Iqra Munir

Formulation and stabilization of riboflavin in liposomal preparations.

A study of the formulation of liposomal preparations of riboflavin (RF) with compositional variations in the content of phosphatidylcholine (PC) and their entrapment efficiency (26-42%) have been conducted. Light transmission characteristics of the liposomal preparations have been determined to evaluate their effect on the amount of light passing through the system to initiate a photochemical reaction. Dynamic light scattering (DLS) and atomic force microscopy (AFM) have been used to study the physical characteristics of liposomes. The liposomal preparations of RF have been subjected to photolysis using visible light and the apparent first- order rate constant, kobs, for the degradation of RF have been determined. The values of kobs (1.73-2.29×10(-3)min(-1)) have been found to decrease linearly with an increase in PC concentration in the range of 12.15 to 14.85 mM. Thus, an increase in PC concentration of liposomes leads to an increase in the stability of RF. RF and its main photoproduct, lumichrome (LC), formed in liposomes have been assayed by a two-component spectrometric method at 356 and 445 nm using an irrelevant absorption correction to compensate for the interference of liposomal components. The fluorescence measurements of RF in liposomes indicate excited singlet state quenching and the formation of a charge-transfer complex between RF and PC. It results in electron transfer from PC to RF to cause photoreduction and stabilization of RF.

Novel quinoxaline based chemosensors with selective dual mode of action: nucleophilic addition and host–guest type complex formation

New quinoxalinium salts 1–5 have been exploited as chemosensors via naked eye, UV-Vis absorption, fluorescence quenching and 1H NMR experiments. New sensors 1–5 showed a dual mode, nucleophilic addition and a host–guest type complex towards anion (F−, AcO− and ascorbate) detection. Small anions (F−/AcO−) showed nucleophilic addition at the C2 position of the quinoxalinium cation, while larger anions (ascorbate), revealed the formation of a host–guest type complex due to the steric hindrance posed by the C3 of the phenyl ring. Nucleophilic addition of small anions (F−/AcO−) leads to the de-aromatization of the quinoxalinium cation. However in the case of the larger anion, ascorbate, the host–guest type complex formation induces changes in the absorption/fluorescence signals of the quinoxalinium moiety. This selective binding has been confirmed on the basis of the 1H NMR spectroscopic technique, whereupon nucleophilic addition of small anions (F−/AcO−) was confirmed by monitoring the characteristic proton NMR signals of Ha and the methylene protons (CH2), which were clearly shifted in the cases of fluoride and acetate ion addition confirming the de-aromatization and nucleophilic addition. Whereas no such peak shifting was observed in the case of ascorbate ion addition confirming the non-covalent addition of ascorbate. Theoretical insight into the selectivity and complexation behavior of the ascorbate ion with the quinoxaline moiety is gained through density functional theory (DFT) calculations. Moreover, the absorption properties of these complexes are modeled theoretically, and compared with the experimental data. In addition, the thermal decomposition of sensors (1 and 2) has been studied by the means of differential scanning calorimetry (DSC), thermogravimetry (TG), and differential thermogravimetry (DTG) to signify their utility at variable temperatures.

Formulation and stabilization of norfloxacin in liposomal preparations.

A number of liposomal preparations of norfloxacin (NF) containing variable concentrations of phosphatidylcholine (PC) (10.8-16.2mM) have been formulated and an entrapment of NF to the extent of 41.7-56.2% was achieved. The values of apparent first-order rate constants (kobs) for the photodegradation of NF in liposomes (pH7.4) lie in the range of 1.05-2.40×10(-3)min(-1) compared to a value of 8.13×10(-3)min(-1) for the photodegradation of NF in aqueous solution (pH7.4). The values of kobs are a linear function of PC concentration indicating an interaction of PC and NF during the reaction. The second-order rate constant for the photochemical interaction of PC and NF has been determined as 8.92×10(-2)M(-1)min(-1). Fluorescence measurements on NF in liposomes indicate a decrease in fluorescence with an increase in PC concentration as a result of formation of NF(-) species which exhibits poor fluorescence. Dynamic light scattering has shown an increase in the size of NF encapsulated liposomes with an increase in PC concentration. The stabilization of NF in liposomes is achieved by the formation of a charge-transfer complex between NF and PC.

Novel acridine-based thiosemicarbazones as ‘turn-on' chemosensors for selective recognition of fluoride anion: a spectroscopic and theoretical study

New thiosemicarbazide-linked acridines 3a–c were prepared and investigated as chemosensors for the detection of biologically and environmentally important anions. The compounds 3a–c were found selective for fluoride (F−) with no affinity for other anions, i.e. −OAc, Br−, I−, HSO4−, SO42−, PO43−, ClO3−, ClO4−, CN− and SCN−. Further, upon the gradual addition of a fluoride anion (F−) source (tetrabutylammonium fluoride), a well-defined change in colour of the solution of probes 3a–c was observed. The anion-sensing process was studied in detail via UV–visible absorption, fluorescence and 1H-NMR experiments. Moreover, during the synthesis of acridine probes 3a–c nickel fluoride (NiF2), a rarely explored transition metal fluoride salt, was used as the catalyst. Theoretical studies via density functional theory were also carried out to further investigate the sensing and anion (F−) selectivity pattern of these probes.

Acridinedione as selective flouride ion chemosensor: a detailed spectroscopic and quantum mechanical investigation

The use of small molecules as chemosensors for ion detection is rapidly gaining popularity by virtue of the advantages it offers over traditional ion sensing methods. Herein we have synthesized a series of acridine(1,8)diones (7a–7l) and explored them for their potential to act as chemosensors for the detection of various anions such as fluoride (F−), acetate (OAc−), bromide (Br−), iodide (I−), bisulfate (HSO4−), chlorate (ClO3−), perchlorate (ClO4−), cyanide (CN−), and thiocyanate (SCN−). Acridinediones were found to be highly selective chemosensors for fluoride ions only. To investigate in detail the mechanism of selective fluoride ion sensing, detailed spectroscopic studies were carried out using UV-visible, fluorescence and 1H NMR spectroscopy. Fluoride mediated (NH) proton abstraction of acridinedione was found to be responsible for the observed selective fluoride ion sensing. Quantum mechanical computational studies, using time dependent density functional theory (TDDFT) were also carried out, whereupon comparison of acridinedione interaction with fluoride and acetate ions explained the acridinedione selectivity for the detection of fluoride anions. Our results provide ample evidence and rationale for further modulation and exploration of acridinediones as non-invasive chemosensors for fluoride ion detection in a variety of sample types.

Protein–drug nanoconjugates: Finding the alternative proteins as drug carrier

Present study was conducted to establish the interaction of bovine fetuin-A to validate its binding modalities with doxorubicin (Dox). Fetuin-A was purified to highest purity and monodispersity. Green synthesis of fetuin-A conjugated gold nanoparticles (F-GNPs) has been performed giving typical UV-maxima with subtle variation in fourier transform infrared spectroscopy (FTIR). Atomic force microscopy (AFM) revealed spherical shaped, polydisperse F-GNPs of varying sizes, complementing the radius of hydration (19.5-62.4nm) by dynamic light scattering (DLS). Circular dichroism (CD) analysis of fetuin-A with respect to Dox interaction shows remarkable reduction in ellipticity with increasing concentrations of Dox (20-120μM). Fetuin-A:Dox and F-GNPs:Dox at variable concentrations revealed significantly enhanced absorption spectra, while a continuous decrease in florescence (560nm). This effect was more drastic when Dox interact with fetuin-A as compared to F-GNPs. Some known antimicrobial drugs were also investigated under similar conditions, giving strong quenching effect in a dose dependent manner suggesting the significant yet differential interactions. In cytotoxicity assay, fetuin-A:Dox conjugates revealed less toxicity as compared to F-GNPs:Dox and Dox alone. In-silico studies of the fetuin-A:Dox complex suggest that the drug binds in the major grove between beta-sheet and long loop region of D1 domain and stabilized by several hydrogen bonds.

Cultivation of New Emerging Agro-Nutritional Crop of Quinoa at Madinat al-Hikmah Karachi, Sindh, Pakistan

1 Faculty of Eastern Medicine, Hamdard Research Institute of Unani Medicine, Hamdard University, Karachi, 74600, Pakistan 2 HEJ Research Institute of Chemistry, International Center for Chemical and Biological Sciences (ICCBS), University of Karachi, Karachi, 75270, Pakistan 3 Department of Chemistry, Federal Urdu University Arts, Science and Technology, Gulshan-e-Iqbal Campus, Karachi, 75300, Pakistan 4 Department of Botany, University of Karachi, Karachi, 75270, Pakistan

Hybridization in the Sida ovata complex (Malvaceae) III. Evidences from seed micro-morphology and seed protein analysis

In this paper, we present a detailed analysis of seed morphological characters and seed protein composition of two closely related species belonging to the Sida ovata complex (Malvaceae), Sida ovata Forssk. and S. tiagii Bhandari. Seed protein profiling was performed by sodium dodesyl sulphate–polyacrylamide gel electrophoresis and size exclusion‐fast protein liquid chromatography. Our data provide additional information to strengthen the existence of hybridization between Sida ovata Forssk. and S. tiagii Bhandari in Pakistan.