Ashok K. Tiwari

α-Glucosidase inhibitory antihyperglycemic activity of substituted chromenone derivatives

Series of 3,4- and 3,6-disubstituted chromenones including new chromenone derivatives were synthesized applying various synthetic strategies including Pechmann condensation, Knoevenagel condensation, Reimer-Tiemann reaction and Suzuki coupling in very good yields. Synthesized compounds (4a-z) were screened for in vitro alpha-glucosidase inhibitory and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activities. Majority of compounds displayed varying degrees of alpha-glucosidase inhibitory and DPPH scavenging activity. Compound 4x emerged as the most potent alpha-glucosidase inhibitor in present series of compounds owing to the presence of 3-acetyl-6-(6-methoxy-3-pyridyl) group on chromenone; however, it could not display DPPH scavenging activity and was found to be mixed non-competitive type inhibitor of rat intestinal alpha-glucosidase. When tested in vivo for antihyperglycemic activity in starch loaded Wistar rats, it displayed significant antihyperglycemic property. This is the first report assigning rat intestinal alpha-glucosidase inhibitory property for this class of new chromenones and presents new family of compounds possessing alpha-glucosidase inhibitory activities and antihyperglycemic property. Compound 4x may serve as an interesting new compound for the development of therapeutics targeted against diet-induced hyperglycemia in diabetes.

Gastroprotective flavonoid constituents from Oroxylum indicum Vent.

Chemical investigation of the stem bark of Oroxylum indicum resulted in the isolation and characterization of two new flavonoid glycosides (1, 2), along with seven known compounds (3-9). Their structures were established on the basis of extensive spectroscopic (IR, MS, 2D NMR) data analysis and by the comparison with spectroscopic data reported in the literature. In addition, all the compounds were tested for their ulcer protective effects against various gastric ulceritis inducing models in rats.

New Labdane diterpenes as intestinal α-glucosidase inhibitor from antihyperglycemic extract of Hedychium spicatum (Ham. Ex Smith) rhizomes

Phytochemical investigation of antihyperglycemic extract of rhizomes of Hedychium spicatum led to the isolation of two new labdane type diterpenes 2, 3 along with seven known compounds (1, 4-9). Their structures were established on the basis of NMR (1D and 2D) and mass spectroscopic analysis. The new compound 2 displayed strong intestinal alpha-glucosidase inhibitory activity. Other compounds also displayed varying degree of intestinal alpha-glucosidase inhibitory potential.

New furanoflavanoids, intestinal α-glucosidase inhibitory and free-radical (DPPH) scavenging, activity from antihyperglycemic root extract of Derris indica (Lam.)

A bioassay-guided fractionation and chemical examination of antihyperglycemic root extract of Derris indica resulted in isolation and characterization of two new furanoflavanoids (1, 2) along with thirteen known compounds (3-15). Their structures were determined on the basis of extensive spectroscopic (IR, MS, 1D and 2D NMR) data analysis and by comparison with the literature data. All the compounds were tested in vitro for intestinal alpha-glucosidase inhibitory and DPPH radical activity. New compounds (1, 2) displayed moderate intestinal alpha-glucosidase inhibitory as well as free radical scavenging activity. Other compounds also displayed varying degrees of moderate intestinal alpha-glucosidase inhibitory activity. Pongamol (6) displayed potent intestinal alpha-glucosidase inhibition.

Reduction in post-prandial hyperglycemic excursion through α-glucosidase inhibition by β-acetamido carbonyl compounds

A series of beta-acetamido carbonyl compounds (S(1)-S(7)) were prepared using Dakin-West reaction from different substituted aldehyde and acetophenone in the presence of lanthanum triflate as a solid catalyst. All the compounds were tested for their alpha-glucosidase inhibitory potential against rat intestinal alpha-glucosidase. The most potent rat intestinal alpha-glucosidase inhibitors S(5) and S(7) were tested for their antihyperglycemic activity following carbohydrate tolerance test. Both the compounds displayed antihyperglycemic activity equivalent to the standard drug acarbose.

Plant HDAC inhibitor chrysin arrest cell growth and induce p21WAF1 by altering chromatin of STAT response element in A375 cells

BackgroundChrysin and its analogues, belongs to flavonoid family and possess potential anti-tumour activity. The aim of this study is to determine the molecular mechanism by which chrysin controls cell growth and induce apoptosis in A375 cells.MethodsEffect of chrysin and its analogues on cell viability and cell cycle analysis was determined by MTT assay and flowcytometry. A series of Western blots was performed to determine the effect of chrysin on important cell cycle regulatory proteins (Cdk2, cyclin D1, p53, p21, p27). The fluorimetry and calorimetry based assays was conducted for characterization of chrysin as HDAC inhibitor. The changes in histone tail modification such as acetylation and methylation was studied after chrysin treatment was estimated by immuno-fluorescence and western blot analysis. The expression of Bcl-xL, survivin and caspase-3 was estimated in chrysin treated cells. The effect of chrysin on p21 promoter activity was studied by luciferase and ChIP assays.ResultsChrysin cause G1 cell cycle arrest and found to inhibit HDAC-2 and HDAC-8. Chrysin treated cells have shown increase in the levels of H3acK14, H4acK12, H4acK16 and decrease in H3me2K9 methylation. The p21 induction by chrysin treatment was found to be independent of p53 status. The chromatin remodelling at p21WAF1 promoter induces p21 activity, increased STAT-1 expression and epigenetic modifications that are responsible for ultimate cell cycle arrest and apoptosis.ConclusionChrysin shows in vitro anti-cancer activity that is correlated with induction of histone hyperacetylation and possible recruitment of STAT-1, 3, 5 proteins at STAT (−692 to −684) region of p21 promoter. Our results also support an unexpected action of chrysin on the chromatin organization of p21WAF1 promoter through histone methylation and hyper-acetylation. It proposes previously unknown sequence specific chromatin modulations in the STAT responsive elements for regulating cell cycle progression negatively via the induction of the CDK inhibitor p21WAF1.

Synthesis and biological evaluation of novel 8-aminomethylated oroxylin A analogues as α-glucosidase inhibitors

A series of 8-aminomethylated derivatives (1a-1j) were prepared by Mannich reaction of oroxylin A (1) with appropriate primary or secondary amines and para-formaldehyde. All the compounds were tested for their alpha-glucosidase inhibition activity against both yeast and rat intestinal alpha-glucosidase. Some of the compounds demonstrated significantly better alpha-glucosidase inhibitory activity than the parent compound (oroxylin A).

Synthesis, biological evaluation and molecular modeling studies of some novel thiazolidinediones with triazole ring

A new series of thiazolidinedione derivatives were synthesized and evaluated for in vitro α-glucosidase inhibition and anticancer activities. Compounds 3d, 3e and 3j showed potential α-glucosidase inhibition with IC₅₀ values ranging between 0.1 and 0.3 μg/ml whereas compounds 3i, 3j and 3k have showed better anticancer activity towards human cancer cell lines IMR-32 (neuroblastoma), Hep-G2 (hepatoma) and MCF-7 (breast). Molecular docking studies revealed compounds 3d, 3e and 3j are potent inhibitors of α-glucosidase and also showed compliance with standard parameters of drug likeness.

Fabrication, characterization and bioevaluation of silibinin loaded chitosan nanoparticles.

Silibinin is reported to possess multiple biological activities. However, its hydrophobic nature limits its bioavailability compromising in vivo biological activities. Nanoparticles-based delivery of such molecules has emerged as new technique to resolve these issues. Bio-degradable, compatible and adhesive nature of chitosan has recently attracted its suitability as a carrier for biologically active molecules. This study presents fabrication and characterization of chitosan-tripolyphosphate based encapsulation of silibinin. Various preparations of silibinin encapsulated chitosan-tripolyphosphate nanoparticles were studied for particle size, morphology, zeta-potential, and encapsulation efficiencies. Preparations were also evaluated for cytotoxic activities in vitro. The optimized silibinin loaded chitosan nanoparticles were of 263.7±4.1nm in particle size with zeta potential 37.4±1.57mV. Nanoparticles showed high silibinin encapsulation efficiencies (82.94±1.82%). No chemical interactions between silibinin and chitosan were observed in FTIR analysis. Powder X-ray diffraction analysis revealed transformed physical state of silibinin after encapsulation. Surface morphology and thermal behaviour were determined using TEM and DSC analysis. Encapsulated silibinin displayed increased dissolution and better cytotoxicity against human prostate cancer cells (DU145) than silibinin alone.

Antioxidants and a new germacrane sesquiteroene from Carissa spinarum.

A new germacrane derivative, carenone (1) was isolated from the stems of a well-known medicinal plant, Carissa spinarum L. together with a new ester, 3′-(4″-methoxyphenyl)-3′-oxo-propionyl hexadecanoate (2). Their structures were established using 1D, 2D NMR spectroscopic and synthetic methods. The chloroform extract of the plant displayed strong antioxidant (DPPH) activity. Several other known compounds were also isolated for the first time from this active extract. The antioxidant activity of major lignans was studied.