Part I, Unified Pharmacophore Protein Models of the Benzodiazepine Receptor Subtypes ; Part II, Subtype

Part I. New models of unified pharmacophore/receptors have been constructed guided by the synthesis of subtype selective compounds in light of recent developments both in ligand synthesis and structural studies of the binding site itself. The evaluation of experimental data in combination with comparative models of the α1β2γ2, α2β2γ2, α3β2γ2 and α5β2γ2 GABA(A) receptors has led to an orientation of the pharmacophore model within the benzodiazepine binding site (Bz BS). These results not only are important for the rational design of new selective ligands, but also for the identification and evaluation of possible roles which specific residues may have within the benzodiazepine binding pocket. More importantly, the process summarized here may be used as a general template to help scientists develop novel ligands for receptors for which the three dimensional structure has not yet been confirmed by X-ray crystallography or cryo-electron microscopy. Presented here are new models of the α1β2γ2, α2β2γ2, α3β2γ2 and α5β2γ2 GABA(A) receptors which have incorporated homology models built based on the acetylcholine binding protein. These new models will further our ability to understand structural characteristics of ligands which act as agonists, antagonists, or inverse agonists to the Bz BS of the GABA(A) receptor. This approach will also serve as a powerful model for structure based approaches carried out using ligand-protein docking methods. Part II. An effective strategy to alleviate memory deficits would be to enhance memory and cognitive processes by augmenting the impact of acetylcholine released from cholinergic neurons of the hippocampus. Using the included volume pharmacophore presented in Part I, a number of a5 selective compounds were synthesized, notably PWZ-029. PWZ-029 was examined in rats in the passive and active avoidance, spontaneous locomotor activity, elevated plus maze and grip strength tests which are indicative of the effects on memory acquisition, locomotor activity, anxiety, and muscle tone. Improvement of task learning was shown at a dose of 5mg/kg in passive avoidance test without effect on anxiety or muscle tone. Moderate negative modulation at GABA(A) receptors containing the α5 subunit using a moderate inverse agonist such as PWZ-029, is a sufficient condition for eliciting enhanced encoding/consolidation of declarative memory. Using low temperature NMR and X-ray analysis, it was shown that enhanced selectivity and potent in vitro affinity of α5 selective benzodiazepine dimers was possible with aliphatic linkers of 3 to 5 carbons in length. Although originally proposed to enhance solubility, oxygen-containing linkers caused the dimer to fold back on itself leading to the inability of dimers to enter the binding pocket. In addition, studies of a series of PWZ-029 analogs found that the electrostatic potential near the ligands\u27 terminal substituent correlated with its binding selectivity toward the α5β2γ2 versus α1β2γ2 Bzr/GABA(A) ergic isoform. Investigations further found that compound PWZ-029, which exhibits reasonable binding selectivity toward GABA(A) receptors containing the a5 subunit and possesses a favorable electrophysiological profile, was able to attenuate scopolamine induced contextual memory impairment in mice. This compound appears to be useful (Harris, Delorey et al.) for the treatment of cognitive deficits in rodents as well as primates (Rowlett et al.) and may well be a compound for the treatment of patients with Alzheimers disease

IN SILICO METHODS FOR DRUG DESIGN AND DISCOVERY

Computer-aided drug design (CADD) methodologies are playing an ever-increasing role in drug discovery that are critical in the cost-effective identification of promising drug candidates. These computational methods are relevant in limiting the use of animal models in pharmacological research, for aiding the rational design of novel and safe drug candidates, and for repositioning marketed drugs, supporting medicinal chemists and pharmacologists during the drug discovery trajectory.Within this field of research, we launched a Research Topic in Frontiers in Chemistry in March 2019 entitled “In silico Methods for Drug Design and Discovery,” which involved two sections of the journal: Medicinal and Pharmaceutical Chemistry and Theoretical and Computational Chemistry. For the reasons mentioned, this Research Topic attracted the attention of scientists and received a large number of submitted manuscripts. Among them 27 Original Research articles, five Review articles, and two Perspective articles have been published within the Research Topic. The Original Research articles cover most of the topics in CADD, reporting advanced in silico methods in drug discovery, while the Review articles offer a point of view of some computer-driven techniques applied to drug research. Finally, the Perspective articles provide a vision of specific computational approaches with an outlook in the modern era of CADD

Antioxidant and DPPH-Scavenging Activities of Compounds and Ethanolic Extract of the Leaf and Twigs of Caesalpinia bonduc L. Roxb.

Antioxidant effects of ethanolic extract of Caesalpinia bonduc and its isolated bioactive compounds were evaluated in vitro. The compounds included two new cassanediterpenes, 1α,7α-diacetoxy-5α,6β-dihydroxyl-cass-14(15)-epoxy-16,12-olide (1)and 12α-ethoxyl-1α,14β-diacetoxy-2α,5α-dihydroxyl cass-13(15)-en-16,12-olide(2); and others, bonducellin (3), 7,4’-dihydroxy-3,11-dehydrohomoisoflavanone (4), daucosterol (5), luteolin (6), quercetin-3-methyl ether (7) and kaempferol-3-O-α-L-rhamnopyranosyl-(1Ç2)-β-D-xylopyranoside (8). The antioxidant properties of the extract and compounds were assessed by the measurement of the total phenolic content, ascorbic acid content, total antioxidant capacity and 1-1-diphenyl-2-picryl hydrazyl (DPPH) and hydrogen peroxide radicals scavenging activities.Compounds 3, 6, 7 and ethanolic extract had DPPH scavenging activities with IC50 values of 186, 75, 17 and 102 μg/ml respectively when compared to vitamin C with 15 μg/ml. On the other hand, no significant results were obtained for hydrogen peroxide radical. In addition, compound 7 has the highest phenolic content of 0.81±0.01 mg/ml of gallic acid equivalent while compound 8 showed the highest total antioxidant capacity with 254.31±3.54 and 199.82±2.78 μg/ml gallic and ascorbic acid equivalent respectively. Compound 4 and ethanolic extract showed a high ascorbic acid content of 2.26±0.01 and 6.78±0.03 mg/ml respectively.The results obtained showed the antioxidant activity of the ethanolic extract of C. bonduc and deduced that this activity was mediated by its isolated bioactive compounds