Inhibitory effect of piperidinoethylesters of alkoxyphenylcarbamic acids on photosynthesis.

Piperidinoethylesters of 2-, 3- and 4-alkoxysubstituted phenylcarbamic acids (alkoxy = methoxy - decyloxy) inhibit photosynthetic processes in algae and plant chloroplasts. The inhibitory activity is strongly dependent on the alkyl chain length of the alkoxy-substituent showing a typical quasi-parabolic dependence with maximum effect at 6-8 carbon atoms in the alkyl chain. The alkoxy-substitution in position 2 decreases the inhibitory activity of a compound when compared with its 3- and 4-substituted analogues. ESR studies of spinach chloroplasts confirm that the compounds studied cause destruction of PS II whereby, in the presence of the most effective of the derivatives tested, Mn2+ ions are released from the protein complex.     

Inhibitory effects of some synthetic monoethanolamine salts of para-substituted benzoic acids and corresponding benzoic acids on cucumber seed germination

Abstract

Benzoates and particularly, benzoic acids are known biologically for their effects in the regulation of seed germination. A series of monoethanolamine salts of para-substituted benzoic acids (MEASPBAs), the corresponding acids (BAs) and monoethanolamine (MEA) were tested at different concentrations, on Cucumis sativus L. germination in order to assess their biological activity. The correlation between the effects of different substituents of these salts and the corresponding acids with germination rate, root and shoot length, fresh and dry biomass, soluble protein content, isocitrate lyase (ICL, EC 4.1.3.1) and catalase (CAT, EC 1.11.1.6.) activity, was evaluated. Data showed that p-OH and p-CH₃ substituents had a lower inhibitory effect compared to the halogenated substituents. Moreover, the inhibition of root and shoot lengths and the dramatic decrease of fresh biomass for halogenated (p-Cl, p-Br, p-I) MEASPBAs and BAs followed the increase of the atomic size of the substituent.     

Molecular mechanics (MM3) study of the conformations of ethyl esters of diastereoisomeric 3-substituted 4,4,4-trichloro-2-cyano-butanoic acids

Molecular mechanics calculation (MM3 force field) were used to study the conformations of diastereoisomeric pairs of ethyl esters of 3-substituted 4,4,4-trichloro-2-cyano-butanoic acids in order to test an assumption from ¹H NMR spectra about their preferred conformations. On the basis of the most probable preferred conformation in each case, an assignment of the relative configurations of these newly synthesized compounds was made in the earlier study. The present computed most favorable conformations are in accord with the earlier qualitative considerations in all cases, thus validating the assignment of the configurations of the diastereoisomers made previously.     

Synthesis of 6- or 7-substituted 1,2,3,4-tetrahydroisoquinoline- 3-carboxylic acids

Summary A straightforward approach for the synthesis of several new, aryl-substituted derivatives of the conformationally constrained phenylalanine analogue 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic) is described. Tic, nitrosubstituted at the 6 or 7 position, was prepared by base-catalyzed cyclization of diethyl acetamidomalonate with α,α-dibromo-4-nitro-o-xylene followed by decarboxylation and deacylation under refluxing conditions in aqueous HCl. Catalytic hydrogenation of nitro-Tic in the presence of 10% Pd/C afforded amino-Tic, which was then converted to iodo-Tic by a modified Sandmeyer reaction. Both amino-Tic and iodo-Tic can easily be transformed to other substituents.     

Synthesis of 6- or 7-substituted 1,2,3,4-tetrahydroisoquinoline- 3-carboxylic acids

A straightforward approach for the synthesis of several new, aryl-substituted derivatives of the conformationally constrained phenylalanine analogue 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid (Tic) is described. Tic, nitro-substituted at the 6 or 7 position, was prepared by base-catalyzed cyclization of diethyl acetamidomalonate with ,-dibromo-4-nitro-o- xylene followed by decarboxylation and deacylation under refluxing conditions in aqueous HCl. Catalytic hydrogenation of nitro-Tic in the presence of 10% Pd/C afforded amino-Tic, which was then converted to iodo-Tic by a modified Sandmeyer reaction. Both amino- Tic and iodo-Tic can easily be transformed to other substituents.     

Synthesis, characterization and antitumor properties of some metal complexes of 3- and 5-substituted salicylaldehyde 2-pyridinylhydrazones

Complexes of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), and Pt(II) with 3- and 5-substituted salicylaldehyde 2-pyridinylhydrazones (XSPH, X = H, 3-NO2, 3-CH3O, 5-Br, 5-Cl, 5-CH3, or 5-NO2) have been prepared and characterized by elemental analysis, conductance measurements, magnetic moments (300-78 K), and spectral studies. On the basis of these studies a monomeric, high-spin, distorted octahedral structure for Mn(XSPH)2 and Fe(XSPH)2, a dimeric, high-spin, five-coordinate structure for Co(XSBH)Cl, a dimeric, low-spin, five-coordinate structure for Ni(XSPH)Cl and Zn(XSPH)(OAc), and a square-planar structure for M(XSPH)Cl.H2O (M = Cu(II) or Pt(II] complexes are suggested. The polycrystalline ESR spectra of Cu(II) complexes are isotropic and suggest dx2-y2 ground state in square-planar stereochemistry. M?ssbauer spectral results indicate distorted octahedral structure for iron(II) complexes. All the metal(II) complexes have been screened for their antitumor activity against P388 lymphocytic leukemia test system in mice and have been found to possess no significant activity at the dosages used.     

Antibacterial effects of some 1-substituted 1,2,4-triazoles

Seventeen synthetic 1-substituted 1,2,4-triazoles exerted a significant effect on the bacteriaB. subtilis, S. aureus, E. coli andP. aeruginosa. The least sensitive to the effects of the triazoles wasS. aureus. With all triazole derivatives and their combinations,B. subtilis andP. aeruginosa exhibited IC₅₀ and MIC values several times higher than with ampicillin. The most effective triazoles have a N-phenyl ring or benzimidinoyl ring substituted with one or several chlorine atoms. The highest tested concentration of the three most effective triazoles influenced the specific growth rate.     

几种银莲花光合特性的初步分析

采用LI6400便携式光合仪分析昆明室外栽培的几种野生银莲花光合作用特性。净光合速率(Pn)和蒸腾速率(Tr)日变化均呈单峰曲线,前者的峰值出现在10～11点,后者的峰值出现在13点前后。在光强0～2000μmol·m2·s1条件下,Pn呈S曲线,光合补偿点为60～80μmol·m2·s1,饱和点为800μmol·m2·s1左右,但光强继续增加到1800μmol·m2·s1,Pn仍有少许提高;Tr随PAR的增加而缓慢地增加。在环境CO2浓度为0～350μmol·mol1条件下,Pn直线上升,草玉梅、秋牡丹和野棉花的光合CO2补偿点均为50μmol·mol1左右;Tr在环境CO2浓度25～350μmol·mol1范围内几乎呈水平线。野生银莲花的Pn和Tr表现较明显的种间差异。     

The antimutagenicity of 2-substituted selenazolidine-4-(R)-carboxylic acids

Selenium can have cancer chemopreventive activity, although the mechanism of action has not been well defined. Selenazolidine-4-(R)-carboxylic acids (SCAs) were devised as prodrugs of L-selenocysteine, to provide selenium in a form and at a concentration commensurate with cancer chemopreventive activity. In the present study, a series of selenazolidines has been evaluated in the Salmonella typhimurium TA98 tester strain and all were found to possess antimutagenic activity. There was little difference between the seven selenazolidines in their effectiveness against either benzo[a]pyrene (B[a]P) or 3,6-bis(dimethylamino)acridine (acridine orange), agents which differ in their requirement for mammalian enzyme bioactivation for mutagenicity. Antimutagenic activity against acridine orange was dependent on selenazolidine concentration, and EC50 values were in the 5-10 microM range. At 25 microM, the concentration tested in common for the two mutagens, the selenazolidines were more effective antimutagens against acridine orange than against B[a]P, with reductions in mutant frequency ranging from 54 to 71% for B[a]P and 79 to 93% for acridine orange. Efficacy against B[a]P was not enhanced when the concentration was increased to 50 microM. The similarity in efficacy among the selenazolidines against B[a]P mutagenicity, contrasted with inter-compound differences in their ability to inhibit S9 CYP1A activity. The CYP1A Ki values ranged from a low of 63 microM (2-[2'-hydroxyphenyl]SCA) to a high of 1.1mM (2-cyclohexylSCA), but all were above the concentration required to inhibit mutagenicity by 50%. Thus, all the SCAs possess antimutagenic activity against both B[a]P and acridine orange, the efficacy varies little between the individual selenazolidines, and for B[a]P, the efficacy is not proportional to the inhibitory effect on the mutagen bioactivating enzyme.     

Inhibitory effects on mushroom tyrosinase by some alkylbenzaldehydes

The inhibition kinetics on the diphenolase activity of mushroom tyrosinase by some alkylbenzaldehydes has been investigated. The results show that the alkylbenzaldehydes assayed can lead to reversible inhibition to the enzyme; o-tolualdehyde and m-tolualdehyde are mixed-type inhibitors and p-alkylbenzaldehydes are uncompetitive inhibitors. For the p-alkylbenzaldehydes, the inhibition potency follows the order: p-tolualdehyde < p-ethylbenzaldehyde < p-propylbenzaldehyde = p-Isopropylbenzaldehyde < p-tert-butylbenzaldehyde = p-butylbenzaldehyde < p-pentylbenzaldehyde < p-hexylbenzaldehyde > p-heptylbenzaldehyde > p-octylbenzaldehyde, indicating the hydrophobic p-alkyl group played an important role in inhibition to the enzyme. The inhibitory effects of alkylbenzaldehydes on the monophenolase activity have also been studied. The results show that o-tolualdehyde and m-tolualdehyde can lengthen the lag time and decrease the steady-state activity of the enzyme, but p-alkylbenzaldehydes only decrease the steady-state activity and do not lengthen the lag time, indicating that their inhibitory mechanisms are different.     

Synthesis and antiviral activity of some 2-substituted 3-formyl- and 3-cyano-5,6-dichloroindole nucleosides

A series of dichlorinated indole nucleosides has been synthesized and tested for activity against human cytomegalovirus (HCMV) and herpes simplex virus type-1 (HSV-1) and for cytotoxicity. The isopropylidene-protected analogs of the previously reported 3-formyl-2,5,6-trichloro-1-(beta-Dribofuranosyl)indole (FTCRI) and 3-cyano-2,5, 6-trichloro-1-(beta-D-ribofuranosyl)indole (CTCRI) were modified by nucleophilic displacement of the 2-chloro substituent using secondary amines. Deprotection of the intermediates provided 2-substituted analogs of FTCRI and CTCRI in good yield. There was a significant difference in reactivity between the isopropylidene-protected and the fully deprotected FTCRI and CTCRI with respect to nucleophilic displacement of the 2-chloro substituent using dialkylamines. This difference in reactivity was not observed with monoalkylamines or with alkoxides, and the corresponding 2-alkylamino- and 2-methoxy substituted analogs were synthesized from FITCRI and CTCRI directly. None of the synthesized analogs demonstrated potent antiviral activity without some corresponding cytotoxicity.     

氯化镧对硝酸盐胁迫下黄瓜幼苗光合特性的缓解效应

采用水培方式研究了LaCl₃对140 mmol·L^-1 NO₃-硝酸盐胁迫下黄瓜幼苗光合特性的影响.结果表明: 硝酸盐胁迫显著降低了黄瓜幼苗叶绿素及类胡萝卜素含量,叶片Mg²⁺ ATPase、Ca²⁺ ATPase活性也随之降低;硝酸盐胁迫7 d,黄瓜幼苗叶片光合速率的降低以气孔限制为主,叶片AQY与CE下降,胁迫12 d则以非气孔限制为主.硝酸盐胁迫下,外加LaCl3可以使黄瓜叶片保持较高的Mg²⁺ ATPase、Ca²⁺ ATPase活性及叶绿素和类胡萝卜素含量,尤其是外加低浓度（20 μmol·L^-1）LaCl3显著增加了叶片类胡萝卜素含量;LaCl₃还具有降低气孔关闭、改善叶片气体交换功能,减缓叶片F_v/F_m、Ф_PSII、AQY、CE及q_P的降低幅度等作用,使叶片在盐胁迫下保持较高的光能利用率及CO₂同化能力.20 μmol·L^-1 LaCl₃可以有效缓解硝酸盐对黄瓜幼苗光合作用的影响,而200 μmol·L^-1LaCl₃在胁迫初期对黄瓜幼苗有缓解效果,后期则效果不明显.该结果可为设施土壤的改良提供新的途径.     

Inhibitory effect of some acetyl esters and acetamides on glycation of the histone H1

Non-enzymatic glycosylation (glycation) is a spontaneous set of reactions between reducing sugars and free amino groups in proteins or other biomolecules leading to the formation of fluorescent and coloured compounds known as advanced glycation end products (AGEs). AGEs cause structural changes of key proteins in humans, and therefore they are related with a number of physiological processes and diseases such as aging, atherosclerosis, cataract, arthritis, Alzheimer's disease. Two main strategies have been employed to prevent the formation of AGEs: a) low carbohydrate diet and b) pharmacological intervention. The latter includes treatment with reactive compounds which might be either sugar competitors (type A), carbonyl traps (type B) or free radical trapping antioxidants (type C). Acetylsalicylic acid (ASA, aspirin) is a good example of sugar competitor capable of inhibiting glycation by acetylating epsilon-amino groups of lysine residues in proteins. Taking into consideration the inhibiting effect of ASA on glycation we designed to study the antiglycation activity of other acetyl group-containing compounds (acetamides and acetyl esters) using the lysine-rich protein histone H1 as a model. The glycation of the histone H1 was carried out by either fructose or a complex mixture of glycating agents obtained from E. coli and monitored by fluorescent spectroscopy, SDS-PAGE and measurement of the content of reactive carbonyl groups in the target protein. Our results showed that the inhibitory effect of phenyl acetate, acetanilide, 4-acetamidophenylacetic acid and isopropenyl acetate was comparable to that of ASA. Based on the obtained results we conclude that these compounds act as free radical scavengers protecting proteins from the damaging effect of reactive oxygen species produced during the formation of AGEs.     

Antimicrobial effects of esters and amides of 3-(5-nitro-2-furyl)acrylic acid

The effect of 18 newly synthesized esters and amides of 3-(5-nitro-2-furyl)acrylic acid on bacteria (Escherichia coli, Staphylococcus aureus), yeasts (Saccharomyces cerevisiae, Candida albicans), molds (Aspergillus niger, Penicillium cyclopium, Rhizopus oryzae) and algae (Chlorella pyrenoidosa, Euglena gracilis, Scenedesmus obliquus) was investigated. The MIC values revealed antimycotic, antialgal and antibacterial activity of the studied derivates. The antimycotic activity was found to decrease with increasing the length of the alkyl chain of esters and after introduction of amino nitrogen into the furylethylene backbone. The inhibitory effect on growth is caused by blocking bioenergetic processes, glycolysis in particular.     

Inhibitory effects of some long-chain unsaturated fatty acids on mitochondrial beta-oxidation. Effects of streptozotocin-induced diabetes on mitochondrial beta-oxidation of polyunsaturated fatty acids.

Evidence showing that some unsaturated fatty acids, and in particular docosahexaenoic acid, can be powerful inhibitors of mitochondrial beta-oxidation is presented. This inhibitory property is, however, also observed with the cis- and trans-isomers of the C18:1(16) acid. Hence it is probably the position of the double bond(s), and not the degree of unsaturation, which confers the inhibitory property. It is suggested that the inhibitory effect is caused by accumulation of 2,4-di- or 2,4,7-tri-enoyl-CoA esters in the mitochondrial matrix. This has previously been shown to occur with these fatty acids, in particular when the supply of NADPH was limiting 2,4-dienoyl-CoA reductase (EC 1.3.1.-) activity [Hiltunen, Osmundsen & Bremer (1983) Biochim. Biophys. Acta 752, 223-232]. Liver mitochondria from streptozotocin-diabetic rats showed an increased ability to beta-oxidize 2,4-dienoyl-CoA-requiring acylcarnitines. Docosahexaenoylcarnitine was also found to be less inhibitory at lower concentrations with incubation under coupled conditions. With uncoupling conditions there was little difference between mitochondria from normal and diabetic rats in these respects. This correlates with a 5-fold stimulation of 2,4-dienoyl-CoA reductase activity found in mitochondria from streptozotocin-diabetic rats.     

Inhibitory effects of D-amino acids on Staphylococcus aureus biofilm development

Biofilms are communities of cells held together by a self-produced extracellular matrix typically consisting of protein, exopolysaccharide, and often DNA. A natural signal for biofilm disassembly in Bacillus subtilis is certain D-amino acids, which are incorporated into the peptidoglycan and trigger the release of the protein component of the matrix. D-amino acids also prevent biofilm formation by the related Gram-positive bacterium Staphylococcus aureus. Here we employed fluorescence microscopy and confocal laser scanning microscopy to investigate how D-amino acids prevent biofilm formation by S. aureus. We report that biofilm formation takes place in two stages, initial attachment to surfaces, resulting in small foci, and the subsequent growth of the foci into large aggregates. D-amino acids did not prevent the initial surface attachment of cells but blocked the subsequent growth of the foci into larger assemblies of cells. Using protein- and polysaccharide-specific stains, we have shown that D-amino acids inhibited the accumulation of the protein component of the matrix but had little effect on exopolysaccharide production and localization within the biofilm. We conclude that D-amino acids act in an analogous manner to prevent biofilm development in B. subtilis and S. aureus. Finally, to investigate the potential utility of D-amino acids in preventing device-related infections, we have shown that surfaces impregnated with D-amino acids were effective in preventing biofilm growth.     

Early effects of illumination on the activity of some photosynthetic enzymes

Leaves of dark-grown corn (Zea mays) were illuminated for periods ranging from 3 minutes to 12 hours. The changes in the activities of ribose-5-phosphate isomerase, ribulose-5-phosphate kinase, and ribulose-1,5-diphosphate carboxylase were followed.

The activity of ribose-5-phosphate isomerase did not change significantly until between 12 and 24 hours of illumination. An increase in ribulose-5-phosphate kinase activity occurred after a lag of about 6 hours. The increase in carboxylase activity began after 3 minutes of illumination and increased until after 3 to 6 hours in the light, after which it began to decline. The increases in these enzymes appear to be the result of protein synthesis.

     

Iso-branched 2- and 3-hydroxy fatty acids as characteristic lipid constituents of some gliding bacteria.

The fatty acids present in the total hydrolysates of several gliding bacteria (Myxococcus fulvus, Stigmatella aurantiaca, Cytophaga johnsonae, Cytophaga sp. strain samoa and Flexibacter elegans) were analyzed by combined gas-liquid chromatography and mass spectrometry. In addition to 13-methyl-tetradecanoic acid, 15-methyl-hexadecanoic acid, hexadecanoic acid, and hexadecenoic acid, 2- and 3-hydroxy fatty acids comprised up to 50% of the total fatty acids. The majority was odd-numbered and iso-branched. Small amounts of even-numbered and unbranched fatty acids were also present. Whereas 2-hydroxy-15-methyl hexadecanoic acid was characteristic for myxobacteria, 2-hydroxy-13-methyl-tetradecanoic acid, 3-hydroxy-13-methyl-tetradecanoic acid, and 3-hydroxy-15-methyl-hexadecanoic acid were dominant in the Cytophaga-Flexibacter group.