Small molecule ago-allosteric modulators of the human glucagon-like peptide-1 (hGLP-1) receptor

Following our previous publication describing the biological profiles, we herein describe the structure-activity relationships of a core set of quinoxalines as the hGLP-1 receptor agonists. The most potent and efficacious compounds are 6,7-dichloroquinoxalines bearing an alkyl sulfonyl group at the C-2 position and a secondary alkyl amino group at the C-3 position. These findings serve as a valuable starting point for the discovery of more drug-like small molecule agonists for the hGLP-1 receptor.     

Effect of light intensity on the oviposition rhythm of the altitudinal strains of Drosophila ananassae

The sensitivity of the circadian photoreceptors mediating entrainment of the eclosion rhythm and phase shifts of oviposition rhythm of the high altitude (HA) strain of Drosophila ananassae originating from Badrinath (5123 m above sea level) in the Himalayas was compared with the low altitude (LA) strain from Firozpur (179 m above sea level). Reduced photic sensitivity of the HA strain is regarded as the result of natural selection, which led to the weakening of the coupling mechanism between the circadian pacemaker and light at the high altitude of origin. The present study was designed to determine whether or not the photic entrainment of the oviposition rhythm of the HA strain of D. ananassae is also altered by the high altitude of its origin, and the results are compared with those of the LA strain. The effects of light intensity on the phase angle difference (Ψ), degree of rhythmicity (R), the percent oviposition in photophase, the threshold light intensity (i.e., the intensity at which stable entrainment occurred), and the saturation light intensity (i.e., the intensity beyond which the values of Ψ or amplitude of rhythm remained unaltered) were determined. Entrainment was studied in light-dark cycles in which the light intensity of 12 h of photophase varied from 1 to 1000 lux, and complete darkness prevailed in all scotophases. The oviposition rhythm of the HA strain was arrhythmic from 1 to 90 lux, weakly rhythmic at 95 lux, but rhythmic at or above 100 lux, while that of the LA strain was weakly rhythmic at 1 lux but rhythmic at or above 2 lux. Oviposition of the HA strain occurred mostly in the photophase, while that of the LA strain occurred in the scotophase; as a result, the oviposition medians of the HA strain were around the subjective forenoons while those of the LA strain were around the subjective evenings. The percent of oviposition in photophase increased from 68 to 98 in the HA strain and from 5 to 33 in the LA strain as light intensity increased from 1 to 1000 lux. In the HA strain, the Ψ values were significantly less and values of R and percent oviposition in photophase were significantly more than those of the LA strain at each level of light intensity. Threshold and saturation intensities for Ψ were 100 and 700 lux, respectively, for the HA strain, but just 2 and 45 lux, respectively, for the LA strain. The saturation intensity for R was 650 and 700 lux for the HA and LA strains, respectively. These results extend the confirmation that the reduced photic sensitivity of the HA strain might have been acquired through natural selection in response to environmental conditions at the high altitude of its origin.     

Evaluation of demineralised,freeze-dried,irradiated bone allografts in the treatment of osseous defects in the oral cavity

Demineralised, freeze-dried bone allografts (DFDBA) have been used extensively by dentists in the treatment of periodontal and periapical osseous defects resulting from inflammatory diseases. Their use in India however, is limited by the availability of quality allografts and the high cost of imported alternatives. A study was conducted to assess the osteogenic potential of DFDBA prepared for the first time in India by the Tata Memorial Hospital (TMH) Tissue Bank. The DFDBA was used in the treatment of osseous defects after removal of periapical lesions associated with devitalised teeth in 10 healthy patients. At the 6-month recall visit all the patients showed a remarkable decrease in the grades of mobility, and 9 out of the 10 patients showed radiographic evidence of complete healing of the osseous defects with evidence of normal bony trabaeculae. These findings indicate that the indigenously prepared DFDBA is a cost effective, biocompatible material with osteogenic potential that can be used effectively in treating osseous defects of periapical lesions associated with non vital teeth.     

Stereoselective synthesis of 1'-functionalized-4'-thionucleosides

Stereoselective functionalization of the 1'-position of 4'-thionucleosides was achieved using a stereoselective S(N)2 reaction controlled by 5-membered ring coordination.     

Asymmetric synthesis of cyclopropyl-fused 2'-C-methylcarbanucleosides as potential anti-HCV agents

Novel 2'-C-methyl-cyclopropyl-fused carbocyclic nucleosides as potential anti-HCV agents were stereoselectively synthesized, utilizing regioselective cleavage of the isopropylidene group and cyclic sulfate chemistry as key steps.     

Varying the length of dim nocturnal illumination differentially affects the pacemaker controlling the locomotor activity rhythm of Drosophila jambulina

Photic entrainment of animals in the field is basically attributed to their exposure to the dimly lit nights flanked by the dawn and dusk twilight transitions. This implicates the functional significance of the dimly lit nights as that of the twilight transitions. Recently, the authors have demonstrated that the dimly lit night at 0.0006 lux altered the attributes of the circadian rhythm of locomotor activity of Drosophila jambulina. The present study examined whether the durations of such dimly lit nights affect the entrainment and free-running rhythmicity of D. jambulina. Flies were subjected for 10 days to two types of 24-h lighting regimes in which the photophase (L) was at 10 lux for all flies but the scotophase, which varied in duration from 9 to 15 h, was either at 0 lux (D phase) for control flies or 0.0006 lux (the artificial starlight or S phase) for experimental flies. Thereafter, they were transferred to constant darkness (DD) to compare the after-effects of the dimly lit nights on the period (τ) of free-running rhythm in DD with that of the completely dark nights. Control flies were entrained by all LD cycles, but the experimental flies were entrained only by five LS cycles in which the duration of the S phases ranged from 10 to 14 h. The two LS cycles with very short (9 h) and long (15 h) S phases rendered the flies completely arrhythmic. Control flies started activity shortly before lights-on and continued well after lights-off. The experimental flies, however, commenced activity several hours prior to lights-on but ended activity abruptly at lights-off as the result of a negative masking effect of nocturnal illumination. Length of the midday rest was considerably shorter in the control than in the experimental flies in each lighting regime. The active phase in the control flies was predictably shortened; nonetheless, it was invariable in the experimental flies as the nights lengthened. Transfer from lighting regimes to DD initiated robust free-running rhythmicity in all flies including the arrhythmic ones subjected to LS cycles with 9 and 15 h of scotophases. The τ was profoundly affected by the nocturnal irradiance of the prior entraining lighting regime, as it was always shorter in the experimental than in the control flies. Thus, these results indisputably demonstrate the changes in fundamental properties of the circadian pacemaker of D. jambulina were solely attributed to the extremely dim nocturnal irradiance. This strain of D. jambulina is entrained essentially by the dimly lit natural nights, since it is never exposed to the prevailing photic cues such as the twilight transitions or bright photoperiod, owing to the dense vegetation of its habitat.     

Novel diarylheptanoids as inhibitors of TNF-α production

Synthesis and anti-inflammatory activity of novel diarylheptanoids [5-hydroxy-1-phenyl-7-(pyridin-3-yl)-heptan-3-ones and 1-phenyl-7-(pyridin-3-yl)hept-4-en-3-ones] as inhibitors of tumor necrosis factor-α (TNF-α) production is described in the present article. The key reactions involve the formation of a β-hydroxyketone by the reaction of substituted 4-phenyl butan-2-ones with pyridine-3-carboxaldehyde in presence of LDA and the subsequent dehydration of the same to obtain the α,β-unsaturated ketones. Compounds 4i, 5b, 5d, and 5g significantly inhibit lipopolysaccharide (LPS)-induced TNF-α production from human peripheral blood mononuclear cells in a dose-dependent manner. Of note, the in vitro TNF-α inhibition potential of 5b and 5d is comparable to that of curcumin (a naturally occurring diarylheptanoid). Most importantly, oral administration of 4i, 5b, 5d, and 5g (each at 100 mg/kg) but not curcumin (at 100 mg/kg) significantly inhibits LPS-induced TNF-α production in BALB/c mice. Collectively, our findings indicate that these compounds may have potential therapeutic implications for TNF-α-mediated auto-immune/inflammatory disorders.     

Discovery of new anti-depressants from structurally novel 5-HT3 receptor antagonists: design, synthesis and pharmacological evaluation of 3-ethoxyquinoxalin-2-carboxamides

A novel series of 3-ethoxyquinoxalin-2-carboxamides were designed as per the pharmacophoric requirements of 5-HT₃ receptor antagonist using ligand-based approach. The desired carboxamides were synthesized from the key intermediate, 3-ethoxyquinoxalin-2-carboxylic acid by coupling with appropriate amines in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC·HCl) and 1-hydroxybenzotriazole (HOBt). The 5-HT₃ receptor antagonism was evaluated in longitudinal muscle myenteric plexus preparation from guinea pig ileum against 5-HT₃ agonist, 2-methy-5-HT, which was expressed in the form of pA₂ values. Compound 6h (3-ethoxyquinoxalin-2-yl)(4-methylpiperazin-1-yl)methanone was found to be the most active compound, which expressed a pA₂ value of 7.7. In forced swim test, the compounds with higher pA₂ value exhibited good anti-depressant-like activity and compounds with lower pA₂ value failed to show activity as compared to the vehicle-treated group.     

Synthesis of anomeric 1,5-anhydrosugars as conformationally locked selective α-mannosidase inhibitors

Anomeric 1,5-anhydrosugar 2 was synthesized from d-glucose derived N-Cbz protected aminodiol 8. The key step involves, acid catalyzed hydrolysis of 1,2-acetonide group in 8 to get hemiacetal that concomitantly undergoes formation of the pyranose ring by attack of C-3 hydroxyethyl group on anomeric C-1, leading to the formation of dioxabicyclo[3.2.1]octane skeleton which on hydrogenolyis gave 2. The glycosidase inhibitory activities of hydroxy- and amino-substituted anomeric 1,5-anhydrosugars 1 and 2, respectively, showed selective inhibition of α-mannosidase. These results were substantiated by molecular docking studies using WHAT IF software and AUTODOCK 4.0 program.