Diethyl norbixin

Bixin, present in Annatto, is an important natural colourant which is obtained commercially from Bixa orellana. It is unusual in not having a typical isoprenoid structure composed of multiples of the fundamental C5 unit. All trans diethyl norbixin has been synthesised readily from crocetindial (ref.55,p221) by the Wittig reaction with two moles of the phosphoran from the triphenylphosphonium salt of ethyl chloracetate as shown in Scheme 20. The natural product is the form in which the colourant is used. 

Dried or freeze dried samples can be extracted with water-immiscible solvents such as EtOAc or diethyl ether. For quantitative extraction, dried samples are preferably rehydrated at different times for example, 5 to 10 min for dried mangoes, 30 min for lyophihzed red peppers and pasta. Rehydration is followed by extraction with acetone or MeOH. Bixin and norbixin from a mix dry powder of annatto and com can quantitatively be extracted with MeOH followed by acetone. In order to improve pigment recovery, extruded foods require pre-digestion with enzymes to liberate the pigment from the matrix. ... 

More severe conditions, 35 ml of 35% methanolic KOH added to 10 mL extract in EtOAc and shaken for 20 min at 50°C, are necessary for the total conversion of bixin, an ester of a carotenoid acid, to norbixin in snacks. Since saponification yields the norbixin salt (K or Na, depending on the alkali) that is soluble in the aqueous phase, the pH should be decreased to 3.5 or even lower to allow extraction of the protonated norbixin by EtOAc and diethyl ether. ... 

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See also in sourсe #XX -- [ ]

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