Extraction yield studies, antioxidants

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]. 

Another Lauraceae is Laurus nobilis (laurel). The EO obtained from the leaves of wild grown shrubs is characterized by a very high content of eugenol. The biological activities, especially the antioxidative properties, of the extract were studied in different in vitro test methods. The scavenging capacity in the DPPH assay yielded an IC50 value of 0.113 mg/mL. Also the P-carotene bleaching test of the nonpolar fractions was able to protect the lipids from oxidation. After an incubation... 

The yield and composition of the volatile fraction of the pentane extracts of leaves, stems and seeds of F. vulgare Mill, have been studied by Guillen and Manzanos (1996). The yield obtained from seeds was much higher than that obtained from leaves and stems. The volatile fraction of the pentane extract of the latter two has a higher concentration of terpene hydrocarbons and a smaller concentration of oxygenated terpene hydrocarbons than that of the seeds. Sesquiterpenes and the antioxidant vitamin E have been detected in the leaves and petroselinic acid in the seeds. Saturated aliphatic hydrocarbons with 25 or more carbon atoms have been found in all the plant parts. 

Some studies have shown that MAE may be superior to other extraction methods. Total phenolics and antioxidant activity were found to be higher in spice samples extracted by MAE than by UAE (Gallo et ah, 2010). In extracting anthraquinones from Morinda citrifolia, commonly known as noni, optimized MAE conditions were found to be 80% ethanol, 60 °C extraction temperature, and 30 min extraction time. MAE was shown to require less extraction time while achieving higher yields when compared to Soxhlet, maceration and UAE methods (Hemwimon et ah, 2007). 

Studies evaluated the correlation between sensory parameters and the oxidative stability indices of soybean oils [4]. Furthermore were carried out comparative studies on the oxidative stability of edible oils evaluating their stability by DSC and OSI [14]. On the other hand investigated the thermal stability of high oleic acid vegetable oils with antioxidants [6]. Was evaluated further the influence of the methods of extraction on the yield and quality of Brazil nut oil [23]. 

Supercritical CO2 has been used to extract oil and tocopherols from wheat germ in several research studies (Ge et al., 2002 Panfili et al., 2003 Eisenmenger et al., 2006 Shao et al., 2008 Piras et al., 2009 Gelmez et al., 2009). These have focused on the effects of extraction parameters (i.e., temperature, pressure, CO2 flow rate, cosolvent flow rate, extraction time) on oil and tocopherol yield and sterol and phospholipid content of the extracted oil. A recent study optimized the SC-CO2 extraction for antioxidant concentration and antioxidant activity of the SC-CO2 extracts rather than simply the oil yield (Gelmez et al., 2009). The effects of pressure (148-602 bar), temperature (40-60°C) and extraction time were modelled. The optimum extraction conditions were 336 bar, 58°C and 10 min, resulting in 5.3% tocopherol yield, 6 mg gallic acid equivalent (GAE) phenolics/g extract, 6.7 mg tocopherol/g extract and 57.3 mg scavenged DPPH/g extract. The tocopherol yield under these conditions corresponded to almost complete recovery. 

In regard to the addition of antioxidants, ascorbic acid was tested to protect astaxanthin during 6 h of cell wall disruption step and using lactic acid at 65 C. Concentrations of ascorbic acid ranged from 0 to 18 mg per mL of lactic acid. Ascorbic acid prevented loss of astaxanthin, but its effect was relatively modest. Additionally, a-tocopherol was used during the extraction step with 100% ethyl lactate. As with ascorbic acid, concentrations ranged from 0 to 18 mg per mL of ethyl lactate and the studied action time was 6 h. With 12 mg of a-tocopherol, maximal amounts of astaxanthin were extracted after 1 h extraction time (a-tocopherol caused an increase of 11% in astaxanthin yield). Quantities above 12 mg did not seem to be effective. 

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