Chemical composition of essential oils from different parts of Protium heptaphyllum (Aubl.) Marchand and their in vitro antibacterial activity

Abstract

In Brazilian folk medicine, Protium heptaphyllum is used to treat inflammatory conditions and to hasten wound repair. This paper aims to investigate the chemical composition and the in vitro antibacterial effects of the essential oils (EOs) obtained from P. heptaphyllum leaves and ripe and unripe fruits against a representative panel of oral pathogens. The GC-FID and GC-MS analysis revealed that the major components determined in P. heptaphyllum essential oils were myrcene (59.0%), β-elemene (17.2%), limonene (12.9%), spathulenol (12.6%), α-cubebene (11.6%), germacrene D (10.6%), trans-nerolidol (9.8%), and α-cadinol (8.8%). The essential oils of the ripe and unripe fruits showed the strongest antibacterial activity against the anaerobic bacteria Prevotella nigrescens (MIC?=?50?µg/mL). The leaf essential oil displayed very promising activity against Streptococcus mutans (MIC?=?50?µg/mL) and Streptococcus mitis (MIC?=?62.5?µg/mL). The antibacterial activity of EOs against oral pathogens is also described for the first time.

     

Derivatives of 7-Oxabicyclo[2.2.1 ]hept-5-ene and 7-Oxabicyclo[2.2.1 ] heptane. Synthesis,transformations, and stereochemistry using nmr methods

Synthesis and stereochemistry of various endo-2- and exo-2-substituted-7-oxabicyclo[2.2.1]-hept-5-enes and -heptanes are described. The nmr spectra of several derivatives are reported and discussed. Use is made of this data to allow determination of the stereochemical integrity of the system. Facile chromatographic separation methods were found for endo- and exo-2-sub-stituted-7-oxabicyclo[2.2.1 ]hept-5-enes and -heptanes.     

Fast chiral separations using sulfated beta-cyclodextrin and short-end injection in capillary electrophoresis

The general applicability of sulfated beta-cyclodextrin as chiral selector and short-end injection in capillary electrophoresis (CE) as a powerful screening tool for fast and efficient chiral separation of Ormeloxifene enantiomers and racemic Ormeloxifene analogues is demonstrated. Using the short-end injection procedure, all of the 16 racemic compounds studied were successfully separated with high efficiencies and with analysis times of less than 1.2 min. Furthermore, long-end injections of eight analogues named C1-C8 afforded separations with extremely high efficiencies. A statistical evaluation of the resolution values obtained in short-end and long-end injections of compounds C1-C8 showed that the sensitivity of the CE method towards structural changes in the studied molecules is intact when the chiral analysis is performed with short-end injection compared to conventional long-end injection.     

Practical enantioselective synthesis of beta-substituted-beta-amino esters

[reaction: see text] A practical, large-scale synthesis of a beta-amino ester 1 was developed. A chiral imine derived from (S)-phenylglycinol and 3-trimethylsilylpropanal was coupled with the Reformatsky reagent 3 with high diastereoselectivity (de > 98%) to give (SS)-4a as the major isomer. The amino alcohol residue of the coupling product 4 was oxidatively cleaved with sodium periodate in the presence of methylamine. An unusual selective oxidative cleavage of the (SS)-isomer was observed and the imine 6 was obtained with ee > 99% while the (RS)-4b isomer was not cleaved. Reaction with p-toluenesulfonic acid monohydrate allowed for the hydrolysis of the imine and the isolation of the amine as its salt. The title compound 1 was then obtained by transesterification, desilylation, and hydrochloride salt formation in a one-pot process. The method was successfully applied toward the synthesis of a wide variety of beta-amino esters.     

Shear and elongational flow behavior of acrylic thickener solutions

We investigate the effect of hydrophobic aggregation in alkali-swellable acrylic thickener solutions on shear and extensional flow properties at technically relevant polymer concentrations using the commercial thickener Sterocoll FD as model system. Apparent molecular weight of aggregates in water is M _w  ≈ 10⁸ g/mol and decreases by more than an order of magnitude in ethanol. Zero shear viscosity η ₀ is low and shear thinning is weak compared to the high molecular weight of the aggregates. Linear viscoelastic relaxation is described by the Zimm theory up to frequencies of 10⁴ rad/s, demonstrating that no entanglements are present in these solutions. This is further supported by the concentration dependence of η ₀ and is attributed to strong association within the aggregates. Extensional flow behavior is characterized using the capillary break-up extensional rheometry technique including high-speed imaging. Solutions with ϕ ≥ 1% undergo uniform deformation and show pronounced strain hardening up to large Hencky strains. Elongational relaxation times are more than one order of magnitude lower than the longest shear relaxation times, suggesting that aggregates cannot withstand strong flows and do not contribute to the elongational viscosity.

Realization of a time-domain Fresnel lens with coherent control

Perturbative chirped pulse excitation leads to oscillations of the excited state amplitude. These coherent transients are governed by interferences between resonant and off-resonant contributions. Control mechanisms in both frequency and time domain are used to modify these dynamics. First, by applying a phase step in the spectrum, we manipulate the phase of the oscillations. By direct analogy with Fresnel zone lenses, we then conceive highly phase-amplitude modulated pulse shapes that slice destructive interferences out of the excitation time structure and enhance the final population.     

Nucleon properties in a few mode bag — an effective approximation to QCD

The Hamiltonian of Quantum Chromodynamics is approximated by restricting the spatial dependencies of the quark-antiquark and gluon fields to a small number of modes (few-mode approximation). As a working hypothesis, we assume that the ground states of the dynamical sectors of the theory are automatically gauge invariant so that Gauss's law need not be strictly satisfied by a trial state. We derive and apply a method for explicit calculation of expectation values for wavefunctions in colour space depending on the twoSU (3) invariants acting as dynamical variables. An interacting ground state is constructed by a dynamical dressing transformation of the bare fermionic vacuum which may be regarded as a few-mode approximation to a quark-gluon (or mesonic) condensate. Based on this vacuum a nucleon state is formulated quite similar to the solition bag construction. Some of its effective properties are calculated by a variational calculation and comparison is made with experimental data as well as with other theoretical models of bag-type.