Note on some Sterol Colour Reactions in their Relation to Vitamin A

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Abstract
Cholesterol in chloroform solution when subjected to mild oxidation with benzoyl peroxide or nascent formaldehyde gives rise to a chromogenic substance which produces with AsCl3 a blue color indistinguishable from that given by cod-liver oil. Cholic acid similarly treated also gives a blue color with AsCl3. These reactions suggest that oxidative changes of the sterol molecule may be concerned in the formation of vitamin A from sterols. When purified cholesterol was added to vegetable or animal oils which do not themselves react with AsCl3, the production of the blue color was completely inhibited. The authors conclude that the chromogen artificially produced from cholesterol is not identical with the chromogen of cod-liver oil.