AMeCI EI Ethanol Eluate MeCl EtAc EtOH Extract Extract Extract
Figure 8.9 TLC analysis of acetone/methylene chloride (AcMeCl) eluates (lane 1) and ethanol eluates
(lanes 2-4) of aloe-adsorbed activated charcoal. The ethanol eluate has been fractionated by successive extractions with methylene chloride (MeCl), ethyl acetate (EtAc), and hot ethanol (EtOH). Along the right side of the plate are indicated the Rfs of reference compounds: C540, a chromone ester of mass 540daltons; C556, a chromone ester of mass 556 d.; THA, tetrahydroxyanthraquinone) (see Colour Plate 7).
shows that it does not always work. Treated aloe subsequently subjected to light, air and heat turns brown/black. It may be that this situation reflects partial oxidation. The oxidation product of a THA, the 'red compound(s)', particularly at elevated temperature, may be hydrophilic enough to avoid complete adsorption on activated charcoal. These 'red compound(s)', however, will still be available after 'decolorization' to undergo polyphenolic condensations. Furthermore, process control by analytical chemistry is unknown in the aloe industry. There is no perceived need to know the exact THA content of the aloe which is to be subjected to charcoal adsorption and thus to adjust the amount of activated carbon added. It might be that the color change potential of a given batch of aloe is greatly in excess of the adsorptive capacity of the activated carbon added and that some of this material will remain. However, a final conclusion will await complete characterization of the compounds responsible for color change.
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