Ajay B. Patil

Diosgenin from Dioscorea bulbifera: Novel Hit for Treatment of Type II Diabetes Mellitus with Inhibitory Activity against α-Amylase and α-Glucosidase

Diabetes mellitus is a multifactorial metabolic disease characterized by post-prandial hyperglycemia (PPHG). α-amylase and α-glucosidase inhibitors aim to explore novel therapeutic agents. Herein we report the promises of Dioscorea bulbifera and its bioactive principle, diosgenin as novel α-amylase and α-glucosidase inhibitor. Among petroleum ether, ethyl acetate, methanol and 70% ethanol (v/v) extracts of bulbs of D. bulbifera, ethyl acetate extract showed highest inhibition upto 72.06 ± 0.51% and 82.64 ± 2.32% against α-amylase and α-glucosidase respectively. GC-TOF-MS analysis of ethyl acetate extract indicated presence of high diosgenin content. Diosgenin was isolated and identified by FTIR, 1H NMR and 13C NMR and confirmed by HPLC which showed an α-amylase and α-glucosidase inhibition upto 70.94 ± 1.24% and 81.71 ± 3.39%, respectively. Kinetic studies confirmed the uncompetitive mode of binding of diosgenin to α-amylase indicated by lowering of both Km and Vm. Interaction studies revealed the quenching of intrinsic fluorescence of α-amylase in presence of diosgenin. Similarly, circular dichroism spectrometry showed diminished negative humped peaks at 208 nm and 222 nm. Molecular docking indicated hydrogen bonding between carboxyl group of Asp300, while hydrophobic interactions between Tyr62, Trp58, Trp59, Val163, His305 and Gln63 residues of α-amylase. Diosgenin interacted with two catalytic residues (Asp352 and Glu411) from α-glucosidase. This is the first report of its kind that provides an intense scientific rationale for use of diosgenin as novel drug candidate for type II diabetes mellitus.

Modified synthesis scheme for N,N´-dimethyl-N,N´-dioctyl-2,(2´-hexyloxyethyl) malonamide (DMDOHEMA) and its comparison with proposed solvents for actinide partitioning

Abstract N,N´-dimethyl-N,N´-dioctyl-2,(2´-hexyloxyethyl) malonamide (DMDOHEMA) has been synthesized by a relatively simpler route with a better yield than the conventional procedures for the synthesis of pentaalkyl substituted diamides. The proposed route replaces the use of acid chlorides and brominating agents (corrosive in nature) by acid diester and p-toluene sulphonyl (tosyl) chloride, respectively. The later easily replaces hydrogen from primary OH group of the 3-oxanonyl side chain and relatively less corrosive. The synthesized product has been tested for the extraction behavior of 241Am, Np, Pu as pure tracers as well as under Pressurized Heavy Water Reactor (PHWR) Simulated High-Level Waste (SHLW) conditions. The stoichiometries of extracted species of Np(IV), Pu(IV), and Am(III) from 3 M HNO3 using varying concentrations of DMDOHEMA in n-dodecane has been determined. The effect of the nature of mineral acid (viz. HCl, HNO3, and HClO4) on the extraction of Am(III) has also been investigated employing DMDOHEMA and N,N´-dimethyl-N,N´-dibutyl-tetradecyl malonamide (DMDBTDMA) as extractants and explained in terms of the aggregation behavior of diamides. The performance of DMDOHEMA has been evaluated vis-à-vis other proposed extractants for actinide partitioning under PHWR-SHLW conditions.

A novel solvent system containing a dipicolinamide in room temperature ionic liquids for actinide ion extraction

Solvent extraction of Am(III), Pu(IV) and Eu(III) was done from nitric acid medium using a solvent system containing a substituted dipicolinamide extractant dissolved in room temperature ionic liquid. The solvent system was found to be more efficient as compared to the previously reported solvents in molecular diluents.

Evaluation of malonic acid diamide analogues as radical scavenging agents

The malonic acid diamide analogues such as N,N′-dimethyl-N,N′-dioctyl-malonamide (DMDOMA), N,N′-dimethyl-N,N′-dioctyl-2,(2′-hexyloxyethyl) malonamide (DMDOHEMA), N,N′-dimethyl-N,N′-dicyclohexyl-malonamide (DMDCMA) and N,N,N′,N′-tetraisopropyl malonamide (TiPMA) were synthesized by an ester amine coupling method. These synthesized diamides were evaluated for the scavenging activity of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, superoxide anion scavenging and ferric reducing antioxidant power (FRAP), by biochemical methods. Antioxidant properties exhibited by these diamides were compared with standard antioxidants like gallic acid and ascorbic acid. The pulse radiolysis technique was employed to generate 2-2′-azinobis 3-ethylbenzothioline-6-sulfonic acid (ABTS˙+), hydroxyl radicals (˙OH), and carbonate (CO3˙−) radicals for evaluating the scavenging activity of the diamides. DMDCMA, TiPMA, and DMDOMA were found to show better antioxidant potential as compared to DMDOHEMA due to their more hydrophilic nature. The pulse radiolysis technique was found to be advantageous for investigating the interaction of the diamide class of compounds with radicals generated under high energy radiation.

Synthesis and Evaluation of N,N′-dimethyl-N,N′-dicyclohexyl-Malonamide (DMDCMA) as an Extractant for Actinides

A malonamide based extractant, i.e., N,N′-dimethyl-N,N′-dicyclohexyl-malonamide (DMDCMA) was synthesized in a single step and tested for the extraction of several actinide ions such as Am(III), U(VI), Np(IV), Np(VI), Pu(IV), Pu(VI), etc., from nitric acid medium. The extractant was soluble in phenyltrifluoromethylsulphone (PTMS or FS-13) unless stated otherwise. The effect of various experimental parameters, such as the aqueous phase acidity (0.01–3 M HNO3), nature of the acid, oxidation states of the metal ions, ligand concentration, nature of the diluent and temperature on the extraction behavior of metal ions was studied. The extracted Am(III) species was determined from slope analysis method as [Am(NO3)3(DMDCMA)2]. The extraction of the metal ions was found to increase with the aqueous phase acidity. The temperature variation studies allowed the calculation of the heat of the two-phase extraction reaction as well as the corresponding extraction constants. These studies revealed that DMDCMA showed good extraction for all the actinide metal ions investigated, and have the advantage of single stage synthesis and easier purification protocol.

A novel dipicolinamide-dicarbollide synergistic solvent system for actinide extraction

Abstract Solvent extraction studies of several actinide ions such as Am(III), U(VI), Np(IV), Np(VI), Pu(IV) were carried out from nitric acid medium using a synergistic mixture of N, N′-diethyl-N, N′-di(para)fluorophenyl-2,6-dipicolinamide, (DEtD(p)FPhDPA, DPA), and hydrogen dicarbollylcobaltate (H+CCD−) dissolved in phenyltrifluoromethylsulphone (PTMS). The effects of different parameters such as aqueous phase acidity (0.01 – 3 M HNO3), oxidation states of metal ions, ligand concentration, nature of diluent and temperature on the extraction behavior of metal ions were studied. The extracted Am(III) species was determined as H+[Am(DPA)2(CCD)4]−. With increasing aqueous phase acidities, the extractability of both Am(III) and Eu(III) was found to decrease. The synergistic mixture showed better extraction in mM concentrations as compared to previously studied dipicolinamides. The thermodynamic studies were performed to calculate heat of extraction reaction and the extraction constants. The proposed synergistic mixture showed good extraction for all the metal ions, though lanthanide actinide separation results are not encouraging.

Gnidia glauca Leaf and Stem Extract Mediated Synthesis of Gold Nanocatalysts with Free Radical Scavenging Potential

Development of eco-friendly and novel method for the synthesis of metal nanoparticles is one of the most popular and emerging aspect of nanobiotechnology. In this report, Gnidia glauca leaf and stem extract are used to synthesize gold nanoparticles (AuNPs). As compared to other biological methods, the syntheses were extremely rapid leading to complete reduction within 20 min. Transmission and high resolution transmission electron micrographs clearly indicated that majority of the bioreduced nanoparticles were spherical within a size range of 10 to 60 nm. Exotic shapes like gold nanotriangles and nanohexagons were found in a range between 100 to 300 nm. Dynamic light scattering validated the size range that was observed in TEM and HRTEM. Unique pattern confirming the self-assembly of spheres into anisotropic nanoparticles of larger dimensions was exhibited in HRTEM images. X-ray diffraction pattern and energy dispersive spectroscopic analysis confirmed the purity of elemental gold in the bioreduced nanoparticles. Fourier infrared spectral analysis indicated the role of the phenolic groups in reduction of chloroauric acid into AuNPs. Efficient reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of AuNPs and NaBH4 with apparent rate constants (k) 1.99 × 10-3 min-1 and 4.498 × 10-3 min-1, for AuNPs reduced by GGLE and GGSE, respectively provided strong evidence for the catalytic potential. AuNPs synthesized by GGSE and GGLE showed a second order rate constant of 1.78 × 107 and 1.31 × 107 respectively confirming the scavenging of ABTS•+ radicals.

Thermoresponsive copolymers with pendant D-galactosyl 1,2,3-triazole groups: synthesis, characterization and thermal behavior

A galactose containing glycomonomer has been synthesized by copper catalyzed azide–alkyne cyclo-addition reaction (CuAAC) of 6-azido-6-deoxy-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose with propargyl acrylate. This monomer was subjected to homopolymerization and copolymerization with N-isopropylacrylamide (NIPAm) at different compositions by free radical polymerization using 2,2′-azobis-isobutyronitrile (AIBN) as an initiator. The composition of the copolymer was determined by 1H-NMR spectroscopy. Upon acid hydrolysis of acetonide protected polymers, water-soluble deprotected polymers were obtained. The polymers were characterized and confirmed by NMR, IR, GPC and thermal analytical techniques. The protected and deprotected copolymers showed a sharp cloud-point temperature and a linear correlation was obtained between the lower critical solution temperatures (LCST) and the concentration of glycomonomer in the copolymers. This allows tuning the thermal response by simply altering the copolymer composition. Water contact angle experiments showed the changes in the hydrophilicity of copolymers with compositions that supported the LCST results. The glass transition temperature of protected copolymers followed a regular monotonic decreasing trend with increasing glycomonomer content, whereas Tg of deprotected copolymers increased due to H-bond interaction. The attempts to develop thermoresponsive polymers having LCSTs at physiological temperature were successful.