Order Ethyl Acetate Research Articles

Antioxidant activity from the stem bark of Albizzia julibrissin.

The antioxidant activity of the stem bark from Albizzia julibrissin was evaluated for its potential to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, to inhibit the generation of the hydroxyl radical (*OH), total reactive oxygen species (ROS) and to scavenge authentic peroxynitrites (ONOO-). The methanol extract of A. julibrissin exhibited strong antioxidant activity in the tested model systems. Therefore, it was further fractionated using several solvents. The antioxidant activity of the individual fractions were in the order of ethyl acetate (EtOAc) > n-butanol (n-BuOH) > dichloromethane (CH2Cl2) > and water (H2O). The ethyl acetate soluble fraction, which exhibited strong antioxidant activity, was further purified by repeated silicagel, Sephadex LH-20 and RP-18 gel column chromatography. Sulfuretin (1) and 3',4',7-trihydroxyflavone (2) were isolated as the active principles. Compounds 1 and 2 exhibited good activity in all tested model systems. Compound 1 exhibited five times more inhibitory activity on the total ROS than Trolox. Compound 2 showed six times stronger DPPH radical scavenging activity than L-ascorbic acid. These results show the possible antioxidant activity of the A. julibrissin crude extract and its major constituents.

In vitro peroxynitrite scavenging activity of diarylheptanoids from Curcuma longa.

Peroxynitrite is a cytotoxic intermediate produced by the reaction between the superoxide anion (O(2)) and nitric oxide (NO). The aim of this study was to investigate the scavenging effects of Curcuma longa L. on authentic peroxynitrite, and further studies are planned that will attempt to identify the active principles from the active fractions. The methanolic extract of C. longa showed 50% scavenging activity (IC(50)) at concentration of 1.7 +/- 0.08 micro g/ml, and was thus fractionated with several solvents. The peroxynitrite scavenging activity potential of the individual fraction was in the order of ethyl acetate > dichloromethane > water fraction. The ethyl acetate soluble fraction exhibiting strong scavenging activity was further purified by repeated silica gel column chromatography. Peroxynitrite scavenging diarylheptanoids, curcumin I (1), curcumin II (2), and curcumin III (3) were isolated as active principles. Compounds 1-3 showed the peroxynitrite scavenging activities with IC(50) values of 4.0 +/- 0.04, 6.4 +/- 0.30, and 29.7 +/- 1.29 micro M, respectively. Penicillamine as positive control exhibited IC(50) value of 2.38 +/- 0.34 micro M. The structure-activity relationship of diarylheptanoids on peroxynitrite was also discussed.

Valorisation of waste fractions from autohydrolysis of selected lignocellulosic materials

AbstractNon‐isothermal processing of lignocellulosic materials in aqueous media (autohydrolysis reaction) under mild conditions leads to solutions containing valuable chemicals (oligosaccharides, sugars and acetic acid) and other, undesired, compounds (belonging to the extractive and acid‐soluble lignin fractions) which have to be removed in further purification treatments. Liquors obtained by non‐isothermal autohydrolysis of Eucalyptus globulus wood and corncobs under a variety of operational conditions were extracted with ethyl acetate in order to remove non‐saccharide components, and the suitability of the fraction dissolved in the organic phase was assayed for possible utilisation as an antioxidant. The yield and antioxidant activity of ethyl acetate extracts (measured by the α,α‐diphenyl‐β‐picrylhydrazyl (DPPH) radical scavenging capacity) showed a strong dependence on the autohydrolysis conditions. The antioxidant activity of extracts obtained under selected operational conditions compared well with synthetic antioxidants.© 2003 Society of Chemical Industry

Extraction of phenolic compounds from red grape marc for use as food lipid antioxidants

Grape marc resulting from red winemaking was extracted with a mixture of ethyl acetate and water in order to obtain its phenolic compounds with a view to their use as food lipid antioxidants. Crushed and uncrushed marcs were extracted for 5, 10, 20 and 30 min in order to determine the minimum time required for ensuring maximal extraction of phenols. The results reveal a higher extraction of these compounds by the ethyl acetate acting on crushed marc, so the cost of this last operation can be largely compensated. The antioxidant lipid activity of the phenolic compounds of this extract was determined by using the Rancimat method on refined olive oil, and compared with the induction periods of BHT, BHA, propyl gallate and pure standards of those phenols identified in the above mentioned organic extract. In this test, the phenols of the extract show a lower antioxidant activity than the synthetic food antioxidants, although close to that of BHT, mostly as a result of its catechin content. ©

Modified pulsed-field gradient NMR experiments for improved selectivity in the measurement of diffusion coefficients in complex mixtures: application to the analysis of the Suwannee River fulvic acid.

To simplify the complex 1H NMR spectrum of a fulvic acid sample and gain structural and molecular size information, spectral editing techniques were used in conjunction with a general PFG NMR pulse sequence. These editing techniques exploit differences in T1 and T2 relaxation times as well as differences in coupling constants. The experiments were initially performed on a model mixture of glutamic acid and ethyl acetate in order to validate the method as a technique for measurement of diffusion coefficients. The editing experiments were then applied to the International Humic Substances Society Suwannee River fulvic acid standard. These editing techniques allowed more selective measurement of diffusion coefficients for broad classes of components within regions of the 1H NMR spectrum of the fulvic acid solution. The average radii of gyration calculated for the Suwannee River fulvic acid sample from the diffusion coefficients are in good agreement with literature values.

Chlorogenic acid, an antioxidant principle from the aerial parts ofArtemisia iwayomogi that acts on 1,1-diphenyl-2-picrylhydrazyl radical

The antioxidant activity ofArtemisia iwayomogi was determined by measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical The methanol extract ofA. iwayomogi showed strong antioxidant activity, and thus fractionated with several solvents. The antioxidant activity potential of the individual fraction was in the order of ethyl acetate>n-butanol>water>chloroform>n-hexane fraction. The ethyl acetate andn-butanol soluble fractions exhibiting strong antioxidant activity were further purified by repeated silica gel and Sephadex LH-20 column chromatography. Antioxidant chlorogenic acid was isolated as one of the active principles from then-butanol fraction, together with the inactive components, 1-octacosanol, scopoletin, scopolin, apigenin 7,4'-di-O-methylether luteolin 6,3'-di-O-methylether (jaceosidin), apigenin 7-methylether (genkwanin), 2,4-dihydroxy-6-methoxyacetophenone 4-O-beta-D-glucopyranoside and quebrachitol. The antioxidant activity of chlorogenic acid was comparable to that of L-ascorbic acid, which is a well known antioxidant.

The antioxidant activity ofEcklonia stolonifera

The antioxidant activity ofEcklonia stolonifera was determined by measuring lipid peroxide produced when a mouse liver homogenate was exposed to the air at 37°C, using 2-thiobarbituric acid (TBA) and the radical scavenging effect on 1,2-diphenyl-2-picrylhydrazyl (DPPH) radical. The methanol extract ofEcklonia stolonifera showed strong antioxidant activity. And the methanol extract was fractionated with several solvents. With regard their fractions, the antioxidative activity were in the order of ethyl acetate>dichloromethane insoluble intermediated phase>dichloromethane>n-butanol>water fraction. The ethyl acetate soluble fraction exhibiting the strongest antioxidant activity was further purified by repeated silica gel and Sephadex LH-20 column chromatography. Antioxidant phloroglucinol was isolated and identified by1H-NMR and13C-NMR. Its antioxidant activity was similar to that of L-ascorbic acid.

Study of iridaceae plants with the capability to induce differentiation of HL-60 promyelocytic leukemia cells

Thirteen species of Iridaceae plants were studied with the capability to induce HL-60 promyelocytic leukemia cells into macrophages. The neutrophil stimulating activity in these plants was also examined by measuring superoxide production. Both activities are known to be possessed by tumor promoters such as 12-O-tetradecanoylphorbol-13-acetate (TPA). Dried parts of Iridaceae plants were extracted with methanol. Then, each extract was added to a culture medium of HL-60 cells and cultured for two days. A morphological change of the cells from suspended to adherent state, which was reported to occur in the process of differentiation, was observed. Nine species, most of which belong to the Iris genus, had the activity to cause cell adhesion. Each of the cell adhesion-positive extract was applied to a silica gel column and eluted with chloroform, ethyl acetate and methanol in order. The activity was recovered only in the ethyl acetate eluate in all the cases. Those partially purified fractions also activated superoxide generation of neutrophils. When ethyl acetate fractions of Iris tectorum and Iris japonica were analyzed by HPLC, three active peaks different from TPA and teleocidins in UV spectra were detected. From these results, it was suggested that several plants of Iridaceae may contain TPA-type and yet structurally-different tumor promoters.

Anoectochilus formosanus Hay. Contains substances that affect arachidonic acid metabolism

AbstractThe whole plant of Anoectochilus formosanus Hay. was extracted with hot water, and the aqueous solution was re‐extracted with ethyl acetate in order to study the effects on thromboxane A2 (TXA2) production in rabbit platelets and prostacyclin (PGI2) production in bovine aortic tissues. Inhibition of TXA2 production, using either arachidonic acid (AA) or PGH2 as precursors, was manifested on incubation of platelets with the crude water extraction, and the ethyl acetate extraction of A. formosanus Hay., respectively; the inhibitory effects were concentration‐dependent. Incubation of platelets with the aqueous remainder caused activation of TXA2 production, using AA as the precursor, but there was no effect on TXA2 production using PGH2 as the precursor. With the AA precursor, there was activation of PGI2 production on incubation of aortic tissues with both crude water extraction and aqueous remainder of A. formosanus Hay., but not with ethyl acetate extraction, and the activating effects were also concentration‐dependent. No effect on PGI2 production was observed on incubation with PGH2 as the precursor. These results suggest that A. formosanus Hay. contains at least two different components affecting TXA2 production in platelets, and PGI2 production in aortic endothelium, respectively, and these effects might play important roles in the pharmacological effects of A. formosanus Hay.

Catalytic hydrogenolysis of esters: a comparative study of the reactions of simple formates and acetates over copper on silica

Previous studies of the gas phase hydrogenolysis of simple esters on a copper-on-silica catalyst have indicated differences in the kinetics and mechanism of formate hydrogenolysis as compared to the reaction of larger esters. The present studies have focused on the reaction of methyl and ethyl formate compared to that of methyl and ethyl acetate in order to quantify these differences. Formates are found to react some 1000 times faster than acetates. The detailed kinetics of formate and acetate hydrogenolysis have been measured and the results correlated with predictions of Langmuir-Hinshelwood models. Experiments with deuterium have been used to explore the mechanisms of the reactions. The results suggest that acetate hydrogenolysis proceeds via dissociative adsorption of ester followed by slow hydrogenation of the acetyl fragment so formed. Formates, on the other hand, appear to involve the reaction of undissociated ester molecules with hydrogen. The latter reaction is controlled, at least in part, by the packing density of formates on the active surface.

Uptake of highly soluble gases in the epithelium of the conducting airways.

Short duration washin and washout experiments were carried out with the gases ether (diethyl ether), ethyl acetate and acetone in order to study the excretion behaviour in the lung of gases highly soluble in blood and tissues. Carbon dioxide (CO2) was analyzed as a reference gas during the washout. The excretion values for acetone were generally the lowest, those for ether the highest, and intermediate ones were obtained for ethyl acetate. These results are in accord with the experimental data of others. Analysis of the washout curves shows that for acetone the volume of gas expired before the beginning of phase II is considerably smaller than found for CO2 and ether. During washout, the slope of the alveolar plateau for acetone is negative for the first few breaths and becomes positive thereafter; however, it remains lower than the slopes for CO2 and ether, which are always positive. These two phenomena occurring during washout clearly demonstrate that the acetone in the expired air must originate from the epithelial tissue lining the conducting airways. We conclude, therefore, that, in terms of gas transport, the conducting airways behave differently for poorly and highly soluble gases and this provides a physiological basis for the deviating excretion behaviour of highly soluble gases.

Extraction of mercury(II) from chloride solutions by ethyl acetate

Studies on the extraction of mercury(II) halides are of considerable interest and importance in the field of pollution control and also of speciation in marine environment. Little [1, 3] is known about mercury(II) extraction from chloride media. The authors have, therefore, taken up a detailed investigation using the radio tracer technique on the extraction of Hg(II) from chloride media into ethyl acetate in order to establish the nature of the extracted species.

Dilute solution properties of styrene–acrylonitrile and styrene–methyl methacrylate copolymers. I. Intrinsic viscosity–molecular weight relations

AbstractStyrene–acrylonitrile (St–AN) copolymers of three compositions—27.4 mole‐% (SA1); 38.5 mole‐% (SA2); and 47.5 mole‐% (SA3) acrylonitrile—and styrene–methyl methacrylate (St–MMA) copolymer (SM) of 46.5 mole‐% methyl methacrylate were prepared by bulk polymerization at 60°C with benzoyl peroxide as the initiator, and were then fractionated. The molecular weights of unfractionated and fractionated samples were determined by light scattering in a number of solvents. The [η] versus M̄w relations at 30°C were established for SA1, SA2, SM, and polystyrene (PSt) in ethyl acetate (EAc), dimethyl formamide (DMF), and γ‐butyrolactone (γ‐BL), and for SA3 in methyl ethyl ketone (MEK), DMF, and γ‐BL. Second virial coefficients A2 and the Huggins constant were determined. From values of A2 and the exponent a of the Mark–Houwink relation it is seen that the solvent power for samples SA1, SA2, and PSt is in the order EAc < γ‐BL < DMF, while for sample SA3 the solvent power is in the order MEK < γ‐BL < DMF. The solvent power decreases with an increase in AN content. The solvent power of the three solvents used for SM copolymer sample is practically the same within experimental errors. From the a values it is concluded that in a given solvent the copolymer chains are more extended than the corresponding homopolymers.

GAS CHROMATOGRAPHIC DETERMINATION OF TYROSOL AND TRYPTOPHOL IN WINES AND BEERS

A gas chromatographic method for the determination of tyrosol and tryptophol in wines and beers has been developed. The aromatic fusel alcohols are extracted with ether or ethyl acetate from a sample made alkaline with Na2CO3 and saturated with NaCl. In beer determinations the extraction is performed with ethyl acetate in order to avoid complications caused by emulsion. Most of the solvent is removed by distillation and the rest is cautiously allowed to evaporate. The gas chromatographic determination of tyrosol and tryptophol is performed in a 0·5-m. Apiezon M-DEGS column at 190°C. According to the infra-red spectra, both components are eluted without being decomposed at this temperature. In the grape wines investigated, tyrosol was found in amounts of 10–40 mg. per litre, in two Finnish berry wines 10–15 mg. per litre and in two different types of pale lager beers 5–10 mg. per litre. The same samples contained about 1–4 mg. tryptophol per litre. The two white grape wines and one red berry wine were exceptional, with only 0·2–0·3 mg. tryptophol per litre.