Abstract
Two major carotenoids of the stick insect were reinvestigated and shown to be .beta.,.beta.-caroten-2-ol and .beta.,.beta.-carotene-2,2''-diol and not isocryptoxanthin (.beta.,.beta.-caroten-4-ol) and isozeaxanthin (.beta.,.beta.-carotene-4,4''-diol). Both pigments are esterified with fatty acids. The identification was based on cochromatography with authentic 2-, 3- and 4-isomers of the mono- and dihydroxy pigment, mass spectra, and chemical behavior. In acid solution .beta.-.beta.-carotene-2,2''-diol was specifically dehydrogenated and rearranged to ketones with retro structures in analogy to the reaction of .beta.,.beta.-caroten-2-ol as recently reported. The final product of the diol was 4,5-dihydro-4,5''-retro-.beta.,.beta.-carotene-2,2''-dione. This is the 1st demonstration of .beta.,.beta.-carotene-2,2''-diol in an animal.

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