Ethanol extracting solvent, antioxidant

Although it is known that DPPH is more soluble in organic solvents, sometimes the modification of the solvent is necessary to solubilize the sample. This can often result in precipitation or degradation of DPPH, and then a study of the stability of DPPH in the solvent used for sample dissolution is necessary. Food samples can be extracted using different solvents. The type of solvent influences the properties of the antioxidants thus, polar solvents (such as methanol and ethanol) extract hydrophilic antioxidants, whereas less polar solvents (such as chloroform or ethyl acetate) extract lipophilic antioxidants. 

Traditionally, polymer dissolution by refiuxing of a polymer in toluene, followed by precipitation of the polymer by another solvent, e.g. ethanol, has been used for the extraction of antioxidants [61], although the method is... 

In a previous work, we studied the possibility of extracting antioxidants from microalgae Spirulina platensis using ASE with different solvents (33-34). Likewise, other authors have studied the carotenoids extraction from microalgae Haematococcus pluvialis and Dunaliella salina using ethanol as solvent and ASE (35). 

In the present work an attempt has been made to optimize the parameters related to the extraction of antioxidants (with ASE) from Spirulina platensis using only environmentally clean solvents such as water, ethanol and mixtures. Thus, as a first approach, a study about different sample pre-treatments and how these affect both, the extraction yield and the final antioxidant activity has been performed. Moreover, a relationship between the efficient concentration (ECso) and the final composition of the solvent (as a function of the dielectric constant) has been studied and a preliminary characterization of the chemical composition of one of the best antioxidant extract has been done using an optimised CE-DAD method. 

SFE is widely used for the extraction of phenolic compounds from grapes or derivatives [48,67,68] (Table 16.4). Furthermore, this technique has been applied in other matrices such as pepper, tomato, and eggplant by Helmja et al., who compared SFE and UAE. This study indicated that SFE provided the poorest results in ctxnparison with the data obtained by UAE [28]. SFE was also compared with traditional techniques such as Soxhlet extraction using ethyl acetate and ethanol as solvents in guava The best results, in terms of extraction yield (total and fraction) and product quality (antioxidant activity and total phenolic content), were obtained when SFE was tqrplied using ethanol as an organic modifier [66]. The effect of pressure and temperature on the SFE was also evaluated, observing that the most appropriate conditions for the extraction of phenolic compounds was an extraction temperature of 60°C and pressure of 102 bar [66]. 

To circumvent interference from the extending oil, no internal chromatographic standard was used to check response. Polymer standards were prepared. These were made by incorporating the oil and antioxidant into unstabilised polybutadiene or styrene-butadiene resin cement at typical levels of concentration. These preparations were then air-dried to a dry polymer condition. For analytical purposes, 10.0 0.01 gram of polymer were ethanol extracted in a Soxhlet apparatus using 165 ml of solvent for 16 hours. The extract solution was then concentrated to about 10 ml volume and taken up in the appropriate solvent to a 50 ml volume and used for chromatographic analysis of the antioxidant. 

A number of experiments were performed to evaluate in vitro total antioxidant status of fruit juices, wines, olive oils, and various aqueous or organic food extracts [33-39]. For example, the ABTS radical-scavenging capacity of various solvent extracts of ginseng leaves with various concentrations was evaluated [35]. The ABTS radical-scavenging activity of ethanol extracts from ginseng leaves was found to be significantly higher than for their water extracts. 

Despite these negative attributes, there are opportunities for these phenolic compounds to be extracted using pure or aqueous solvents like ethanol to be further utilized as natural antioxidants. Studies showed that the extracts obtained from the oilseed residues displayed remarkable antioxidant activity, the extent of which depends on the type of residue and the solvent used for the extraction (Amarowicz et al 2000). Wanasundara et al. (1994) reported that the best antioxidant activity was exhibited by a fraction of canola meal phenolics that contained only 34 mg of phenolic compounds/g of sample. On the other hand, Amarowicz et al. (1996) observed that the antioxidant activity of ethanolic extracts of mustard correlated well with the total content of phenolic... 

Pino and co-workers [9] carried out a comparative study of chromatographic and colorimetric methods for the identification of phenolic antioxidants in edible fats. They found that the best solvent for extracting the antioxidants from the oil is acetonitrile saturated with light petroleum (bp 40 to 60 °C). The best separation was obtained on layers of polyamide powder with light petroleum - benzene - acetic acid - dimethylformamide (40 40 20 1) as solvent. For locating the spots, 0.5% ethanolic 2,5-dichloro-p-benzoquinonechlorimine was used. 

Plant extracts containing xanthophyll diesters are saponified in composition of propylene glycol and aqueous alkali to form crystals crystallization of xanthophylls is achieved without use of organic solvents crystals are isolated and purified Xanthophylls obtained from corn gluten meal at 50 C using ethanol with ethoxyquin as antioxidant... 

Lussier [71] has given an overview of Uniroyal Chemical s approach to the analysis of compounded elastomers (Scheme 2.2). Uncured compounds are first extracted with ethanol to remove oils for subsequent analysis, whereas cured compounds are best extracted with ETA (ethanol/toluene azeotrope). Uncured compounds are then dissolved in a low-boiling solvent (chloroform, toluene), and filler and CB are removed by filtration. When the compound is cured, extended treatment in o-dichlorobenzene (ODCB) (b.p. 180 °C) will usually suffice to dissolve enough polymer to allow its separation from filler and CB via hot filtration. Polymer identification was based on IR spectroscopy (key role), CB analysis followed ASTM D 297, filler analysis (after direct ashing at 550-600 °C in air) by means of IR, AAS and XRD. Antioxidant analysis proceeded by IR examination of the nonpolymer ethanol or ETA organic extracts. For unknown AO systems (preparative) TLC was used with IR, NMR or MS identification. Alternatively GC-MS was applied directly to the preparative TLC eluent. 

A multiwavelength approach might have been considered as an alternative to chemical derivatisation. Ruddle and Wilson [62] reported UV characterisation of PE extracts of three antioxidants (Topanol OC, Ionox 330 and Binox M), all with identical UV spectra and 7max = 277 nm, after reaction with nickel peroxide in alkaline ethanolic solutions, to induce marked differentiation in different solvents and allow positive identification. Nonionic surfactants of the type R0(CH2CH20) H were determined by UV spectrophotometry after derivatisation with tetrabromophenolphthalein ethyl ester potassium salt [34]. Magill and Becker [63] have described a rapid and sensitive spectrophotometric method to quantitate the peroxides present in the surfactants sorbitan monooleate and monostearate. The method, which relies on the peroxide conversion of iodide to iodine, works also for Polysorbate 60 and other surfactants and is more accurate than a titrimetric assay. 

Carotenoids should be extracted from tissues as rapidly as possible. If an immediate extraction is not possible, samples should be stored below — 18°C until required. For the extraction the exactly weighed sample and the solvent are transferred into a blender, where the sample is simultaneously grinded and extracted. Since fresh tissues contain a high percentage of water, and carotenoids are lipo-soluble, the first organic solvent must be miscible with water (e.g., acetone, ethanol, methanol). After one or two extraction steps, water-immiscible solvents (e.g., diethyl ether, benzene) can be applied. Dried materials may be also extracted with water-immiscible solvents, but carotenoid recovery is usually better if the tissue is first treated with a little water and then extracted with water-miscible solvents. Prior to the extraction of fruits the addition of antioxidants [e.g.,... 

Dapkevicius et al. (1998) compared yields and antioxidant activities of four different extracts from rosemary and sage leaves an acetone, a water extract (both from deodorized plant material), and an acetone and SFC C02 extract (both from nondeodorized plant material). The yields (g per kg dry matter) ranged from 50.2 for the SFC C02 to 90.8 for the water extract from deodorized plant material. High antioxidant activity was found for the SFC C02 and the acetone extracts, but low activity was determined for all water extracts. This emphasizes the importance of camosol and carnosic acid that are extracted from leaves with water-ethanol solvent... 

The highest antioxidant activity was found in those extracts that contain ethanol in their solvent composition. Moreover, the best antioxidant activity were achieved working with 90% and 100% ethanol and temperatures of 115°C (and 170°C) and 25" C, respectively. 

A simpler, lower cost technique which can readily separate the antioxidants from plastic extracts and give a qualitative analysis is thin layer chromatography (BS6630, 1985). In thin layer chromatography (TLC), the stationary phase is comprised of a thin layer of adsorbent such as cellulose, alumina, or silica gel on a plastic sheet, thick aluminium foil, or a glass plate. A small spot of solution containing the sample is applied to a plate, about 1 cm from the base. The plate is then placed in a sealed container which holds a suitable solvent, such as ethanol, so that it does not come into contact with the spots. The solvent moves up the plate by capillary action and meets the sample mixture, which is dissolved and is carried up the plate by the solvent. Components in the sample mixture travel at different rates due to differences in solubility in the solvent, and due to differences in their attraction to the plate. 

Carotenoids are commonly extracted from liquid samples (plasma/serum) into lipophilic solvents such as hexane, hexane-ethyl acetate, or diethyl ether, mostly after deproteinization with ethanol or methanol, which also helps to liberate the lipidic substances from protein binding. Extracts should be protected from light and acids and antioxidants may usefully be added. The extract is either used as such or is concentrated under oxygen-free nitrogen. Solid samples, e.g., foods, are either extracted with a solvent miscible with water (acetone, methanol) or, after dehydration of the sample, with a water immiscible solvent. Cleanup of the extract and fractionation of the pigments may involve saponification and/or open-column chromatography. 

These workers point out that usually the additive must be separated in a pure state from co-extracted additives usually by thin-layer chromatography (TLC) and then identified by measurement of the UV, IR, nuclear magnetic resonance (NMR) and mass spectra of the compound. This full treatment is required only for new stabilisers - for a characterisation of well known compounds the simplest method is by direct comparison of the UV absorption spectra with those of a series of known stabilisers. For some compounds this will probably be sufficient, but many substituted phenols have similar spectra, and for three of the most frequently used antioxidants the UV spectra are identical. Topanol OC, lonox 330 and Binox M (see Table 2.11 for their chemical constitution) in ethanolic solution all have = 277 nm, with a shoulder at 282 nm. To extend this procedure Ruddle andWilson [66] prepared the spectra of alkaline solutions of the phenols, which were then measured either directly against a solvent blank or as difference spectra measured against the neutral solution. This still gives almost identical spectra for the three compounds mentioned previously. 

Kirkbright and co-workers [86] carried out a study of the general feasibility of the fluorimetric or phosphorimetric determination of stabiliser compounds after their extraction from polymers with organic solvents. They examined the fluorescence and phosphorescence characteristics of 29 common antioxidants and UV absorbers in an organic solvent medium at room temperature and -200 °C, respectively, and they report the fluorescence and phosphorescence spectral characteristics in a mixture of diethylether, isopentane, ethanol and chloroform and the calibration data phosphorescence detection limits and phosphorescence life-times. 

Fiorenza and co-workers [50] have described a technique based on column chromatography on neutral alumina for the separation of antioxidants, plasticisers, and so on, in rubber extracts (Figure 3.8). They detected the separated compounds by monitoring the effluent with a LKB 254 nm UV detector (Figure 3.9). In this procedure a carbon tetrachloride solution of the sample is applied to an alumina column wetted with the same solvent and the column is successively eluted with carbon tetrachloride, mixtures of carbon tetrachloride and benzene, benzene, mixtures of benzene and absolute ethanol, and finally, ethanol. Separations were carried out on a scale to provide enough of each separated compound for the preparation of IR and UV spectra. 

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