Lipid length and iso-branching of trehalose diesters influences Mincle agonist activity

We report on the efficient synthesis of linear trehalose diesters (TDEs) and iso-branched TDEs (maradolipids or iso-TDEs) and their ability to activate bone marrow-derived macrophages (BMDMs) as determined by cytokine (IL-1β, IL-12, IL-6, IL-10) and chemokine (MIP-2) production. Both classes of TDEs were found to activate BMDMs in a Mincle-dependent manner, with longer-chain (≥C18) lipids leading to a robust inflammatory response. On the whole, the iso-branched TDEs led to greater cytokine production and a faster immune response when compared to their linear counterparts. Moreover, C12-TDE and iso-C12-TDE elicited the production of MIP-2 by BMDMs, thereby providing the first example of TDEs with a chain length of ≤ C12 leading to a Mincle-dependent immune response and one that is less inflammatory in nature.     

Herbicidal activity of pure compound isolated from rhizosphere inhabiting Aspergillus flavus

In the quest for bioactive natural products of fungal origin, Aspergillus flavus was isolated from rhizosphere of Mentha piperita using Potato Dextrose Agar (PDA) and Czapec Yeast Broth (CYB) nutrient media for metabolites production. In total, three different metabolites were purified using HPLC/LCMS and the structures were established using 500 Varian NMR experiments. Further the isolated metabolites in different concentrations (10, 100, 1000 μg/mL) were tested for herbicidal activity using Completely Randomized design (CRD) against the seeds of Silybum marianum and Avena fatua which are major threats to wheat crop in Pakistan. Among the isolated metabolites, one compound was found active against the test weed species whose activity is reported in the present work. The chemical name of the compound is 2-(1, 4-dihydroxybutan-2-yl)-1, 3-dihydroxy-6, 8-dimethoxyanthracene-9, 10(4aH, 9aH)-dione with mass of 388. Results showed that all seeds germinated in control treatment; however, with the metabolite treated, the growth was retarded to different levels in all parts of the weeds. At a dose of 1000 μg/mL of the pure compound, 100% seeds of S. marianum and 60% seeds of A. fatua were inhibited. Interestingly, the pure compound exhibited less inhibition of 10% towards the seeds of common wheat (Triticum aestivum).     

Kinetics and electrochemical studies on superoxide

Rate constants for the reaction of superoxide O^- ₂ with various substrates were obtained through stationary electrode polarography theory and technique. In solvent acetonitrile, the substrate and the rate constants of the reaction O^- ₂ + AH^{- k2}Product, are, AH = isopropanol (k₂ < 0.01 M^-1 s^-1); ethanol (k₂ = 1.42 × 10² M^-1 s^-1); methanol (k₂ = 1.1 × 10⁷ M^-1 s^-1), H₂O (k₂ = 1.0 × 10⁵ M^-1 s^-1). In MeCN, O^-2 was found to be rather unreactive towards glucose and acetone but it reacts with fructose and sucrose catalytically. However, in DMF2, O^- ₂reacts with glucose and fructose with k2 order of 105 M-1 s-1. The mechanism of the reaction of O^- ₂ with the substrates (AH) is proposed as O^- ₃ + AH k₂O, AH^k2 _k-1 k [O₂H + AH]^-, _k-2O₂H + A^- with k₁ = 10⁹ M^-1 s^-1 and k^-1 = 10⁸ -10⁹ s^-1. With these values of k_-1 and k₁, k k₂(obs). The reversible E_1/2 for O₂ + e O^- ₂ in various solvents: MeCN, acetone, isopropanol, methanol, H₂O were obtained either directly from the reversible voltammogram or from experimental voltammograms and the rate constants obtained (as above) using stationary electrode polargraphy theory; E_1/2 being -0.82 (MeCN),-0.85 (acetone),-0.72 (isopropanol);-0.66 (MeOH),-0.56 (H2O) vs SCE.     

Effects of Nonionic and Mixed Cationic-Nonionic Micelles on the Rate of Alkaline Hydrolysis of 4-Nitrophthalimide

Pseudo-first-order rate constants (k_obs) for alkaline hydrolysis of 4-nitrophthalimide show a monotonic decrease with increase in [C₁₂E₂₃]_T (total concentration of Brij 35) at constant [CH₃CN] and [NaOH]. This micellar effect is explained in terms of a pseudophase micelle model. The rate of hydrolysis becomes too slow to monitor at [C₁₂E₂₃]_T≥0.03 M in the absence of cetyltrimethylammonium bromide (CTABr) and at [C₁₂E₂₃]_T≥0.04 M in the presence of 0.006–0.02 M CTABr at 0.01 M NaOH. The plots of k_obs versus [C₁₂E₂₃]_T show minima at 0.006 and 0.01 M CTABr, while such a minimum is not visible at 0.02 M CTABr.     

A convergent strategy for the synthesis of beta-carba-galacto-disaccharides

[reaction in text] A convergent strategy for the synthesis of beta-carba-galacto-disaccharides is illustrated by the preparation of 1 and 4, from a central "glycone" component 22, and the corresponding "aglycone" segments, monosaccharide alcohols, 23a or 23b. The key step is the formation of the carbasugar ring via an oxocarbenium ion-enol ether cyclization.     

Trojanosides I-K: new cycloartane-type glycosides from the aerial parts of Astragalus trojanus.

Three new cycloartane-type triterpene glycosides have been isolated from the aerial parts of Astragalus trojanus. The structures were established mainly by a combination of one- and two-dimensional NMR techniques [1H-1H-correlation spectroscopy (COSY), 1H-13C-heteronuclear multiple quantum correlation spectroscopy (HMQC), and 1H-13C-heteronuclear multiple-bond correlation spectroscopy (HMBC)] and high resolution electrospray ionization mass spectrometry (HR-ESI-MS) as 3-O-beta-(2',3'-di-O-acetyl)-D-xylopyranosyl-6-O-beta-D-glucopyranosyl-16-O- acetoxy-20(R),24(S)-epoxycycloartane-3beta,6alpha,16beta,25-tetrol, 3-0-[alpha-L-rhamnopyranosyl-(1-->2)-beta-(3',4'-di-O-acetyl)-D-xylopyranosyll-6-O-beta-D-xylopyranosyl-20(R),24(S)-epoxycycloartane-3p,6alpha,16beta,25-tetrol, 3-O-beta-D-xylopyranosyl-6,16-di-O-beta-D-glucopyranosyl-20(R)24(S)-epoxycycloartane-3beta,6alpha,16beta,25-tetrol.     

Cohirsine - a novel isoquinolone alkaloid from

A novel alkaloid, cohirsine (1) was isolated from . Its structure has been investigated by extensive NMR studies including 2D NMR experiments. Its stereochemistry has been determined by 2D NOESY and NOE difference measurements.     

Oxidation of triethylamine by molecular oxygen catalyzed by Ru(III)-ion

The kinetics of Ru(III) catalyzed oxidation of triethylamine by molecular oxygen has been investigated in the pH range 1.5 to 2.5 at 35°C and I=0.1 M KCl. The reaction is first order with respect to substrate, catalyst and molecular oxygen concentrations. The rate of the reaction increases with the increase of pH from 1.5 to 2.5 and then there is a slight decrease in the rate above pH 2.5. Based on the kinetic data, a mechanism for the catalytic oxidation of triethylamine is proposed. The major products in the oxidation of triethylamine are the N-oxide, diethylamine and acetaldehyde.

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, Ru(III), pH=1,5+2,5 35°C I=0,1M KCl. , . pH 1,5 2,5, pH 2,5. , . N-, .

     

Kinetics of anation of chromium(III) by L-phenylalanine

Summary The kinetics of anation of chromium(III) species, [Cr(H₂O)₆]⁴⁺ and [Cr(H₂O)₅OH]²⁺, by L-phenylalanine in aqueous acid has been studied spectrophotometrically. Effects of varying [substrate], [ligand], [H⁺], , % ethanol and temperature were investigated. The kinetic data suggest a mechanism where outersphere-associations [between chromium(III) species and phenylalanine in the zwitterionic form] precede anation. Comparison of the results with published data suggest an I_a path for the [Cr(H₂O)₆]³⁺ reaction and I_d path for the [Cr(H₂O)₅OH]²⁺ reaction.