Ethyl acetate

Abstract: Antioxidant-rich fractions were extracted from grape seeds (Vitis vinifera) using various solvents, such as acetone, ethyl acetate, methanol and mixtures of different solvents, such as ethyl acetate (EtOAc) and water in 9:1, 17:3 and 4:1 ratios. The antioxidant activity of the extracts was evaluated using a β-carotene-linoleate model system and linoleic acid peroxidation method. At 100 ppm concentration, various extracts showed 65–90% antioxidant activity. Mixtures of EtOAc and water at different concentrations exhibited more antioxidant activity than other extracts. These extracts also showed good reducing power, at 500 μg/ml concentration, by the potassium ferricyanide reduction method. Grape seed extracts may be exploitable for the preservation of food products as well as for health supplements and nutraceuticals.

Abstract: The kinetics of photooxidation to CO2 of 22 organic solutes over a UV illuminated film of Degussa P25 titanium dioxide have been studied over a 100-fold concentration range for each solute, generally from about 1 to 100 mg liter−1. The dependence of the photooxidation rate on concentration obeyed a simple two-coefficient Langmuir expression for each solute. The coefficients reflecting the degree of adsorption on the TiO2 and the limiting rate at high concentrations enable the prediction of photocatalytic rates in any TiO2-based photoreactor of a similar type once a reference rate has been determined for one of the solutes. A reaction mechanism is proposed for the oxidation of aromatic compounds involving peroxyhydroxycyclohexadienyl- and mucondialde-hyde-type compounds as important intermediates. The solutes studied were benzoic acid, salicylic acid, phenol, biphthalate, 2-chlorophenol, 4-chlorophenol, monochlorobenzene, nitrobenzene, methanol, ethanol, n-propanol, 2-propanol, acetone, ethyl acetate, acetic acid, formic acid, sucrose, 2-naphthol, umbelliferone, chloroform, trichloroethylene, and dichloroethane.

Abstract: A high-performance liquid chromatographic (HPLC) method is developed for the determination of the pharmacologically active terpenoids Ginkgolide A, B, and C and bilobalide in Ginkgo biloba L. leaves extract (GBE). The extracts are dissolved in methanol-water (1:4) and extracted by ethyl acetate after evaporation of the organic solvent, the residue is dissolved in methanol, and the terpenoids in the resultant solution are determined by means of HPLC on a C 1 8 column with methanol-water (23:77) as an eluent. The recovery provided by the method is above 96.5%, and the minimum concentration that can be determined is 80 μg of terpenoid per gram of GBE. The method is suitable for GBE production process control.

Abstract: We explored the application of three different aqueous solutions derived from Black Tea leaf extracts in the synthesis of Au and Ag nanoparticles. The plain tea leaf broth, as well as that containing the ethyl acetate extract of tea leaves, were found to be extremely efficient, leading to rapid formation of stable nanoparticles of various shapes: spheres, trapezoids, prisms and rods. For a given metal ion precursor, the kinetics of particle synthesis were remarkably similar in these two solutions, as evidenced from their absorption spectroscopy monitored over time. Moreover, they exhibited similar redox behavior. In contrast, with the other solution, containing the dichloromethane (CH2Cl2) extract of tea leaves, we failed to detect any nanoparticle generation under similar reaction conditions. Our results suggest that the reduction of metal ions and stabilization of the resultant particles in the first two solutions involved the same class of biomolecules. We identified these biomolecules as the tea polyphenols, including flavonoids, which were present in comparable amounts in both the tea leaf broth and ethyl acetate extract, but are absent in the CH2Cl2 extract of tea leaves. The efficiency of the tea leaf extracts towards Au and Ag nanoparticle synthesis were compared with that of a naturally occurring hydroxyflavonoid, quercetin.

Abstract: Seven different extracts, fractions and residues of Navel sweet orange (Citrus sinensis) peel were evaluated for their radical scavenging activity by the DPPH and luminol induced chemiluminescence methods Also, the Folin–Ciocalteu method was used to determine the total phenolic content High phenolic content and radical scavenging activities were found for the ethyl acetate fraction Comparison was made with reference compounds, Trolox, ascorbic acid, quercetin, which are already known for their good antioxidant activity The radical scavenging activity of the ethyl acetate fraction approached the activity of the standards Total phenolic content showed a small relation with radical scavenging activity The radical scavenging activity examined with the DPPH method correlated well to values obtained by chemiluminescence The antioxidant activity found in the fractions of Citrus sinensis, should be attributed to the presence of flavonoids and other phenolic compounds Among the various classes of flavonoids: flavanone glycosides, flavones and flavonols seem to prevail as indicated by two dimensional thin layer chromatography and color reactions This information shows that ethyl acetate fraction of navel sweet orange peel can be used as antioxidant in food and medicinal preparations