Through this work, we have elucidated the mechanism of hydroxyl radicals (OH(•)) generation and its life time measurements in biosolution. We observed that plasma-initiated ultraviolet (UV) photolysis were responsible for the continues generation of OH(•) species, that resulted in OH(•) to be major reactive species (RS) in the solution. The density and lifetime of OH(•) species acted inversely proportional to each other with increasing depth inside the solution. The cause of increased lifetime of OH(•) inside the solution is predicted using theoretical and semiempirical calculations. Further, to predict the mechanism of conversion of hydroxide ion (OH(-)) to OH(•) or H2O2 (hydrogen peroxide) and electron, we determined the current inside the solution of different pH. Additionally, we have investigated the critical criterion for OH(•) interaction on cancer cell inducing apoptosis under effective OH(•) exposure time. These studies are innovative in the field of plasma chemistry and medicine.
A formal total synthesis of the spiroketal containing cytotoxic myxobacteria metabolite spirangien A (1) is described. The approach utilizes a late introduction of the C20 alcohol that mirrors the biosynthesis of this compound. The key steps involved a high yielding cross metathesis reaction between enone 6 and alkene 7 to give E-enone 4 and a Mn-catalyzed conjugate reduction α-oxidation reaction to introduce the C20 hydroxyl group. Acid treatment of the α-hydroxyketone 4 gave spiroketal 19 which was converted into known spirangien A (1) advanced intermediate spiroketal 3.
Regioselective alkylation of gamma-cyclodextrin with allyl or propargyl bromide, using optimized reaction conditions, followed by peracetylation of remaining hydroxyl groups and separation of isomers resulted in the set of peracetylated 2(I)-O-, 3(I)-O- and 6(I)-O-alkylated cyclodextrins in up to 19% yields. Ozonolyzis or oxidative cleaveage of peracetylated allyl derivatives resulted in a complete set of peracetylated 2(I)-O-, 3(I)-O- and 6(I)-O- formylmethyl or carboxymethyl derivatives. All these derivatives are useful precursors for further preparation of regioselectively monosubstituted derivatives of gamma-cyclodextrin.
In our continued efforts to develop α4β2-nicotinic acetylcholine receptor (nAChR) partial agonists as novel antidepressants having a unique mechanism of action, structure-activity relationship (SAR) exploration of certain isoxazolylpyridine ethers is presented. In particular, modifications to both the azetidine ring present in the starting structure 4 and its metabolically liable hydroxyl side chain substituent have been explored to improve compound druggability. The pharmacological characterization of all new compounds has been carried out using [(3)H]epibatidine binding studies together with functional assays based on (86)Rb(+) ion flux measurements. We found that the deletion of the metabolically liable hydroxyl group or its replacement by a fluoromethyl group not only maintained potency and selectivity but also resulted in compounds showing antidepressant-like properties in the mouse forced swim test. These isoxazolylpyridine ethers appear to represent promising lead candidates in the design of innovative chemical tools containing reporter groups for imaging purposes and of possible therapeutics.
c-Jun NH2-terminal kinases (JNKs) and phosphatidylinositol 3-kinase (PI3-K) play critical roles in chronic diseases such as cancer, type II diabetes, and obesity. We describe here the binding of quercetagetin (3,3',4',5,6,7-hydroxyflavone), related flavonoids, and SP600125 to JNK1 and PI3-K by ATP-competitive and IMAP-based FP assays and measure the effect of quercetagetin on JNK1 and PI3-K activities. Quercetagetin attenuated the phosphorylation of c-Jun and AKT, suppressed AP-1 and NF-κB promoter activities and also reduced cell transformation. It attenuated tumor incidence and reduced tumor volumes in a two-stage skin carcinogenesis mouse model. Our crystallographic structure determination data show that quercetagetin binds to the ATP-binding site of JNK1. Notably, the interaction between Lys55, Asp169, and Glu73 of JNK1 and the catechol moiety of quercetagetin reorients the N-terminal lobe of JNK1, thereby improving compatibility of the ligand with its binding site. The results of a theoretical docking study suggest a binding mode of PI3-Kwith the hydroxyl groups of the catechol moiety forming hydrogen bonds with the side chains of Asp964 and Asp841 in the p110γ catalytic subunit. These interactions could contribute to the high inhibitory activity of quercetagetin against PI3-K. Our study suggests the potential use of quercetagetin in the prevention or therapy of cancer and other chronic diseases.
Lamotrigine is recently recognized as a persistent pharmaceutical in the water environment and wastewater effluents. Its degradation was studied under UV and ozone advanced oxidation treatments with reaction kinetics of lamotrigine with ozone (≈4M(-1)s(-1)), hydroxyl radical [(2.1±0.3)×10(9)M(-1)s(-1)] and by UV photolysis with low and medium pressure mercury vapor lamps [quantum yields ≈0 and (2.7±0.4)×10(-4) respectively] determined. All constants were measured at pH 6 and at temperature ≈20°C. The results indicate that lamotrigine is slow to respond to direct photolysis or oxidation by ozone and no attenuation of the contaminant is expected in UV or ozone disinfection applications. The compound reacts rapidly with hydroxyl radicals indicating that advanced oxidation processes would be effective for its treatment. Degradation products were identified under each treatment process using accurate mass time-of-flight spectrometry and pathways of decay were proposed. The main transformation pathways in each process were: dechlorination of the benzene ring during direct photolysis; hydroxyl group addition to the benzene ring during the reaction with hydroxyl radicals; and triazine ring opening after reaction with ozone. Different products that form in each process may be to a varying degree less environmentally stable than the parent lamotrigine. In addition, a novel method of ozone quenching without addition of salts is presented. The new quenching method would allow subsequent mass spectrometry analysis without a solid phase extraction clean-up step. The method involves raising the pH of the sample to approximately 10 for a few seconds and lowering it back and is therefore limited to applications for which temporary pH change is not expected to affect the outcome of the analysis.
Claisen rearrangement reaction was employed for the first time to obtain a novel PPTA bearing reactive allyl and hydroxyl groups which may act as a sizing agent of Kevlar fibers to improve the interface structure and interfacial adhesion of rubber or epoxy based composites.
Cationic ruthenium(II) complexes have been employed for the highly effective oxidative annulation of alkynes with benzyl alcohols to deliver diversely decorated isochromenes. The hydroxyl-directed CH/OH functionalization process proceeded efficiently under an atmosphere of air. Detailed mechanistic studies were indicative of a kinetically relevant CH metalation.
Allene carboxylates, scarcely used as Michael acceptors, serve as acceptors in the annulation with phthalides in the presence of LDA, and provide a one-pot synthesis of naphtho[c]furanones in very good yields. This tandem annulation is proposed to proceed via transposition of the hydroxy group resulting from the initial annulation.
Graphene oxide quantum dots (GOQDs) attract great attention for their unique properties and promising application potential. The difficulty in the formation of a confined structure, and the numerous and diverse oxygen-containing functional groups results in a low emission yield to GOQDs. Here, GOQDs with a size of about 5 nm, exfoliated from carbon fibers by microwave irradiation, are detected and analyzed. The exfoliated GOQDs are deeply oxidized and induce large numbers of epoxy groups and ether bonds, but only a small amount of carbonyl groups and hydroxyl groups. The subdomains of sp2 clusters, involving epoxy groups and ether bonds, are responsible for the two strong photoluminescence emissions of GOQDs under different excitation wavelengths. Moreover, GOQDs tend to self-assemble at the edges of their planes to form self-assembly films (SAFs) with the evaporation of water. SAFs can further assemble into different 3D patterns with unique microstructures such as sponge bulk, sponge ball, microsheet, sisal, and schistose coral, which are what applications such as supercapacitors, cells, catalysts, and electrochemical sensors need. This method for preparation of GOQDs is easy, quick, and environmentally friendly, and this work may open up new research interests about GOQDs.