Ethanol anthocyanin extraction

Many solvents such as methanol, acetone, ethanol, and water are used for anthocyanin extraction due to their polar character since most anthocyanins occur naturally as glycosides. Anthocyanin glycosides have higher solubility in water than the corresponding aglycons. In addition, in most fruits and vegetables, anthocyanin pigments are located in cells near the surface. " ... 

To obtain anthocyanins closer to their natural state, a number of researchers have used neutral solvents for initial extraction such as 60% methanol, n-butanol, cold acetone, mixtures of acetone, methanol, and water, or simply water. Methanol is the most common solvent used for anthocyanin extraction. Metivier et al. (1980) compared the efficiency of extraction with three different solvents (methanol, ethanol, and water) and different acids, and found that methanol extraction was 20% more effective than ethanol and 73% more effective than water when used for anthocyanin recovery from grape pomace. 

Obi, F.O., Usenu, I.A., and Osayande, J.O., Prevention of carbon tetrachloride-induced hepatotoxicity in the rat by H. rosasinensis anthocyanin extract administered in ethanol. Toxicology, 131, 93-98, 1998. 

Alternatively berries can be freeze dried prior to extraction. Dried, berry anthocyanin extracts are dissolved in methanol or ethanol containing 0.1-2.0 % cone. HCl, kept for 5 minutes in an ultrasonic bath and finally cleared by filtration. Deny juice is best acidified with HCl (0.1-2.0 %) for stabilization and diluted with an appropriate solvent. If anthocyanins are extracted from dietary supplements or from processed food products (i.e., beny jam or ice cream), repeated extraction with mixtures of polar organic solvents and aqueous acids is usually appropriate. The aqueous part is most often necessary for dissolution of the other ingredients (e.g., sugars, proteins). 

The most common supercritical medium is CO2 because of its low critical temperature (31°C) and critical pressure (7.3 MPa), its cost effectiveness, its food grade status, and overall environmental friendliness. However, due to its low polarity, supercritical CO2 (SC-CO2) alone did not perform well in the extraction of phenolic compounds and anthocyanins from grape skins (Mantell et al. 2003 Vatai et al. 2009). A cosolvent, usually ethanol, can be added to SC-CO2 during extraction to enhance polarity. Such a mixture can result in a two-fold increase in phenols and three-fold increase in anthocyanins extracted. Isolation of quercetin might also be improved as SC-CO2 can remove the nonpolar components, thus concentrating the quercetin in the feed material. Water and methanol can also be added as cosolvents to increase the polarity of SC-CO2. 

Betalains are vacuolar plant pigments. Hence their hydrophilic nature is comprehensible. Although they are slightly soluble in ethanol and methanol, water is the best snited solvent both for stability and solnbility reasons. In contrast to the antho-cyanins, the betalains are even more polar as can be demonstrated by shorter retention times in RP-HPLC and lower solubilities in alcoholic solutions. The varying polarities may also be beneficially used to separate anthocyanins from betalains on an RP-18 solid-phase extraction cartridge (Stintzing, unpublished data). 

When ethanol was used to extract the dye, the efficiency increased to 0.71% the rationale is the higher solubility of the sensitizer in alcohol and minor association which favors a more homogeneous distribution of the anthocyanins on the Ti02 surface. However, exposure to simulated sunlight (AM = 1.5,100 mWcm 2) caused a significant decrease in efficiency after 3h, probably because alcohol favors the photocatalytic decomposition of anthocyanin. 

Extraction of flavonoids from grapes is classically carried out with organic solvents, starting from fresh, frozen, or freeze-dried material. The most commonly used solvents are methanol, ethanol, and acetone, which can be used pure or mixed with water. Extraction of anthocyanins is commonly achieved at low temperatures with acidified methanol. The use of acid maintains the anthocyanins in the most stable flavylium forms but may cause degradation of... 

Anthocyanins are generally more stable at an acidic pH. Therefore, anthocyanins are commonly extracted under cold conditions using either acidic methanol or ethanol to avoid degradation1 5169 (Table 3.4). In comparison, acetone allows more reproducible extraction and avoids problems with pectins. However, it is limited by the coextraction of proanthocyanins.39 In general, ethanol is preferable as an extraction solvent, although it can require an additional step for the removal of lipid-soluble substances. SPE using Ci8, polyamide, HLB (hydrophilic lipophilic balanced stationary phases), or Amberlite has been employed for the purification of anthocyanidins prior to HPLC analysis.39-51 66 69... 

Seabra, I.J. Braga, M.E.M. Batista, M.T. de Sousa, H.C. 2010. Effect of solvent (CO2/ ethanol/Fl20) on the fractionated enhanced solvent extraction of anthocyanins from elderberry pomace. J. Supercrit. Fluids 54 145-152. 

Thus, ethanol-water (7 3 v/v) and methanol-water in various ratios for flavonoids, methanol-25 % HCl (9 1 v/v), methanol-acetic acid (5%), methanol-tri-fluoroacetic acid (3%) for unstable anthocyanins, acetone, methanol-acetone mixtures for carotenoids, acetone and petroleum ether for chlorophylls, and so forth. The pigments are fairly stable in their natural environment, but they generally become unstable in extracts this has to be taken into consideration in the development of new, more efficaceous extraction procedures. 

FIGURE 11.17 Extraction of anthocyanins from grape pomace at room temperature with ethanol containing 1% HC1. (From Metivier et al., 1980)... 

The MALDI-TOF mass spectra of the Sephadex-water/ethanol (1 1) eluate (fraction 2) of both the spray ed cranberry juice and cranberry fruit showed a series of anthocyanins cyanidin-pentoside m/z 419.3), peonidin-pentoside m/z 433.3), cyanidin-hexoside m/z 449.3) and peonidin-hexoside m/z 463.3) (Figure 2A). MALDI-TOF MS equipped with delayed extraction provide unit mass resolution, allowing for the visualization of isotopic distribution. The reported observed masses (m/z) correspond to the monoisotope of the predicted compound. For example the predicted and observed monoisotope of cyanidin-pentoside is m/z 419.3) representing the contribution of C, H and 0 to the compound. The mass at m/z 420.3) represents one C, or one H, or one The mass at m/z 421.3) represents two or one C and one H, or one 0, or two H. Mass calculating programs such as IsoPro 3.0 [Shareware at http //members.aol.com/msmsoft] can be used to predict the isotopic distribution of compounds and allow for comparison between predicted and observed isotopic distributions. 

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