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Copyright of Sultan Qaboos University Journal for Science is the property of Sultan Qaboos University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In aqueous and solid media, 2-HP-β/γ-CD inclusion complexes with poly aromatic hydrocarbon (PAH) Phenanthrene (PHN), Anthracene (ANT), Benz(a)pyrene (BaP), and Fluoranthene (FLT) were investigated for the first time. The inclusion complexes were characterized and investigated using fluorescence and 1HNMR spectroscopy. The most prevalent complexes consisting of both guests and hosts were those with a 1:1 guest-to-host ratio. The stability constants for the complexes of PHN with 2-HP-β-CD and 2-HP-γ-CD were 85 ± 12 M−1 and 49 ± 29 M−1, respectively. Moreover, the stability constants were found to be 502 ± 46 M−1 and 289 ± 44 M−1 for the complexes of ANT with both hosts. The stability constants for the complexes of BaP with 2-HP-β-CD and 2-HP-γ-CD were (1.5 ± 0.02) × 103 M−1 and (9.41 ± 0.03) × 103 M−1, respectively. The stability constant for the complexes of FLT with 2-HP-β-CD was (1.06 ± 0.06) × 103 M−1. However, FLT was observed to form a weak complex with 2-HP-γ-CD. Molecular dynamic (MD) simulations were used to investigate the mechanism and mode of inclusion processes, and to monitor the atomic-level stability of these complexes. The analysis of MD trajectories demonstrated that all guests formed stable inclusion complexes with both hosts throughout the duration of the simulation time, confirming the experimental findings. However, the flexible Hydroxypropyl arms prevented the PAHs from being encapsulated within the cavity; however, a stable exclusion complex was observed. The main forces that influenced the complexation included van der Waals interactions, hydrophobic forces, and C–H⋯π interaction, which contribute to the stability of these complexes. [ABSTRACT FROM AUTHOR]

Thymoquinone (TQ) is a quinone derived from the black seed Nigella sativa and has been extensively studied in pharmaceutical and nutraceutical research due to its therapeutic potential and pharmacological properties. Although the chemopreventive and potential anticancer effects of TQ have been reported, its limited solubility and poor delivery remain the major limitations. In this study, we aimed to characterize the inclusion complexes of TQ with Sulfobutylether-β-cyclodextrin (SBE-β-CD) at four different temperatures (293–318 K). Additionally, we compared the antiproliferative activity of TQ alone to TQ complexed with SBE-β-CD on six different cancer cell lines, including colon, breast, and liver cancer cells (HCT-116, HT-29, MDA-MB-231, MCF-7, SK-BR-3, and HepG2), using an MTT assay. We calculated the thermodynamic parameters (ΔH, ΔS, and ΔG) using the van't Holf equation. The inclusion complexes were characterized by X-ray diffraction (XRD), Fourier transforms infrared (FT-IR), and molecular dynamics using the PM6 model. Our findings revealed that the solubility of TQ was improved by ≥60 folds, allowing TQ to penetrate completely into the cavity of SBE-β-CD. The IC50 values of TQ/SBE-β-CD ranged from 0.1 ± 0.01 µg/mL against SK-BR-3 human breast cancer cells to 1.2 ± 0.16 µg/mL against HCT-116 human colorectal cancer cells, depending on the cell line. In comparison, the IC50 values of TQ alone ranged from 0.2 ± 0.01 µg/mL to 4.7 ± 0.21 µg/mL. Overall, our results suggest that SBE-β-CD can enhance the anticancer effect of TQ by increasing its solubility and bioavailability and cellular uptake. However, further studies are necessary to fully understand the underlying mechanisms and potential side effects of using SBE-β-CD as a drug delivery system for TQ. [ABSTRACT FROM AUTHOR]

The inclusion complexes of cucurbit[n]uril, CB[n] (n = 6–8), with poly aromatic hydrocarbon (PAH) Benzo(a)Pyrene (BaP), and fluoranthene (FLT) were investigated carefully in aqueous media. Fluorescence and 1H NMR spectroscopy were used to characterize and investigate the inclusion complexes that were prepared in the aqueous media. The most predominant complexes of both guests with hosts were the 1:1 guest: host complexes. Stability constants of 2322 ± 547 M−1, 7281 ± 689 M−1, 3566 ± 473 M−1 were obtained for the complexes of BaP with CB[6], CB[7], and CB[8], respectively. On the other hand, stability constants of 5900.270 ± 326 M−1, 726.87 ± 78 M−1, 3327.059 ± 153 M−1 were obtained for the complexes of FLT with CB[6], CB[7], and CB[8], respectively. Molecular dynamic (MD) simulations were used to study the mode and mechanism of the inclusion process and to monitor the stability of these complexes in aqueous media at an atomistic level. Analysis of MD trajectories has shown that both BaP and FLT form stable inclusion complexes with CB[7] and CB[8] in aqueous media throughout the simulation time, subsequently corroborating the experimental results. Nevertheless, the small size of CB[6] prohibited the encapsulation of the two PAHs inside the cavity, but stable exclusion complex was observed between them. The main driving forces for the stability of these complexes are the hydrophobic forces, van der Waals interactions, electrostatic effect, the π····π and C–H···π interaction. These results suggest that BaP and FLT can form stable complexes with CB[n] (n = 6–8) in solution. [ABSTRACT FROM AUTHOR]

Copyright of Sultan Qaboos University Journal for Science is the property of Sultan Qaboos University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The supramolecular interaction of anthracene (ANT) and phenanthrene (PHN) with cucurbit[n]uril, CB[n] (n=6‐8) has been investigated in aqueous media for the first time. The inclusion complexes were investigated and characterized by fluorescence spectroscopy, matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) mass spectrometry, and 1HNMR. The stability of these complexes and the mode of inclusion in aqueous media at atomistic levels were monitored by molecular dynamic (MD) simulations. The results obtained from the experimental and MD studies have demonstrated the formation of stable 1 : 1 complexes between the two guests with all hosts in aqueous media. From the fluorescence study, the binding constants of PHN with CB[6], CB[7], and CB[8] were found to be 398±63, 544±128, and 655±162 M−1, respectively. Whereas, ANT‐ CB[n] formation constants are 213±37 M−1 270±35 M−1, and 356±94 M−1 for CB[6], CB[7], and CB[8], respectively. The results obtained show that the size of the cavity of the macrocycle and the polarity of the rim play an important role in the stability of the formed complex. Surprisingly, CB[6] forms an inclusion complex with ANT while it interacts by its side with PHN through dipole‐dipole interaction. The larger cavity sizes of CB[7], CB[8], were found to encapsulate the two guests forming highly stable inclusion complexes. [ABSTRACT FROM AUTHOR]

Various synthesized Pillar[5]arene macrocycles were allowed to form complexes with the ionic liquid; 1‐Butyl‐3‐methyl‐imidazolium tetrafluoroborate (IL). The pillar[5]arenes used in the study were synthesized by the established pioneering method of Ogoshi that involves treatment of 1,4‐disubstituted benzenes with paraformaldehyde in the presence of BF3.OEt2. Selected synthesized pillar[5]arenes; DMpillar[5]arene (4a), DPpillar[5]arene (4b), DPGpillar[5]arene (4c) were allowed to form complexes with the ionic liquid, and complexations were confirmed by MALDI‐TOF, ESI‐MS, 1H NMR, and DOSY spectroscopy. ESI‐MS reveals highly intense ion peaks that correspond to [pillar[5]arene+IL]+ for the complexes of the three pillar[5]arenes with the ionic liquid. Changes in characteristic peaks in hosts and guests, as a result of complexation, were studied by 1H NMR. Results obtained suggest a formation of 1 : 1 complexes between the pillar[5]arene host and the IL guest. Host‐guest interactions in such complexes have also been studied using 1H‐1H 2D ROESY NMR spectroscopy. Obtained through‐space correlations revealed interactions between certain parts of the pillar[5]arene hosts and the ionic liquid. The complexation between the three pillar[5]arenes and the IL was studied by molecular dynamics (MD) simulations. The obtained results suggest the insertion of the IL inside the nanocavities of the hosts. [ABSTRACT FROM AUTHOR]

Selected amines were allowed to form inclusion complexes with selected synthesized pillar[5]arenes. Formation of inclusion complexes were confirmed by MALDI–TOF, ESI–MS analyses and 1H NMR spectroscopy. The complexation was supported by molecular dynamics calculations. Various pillar[5]arenes have been synthesized by BF3·OEt2 (Lewis acid) catalyzed cyclization of 1,4-disubstitutedbenzenes with paraformaldehyde. Selected synthesized host macrocycles; DMpillar[5]arene (7), DPpillar[5]arene (8a), DPGpillar[5]arene (8b) were allowed to form inclusion complexes with N-containing guests; hexamethylenediamine (GA), di-n-octyl amine (GB) and diethyl amine (GC). Host–guest complex formation of the selected pillar[5]arenes with the N-containing guests has been confirmed by MALDI–TOF, ESI–MS analyses and 1H NMR spectroscopy. ESI–MS revealed highly intense ion peaks that correspond to [pillar[5]arene@GA+Na]+ for inclusion complexes of pillar[5]arenes with hexamethylenediamine (GA). ESI–MS confirmed formation of inclusion complexes between pillar[5]arenes with di-n-octyl amine (GB) and diethyl amine (GC) as evidenced by intense peaks that corresponds to [pillar[5]arene@GB+H]+ and [pillar[5]arene@GC+H]+, respectively. Performed molecular dynamics (MD) simulations provided supportive results that indicate the formation of stable complexes between the three pillar[5]arene hosts and the guests included in this study. Hydrogen bonding and CH–π interactions were found amongst the factors that contribute significantly to the stability of these complexes. [ABSTRACT FROM AUTHOR]

Inclusion complexes of cucurbit[n]uril, CBn, with atrazine (ATZ) and ametryne (AME) herbicides were investigated in aqueous media and solid state. Mass spectrometry using matrix assisted laser desorption time-of-flight, MALDI-TOF, and 1HNMR techniques were used to characterize the inclusion complexes prepared in aqueous media. The solid complexes between the triazine herbicides and CBn hosts were prepared by lyophilization and were characterized by Fourier transform infrared spectroscopy (FT-IR) and powder X-ray diffraction (PXRD) technique. Molecular dynamics (MD) simulations were used to study the mechanism of inclusion and to monitor the stability of these complexes in aqueous media. Analysis of the MD trajectories has shown that both triazines form stable complexes with CBn in aqueous media throughout the simulation time. The stability of these complexes was found to originate from the hydrophobic effects where both hosts prefer to accommodate the nonpolar cavity of the hosts. It was observed that CB6 is capable of encapsulating only the isopropyl side chain of the guests, whereas the other two hosts were able to accommodate the major parts of the guests. A number of strong hydrogen bonds between the hosts and the guests further increased the stability of the complexes. [ABSTRACT FROM AUTHOR]

Inclusion complexes of ephedrine (EPh) with β-cyclodextrin (βCD), 18-crown-6 (18C6) and cucurbit[7]uril (CB7) were investigated using experimental and theoretical methods. The addition of βCD to the aqueous solution of EPh enhances the fluorescence emission spectrum at 312 nm. Whereas, the addition of CB7 and 18C6 cause enhancement of this band accompanied by growth of a band at around 412 nm. Electrospray ionization mass spectrometry, ESI-MS, results suggested that complexes of various stoichiometries are formed. The 1:1 complexes are the most dominant ones however, 1:2 (host: guest) stoichiometry and 2:1 (host: guest) stoichiometry for EPh with βCD and CB7 are also observed. The 1HNMR has indicated that EPh enters the CD hydrophobic cavity from the secondary rim and the aromatic ring is deeply inserted into the cavity with the ammonium ion left outside exposed to the aqueous solution. The molecular dynamics, MD, calculations show that EPh forms a stable complex with βCD and CB7 but not with 18C6. Furthermore, the ternary complexes of EPh-βCD with 18C6 and CB7 were found unstable according to the MD simulation studies, and ESI-MS experiments. The solid-state complexes prepared by freeze-drying and characterized by Fourier transform infrared spectroscopy and powder X-ray diffraction confirmed that only binary complexes are formed. [ABSTRACT FROM AUTHOR]

Abstract: A novel mixing approach was utilized with a highly sensitive chemiluminescence (CL) method to determine the total phenolic content (TPC) in honey samples using an acidic potassium permanganate–formaldehyde system. The mixing approach was based on exploiting the mixing efficiency of nanodroplets generated in a microfluidic platform. Careful optimization of the instrument setup and various experimental conditions were employed to obtain excellent sensitivity. The mixing efficiency of the droplets was compared with the CL signal intensity obtained using the common serpentine chip design, with both approaches using at a total flow rate of 15 μl min−1; the results showed that the nanodroplets provided 600% higher CL signal intensity at this low flow rate. Using the optimum conditions, calibration equations, limits of detection (LOD) and limits of quantification (LOQ) for gallic acid (GA), caffeic acid (CA), kaempferol (KAM), quercetin (QRC) and catechin (CAT) were obtained. The LOD ranged from 6.2 ppb for CA to 11.0 ppb for QRC. Finally, the method was applied for the determination of TPC in several local and commercial honey samples. [ABSTRACT FROM AUTHOR]

The inclusion complexes of the proton pump inhibitor (PPI) pantoprazole sodium (PNZNa) with β-cyclodextrin (βCD) and cucurbit[7]uril (CB[7]) have been investigated. Fluorescence spectroscopy and electrospray ionization mass spectrometry (ESI-MS) were used to characterize these complexes. The fluorescence intensity of PNZNa was remarkably enhanced by both hosts, indicating the formation of the complexes. Nevertheless, the two hosts are of comparable cavity size their effect on the fluorescence of PNZNa was quite different. The ESI-MS data on the other hand confirmed the formation of a 1:1 PNZNa: host inclusion complexes for the two hosts. We further utilized molecular dynamics to shed more light on the mechanism of complexation and on the stability of these complexes in aqueous media. The complexes were stabilized over the 20 ns of simulation time mainly via hydrogen bonding interactions in addition to hydrophobic effects and van der Waals interactions. Snapshots collected during the simulations for both complexes have clearly shown that the mode of insertion of PNZ into the two host’s cavities are different which explain the difference in fluorescence enhancement of PNZ obtained in presence of each of these hosts. [ABSTRACT FROM AUTHOR]

The binary and ternary complexes of epinephrine (EP) with β-cyclodextrin (βCD), 18-crown-6 (18C6) and cucurbit[7]uril (CB7) were probed using different experimental techniques. The results show that EP forms a stable binary complex with the three hosts. The fluorescence spectroscopy measurements showed enhancement in the emission spectrum at around 312 nm when βCD was added to the aqueous solution of EP, whereas the addition of CB7 and 18C6 caused quenching of this band accompanied by evolution of a band at around 412 nm. The 1H NMR spectroscopy confirmed the formation of the inclusion complexes. The 1H NMR spectroscopy indicated that the drug enters the CD nanocavity from its wider rim and deeply inserts the catechol moiety into the cavity. The association constants of binary complexes estimated by diffusion-ordered spectroscopy, DOSY, indicated a more stable complex was formed between EP and CB7. On the other hand, ESI-MS and MALDI-TOF data suggest that complexes of various stoichiometries are formed. This discloses the presence of binary and ternary complexes between EP and the three hosts. These data together with IR, Raman and PXRD for the lyophilized complexes clearly suggest that EP forms stable complexes with the three hosts in the solid and aqueous phase. These results were further clarified using molecular dynamics simulations for the five different complexes in aqueous media for 30 ns. The results obtained indicated that the hydrophobic effects and the hydrogen bonding interactions are the driving forces for the formation of the complexes and are responsible for their stabilities. [ABSTRACT FROM AUTHOR]

High-performance liquid chromatography coupled to tandem mass spectrometry was used to develop and validate a rapid method to qualitatively and quantitatively analyse 18 common adulterants in herbal medicine and food samples. Initially, the mobile phase composition was optimized in three different columns: core-shell, monolithic and standard 3.5-μm-particle-size columns. The results show that the core-shell column provides the best separation. Moreover, the tandem mass spectrometry was optimized. The linear range for all adulterants was 0.5-500 μgmL-1. Finally, the samples that were supplied by the Public Authority of Customer Protection, Ministry of Health, and those collected from the local market were analysed. The results indicate that 7 of 33 analysed samples contained adulterants. The adulterated samples mainly contain sildenafil, tadalafil or vardenafil. The concentrations of these three adulterants in the samples were 0.18-39 wt%. This study is the first report in the Sultanate of Oman about adulteration in herbal medicine and food samples. The results clearly raise some concern and require proper plan of action to increase public awareness about this serious issue. [ABSTRACT FROM AUTHOR]

A novel automated precolumn derivatization followed by separation using liquid chromatography for the determination of pseudoephedrine (PSE) by a microfluidic chemiluminescence detector has been developed. An on-line derivatization procedure was utilized by converting PSE into a highly light emitting species in a Ru(bipy)3 2+-peroxydisulphate chemiluminescence (CL) system by derivatizing it with a 1.0 M formaldehyde solution. The derivatized analyte was directly injected into a microbore high-performance liquid chromatography (HPLC) system coupled to an on-chip chemiluminescence detector. The newly developed highly selective, sensitive and fast HPLC-CL method was validated and successfully applied for the analysis of PSE in pharmaceutical formulations and a human urine sample. The selectivity of the method is not only due to the HPLC separation but is also due to the highly selective detection principle of the Ru(bipy)3 2+-peroxydisulphate CL system used. There was no interference observed from the common preservatives and excipients used in pharmaceutical preparations, which did not show any significant CL signal. The retention time of PSE was less than 3 min, and the detection limits and quantification limits were found to be 5.7 and 26.0 μg L-1, respectively. [ABSTRACT FROM AUTHOR]

A simple, fast, sensitive and versatile method for the analysis of phenols in water is proposed using microfluidic precolumn derivatization with the fluorogenic label coumarin-6-sulfonyl chloride (C6SCl) and HPLC separation on monolithic columns. Phenols react with C6SCl within 3.0 min in the microreactor at ambient temperature to produce phenol–coumarin sulphonamides derivatives which were separated in reversed phase high-performance liquid chromatography followed by postcolumn ring-opening and fluorescence detection at λexc = 360 nm and λem = 460 nm. The optimum conditions for the derivatization, separation and ring-opening reaction have been established. The calibration curves were linear for the studied phenols in the range of 0.75-12.5 mg L-1. The application of the method to environmental samples was demonstrated by analyzing tap and fountain water samples spiked with the phenolic compounds. [ABSTRACT FROM AUTHOR]

3(2H)-Furanones are a type of five-membered heterocyclic compounds of synthetic and biological importance. For exploring the utilities of this “sweet” aroma component for bio-analytical purposes we have prepared and characterized two novel fluorophores (2Z)-2-(5-fluoro-2-ntro benzylidene)-5-phenyl-3(2H)-furanone (FNPF) and (2Z)-2-(4-carboxy benzylidene)-5-phenyl-3-(2H)-furanone (CBPF) on a 3-furanone skeleton. In order to expand their application potential, the photophysical properties have been investigated using absorption and emission spectroscopy, in combination with quantum chemical calculations. As expected, both compounds showed efficient solvatochromic properties and the excited state dipole moments are larger than those of the ground state. Solvent dependent spectral data using TD-DFT calculations on the optimized ground and excited state structures of both compounds were found to correlate well with the experimental findings. [ABSTRACT FROM AUTHOR]

ABSTRACT A new method for the analysis of mebeverine hydrochloride (MEB) has been developed using a two-chip device. The method is highly selective, sensitive, rapid and consumes minute amount of reagents. The developed method is free of interference from the degradation products of MEB and from common ingredients present in pharmaceutical formulations. The limit of detection was 0.043 µg/mL, and the limit of quantification was 0.138 µg/mL. The short analysis time per sample (20 s) allowed a large number of analyses to be performed within a very short time. Various samples were analyzed, including two different pharmaceutical formulations and a uniformity of content analysis for 20 tablets from a known batch and two biological samples at different concentrations. In addition, the method was compared with a validated high-performance liquid chromatography (HPLC) method and the results clearly indicated the suitability of the developed method for routine analyses. A new mechanism for the tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)32+)-peroxodisulfate (S2O82−) chemiluminescence (CL) system has also been proposed. The mechanism is based on photoinduced oxidation of Ru(bpy)32+ to Ru(bpy)33+ via the formation of Ru(bpy)32+* upon irradiation with visible light. S2O82− then oxidizes Ru(bpy)32+* to Ru(bpy)33+ and the analyte subsequently reduces the resultant Ru(bpy)33+ to Ru(bpy)32+*, which then produces the CL signal. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]