl substituted hydroxy and methoxy derivatives of the Hoechst dye with poly[d(A-T)], d(CGCGAATTCGCG)2, and its corresponding T4-looped 28-mer hairpin was used to monitor the binding by equilibrium titrations and by stopped-flow kinetics. The affinity increases in the same order for the three DNAs: p-OH<m-OCH3, p-OH<m-OH<m-OH, p-OCH3<bis-m-OH. The association constants K(a) are three to 11 times larger for the AATT site than for poly[d(A-T)]. The AATT site binds m-OH Hoechst with K(a)=3.8 x 10(9 )M(-1) and bis-m-OH Hoechst with K(a)=1.9 x 10(10 )M(-1), which are seven and 37 times higher than p-OH Hoechst (Hoechst 33258), respectively. The high K(a )values determined at equilibrium agree with the kinetically defined association constants K(kin)=k(on)/k(off). The association-rate parameters k(on) were obtained by stopped-flow kinetics and the dissociation-rate parameters k(off) by dissociation kinetics using poly[d(A-5BrU)]. For binding to the AATT site, k(on) values are similar and nearly diffusion-controlled (2.0 x 10(8) M(-1) x s(-1) to 2.9 x 10(8) M(-1) x s(-1)), while k(off) values (0.42 s(-1) to 0.012 s(-1)) depend on the phenyl substitution and determine the affinity. At the AATT site, the longest-living complex is formed when the dye carries a bis-m-OH phenyl group that probably integrates in a hydrogen-bonding network of water molecules. With poly(dA).poly(dT), poly[d(A-T)] and poly[d(A-5BrU)], k(on) (between 6.1 x 10(7) M(-1) x s(-1) and 5.2 x 10(8) M(-1) x s(-1)) depends on the DNA.