Solvent-extraction complex of uranium(VI) with cis,syn, cis-dicyclohexano-18-crown-6

The extraction of U(VI)with dicyclohexano-18-crown-6 (mixed isomers or isomer A) from HCl medium is effective and selective, and can be used for separating and analysing uranium and thorium. However, little is known of the properties of the extraction complex of uranium with crown-ether in organic phase. In this paper we report the preparation, characteristic and structure of the crystalline extraction complex IaUO₂Cl₂HClH₂O, Iabeing isomer A of dicyclohexano-18-crown-6.After extracting uranium(VI) from aqueous hydrochloric acid solution with Ia in 1,2-dichloroethane, the crystalline product of the extraction complex was prepared from the organic phase by diluting with a non-polar solvent at 25 °C. The content of uranium, crown-ether and HCl was determined. The IR spectrum of the crystals shows that the strong hydronium-crown ether/oxygen hydrogen bond absorption is found in the region 2300–2400 cm⁻¹. The chemical shift in the range 9–12 ppm was observed. The ¹H NMR signal of hydronium protons appears at 9.890 ppm. The results of assay correspond to the formula Ia₂·(H₃O⁺)₂·UO₂Cl₄²⁻.Crystal structure of the extraction complex has been determined by X-ray crystallography. Crystals are monoclinic, space group C_2/c (No. 15) a=32.464, b=10.203, c=21.616 Å, β=119.73° and Z=4. In the complex each of the two H₃O⁺ cations is anchored in the crown-ether cavity by three stronger hydrogen bonds (distances approximately 2.65 Å), whereas uranium forms UO₂Cl₄²⁻ with Cl⁻ as counterion about 8 Å away from the H₃O⁺.     

Synthesis and cytotoxic activity of a new potential DNA bisintercalator: 1,4-Bis{3-[N-(4-chlorobenzo[g]phthalazin-1-yl)aminopropyl]}piperazine

The synthesis of new 1,4-bisalkylamino (2–4) and 1-alkylamino-4-chloro (5–6) substituted benzo[g]phthalazines is reported. Compounds 2–4 and 6 were prepared both in the free and heteroaromatic ring protonated forms. Bifunctional 6 contains the 1,4-bisaminopropylpiperazine chain as a linker between the two heteroaromatic units, whereas 5 is its monofunctional analogue. The in vitro antitumour activity of the synthesized compounds has been tested against human colon, breast and lung carcinoma cells, and also against human glioblastoma cells. Results obtained show that all of them are active in all cases, but bifunctional 6·2HCl is remarkably effective against the four cell lines tested, exhibiting IC₅₀ values in the range of 10^?7 M, similar to those found for doxorubicin. The bifunctional structure of 6·2HCl enhances activity with respect to the monofunctional related compounds 5 and 7, leading to the highest activity among all the compounds tested. Molecular modelling of 6 suggests that those results could be indicative of DNA bisintercalation, which should be specially favoured in the diprotonated form 6·2HCl, a compound suitable for being studied more in depth in further biological tests. Measure of the DNA thermal melting curves show that the linear rise in T_m for bifunctional 6·2HCl is nearly twice than that one obtained for monofunctional 5, and supports the DNA-binding hypothesis.     

Stereoselective synthesis of caffeic acid amides via enzyme-catalyzed asymmetric aminolysis reaction

In this study, a new method was developed to prepare enantiopure caffeic acid amides by enzyme-catalyzed asymmetric aminolysis reaction. Methoxymethyl chloride (MOMCl) was first introduced as a protective and esterified reagent to obtain the MOM-protected caffeic acid MOM ester 1d. Aminolysis reaction occurred between 1d and (R, S)-α-phenylethylamine in the presence of an immobilized lipase (Novozym 435) from Candida antarctica. Compared with the methyl-protected caffeic acid methyl ester 1c, 1d as substrate improved the lipase-catalyzed reaction rate by 5.5-fold. After Novozym 435-catalyzed aminolysis reaction was established, we evaluated the effects of synthesis parameters on the catalytic activity and enantioselectivity of Novozym 435. A reaction conversion rate of 25.5% and an E value of >100 were achieved under the following optimum conditions: reaction solvent, anhydrous isooctane; reaction temperature, 70 °C; reaction time, 24 h; ester-to-amine substrate molar ratio, 1:40; and enzyme additive amount, 40 mg. Kinetic and thermodynamic analyses were conducted to determine the main factors affecting enantiomeric discrimination. Novozym 435 still showed 80% of its initial activity after recycling five times. Highly optically pure caffeic acid amides with an enantiomeric excess of 98.5% were finally obtained by HCl deprotection. The established enzyme-catalyzed asymmetric aminolysis method in this study might be used to prepare other caffeic acid amides.     

Validation of analytical method for (E)-2-decenedioic acid quantification in honey samples

Natural honey is a highly sought-after product owing to its biological uniqueness. We developed a suitable analytical method for the quantitative analysis of (E)-2-decenedioic acid in Korean natural and sugar-fed honey samples. A total of 258 honey samples were screened using ultra-performance liquid chromatography (UPLC) for the detection and quantification of (E)-2-decenedioic acid. (E)-2-decenedioic acid was present in high concentrations (122–127 mg/kg) in sugar-fed honey but only in trace amounts (10.9–14.8 mg/kg) in natural honey. Findings indicate that the UPLC method is suitable and reliable for the quantitative evaluation of (E)-2-decenedioic acid in honey. We expect that this method will be applicable for detecting honey adulteration.     

The amino acid composition of proteins: a method of analysis.

Four quasiloglinear models are proposed for describing relationships between the amino acid composition of proteins and the structure of the genetic code. The models allow estimation of base frequencies in all three codon positions and can be used to investigate “interactions” between any two codon positions. The estimation procedure proposed by Ohta and Kimura (Genetics64 (1970), 387–395) is discussed and using two of the proposed quasiloglinear models an analysis of the amino acid composition of human cytochrome c is presented. The analysis suggests that of the six codons which code for leucine (CUU, CUC, CUA and CUG) do not occur in human cytochrome c.     

Fertilization acid release in Urechis eggs: I. The nature of the acid and the dependence of acid release and egg activation on external pH

The amount of fertilization acid produced by eggs of Urechis caupo, monitored by automatically back-titrating egg suspensions with base, depends linearly on the pH of the seawater. Above pH 7.0, at which no acid is released (Paul, M., Dev. Biol.43, 299–312, 1975), acid release increased approximately 0.34 pmole/egg/0.1 pH unit. Activation (germinal vesicle breakdown) depended on the amount of acid release in natural seawater; it did not occur if eggs released <1.5 pmole acid/egg. When fertilization acid is released into HCO^?₃-free seawater and the pH permitted to decrease, the supernatant can be tested for the presence of a volatile acid, such as CO₂, by bubbling with N₂ and comparing the increase in pH as volatile acid is driven off with experiments in which HCl or CO₂ is substituted for fertilization acid. An increase in pH of <0.2 pH units occurred on N₂ bubbling when fertilization acid or HCl was used to acidify HCO^?₃-free seawater compared to an increase of >0.5 pH units when CO₂ was used. Therefore, most, if not all, of Urechis fertilization acid is not volatile, and since Paul (1975) showed that it is not a nonvolatile weak acid, it must be H⁺.     

Lactic Acid Permeabilizes Gram-Negative Bacteria by Disrupting the Outer Membrane

The effect of lactic acid on the outer membrane permeability of Escherichia coli O157:H7, Pseudomonas aeruginosa, and Salmonella enterica serovar Typhimurium was studied utilizing a fluorescent-probe uptake assay and sensitization to bacteriolysis. For control purposes, similar assays were performed with EDTA (a permeabilizer acting by chelation) and with hydrochloric acid, the latter at pH values corresponding to those yielded by lactic acid, and also in the presence of KCN. Already 5 mM (pH 4.0) lactic acid caused prominent permeabilization in each species, the effect in the fluorescence assay being stronger than that of EDTA or HCl. Similar results were obtained in the presence of KCN, except for P. aeruginosa, for which an increase in the effect of HCl was observed in the presence of KCN. The permeabilization by lactic and hydrochloric acid was partly abolished by MgCl₂. Lactic acid sensitized E. coli and serovar Typhimurium to the lytic action of sodium dodecyl sulfate (SDS) more efficiently than did HCl, whereas both acids sensitized P. aeruginosa to SDS and to Triton X-100. P. aeruginosa was effectively sensitized to lysozyme by lactic acid and by HCl. Considerable proportions of lipopolysaccharide were liberated from serovar Typhimurium by these acids; analysis of liberated material by electrophoresis and by fatty acid analysis showed that lactic acid was more active than EDTA or HCl in liberating lipopolysaccharide from the outer membrane. Thus, lactic acid, in addition to its antimicrobial property due to the lowering of the pH, also functions as a permeabilizer of the gram-negative bacterial outer membrane and may act as a potentiator of the effects of other antimicrobial substances.     

An improved method for the determination of γ-carboxyglutamic acid in proteins,bone, and urine

A method of high-performance liquid chromatographic separation of the fluorescence derivative of γ-carboxyglutamic acid (Gla) is presented. Alkaline hydrolysates of protein samples were reacted with o-phthalaldehyde in the presence of ethanethiol for 2 min, and the fluorescence derivative of γ-carboxyglutamic acid was resolved from the other amino acids by a short column packed with silica-based anion exchanger under isocratic conditions. By this method, as low as 200 fmol of γ-carboxyglutamic acid can be quantitatively analyzed within 10 min. The method presented here shortened the analysis time for Gla and was at least 10 times more sensitive than the method we described previously (Anal. Biochem.117, 259–265, 1981). The application of this method to the formic acid-soluble or insoluble γ-carboxyglutamic acid-containing proteins in chicken bone and the concomitant increase of γ-carboxyglutamic acid content in chicken bone with age are reported.     

cis-Dichloroplatinum (II) complexes with aminomethylnicotinate and -isonicotinate ligands

6-Aminomethylnicotinic acid (1a) and 2-aminomethylisonicotinic acid (1b) were each reacted with K₂PtCl₄ in aqueous 1 M HCl to give the corresponding N,N-chelated cis-dichloroplatinum(II) complexes 2. These were converted into amides 3 via their mixed anhydrides by treating them first with ethyl chloroformate and then with the respective 1° or 2° amine. The analogous 6-aminomethylnicotinic acid ester complexes 7 were obtained by reaction of the preformed ligands with K₂PtCl₄.     

Bioactive compounds from sclerotia extract of Poria cocos that control adipocyte and osteoblast differentiation

Poria cocos Wolf confers edible sclerotia also known as ‘Indian bread’ in North America, that have been used for the treatment of various diseases in Asian countries. As part of our ongoing aim to identify biologically new metabolites from Korean edible mushrooms, we investigated the ethanol (EtOH) extract of the sclerotia of P. cocos by applying a comparative LC/MS- and bioassay-based analysis approach, since the EtOH extract reciprocally regulated adipocyte and osteoblast differentiation in mouse mesenchymal stem cells (MSCs). Bioassay-based analysis of the EtOH extract led to the successful isolation of two sterols, ergosterol peroxide (1) and 9,11-dehydroergosterol peroxide (2); three diterpenes, dehydroabietic acid (3), 7-oxocallitrisic acid, (4) and pimaric acid (5); and two triterpenes, dehydroeburicoic acid monoacetate (6) and eburicoic acid acetate (7) from the active hexane-soluble fraction. The isolated compounds (1–7) were examined for their effects on the regulation of MSC differentiation. The two sterols (1 and 2) were able to suppress MSC differentiation toward adipocytes. In contrast, the three diterpenes (3–5) showed activity to promote osteogenic differentiation of MSC. These findings demonstrate that the EtOH extract of P. cocos sclerotia is worth consideration as a new potential source of bioactive compounds effective in the treatment of osteoporosis in the elderly, since the extract contains sterols that inhibit adipogenic differentiation as well as diterpenes that promote osteogenic differentiation from MSCs.     

Bioassay-guided isolation of antifungal cyclopeptides from the deep-sea-derived fungus Simplicillium obclavatum EIODSF 020

Two new cyclopeptides simplicilliumtides N and O (1 and 2) along with three known analogues verlamelins A, B and simplicilliumtide J (3-5) were isolated from the deep-sea-derived fungal strain Simplicillium obclavatum EIODSF 020 by bioassay-guided isolation method. Their structures of 1 and 2 were elucidated by spectroscopic analysis, and their amino acid configurations were determined by Marfey’s method. All isolated compounds showed significant antifungal activity against two phytopathogenic fungi Alternaria solani and Colletotricum asianum with MIC values of 0.195–6.250 μg/disc. This study suggests the fungal strain S. obclavatum EIODSF 020 is a new source for developing natural fungicides.     

Kakeromamide A,a new cyclic pentapeptide inducing astrocyte differentiation isolated from the marine cyanobacterium Moorea bouillonii

Kakeromamide A (1), a new cyclic pentapeptide encompassing a thiazole ring moiety and a β-amino acid, was isolated from the marine cyanobacterium Moorea bouillonii. Its structure was elucidated by the spectral analysis and the modified Marfey’s method. Compound 1 induced differentiation of neural stem cells into astrocytes at the concentration of 10?µM.     

Synthesis,computational molecular docking analysis and effectiveness on tyrosinase inhibition of kojic acid derivatives

Tyrosinase inhibitors have become increasingly important as whitening agents and for the treatment of pigmentary disorders. In this study, the synthesis of kojic acid derivatives having 2-substituted-3-hydroxy-6-hyroxymethyl/chloromethyl/methyl/morpholinomethylpiperidinyl- methyl/pyrrolidinylmethyl-4H-pyran-4-one structure (compounds 1–30) with inhibitory effects on tyrosinase enzyme were described. One-pot Mannich reaction was carried out by using kojic acid/chlorokojic acid/allomaltol and substituted benzylpiperazine derivatives in presence of formaline. Subsequently, cyclic amine (morpholine, piperidine and pyrrolidine) derivatives of the 6th-position of chlorokojic acid were obtained with nucleophilic substitutions in basic medium. The structures of new compounds were identified by FT-IR, ¹H- and ¹³C NMR, ESI-MS and elemental analysis data. The potential mushroom tyrosinase inhibitory activity of the compounds were evaluated by the spectrophotometric method using l-DOPA as a substrate and kojic acid as the control agent. The potential inhibitory activity was also investigated in silico using molecular docking simulation method. Tyrosinase inhibitory action was significantly more efficacious for several compounds (IC₅₀: 86.2–362.1 µM) than kojic acid (IC₅₀: 418.2). Compound 3 bearing 3,4-dichlorobenzyl piperazine moiety was proven to have the highest inhibitory activity. The results of docking studies showed that according to the predicted conformation of compound 3 in the enzyme binding site, hydroxymethyl group provides a metal complex with copper ions and enzyme. Thus, this interaction explain the high inhibitory activities of the compounds 1, 3 and 4 possessing hydroxymethyl substituent supporting the mushroom assay results with docking studies. In accordance with the results, it is suggested that Mannich bases of kojic acid bearing substituted benzyl piperazine groups (compounds 1, 3, 4, 11, 13, 14, 23, 24, 28, and 29) could be promising antityrosinase agents. Additionally, considering the relationship between tyrosinase inhibitory activity results and molecular docking, a new tyrosinase inhibition mechanism can be proposed.     

Chemotaxonomic implications of the absence of sesquiterpene lactones in Grazielia multifida (DC.) R.M.King & H.Rob. (Asteraceae)

The phytochemical investigation of Grazielia multifida aerial parts yielded eight compounds, including four ent-kaurenic acid diterpenes derivatives, 15-tiglinoyloxy-ent-kaur-16-en-19-oic acid (1), 15-hydroxy-ent-kaur-16-en-19-oic acid (2), 17-hydroxy-ent-kaur-15-en-19-oic acid (3) and 15-isovaleroyloxy-ent-kaur-16-en-19-oic acid (4), one amino acid, tryptophan (5), and three flavonoids, eupafolin (6), guaijaverin (7) and quercitrin (8). The structures of the isolated compounds were established based on analysis of their spectroscopic data and comparison with literature. All the compounds were isolated from this species for the first time. The chemotaxonomic significance of the absence of sesquiterpene lactones in G. multifida has also been summarized.     

Secondary metabolites of Rubus caesius (Rosaceae)

The European dewberry (Rubus caesius) is a perennial shrub that is widely distributed in Europe but can also be found in North America. In folk medicine, the European dewberry is used to treat hyperglycaemia, diarrhoea and inflammation. LC-MS analysis of the European dewberry confirmed the presence of 35 compounds, mostly flavonoids, phenolic acids and derivatives of ellagic acid. Phytochemical analysis of R. caesius leaves led to the isolation of nine phenolics, namely: quercetin 3-O-β-D-rutinoside (1), kaempferol 3-O-β-D-glucuronide (2), quercetin 3-O-β-D-glucuronide (3), methyl brevifolincarboxylate (4), kaempferol 3-O-β-D-(6″-O-(E)-p-coumaroyl)-glucoside (5), kaempferol (6), quercetin (7), pedunculagin (8), and ellagic acid (9). Compounds 1–8 were isolated from this species for the first time. The chemophenetic significance was discussed.     

Dihydroxylation of alkenes using a Tp-osmium complex

The reaction of TpOs^VI(N)(OH)₂ (1) [Tp = hydrotris(1-pyrazolyl)borate], m-chloroperbenzoic acid (m-CPBA), and trans-stilbene in C₆H₆ at room temperature gives the diolate complex TpOs^VI(N)(trans-O₂C₂H₂Ph₂) (2) and m-chlorobenzoic acid (m-CBA). The trans configuration of the stilbene is retained in the diolate complex as shown in the crystal structure of 2. Complex 2 is hydrolyzed by 2 equivalents of aqueous HCl in CD₂Cl₂ to give rac-hydrobenzoin, the product of cis-dihydroxylation, and TpOs^VI(N)Cl₂. cis-Stilbene, styrene, cyclohexene, trans-dimethyl fumarate, trans-methyl cinnamate, and trans-4-dimethylamino-4′-nitrostilbene are also converted to their corresponding free diol products by reaction with 1 and m-CPBA in CD₂Cl₂, and then aqueous HCl. In aqueous HBF₄, oxidation of the water-soluble olefin, 4-styrenesulfonic acid, by 1 is modestly catalytic (15 turnovers in 3 h) with excess PbO₂ as the oxidant. Under non-acidic conditions, the diolate complexes are inert and catalysis is precluded. Mechanistic experiments implicate an oxidizing osmium complex as an intermediate in these reactions.     

A convenient synthesis of phosphine-functionalized N-heterocyclic carbene ligand precursors, structural characterization of their palladium complexes and catalytic application in Suzuki coupling reaction

A series of imidazolium chlorides as ligand precursors, L · HCl (L = (1-R)-(3-diphenylphosphanylethyl)-imidazol-2-ylidene; R = aryl, benzyl, naphthylmethyl), for the phosphine-functionalized N-heterocyclic carbene (NHC), L, were prepared by a convenient synthetic procedure of reacting 1,2-dichloroethane with appropriate N-substituted imidazoles to give (β-chloroethyl)imidazolium chlorides, which were subsequently reacted with HPPh₂ producing L · HCl in good yield. Palladium complexes of L, PdLCl₂ (4), were prepared by a one pot reaction of PdCl₂, sodium acetate, and L · HCl in DMSO. Complexes 4b (R = naphthylmethyl) and 4e (R = m-methoxybenzyl) were characterized by X-ray crystallography. Catalytic studies have shown that the palladium complexes are efficient in Suzuki coupling reactions of aryl bromides with phenylboronic acid.     

Hydroxyl substituted benzoic acid/cinnamic acid derivatives: Tyrosinase inhibitory kinetics,anti-melanogenic activity and molecular docking studies

The inhibition of tyrosinase is an established strategy for treating hyperpigmentation. Our previous findings demonstrated that cinnamic acid and benzoic acid scaffolds can be effective tyrosinase inhibitors with low toxicity. The hydroxyl substituted benzoic and cinnamic acid moieties of these precursors were incorporated into new chemotypes that displayed in vitro inhibitory effect against mushroom tyrosinase. The most active compound, (2-(3-methoxyphenoxy)-2-oxoethyl (E)-3-(4-hydroxyphenyl) acrylate) 6c, inhibited tyrosinase with an IC₅₀ of 5.7 µM, while (2-(3-methoxyphenoxy)-2-oxoethyl 2, 4-dihydroxybenzoate) 4d had an IC₅₀ of 23.8 µM. In comparison, the positive control, kojic acid showed tyrosinase inhibition with an IC₅₀ = 16.7 µM. Analysis of enzyme kinetics revealed that 6c and 4d displayed noncompetitive reversible inhibition of the second tyrosinase enzymatic reaction with K_i values of 11 µM and 130 µM respectively. In silico docking studies with mushroom tyrosinase (PDB ID 2Y9X) predicted possible binding modes in the catalytic site for these active compounds. The phenolic para-hydroxy group of the most active compound 6c is predicted to interact with the catalytic site Cu⁺⁺ ion. The methoxy part of this compound is predicted to form a hydrogen bond with Arg 268. Compound 6c had no observable toxic effects on cell morphology or cell viability at the highest tested concentration of 91.4 µM. When dosed at 91.4 µM onto B16F10 melanoma cells in vitro 6c showed anti-melanogenic effects equivalent to kojic acid at 880 µM. 6c displayed no PAINS (pan-assay interference compounds) alerts. Our results show that compound 6c is a more potent tyrosinase inhibitor than kojic acid and is a candidate for further development. Our exposition of the details of the interactions between 6c and the catalytic pocket of tyrosinase provides a basis for rational design of additional potent inhibitors of tyrosinase, built on the cinnamic acid scaffold.