Repurposing of genistein as anti-sickling agent: elucidation by multi spectroscopic, thermophoresis, and molecular modeling techniques.

Sickle cell disease (SCD) is a major medical problem in which mono-therapeutic interventions have so far shown only limited effectiveness. We studied the repurpose of genistein, which could prevent sickle hemoglobin from polymerizing under hypoxic conditions in this disease. Genistein an important nutraceutical molecule found in soybean. The present study examines the repurposing genistein as an anti- sickling agent. Genistein shows inhibition of Hb S polymerization as well as a sickle reversal. Also, we have explored the interaction of the genistein with sickle hemoglobin (Hb S), using fluorescence, far-UV-CD spectroscopy, MicroScale Thermophoresis (MST), FTIR, combined with molecular modeling computations. The quenching constant decreases with increasing temperature, a characteristic that coincides with the static type of quenching mechanism. Temperature-dependent fluorescence measurements and molecular modeling studies reveal that apart from the hydrogen bonding, electrostatic interactions also play a crucial role in genistein and Hb S complex formation. In silico, distribution prediction of adsorption, digestion, metabolism, excretion, and toxicity (ADME/Tox) based on physical and chemical properties show that genistein is nontoxic and has ideal drug properties. The helicity and thermophoretic mobility of Hb S was a change in the presence of genistein, which leads to the destabilizing the Hb S polymer was examined using CD and MST, respectively. Our results open up the possibility for a promising therapeutic approach for the SCD by repurposed genistein as an anti-sickling agent.Communicated by Ramaswamy H. Sarma.

Insights into the Inhibition Mechanism of Human Pancreatic α-Amylase, a Type 2 Diabetes Target, by Dehydrodieugenol B Isolated from Ocimum tenuiflorum.

Use of human pancreatic α-amylase (HPA) inhibitors is one of the effective antidiabetic strategies to lower postprandial hyperglycemia via reduction in the dietary starch hydrolysis rate. Many natural products from plants are being studied for their HPA inhibitory activity. The present study describes isolation of dehydrodieugenol B (DDEB) from Ocimum tenuiflorum leaves using sequential solvent extraction, structure determination by one-dimensional (1D) and two-dimensional (2D) NMR analyses, and characterization as an HPA inhibitor using kinetics, binding thermodynamics, and molecular docking. DDEB uncompetitively inhibited HPA with an IC50 value of 29.6 µM for starch and apparent K i ' of 2.49 and Ki of 47.6 µM for starch and maltopentaose as substrates, respectively. The circular dichroism (CD) study indicated structural changes in HPA on inhibitor binding. Isothermal titration calorimetry (ITC) revealed thermodynamically favorable binding (ΔG of -7.79 kcal mol-1) with a dissociation constant (K d) of 1.97 µM and calculated association constant (K a) of 0.507 µM. Molecular docking showed stable HPA-inhibitor binding involving H-bonds and Pi-alkyl, alkyl-alkyl, and van der Waals (vDW) interactions. The computational docking results support the noncompetitive nature of DDEB binding. The present study could be helpful for exploration of the molecule as a potential antidiabetic drug candidate to control postprandial hyperglycemia.

Potential of isoquercitrin as antisickling agent: a multi-spectroscopic, thermophoresis and molecular modeling approach.

Sickle cell disease is an inherited disease caused by point mutation in hemoglobin (ß-globin gene). Under oxygen saturation, sickle hemoglobin form polymers, leading to rigid erythrocytes. The transition of the blood vessels is altered and initiated by the adhesion of erythrocytes, neutrophils and endothelial cells. Sickle Hemoglobin (HbS) polymerization is a major cause in red blood cells (RBC), promoting sickling and destruction of RBCs. Isoquercitrin, a medicinal bioactive compound found in various medicinal plants, has multiple health benefits. The present study examines the potential of isoquercitrin as an anti-sickle agent, showing a significant decrease in the rate of polymerization as well as sickling of RBCs. Isoquercitrin-induced graded alteration in absorbance and fluorescence of HbS, confirmed their interaction. A negative value of ΔG° strongly suggests that it is a spontaneous exothermic reaction induced by entropy. Negative ΔH° and positive ΔS° predicted that hydrogen and hydrophobic binding forces interfered with a hydrophobic microenvironment of ß6Val leading to polymerization inhibition of HbS. HbS-Isoquercitrin complex exhibits helical structural changes leading to destabilization of the HbS polymer as confirmed by CD spectroscopy. MST and DSC results indicate greater changes in thermophoretic mobility and thermal stability of sickle hemoglobin in the presence of isoquercitrin, respectively. These findings were also supported by molecular simulation studies using DOCK6 and GROMACS. Hence, we can conclude that isoquercitrin interacts with HbS through hydrogen bonding, which leads to polymerization inhibition. Consequently, isoquercitrin could potentially be used as a medication for the treatment of sickle cell disease.Communicated by Ramaswamy H. Sarma.

Sugar-derived oxazolone pseudotetrapeptide as γ-turn inducer and anion-selective transporter.

The intramolecular cyclization of a C-3-tetrasubstituted furanoid sugar amino acid-derived linear tetrapeptide afforded an oxazolone pseudo-peptide with the formation of an oxazole ring at the C-terminus. A conformational study of the oxazolone pseudo-peptide showed intramolecular C=O···HN(II) hydrogen bonding in a seven-membered ring leading to a γ-turn conformation. This fact was supported by a solution-state NMR and molecular modeling studies. The oxazolone pseudotetrapeptide was found to be a better Cl--selective transporter for which an anion-anion antiport mechanism was established.

Synthesis and anti-leishmanial activity of TRIS-glycine-ß-alanine dipeptidic triazole dendron coated with nonameric mannoside glycocluster.

Tripodal nonameric mannoside glycodendrimer 1 with carbohydrate tethered triazole linked with the TRIS-glycine-ß-alanine dipeptidic aromatic centered core was synthesized. Glycodendrimer 1 demonstrated potential in vitro anti-leishmanial activity. The bio-activity data was substantiated with molecular modelling and docking studies of 1 with the three-dimensional protein structure of Leishmanolysin.

Retraction: Organocatalytic stereoselective synthesis of passifloricin A.

Retraction of 'Organocatalytic stereoselective synthesis of passifloricin A' by Pradeep Kumar et al., Org. Biomol. Chem., 2012, 10, 1820-1825.

Alizarin interaction with sickle hemoglobin: elucidation of their anti-sickling properties by multi-spectroscopic and molecular modeling techniques.

Polymerization of hemoglobin S is a major cause of morbidity and mortality in sickle cell disease, which leads to sickling and destruction of red blood cell. Alizarin, a bioactive compound from Rubia cordifolia, is reported to be blood purifier. This study investigates the potential of alizarin as an anti-sickling agent, showing a significant decrease in the rate of polymerization, therefore inhibiting the rate of sickling with increasing concentration. Interaction studies indicated that the fluorescence intensity of sickle hemoglobin (Hb S) decreases gradually with increasing alizarin concentration. This suggests the static quenching, where binding constant and the number of binding sites were deduced at different temperatures. The negative values of Gibbs energy change (ΔG0) strongly suggest that it is entropy-driven spontaneous and exothermic reaction. Negative enthalpy (ΔH0) and positive entropy (ΔS0) stipulated that hydrogen and hydrophobic bonding forces were interfering in a hydrophobic micro-environment of ß6Val leading to Hb S polymerization inhibition. In circular dichroism (CD) spectra, Hb S in the presence of alizarin shows helical structural changes leading to destabilization of Hb S polymer. These findings were also supported by molecular docking simulation studies using DOCK6 and GROMACS. So, from these findings, we may conclude that alizarin interacts with Hb S through hydrogen bonding and leading to inhibition of Hb S polymerization. Consequently, alizarin may have potential use as an anti-sickle cell medication for sickle cell disorder. Communicated by Ramaswamy H. Sarma.

Purification and Characterization of an Active Principle, Lawsone, Responsible for the Plasmid Curing Activity of Plumbago zeylanica Root Extracts.

Plasmid curing is the process of obviating the plasmid encoded functions such as antibiotic resistance, virulence, degradation of aromatic compounds, etc. in bacteria. Several plasmid curing agents have been reported in literature, however, no plasmid curing agent can eliminate all plasmids from different hosts. Hence, there is always a need for novel plasmid curing agents that can be effectively used for reversal of plasmid encoded functions such as virulence, antibiotic resistance, etc. In the present study, an active principle responsible for the plasmid curing activity was purified from roots of Plumbago zeylanica by bioassay guided fractionation and identified as 2-hydroxy-1,4-naphthoquinone (lawsone), on the basis of spectral and analytical data such as NMR, GCMS, FTIR. Plasmid curing activity of lawsone was observed against reference as well as wild plasmids (pBR322, pRK2013, R136, pUPI281, and pUPI282) residing in a range of hosts. Curing of plasmid was confirmed by agarose gel electrophoresis. MICs of antibiotics against A. baumannii A24 (pUPI281) and E. coli (pRK2013) decreased significantly in presence of lawsone suggesting synergy between lawsone and antibiotics. Lawsone also inhibited transfer of plasmid pRK2013 to E. coli either by transformation or conjugation. Viability assays (MTT) revealed that lawsone was not toxic to mammalian cells. Thus, the present investigation has revealed lawsone as an effective plasmid curing agent capable of suppressing development and spread of antibiotic resistance. Further, lawsone has important application in basic research to identify phenotypes encoded by the plasmids in plasmid curing experiments. To the best of our knowledge this is the first report of plasmid curing activity of lawsone isolated from roots of P. zeylanica.

Preparation and characterization of microencapsulated DwPT trivalent vaccine using water soluble chitosan and its in-vitro and in-vivo immunological properties.

The paper explained the microencapsulation of three different antigenic materials viz. Diphtheria toxoid (DT), whole cell pertussis antigens (PT and FHA) and tetanus toxoid (TT) by coacervation method using water soluble chitosan as a polymer crosslinked by vanillin/TPP co-crosslinkers for the development of oral trivalent DwPT vaccine. Instrumental characterization of chitosan microspheres suggested specific interaction with vanillin/TPP, higher thermal stability, amorphous nature, spherical morphology with size less than 2µm along with positive charge density offering mucoadhesive properties. Furthermore, PT and FHA showed higher encapsulation up to 94% followed by TT and DT. Cumulative release rate of DT was (68.47%), TT (73.67%), PT (43%) and FHA (53%). Release kinetics interpreted using DD solver program, indicated protein release followed first order kinetics and obeyed Korsmeyer-peppas model, stating fickian diffusion relates to diffusion, erosion and controlled release rate of the encapsulated toxoids. Application of formulations on caco-2 cell line showed negligible cytotoxic effect and efficient uptake of FITC labelled microspheres. The obtained in-vivo results suggests that the final trivalent DwPT formulation were having successful elicitation of both systemic (IgG) and mucosal (sIgA) immune response in balb/c mice. Overall studies indicated that DwPT formulation could be a suitable alternative to available injectable DaPT vaccine.

Self-Assembly of Fluorinated Sugar Amino Acid Derived α,γ-Cyclic Peptides into Transmembrane Anion Transport.

Syntheses of fluorinated sugar amino acid derived α,γ-cyclic tetra- and hexapeptides are reported. The IR, NMR, ESI-MS, CD, and molecular modeling studies of cyclic tetra- and hexapeptides showed C2 and C3 symmetric flat oval- and triangular-ring shaped ß-strand conformations, respectively, which appear to self-assemble into nanotubes. The α,γ-cyclic hexapeptide (EC50 = 2.14 µM) is found to be a more efficient ion transporter than α,γ-cyclic tetrapeptide (EC50 = 14.75 µM). The anion selectivity and recognition of α,γ-cyclic hexapeptide with NO3- ion is investigated.

α-Geminal disubstituted pyrrolidine iminosugars and their C-4-fluoro analogues: Synthesis, glycosidase inhibition and molecular docking studies.

A simple strategy for the synthesis of α-geminal disubstituted pyrrolidine iminosugars 3a-c and their C-4 fluorinated derivatives 4a-c has been described from d-glucose. The methodology involves the Corey-Link and Jocic-Reeve reaction with 3-oxo-α-d-glucofuranose and nucleophilic displacement reaction to get the furanose fused pyrrolidine ring skeleton with requisite CH2OH/CO2H functionalities at C-3. The fluorine substituent in target molecules was introduced by nucleophilic displacement of -OTf in 9a/9c with CsF. Appropriate manipulation of the anomeric carbon in the furanose fused pyrrolidine ring skeleton afforded α-geminal disubstituted pyrrolidine iminosugars 3a-c and C-4 fluoro derivatives 4a-c. The pyrrolidine iminosugars 3a and 3c were found to be potent inhibitors of α-galactosidase while, the fluoro derivatives 4a and 4b showed strong inhibition of ß-glucosidase and ß-galactosidase, respectively. These results were substantiated by in silico molecular docking studies.

Acyclic αγα-Tripeptides with Fluorinated- and Nonfluorinated-Furanoid Sugar Framework: Importance of Fluoro Substituent in Reverse-Turn Induced Self-Assembly and Transmembrane Ion-Transport Activity.

Acyclic αγα-tripeptides derived from fluorinated-furanoid sugar amino acid frameworks act as reverse-turn inducers with a U-shaped conformation, whereas the corresponding nonfluorinated αγα-tripeptides show random peptide conformations. The NMR studies showed the presence of bifurcated weak intramolecular hydrogen bonding (F···HN) and N+···Fδ- charge-dipole attraction compel the amide carbonyl groups to orient antiperiplanar to the C-F bond, thus, demonstrating the role of the fluorine substituent in stabilizing the U-shaped conformation. The NOESY data indicate that the U-shaped tripeptides self-assembly formation is stabilized by the intermolecular hydrogen bonding between C═O···HN with antiparallel orientation. This fact is supported by ESI-MS data, which showed mass peaks up to the pentameric self-assembly, even in the gas phase. The morphological analysis by FE-SEM, on solid samples, showed arrangement of fibers into nanorods. The antiparallel self-assembled pore of the fluorinated tripeptides illustrates the selective ion-transport activity. The experimental findings were supported by DFT studies.

Iminosugars Spiro-Linked with Morpholine-Fused 1,2,3-Triazole: Synthesis, Conformational Analysis, Glycosidase Inhibitory Activity, Antifungal Assay, and Docking Studies.

Synthesis of iminosugars 1, 2, 3a, and 4a and N-alkyl (ethyl, butyl, hexyl, octyl, decyl, and dodecyl) derivatives 3b-g and 4b-g spiro-linked with morpholine-fused 1,2,3-triazole is described. Conformation of the piperidine ring in each spiro-iminosugar was evaluated by 1H NMR spectroscopy, and conformational change in N-alkylated compounds 4b-g with respect to parent spiro-iminosugar 4a is supported by density functional theory calculations. Out of 16 new spiro-iminosugars, the spiro-iminosugars 3a (IC50 = 0.075 µM) and 4a (IC50 = 0.036 µM) were found to be more potent inhibitors of α-glucosidase than the marketed drug miglitol (IC50 = 0.100 µM). In addition, 3a (minimum inhibition concentration (MIC) = 0.85 µM) and 4a (MIC = 0.025 µM) showed more potent antifungal activity against Candida albicans than antifungal drug amphotericin b (MIC = 1.25 µM). In few cases, the N-alkyl derivatives showed increase of α-glucosidase inhibition and enhancement of antifungal activity compare to the respective parent iminosugar. The biological activities were further substantiated by molecular docking studies.

Synthesis of the C8'-epimeric thymine pyranosyl amino acid core of amipurimycin.

The C8'-epimeric pyranosyl amino acid core 2 of amipurimycin was synthesized from D-glucose derived alcohol 3 in 13 steps and 14% overall yield. Thus, the Sharpless asymmetric epoxidation of allyl alcohol 7 followed by trimethyl borate mediated regio-selective oxirane ring opening with azide, afforded azido diol 10. The acid-catalyzed 1,2-acetonide ring opening in 10 concomitantly led to the formation of the pyranose ring skeleton to give 2,7-dioxabicyclo[3.2.1]octane 12. Functional group manipulation in 12 gave 21 that on stereoselective ß-glycosylation afforded the pyranosyl thymine nucleoside 2 - a core of amipurimycin.

Interaction of a Julolidine-Based Neutral Ultrafast Molecular Rotor with Natural DNA: Spectroscopic and Molecular Docking Studies.

Ultrafast molecular rotors (UMRs) are reported to be one of the best fluorescent sensors to study different microenvironments, including biomolecules. In the present work, we have explored the possibility of application of a julolidine-based neutral UMR, 9-(2,2-dicyano vinyl) julolidine (DCVJ), as a DNA sensor and studied its mode of binding with DNA in detail using spectroscopic and molecular docking techniques. Our spectroscopic studies indicate that association of DCVJ with DNA leads to a very large enhancement in its emission intensity. Detailed investigation reveals that, despite being a neutral molecule, binding of DCVJ with DNA is largely modulated in the presence of salt. Such an unusual salt effect has been explained by invoking the ion-dipole interaction between DCVJ and the phosphate backbone of DNA. The ion-dipole interaction has also been established by studying the interaction of DCVJ with nucleosides. Detailed time-resolved studies show that the twisting motion around the vinyl bond in DCVJ gets retarded to a great extent because of its association with DNA molecules. Through competitive binding studies, it has also been established that DCVJ also binds to DNA through intercalation. Finally, quantum chemical calculations and molecular docking studies have been performed to confirm the mode of binding of DCVJ with DNA.

Synthesis of 2,4,6-Trisubstituted Pyridines by Oxidative Eosin Y Photoredox Catalysis.

Eosin Y, an organic dye, was activated as a photoredox catalyst in the presence of molecular oxygen using visible light and, when it was used in the reaction of aryl ketones and benzyl amines, afforded good yields (52-87%) of 2,4,6-triarylpyridines (21 examples) at ambient temperature. The aryl groups at the 2- and 6-positions are derived from ketones, while benzyl amine plays the dual role of providing an aryl functionality at the 4-position of pyridine as well as being a nitrogen donor.

Tartrate/tripolyphosphate as co-crosslinker for water soluble chitosan used in protein antigens encapsulation.

In drug delivery research, several toxic chemical crosslinkers and non-toxic ionic crosslinkers have been exploited for the synthesis of microparticles from acetic acid soluble chitosan. This paper hypothesized the implementation of sodium potassium tartrate (SPT) as an alternative crosslinker for sodium tripolyphosphate (TPP) and SPT/TPP co-crosslinkers for synthesis of the microparticles using water soluble chitosan (WSC) for encapsulation of Bovine serum albumin (BSA) as a model protein, and Tetanus toxoid (TT) as a model vaccine. The crosslinking was confirmed by FT-IR, SEM with EDS. The XRD entailed molecular dispersion of proteins and thermal analysis confirmed the higher stability of STP/TPP co-crosslinked formulations. The resultant microparticles were exhibiting crosslinking degree (52-67%), entrapment efficiency (72-80%), particle size (0.3-1.7µm), zeta potential (+24 to 46mV) and mucoadhesion (41-68%). The superiority of SPT over TPP was confirmed by higher crosslinking degree and entrapment efficiency. However, co-crosslinking were advantageous in higher regression values for Langmuir adsorption isotherm, slower swelling tendency and extended 30days controlled in-vitro release study. TT release obeyed the Quasi-Fickian diffusion mechanism for single and cocrosslinked formulations. Overall, in crosslinking of chitosan as biological macromolecules, STP/TPP may be alternative for single ionic crosslinked formulations for protein antigen delivery.

Correction: Multivalent presentation of carbohydrates by 3(14)-helical peptide templates: synthesis, conformational analysis using CD spectroscopy and saccharide recognition.

Correction for 'Multivalent presentation of carbohydrates by 314-helical peptide templates: synthesis, conformational analysis using CD spectroscopy and saccharide recognition' by Nitin J. Pawar et al., Org. Biomol. Chem., 2015, 13, 11278-11285.

Diosgenin Functionalized Iron Oxide Nanoparticles as Novel Nanomaterial Against Breast Cancer.

Iron oxide nanoparticles (IONPs) have gained immense importance recently as drug nanocarriers due to easy multifunctionalization, simultaneous targeting, imaging and cancer hyperthermia. Herein, we report a novel nanomedicine comprising of IONPs core functionalized with a potent anticancer bioactive principle, diosgenin from medicinal plant Dioscorea bulbifera via citric acid linker molecule. IONPs were synthesized by reverse co-precipitation and characterized using field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and dynamic light scattering (DLS). Diosgenin functionalization was confirmed using fourier transform infrared spectroscopy (FTIR) and biochemical methods. Synthesized IONPs, citrate linked IONPs (IONPs-CA), diosgenin functionalized IONPs (IONPs-D) along with free citric acid and diosgenin were checked for anticancer activity against MCF7 breast cancer cells by MTT assay, wound migration assay, confocal microscopy and protein expression by western blotting. Size of IONPs, IONPs-CA and IONPs-D gradually increased ranging from 12 to 21 nm as confirmed by FESEM and HRTEM. Signature peaks of diosgenin at 2914, 1166 and 1444 cm-1 IONPs-D, revealed in FTIR indicated the presence of functionalized diosgenin. IONPs-D exhibited 51.08 ± 0.37% antiproliferative activity against MCF7 cells, which was found to be superior to free citric acid (17.71 ± 0.58%) and diosgenin (33.31 ± 0.37%). Treatment with IONPs-D exhibited reduced wound migration upto 40.83 ± 2.91% compared to bare IONPs (89.03 ± 2.58%) and IONPs-CA (50.35 ± 0.48%). IONPs-D and diosgenin exhibited apoptosis induction, confirmed by Alexa Fluor 488 annexin V/PI double-stained cells indicating extensive cell membrane damage coupled with PI influx leading to nuclear staining in treated cells. IONPs-D mediated selective PARP cleavage strongly rationalized it as superior apoptotic inducers. Based on these findings, IONPs-D can be considered as first diosgenin functionalized novel magnetic nanomedicine with antiproliferative, migration inhibiting and apoptosis inducing properties against breast cancer.

Multivalent presentation of carbohydrates by 3(14)-helical peptide templates: synthesis, conformational analysis using CD spectroscopy and saccharide recognition.

A well defined 314-helical tetravalent ß-galactopeptide site-specific functionalised template (SSFT) 1 was prepared containing d-galactose units, with free anomeric carbons as the aldehyde tags, and was explored via ligation with different aminoxy sugars (α-/ß-d-glucose, α/ß-d-galactose, α-d-mannose and ß-d-lactose) to get 314-helical carbohydrate-functionalised multivalent glycoconjugates 2-7. Preliminary recognition studies of tetramannosyl glycoconjugate 4 with a specific lectin (concanavalin A) using fluorescence anisotropy showed an increase in binding affinity and the multivalency effect was found to be increased by 6.5 times per glycan.