Anti-Inflammatory Activity of Oxyresveratrol Tetraacetate, an Ester Prodrug of Oxyresveratrol, on Lipopolysaccharide-Stimulated RAW264.7 Macrophage Cells.

Oxyresveratrol (OXY) has been reported for its anti-inflammatory activity; however, the pharmaceutical applications of this compound are limited by its physicochemical properties and poor pharmacokinetic profiles. The use of an ester prodrug is a promising strategy to overcome these obstacles. In previous researches, several carboxylate esters of OXY were synthesized and oxyresveratrol tetraacetate (OXY-TAc) was reported to possess anti-melanogenic and anti-skin-aging properties. In this study, in addition to OXY-TAc, two novel ester prodrugs of OXY, oxyresveratrol tetrapropionate (OXY-TPr), and oxyresveratrol tetrabutyrate (OXY-TBu), were synthesized. Results from the Caco-2-permeation assay suggested that synthesized ester prodrugs can improve the membrane-permeation ability of OXY. The OXY-TAc exhibited the most significant profile, then this prodrug was chosen to observe anti-inflammatory activities with lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Our results showed that OXY-Tac significantly alleviated secretion of several pro-inflammatory mediators (nitric oxide (NO), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α)), mitigated expression of enzyme-regulated inflammation (inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2)), and suppressed the MAPK cascades. Interestingly, the observed anti-inflammatory activities of OXY-TAc were more remarkable than those of its parent compound OXY. Taken together, we demonstrated that OXY-TAc improved physicochemical and pharmacokinetic profiles and enhanced the pharmacological effects of OXY. Hence, the results in the present study would strongly support the clinical utilities of OXY-TAc for the treatment of inflammation-related disorders.

Ratiometric Fluorescent Sensor for Copper(II) and Phosphate Ions from Aminopyrene Derivatives.

Three derivatives of 1-aminopyrene are functionalized with 2-picolyl and 2-picolinyl groups and are tested as fluorescent sensors for metal ions. The target compounds are successfully synthesized in yields of 50-90% and characterized by 1 H-NMR, 13 C-NMR, and HRMS. The compound with an amino picolyl group (P1) exhibits an excellent selectivity toward Cu(II) ion as the fluorescent signal shifts from 433 to 630 nm. From a fluorescence titration experiment, the limit of detection for Cu(II) ion is estimated as 0.19 µm. The fluorescence spectral shift by Cu(II) ion is reliant on the use of acetonitrile as a co-solvent, and the results from cyclic voltammetry and UV-Vis spectroscopy suggest that the sensing mechanism involves a coordination complex between the P1, acetonitrile and Cu(II) ion. Furthermore, this P1-Cu complex can also be used as a selective fluorescent sensor for PO4 3- ion with a detection limit of 0.44 µm.

Fluorescent Sensor for Copper(II) and Cyanide Ions via the Complexation-Decomplexation Mechanism with Di(bissulfonamido)spirobifluorene.

A novel spirobifluorene derivative bearing two bissulfonamido groups is successfully synthesized by Sonogashira coupling. This compound exhibits a strong fluorescence quenching by Cu(II) ion in a 50% mixture between acetonitrile and 20 mM pH 7.0 N-(2-hydroxyethyl)piperazine-N'-ethanesulfonic acid (HEPES) buffer with a detection limit of 98.2 nM. However, this sensor also shows ratiometric signal shifts from blue to yellow in the presence of Zn(II), Pb(II), and Hg(II) ions. The static quenching mechanism is verified by the signal reversibility using ethylenediaminetetraacetic acid (EDTA) and the Stern-Volmer plots at varying temperatures. The Cu(II)-spirobifluorene complex shows a highly selective fluorescence enhancement upon the addition of CN- ion with the detection limit of 390 nM. The application of this complex for quantitative analysis of spiked CN- ion in real water samples resulted in good recoveries.

Protective Effects of a Lutein Ester Prodrug, Lutein Diglutaric Acid, against H2O2-Induced Oxidative Stress in Human Retinal Pigment Epithelial Cells.

Oxidative stress-induced cell damage and death of the retinal pigmented epithelium (RPE), a polarized monolayer that maintains retinal health and homeostasis, lead to the development of age-related macular degeneration (AMD). Several studies show that the naturally occurring antioxidant Lutein (Lut) can protect RPE cells from oxidative stress. However, the poor solubility and low oral bioavailability limit the potential of Lut as a therapeutic agent. In this study, lutein diglutaric acid (Lut-DG), a prodrug of Lut, was synthesized and its ability to protect human ARPE-19 cells from oxidative stress was tested compared to Lut. Both Lut and Lut-DG significantly decreased H2O2-induced reactive oxygen species (ROS) production and protected RPE cells from oxidative stress-induced death. Moreover, the immunoblotting analysis indicated that both drugs exerted their protective effects by modulating phosphorylated MAPKs (p38, ERK1/2 and SAPK/JNK) and downstream molecules Bax, Bcl-2 and Cytochrome c. In addition, the enzymatic antioxidants glutathione peroxidase (GPx) and catalase (CAT) and non-enzymatic antioxidant glutathione (GSH) were enhanced in cells treated with Lut and Lut-DG. In all cases, Lut-DG was more effective than its parent drug against oxidative stress-induced damage to RPE cells. These findings highlight Lut-DG as a more potent compound than Lut with the protective effects against oxidative stress in RPE cells through the modulation of key MAPKs, apoptotic and antioxidant molecular pathways.

Fluorescence Sensors for Bismuth (III) Ion from Pyreno[4,5-d]imidazole Derivatives.

Three pyreno[4,5-d]imidazole derivatives are synthesized and evaluated as fluorescent sensors for bismuth (III) ion. The target compounds are prepared in 55-86% yields from a condensation reaction between pyrene-4,5-dione and aromatic aldehydes. The compound bearing a phenolic group can selectively detect bismuth (III) ion via fluorescence enhancement with a detection limit of 1.20 µm in CH3 CN-DMSO mixture and 3.40 µm in 10% pH5 aqueous in CH3 CN-DMSO mixture. The sensing mechanism involving a formation of coordination complex is investigated by UV-VIS and fluorescence titrations, 1 H-NMR and the decomplexation of the bismuth complex by sulfide ion. The application of this sensor for quantitative analysis of spiked bismuth (III) ion in real water samples from two different sources is demonstrated.

Hydrophilic Truxene Derivative as a Fluorescent off-on Sensor for Copper (II) Ion and Phosphate Species.

A new symmetrical truxene derivative (TP3) containing three dipicolylamino peripheral groups is successfully synthesized in four synthetic steps with an overall yield of 42%. This hydrophilic fluorescent compound exhibits a maximum absorption wavelength at 375 nm, an emission maximum at 474 nm with an outstanding 58% quantum efficiency in THF-HEPES buffer mixture. The compound shows a highly selective fluorescence quenching towards Cu(II) ion with a detection limit of 0.06 ppm. The results from mass spectrometry and Job plot indicate that a 1:1 complex between TP3 and Cu(II) ion is responsible for the signal quenching. Interestingly, this TP3-Cu complex can be used as a turn-on sensor for hydrogen phosphate and nucleoside phosphates. The limit of detection for hydrogen phosphate is estimated at 8.7 nM. The signal restoration involves a displacement of TP3 in the complex by the phosphates which have strong coordination abilities with Cu(II) ion.

Novel sulfonamidospirobifluorenes as fluorescent sensors for mercury(ii) ion and glutathione.

Novel spirobifluorene derivatives containing two and four sulfonamide groups are successfully synthesized from the commercially available bromo-9,9'-spirobifluorene by Sonogashira couplings. These compounds exhibit an excellent selective fluorescence quenching by Hg(ii) in DMSO/HEPES buffer mixture with three-times-noise detection limits of 10.4 to 103.8 nM. A static aggregation induced quenching mechanism is proposed based on the data from 1H-NMR and UV-Vis spectroscopy, as well as the observation of the Tyndall effect. Quantifications of Hg(ii) using these sensors are in good agreement with those obtained from ICP-OES. The reversibility of these sensors is demonstrated by a complete fluorescence restoration upon addition of EDTA or l-glutathione. The application as a turn-on sensor for l-glutathione is demonstrated in a quantitative analysis of three samples of l-glutathione supplement drinks.

A novel indolium salt as a highly sensitive and selective fluorescent sensor for cyanide detection in water.

A highly sensitive fluorescent turn-on cyanide probe is developed based on benzylidenes containing methylindolium group. Three benzylidene derivatives were synthesized from the condensations of three benzaldehyde derivatives and methyleneindoline. Only one of these three derivatives shows strong blue fluorescent response selectively to CN- which can be clearly observed in submicromolar range as the result of the cyanide addition to the indolium group. The detection of cyanide with this compound is optimized in aqueous media using non-ionic surfactant and sonication method to give very low limit of detection in subnanomolar range. The probe is also developed into a paper-based and gel-based sensing kits that can readily detect cyanide ion in micromolar range by naked eye under a common black light (360nm) illumination.

A highly selective turn-on fluorescent sensor for glucosamine from amidoquinoline-napthalimide dyads.

Three amidoquinoline-naphthalimide dyads are designed and synthesized in 67-73% overall yields in 3 steps from commercially available starting materials. Compounds with unsubstituted and nitro naphthalimide (1 and 2) show excellent selective fluorescent responses towards glucosamine with the enhancement of fluorescence quantum yields by 14 folds. The determination of HOMO-LUMO levels by linear sweep voltammetry suggests that the sensing mechanism likely involves the inhibition of photo-induced electron transfer (PET) between the aminoquinoline and naphthalimide moieties by glucosamine. The association constants of 1.55×10(4) and 1.45×10(4)M(-)(1), along with the glucosamine detection limits of 1.06 and 0.29µM are determined for 1 and 2, respectively. The application of 2 as a fluorescent probe for real-time detection of cellular glucosamine at micromolar level in living Caco-2 cells is also demonstrated.

Salicylyl Fluorene Derivatives as Fluorescent Sensors for Cu(II) Ions.

Two derivatives of fluorene containing salicylic acid groups are successfully synthesized by palladium-catalyzed coupling reactions and subsequent hydrolysis of salicylate esters. The compounds are characterized by various spectroscopic methods. In phosphate buffer (pH 8.0) solutions, these compounds are well soluble. They show maximum absorption wavelengths in the range of 304-330 nm and exhibit maximum emission wavelength around 420 and 430 nm with the quantum yields of 2.7 and 4.4 %, respectively. The compound with alkynyl salicylate groups (2) exhibits a selective fluorescence quenching towards Cu(II) and Fe(II) with a relatively similar sensitivity. The selectivity favoring Cu(II) over Fe(II) and other metal ions can be achieved upon the addition of 30 µM Triton X-100. The Cu(II) detection limit in solution phase is 1.47 ppb. The fluorescence signal recovery upon the addition of EDTA indicate a reversible complexation between 2 and Cu(II) ion. Fabrication of 2 on filter paper using a 50 µM solution in THF affords a naked-eye detection for Cu(II) and Fe(II) in aqueous media at picomole level.

New water soluble terphenylene diethynylene fluorophores.

Inspired by our earlier works on sensors from dendritic phenyleneethynylenes, two new star-shaped water-soluble fluorophores containing terphenylene diethynylene units and anionic carboxylate peripheries are successfully synthesized. The convergent synthesis relies on Sonogashira cross-coupling reactions between tris-(4-ethynylphenyl)amine and the iodophenyleneethynylene branches. All of the compounds are characterized by (1)H, (13)C NMR, and mass spectrometry. In aqueous solution, the less polar fluorophore 1 shows lower quantum yield than 2 (18 vs 33%) as a result of hydrophobic induced aggregation. One of these anionic water-soluble fluorophores exhibits a selective fluorescence quenching by Fe(3+) ion in phosphate buffer pH 8.

Tunable star-shaped triphenylamine fluorophores for fluorescence quenching detection and identification of nitro-aromatic explosives.

Triphenylamine-based fluorophores containing pyrene or corannulene show variable fluorescence quenching sensitivity toward nitro explosives. The most sensitive fluorophore is capable of detecting TNT on the ng cm(-2) scale; the array is useful for identifying nitro aromatics.

Inclusion complexes between amphiphilic phenyleneethynylene fluorophores and cyclodextrins in aqueous media.

Binding events of cyclodextrins (CyD's) in aqueous media are important for designing and explaining the host-guest chemistry applied in sensing and controlled release systems. A water-soluble tricationic compound (3N(+)) with three branches of phenyleneethynylene fluorescent moieties and its related amphiphilic compounds (3C(-), N(0)N(+), N(+), and 2N(+)) are employed as molecular probes in the systematic characterization of the supramolecular interactions with CyD's (α, ß, and γ). The strong fluorescence enhancement, combined with induced circular dichroism (CD) signals and (1)H NMR data, is evidence of 1:1 static inclusion complexes of 3N(+)/γ-CyD and 2N(+)/γ-CyD. 3N(+) presents a structural design which can form inclusion complexation with γ-CyD with one of the highest binding constants of 3.0 × 10(4). The relatively moderate fluorescence enhancement, shift of (1)H NMR signals, and weak induced CD signals indicate fast exchange complexation of ß-CyD with the amphiphilic guest molecules. The interaction with α-CyD is perceived only for N(0)N(+), the only nonbranched fluorescent guest model, via its strong fluorescence enhancement. However, the lack of (1)H NMR signal splitting and the lack of induced CD signals suggest the noninclusion mode of binding between N(0)N(+) and α-CyD.

FRET detection of DNA sequence via electrostatic interaction of polycationic phenyleneethynylene dendrimer with DNA/PNA hybrid.

Interaction between a polycationic compound and DNA is a useful phenomenon for development of a new DNA sensing system. In this work, dendritic polycationic phenyleneethynylene fluorophores are investigated as a Förster resonance energy transfer (FRET) donor for the detection of DNA hybridization in conjunction with a fluorescein-labeled pyrrolidinyl peptide nucleic acid (Fl-acpcPNA) probe. The first generation dendrimer is an efficient energy donor for the fluorescein acceptor but also shows non-specific FRET signal with Fl-acpcPNA. The addition of N-methyl 2-pyrrolidone can virtually completely remove the non-specific interaction between Fl-acpcPNA and the dendrimer. Under the optimal condition, the complementary DNA gives a distinctively high FRET ratio (1.42) comparing with those of the non-complementary (0.26) and singly mismatched (0.51) DNAs. The FRET ratio responses linearly with the DNA concentration with the detection limit lower than 1nM. The FRET ratio is even higher for the complementary target DNAs with extra hanging nucleotide sequences, which is a more frequently encountered scenario in real applications.

Phenylene-ethynylene trication as an efficient fluorescent signal transducer in an aptasensor for potassium ion.

A tricationic phenylene-ethynylene (N(3+)) fluorophore is investigated as a fluorescent transducer in homogeneous aptasensing system for potassium ion (K(+)) assay in aqueous media. The enhancement of the fluorescent signal of N(3+) by three K(+) aptamers consisting of 12, 15, and 21 nucleotides are observed and used for the determination of N(3+)-aptamer binding affinities. The binding affinities increase with the length of the aptameric oligonucleotides and are proven to be important to the sensitivity and selectivity of the aptasensors. The enhanced fluorescent signal of each N(3+)-aptamer solution is selectively quenched by K(+) due to the ability of K(+) in stabilizing the G-quadruplex structure of the aptamer. Among three aptamers, the 15-base aptamer provides optimal sensitivity and selectivity over other ions such as Li(+), Na(+), NH(4)(+), Mg(2+), Ca(2+) and Sr(2+). The sensing system shows the detection limit of 1 µM of K(+) in clean buffered solution and 30 µM of K(+) in the solution containing 4800-fold excess of Na(+), with wide linear dynamic ranges of micro- to millimolar concentration. This label-free fluorescence aptasensor is conveniently and effectively applicable for analysis of K(+) in urine samples.

1,3,5-Triphenylbenzene fluorophore as a selective Cu2+ sensor in aqueous media.

Three water-soluble fluorophores are synthesized from 1,3,5-tris-(4'-iodophenyl)benzene. The compound with salicylate groups exhibits a selective fluorescent quenching by Cu(2+)via a static quenching mechanism. The addition of Triton X-100 improves the quantum efficiency of the fluorophore as well as the detection limit for Cu(2+) from 6.49 to 0.19 ppb.

Protein discrimination by fluorescent sensor array constituted of variously charged dendritic phenylene-ethynylene fluorophores.

A protein fluorescent sensor array based on variously charged dendritic fluorophores is developed. The variation of charge is achieved by different combinations of cationic trimethylammonium, anionic carboxylate and non-ionic methyl ester or N,N-dimethylamino on the peripheries of the fluorophores. Nine phenylene-ethynylene dendritic fluorophores, seven zeroth generation bearing charges varied from -3 to +3 and two first generation bearing -6 and +6 charges, are synthesized from triiodotriphenylamine through series of Sonogashira coupling. In phosphate buffer saline pH 7.4, five out of these nine compounds fluorogenically response to eight protein analytes distinctively. The data set of fluorescent intensities obtained from 5 fluorophores×8 proteins×9 replicated measurements can be statistically sorted into eight clusters corresponding to each protein by principal component analysis (PCA). Factorial discriminant analysis (FDA) cross-validation is applied to locate the optimum detection wavelength and reduce the number of sensing elements from nine to two with 100% discriminating accuracy. The method described should be generally practical for the development of electronic tongue for protein related food analysis and medical diagnosis.

UVA absorption and photostability of coumarins.

Various substituted 4-methylcoumarin derivatives were synthesized in order to obtain photostable derivatives with UVA absorption property. It was found that substitution positions affected maximum absorption wavelength, whereas types of substituents, whether hydroxy or alkoxy groups, caused no significant effect. Photostability, however, was affected by both the substitution positions and the types of substituents. An acid-catalyzed mechanism through enolization coupled with pre-organization via hydrogen bonding between two coumarin moieties is proposed as an explanation for the different extents of the [2+2] cycloaddition (dimerization) amongst different derivatives, which results in a different photostability amongst them. Photostable coumarin derivatives with an absorption maximum in the UVA region are reported.

A polyanionic dendritic fluorophore for selective detection of Hg2+ in Triton X-100 aqueous media.

A series of water-soluble fluorescent dendritic compounds composed of phenylene-ethynylene repeating units and anionic carboxylate or cationic ammonium peripheral groups were synthesized. The first generation fluorescent dendrimer containing nine phenylene-ethynylene units and six carboxylate peripheral groups exhibited a highly selective fluorescence quenching by Hg(2+) ions. The Stern-Volmer constant (K(sv)) was 33,700 M(-1) in aqueous media in the presence of Triton X-100 surfactant.