l-Isofucoselenofagomine and derivatives: dual activities as antioxidants and as glycosidase inhibitors

The synthesis of a series of l-fuco-configured selenosugars, isosters of the potent glycosidase inhibitor isofucofagomine has been accomplished by a double nucleophilic displacement of a dimesylated derivative with selenide anion generated in situ. Se-Alkylation and oxidation of the corresponding selenane afforded a selenonium and a selenoxide, respectively. The biological activities of such compounds have been evaluated, finding a dual activity caused by the presence of the selenium atom: the selenane exerted a good glutathione peroxidase mimicry by efficiently scavenging H₂O₂ in the presence of thiols, whereas the stable selenoxide derivative was found to be the first example of a selenosugar acting as a good α-l-fucosidase inhibitor.     

Synthesis and biological evaluation of some new substituted benzoxazepine and benzothiazepine as antipsychotic as well as anticonvulsant agents

Various 2-((2-((5-benzylideneamino)-1,3,4-oxa/thiadiazol-2-yl)methyl)hydrazinyl) methyl)benzo[b][1,4]oxa/thiazepin-4(5H)-ones (4a–4l), 2-((2-((5-(4-oxo-2-substitutedphenyl thiazolidin-3-yl)-1,3,4-oxa/thiadiazol-2-yl)methyl)hydrazinyl)methyl)benzo [b] [1,4]oxa/thiazepin-4(5H)-ones (5a–5l) and 2-((2-((5-(3-chloro-2-(substitutedphenyl)-4-oxoazetidin-1-yl)-1,3,4-oxa/thia diazol-2-yl)methyl)hydrazinyl)methyl)benzo[b][1,4]oxa/thiazepin-4(5H)-ones (6a–6l) have been synthesized. The structures of these compounds have been established by elemental (C, H, N) and spectral (IR, ¹H-NMR and Mass) analysis. The synthesized compounds were screened for their antipsychotic and anticonvulsant activities. Compound 5l was found to be the most active compound of this series.     

朱砂中汞的生物可接受性及其吸收与排泄

研究了朱砂中汞的生物可接受性及其在体内的吸收与排泄.采用体外消化透析法测定了朱砂中汞的生物可接受性;计算了大鼠灌胃给予临床剂量(50mg/kg)朱砂后汞的药动学参数;测定了给予临床剂量的朱砂后大鼠粪样中汞的排泄量.结果表明,朱砂中汞的溶出率为0.011%,生物可接受率为0.003 3%.大鼠灌胃给予临床剂量的朱砂后,汞的药动学参数为:最高血药浓度(ρmax)为(6.3±1.3)μg/L,达峰时间(tmax)为(1.3±0.4)h,半衰期(t1/2)为(4.2±0.5)h,血药浓度-时间曲线下面积(AUC)为(54.7±8.7)μg.h.L-1.给予朱砂12h后汞在粪便中排泄量最大,96h后在粪样中仍可检测到少量汞.朱砂中汞的生物可接受性较低,在体内吸收少,滞留时间较长,排泄缓慢,长期服用可在体内蓄积,产生毒性.     

New transition-metal-dependent DNAzymes as efficient endonucleases and as selective metal biosensors

Like proteins and RNA molecules, many DNA molecules have now been shown to catalyze a variety of reactions and are thus called DNAzymes. With limited building blocks, DNAzymes need to recruit other cofactors in order to match other enzymes in terms of reaction diversity and catalytic efficiency. Several unique properties make transition-metal ions an ideal choice of cofactor for DNAzymes. Indeed, new DNAzymes that bind transition-metal ions with high affinity and selectivity have been obtained through the use of a powerful combinatorial biology tool called in vitro selection. This accomplishment now makes it possible to obtain different classes of metallo-DNAzymes in the laboratory within a short period of time. It also offers a rare opportunity to compare and contrast structural and functional properties of metal-binding sites in proteins and in DNAzymes. The resulting transition-metal-dependent DNAzymes have displayed high activity toward cleavage of DNA and RNA and thus hold promise for their biochemical and pharmaceutical applications. Finally, the use of DNAzymes as a new class of highly sensitive and selective biosensors for metal ions has been demonstrated recently.     

Synthesis of novel bis- and poly(benzimidazoles) as well as bis- and poly(benzothiazoles) as anticancer agents

A synthesis of bis- and poly(benzimidazoles) as well as bis- and poly(benzothiazoles) was attempted using different protocols. The best results were obtained by employing the reaction of the appropriate bis- or poly(aldehydes) with o-phenylenediamine or 2-aminothiophenol, respectively, in ethanol at reflux in the presence of NaHSO₃. The anticancer activities of the synthesized compounds were evaluated against human breast adenocarcinoma cell line (MCF-7), liver cancer cell line (HepG-2), and epithelial colorectal adenocarcinoma cells (CaCO-2). Hexakis(benzothiazole) was found to exhibit the highest activity against HepG-2 and MCF-7 cell lines with IC₅₀ values of 21.16 and 13.25 μM, respectively.     

Production of Dihydrogen Using Ammonia Borane as Reagent and Pyrazole as Catalyst

Theoretical chemistry (DLPNO-CCSD(T)/def2-TZVP//M06-2x/aug-cc-pVDZ) was used to design a system based on ammonia boranes catalyzed by pyrazoles with the aim of producing dihydrogen, nowadays of high interest as clean fuel. The reactivity of ammonia borane and cyclotriborazane were investigated, including catalytic activation through 1H-pyrazole, 4-methoxy-1H-pyrazole, and 4-nitro-1H-pyrazole. The results point toward a catalytic cycle by which, at the same time, ammonia borane can initially store and then, through catalysis, produce dihydrogen and amino borane. Subsequently, amino borane can trimerize to form cyclotriborazane that, in presence of the same catalyst, can also produce dihydrogen. This study proposes therefore a consistent progress in using environmentally sustainable (metal free) catalysts to efficiently extract dihydrogen from small B−N bonded molecules.     

Isocytosine as a hydrogen-bonding partner and as a ligand in metal complexes

Isocytosine (ICH; 1) exists in solution in an equilibrium of tautomers 1a and 1b with the N1 and N3 positions carrying the acidic proton, respectively. In the solid state, both tautomers coexist in a 1:1 ratio. As we show, the N3H tautomer 1b can selectively be crystallized in the presence of the model nucleobase 1-methylcytosine (1-MeC). The complex 1b x (1-MeC)2 x H2O (2) forms pairs through three hydrogen bonds between the components; hydrogen bonds between identical molecules are also formed, leading to an infinite tape structure. On the other hand, the N1H tautomer 1a co-crystallizes with protonated ICH to give [1a x ICH2]NO3 (3), again with three hydrogen bonds between the partners, yet the acidic proton is disordered over the two entities. With M(II)(dien) (M=Pt, Pd; dien=diethylenetriamine) preferential coordination of tautomer 1a through the N3 position is observed. DFT calculations, which were also extended to Pt(II)(tmeda) linkage isomers (tmeda=N,N,N',N'-tetramethylethylenediamine), suggest that intramolecular hydrogen bonding between the ICH tautomers and the co-ligands at M, while adding to the preference for N3 coordination, is not the major determining factor. Rather it is the inherently stronger Pt-N3 bond which favors complexation of 1a. With an excess of M(II)(dien), dinuclear species [M2(dien)2(IC-N1,N3)]3+ (M=Pd(II), 4 and Pt(II), 5) also form and were isolated as their ClO4(-) salts and structurally characterized. In strongly acidic medium 5 is converted to [Pt(dien)(ICH-N1)]2+ (6), that is, to the Pt(II) complex of tautomer 1b.     

Titanium compounds as coatings on polystyrene latices and as hollow spheres

Sub-micron-sized anionic polystyrene latices have been coated with uniform layers of amorphous titanium dioxide by hydrolysis of titanium tetrabutoxide in ethanolic solutions containing the polymer cores. The thickness of the coating layer could be altered by adjusting the concentration of titanium tetrabutoxide and the amount of polymer latex added to the system. Hollow colloidal spheres of crystal titanium dioxide were obtained by calcination of the so-coated polystyrene latices at an elevated temperature. Received: 29 July 1999/Accepted in revised form: 15 October 1999     

两性高分子与小分子及大分子的相互作用（下）

2 两性高分子与染料及表面活性剂的相互作用文献中对阳离子聚电解质、阴离子聚电解质及非离子性高分子与染料、去污剂、表面活性剂等小分子物质的相互作用有较多报道,而有关两性高分子与这些小分子物质相互作用的报道极少。本节就合成两性高分子与染料等小分     

Evaluation of titania as an ion-exchanger and as a ligand-exchanger in HPLC

Summary The chromatographic properties of titania have been compared with those of zirconia and alumina, by comparison of their relative Lewis acidities whenp-substituted benzoic acids were chromatographed with aqueous mobile phases. The retention behavior ofp-substituted benzoic acids on titania was found to be similar to that on zirconia; the slopes of plots of retention factors against solute pK _a were approximately parallel for all pH values and the slopes obtained were similar to the average slope for zirconia. The shapes of solute peaks on titania were more symmetrical than on alumina and zirconia. The effect of calcination temperature on the chromatographic properties of titania was examined by use of titania prepared at different temperatures. The results obtained clearly showed that the preparation temperature affected the chromatographic properties of titania. It seemed, for example, that titania dried at 40°C behaved as a cation-exchanger, titania heated at 200°C behaved as an amphoteric exchanger, and titania calcined at 600°C behaved as an anion-exchanger in the pH range 4.1–6.5 It was found that the control of the preparation temperature enabled us to make effective use of titania.     

Poly-Diels-Alder Addition with a Bisoxazole as Bisdiene and a Bismaleinimide as Bisdienophile

Abstract

The poly-Diels-Alder addition between the new bisdiene 1,4-bis(5-methoxy-2-oxazolyl)benzene (4) and N,N′-hexamethylene-bis[2-(2,5-dihydro-2,5-dioxo-pyrrole-1-yl) acetamide] (7) is described. The structure of the resulting polyadduct 12 was proved by ¹H NMR spectroscopy with the aid of the low-molecular-weight model compounds 1,4-bis(1,3-dihydro-7-hydroxy-1,3-dioxo-2-phenyl-pyrrolo[3,4-c] pyridine-4-yl)benzene (9) and N,N'-hexamethylene-bis[2-(1, 3-dihydro-7-hydroxy-6-methyl-1,3-dioxo-4-phenyl-pyrrolo [3,4-c]pyridine-2-yl)acetamide] (11). The reaction proceeds via the aromatization of the primarily formed cycloadducts. Polyadduct 12 shows a number average degree of polymerization P_n of about 11 – 12 (M_n = 8500 ? 9200 g/mol), calculated from ¹H NMR endgroup signals.     

Some Monohydroxy Tetradecanoic Acid Isomers as Novel Urease and Elastase Inhibitors and as New Antioxidants

A series of some 3-,6-,7-,9-,12- monohydroxy tetradecanoic acids were evaluated for their antiurease, antielastase and antioxidant activities for the first time in this study. All the test compounds exhibited antioxidant, antielastase and antiurease activities. The relationship between the position of the hydroxy group and the enzyme inhibition effect is studied in this work. The mentioned biological activities are depending on the position of hydroxy group of tetradecanoic acid isomers. The results obtained in this work are indicating that 3-,6-,7-,9-,12-monohydroxy tetradecanoic acid isomers can be used in agriculture, pharmacy and cosmetic industries due to their excellent antielastase, antiurease and antioxidant activities.     

Cyanobacteria as Natural Therapeutics and Pharmaceutical Potential: Role in Antitumor Activity and as Nanovectors

Cyanobacteria (blue-green microalgae) are ubiquitous, Gram-negative photoautotrophic prokaryotes. They are considered as one of the most efficient sources of bioactive secondary metabolites. More than 50% of cyanobacteria are cultivated on commercial platforms to extract bioactive compounds, which have bene shown to possess anticancer activity. The chemically diverse natural compounds or their analogues induce cytotoxicity and potentially kill a variety of cancer cells via the induction of apoptosis, or altering the activation of cell signaling, involving especially the protein kinase-C family members, cell cycle arrest, mitochondrial dysfunctions and oxidative damage. These therapeutic properties enable their use in the pharma and healthcare sectors for the betterment of future generations. This review provides a baseline overview of the anti-cancerous cyanobacterial bioactive compounds, along with recently introduced nanomaterials that could be used for the development of new anticancer drugs to build a healthy future for mankind.     

A Novel Amperometric Biosensor for Determination of Hydrogen Peroxide Based on Nafion and Polythionine as Well as Gold Nanoparticles and Gelatin as Matrixes

Abstract

A new biosensor for the amperometric detection of hydrogen peroxide was developed by means of immobilized horseradish peroxidase (HRP) on a platinum disk based on gold nanoparticles, nafion, polythionine (PTn), and gelatin as matrixes. The mediator (PTn) was embedded in nafion film effectively without leaching even after long periods of operation, the immobilization of the enzyme comes from the cooperative binding by the Au nanoparticles and gelatin. The fabrication procedure of the biosensor was characterized by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The electrochemical characteristics of the enzyme electrode with respect to the effect of pH, temperature, and the operational and storage stabilities were studied. The test demonstrated that the biosensors show high stability, fast response (<20 s), and a working range 0.05 to 30.6 mM (correlation coefficient: 0.9986), a detection limit of 0.02 mM to hydrogen peroxide (H₂O₂). The analytical results by this approach were in satisfactory agreement with those by conventional methods of titration.     

Synthesis of Dihydrobenzofuran Neoligans Licarin A and Dihydrocarinatin as Well as Related Triazolylglycosides

Two natural dihydrobenzofuran neolignans licarin A（1） and dihydrocarinatin（2） were systhesized from isoeugenol with Ag20-catalyzed biomimetic oxidative coupling as the key step. Four novel dihydrobenzofuran triazolylglycoside（3--6） were achieved in good yields via Cu（I）-catalyzed azide-alkyne cycloadditions of licarin A terminal alkynes with different azide acetylated sugar and deacetylation with sodium methoxide in anhydrous methanol. The structures of all the compounds synthesized were determined by elemental analysis, MS, 1H NMR and ~3C NMR. And the inhibition activity of synthesized compounds on a-glucosidase was determined by in vitro experiments. The results show that triazolyglycosides 3, 4, 5 and 6 show moderate inhibitory activity on a-glucosidase.     

Complete NMR data of methoxylated cis- and trans-stilbenes as well as 1,2-diphenylethanes

Resveratrol is a polyphenol isolated from many natural sources including grapes, mulberries, eucalyptus, spruce, lilies, and peanuts. The hydroxyl groups in polyphenols can be substituted with various functional groups, allowing production of multiple derivatives. NMR spectroscopy is used to identify new derivatives. Since the complete NMR data of the known derivatives can be useful for identification of the newly isolated derivatives, here, we report the synthesis of 14 methoxylated stilbenes and four 1,2-diphenylethanes and their NMR data.     

Efficient Synthesis of meso-Tetraarylporphyrins Using I2 as Catalyst and IBX as Oxidant

meso-Tetraarylporphyrins are synthesized from pyrrole and substituted benzaldehydes by a catalytic amount of I₂ as catalyst and o-iodoxybenzoic acid (IBX) as oxidant in two steps and one flask. The advantages of this method include the use of inexpensive and easily available catalyst, avoidance of heavy consumption of CH₂Cl₂, innocuous oxidant, and good yields.     

酪氨酸酶催化下以吡啰红为指示剂荧光测定青蒿素

Fluorescence decrease ratio （F0/F） was applied to determination of artemisinin （qinghaosu, QHS） based on the catalytic effect of tyrosinase using tetraethyldiaminoxanthenyl chloride （pyronine B, PB） as monitor. A catalyst used commonly in the decomposition of QHS, tyrosinase, exhibited higher binding activity than hemin, which was expressed as Michaelis-Menten parameters, km, Vmax, and kcat respectively. Interaction of QHS with tyrosinase was inhibited in the presence of deactivating agents at high temperature whereas enhanced by ethanol. Under optimal conditions, a concentration of 1.4×10^-7-8.4×10^-7 mol·L^-1of QHS could be determined on the basis of fluorescence decrease ratio of PB, with a detection limit 3tr of 2.6×10^-9 mol·L^-1. The proposed method was applied to detection of the concentration of QHS in the media of plasma and urine.     

Synthesis and derivatization of naphthylcalcium halides as well as degradation in THF solution

The direct synthesis of 1-naphthyliodide and -bromide with calcium powder yields (thf)₄Ca(Naph)I (1) and [(thf)₃Ca(Naph)Br]₂ (2), respectively. The metathesis reaction of 1 with KN(SiMe₃)₂ gives (thf)₃Ca(Naph)-N(SiMe₃)₂ (3). In 2 and 3 very small Ca-C bond lengths of 252.8(4) and 251.4(6) pm, respectively, are observed. These compounds slowly decompose in THF solution via ether cleavage reactions. From this degradation, [(thf)₄CaBr₂] · naphthalene (4) crystallizes from THF solutions. Furthermore, decomposition of 1 in THF solution yields ethene and naphthalene whereas intermediate ethenolate undergoes subsequent degradation to an acetylide.