Extraction betalains

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be beneficially used to separate anthocyanins from betalains on an RP-18 solid-phase extraction cartridge (Stintzing, unpublished data). 

Lee, Y.N. and Wiley, R.C., Betalaine yield from a continuous solid-liquid extraction system as influenced by raw product, post-harvest and processing variables, J. Food ScL, 46, 421, 1981. 

Despite their potential health-promoting effects as dietary antioxidants, the fate of betalains in humans has been poorly studied. Betalain bioavailability was first demonstrated in humans by the appearance of betacyanins in urines after ingestion of beetroot extract" and red beet juice," indicating that these compounds are indeed absorbed. Although intact betacyanins (betanin and isobetaiun) appeared rapidly in human urine with a maximum excretion rate observed within 2.5 to 8 hr," betacy-anin recoveries in human urine were usually low (< 1% of the dose) over 24 hr postdose, suggesting that either the bioavailabifity of betacyaiuns from red beetroot is low or that renal clearance is a minor excretion route for these compounds. 

Butera, D. et al.. Antioxidant activities of Sicilian prickly pear (Opuntia ficus indica) fruit extracts and reducing properties of its betalains betanin and indicaxanthin, J. 

As soon as betalains are extracted from the vacuoles through plant tissue decom-partmentalization, they are prone to degradation. Factors supporting stabilization or rather destabilization are summarized in Figure 4.4.2. 

Two main groups can be discerned (1) endogenous factors such as plant enzymes like polyphenoloxidase, peroxidase, and P-glucosidase and (2) conditions prevailing in the extraction medium will decide the fates of betalain pigments among which temperature, oxygen, and pH are considered the most important conditions. 

Kujala, T., Loponen, J., and Pihlaja, K., Betalains and phenolics in red beetroot Beta vulgaris) peel extracts extraction and characterisation. Ztschr. Naturforsch. C/J. Biosci., 56, 343, 2001. 

Lee, C.-H. et al., Betalains, phase II enzyme-indncing components from red beetroot (Beta vulgaris L.) extracts, Nutr. Cancer, 53, 91, 2005. 

In contrast to colorless phenolics, betalains are most soluble in water and are even more hydrophilic than the anthocyanins that readily dissolve in methanol. However, to preclude activities of endogenous enzymes during extraction, aqueous methanol at a ratio of 60 40 or 80 20 (v/v) is recommended. 

The Betalaines. The main pigment in the concentrated colour beet red is betanin. This is classified as El62 by the EU. The pure pigment is obtained by aqueous extraction of the red table beet. Approximately 80% of the pigment present in beetroot is betanin. 

Natural colours include annatto, anthocyanins, beetroot red (betalaines), caramel, carotenoids, cochineal and lac pigments, flavanoids, chlorophylls and tumeric. There is a trend towards encapsulating natural colours for food use, but this is not yet reflected in the extraction techniques described in the published analytical methods. Lancaster and Lawrence (1996) described the extraction and... 

Betalain pigments have been tested on rodents by feeding 50mg/kg pure betanin, 2000 ppm betanine in the diet and several other conditions.11 No carcinogenic or other toxic effects were observed and the authors concluded that red beet extracts were safe as food colorants. 

Support Protocol Extraction of Betalains from Beets F3.1.4... 

In addition, a protocol describing the extraction of betalains from beets is provided (see Support Protocol). 

Betalains Materials Solvent A 18/82(v/v) CH3OH/0.05 M KH2PO, adjust to pH 2.75 with H3P04 Solvent B. CH3OH Sephadex G-25 (Amersham Pharmacia Biotech) water slurry, pH 2.0 adjust pH with HC1 Sample of beet juice or beet tissue extract (see Support Protocol), pH 2.0 adjust pH with HC1 1% acetic acid Four 7.88-mm x 61-cm Bondapak C,8/Porasil B columns connected in series 17.8/81.2/1.0 (v/v/v) CH3OH/0.05 M KH2P04/acetic acid 0.1% HC1... 

The documented use of betalain pigments as food colorants dates back at least one century, when inferior red wines were colored with betalain-containing juices (e.g., red beet juice). This common practice was, however, soon prohibited, and the application of betalain colorants was widely replaced by artificial dyes, which displayed better stability, at a lower price, and with higher purity. But in recent years the interest in natural food colorants has been renewed, mainly because of consumers concerns about the safety of some artificial colorants, which may be hazardous to human health (234). As a result, the number of permitted artificial dyes has been markedly reduced, and new efforts had to be made to develop natural food colorants (235). However, current legislation restricts the application of betalain colorants to concentrates or powders (E 162) obtained from aqueous extracts of beets (211). 

Fig. 22 HPLC separation of betalains in fermented red beet root extract, (a) Detection of betacyanins at 538 nm. Peaks 1 = betanin, 2 = isobetanin, 3 = betanidin, 4 = isobetanidin, 5 = prebetanin. (b) Detection of betaxanthins at 477 nm. Peaks 1 = vulgaxanthin I, 2 = vulgaxanthin II, 3 = betanin, 4 = isobetanin, 5 = betanidin, 6 = isobetanidin, 7 = prebetanin. (From Ref. 239.)...

Betalains have received much attention from the food industry as natural colour additives (Adams et at, 1976 Pourrat et at, 1983). The betacyanins from red beet are used for colouring ice cream, jam and fruit conserves. Earlier interest in betacyanins came from their use in colouring red wine, although this was prohibited by law in 1892 due to the use of the apparently harmful pokeberry Phytolacca americana, extract (Dreiding, 1961). 

Terradas, F. and Wyler, H. (1991a) 2,3- and 4,5-Secodopa, the biosynthetic intermediates generated from L-Dopa by an enzyme system extracted from the fly agaric. Amanita muscaria L., and their spontaneous conversion to muscaflavin and beta-lamic acid, respectively, and betalains. Helv. Chim. Acta, 74,124—40. 

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