. Carotenoids. Carotenoids; Carotenoids. 5 ANTHERAXANTHIN 191 Violaxanthin is formed together with antheraxanthin, though in somewhat poorer yield. It is a natural pigment of wide occurrence and has been repeatedly investigated within recent years. It will be described in detail on p. 193. d) Auroxanthin: CH, CH, CH3 CH, \/. C CH CH3 CH3 CH3 H3C CH=C CHg CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH C CHOH Auroxanthin The furanoid dioxide of zeaxanthin, auroxanthin, is a carotenoid occurring in blossoms. It can be obtained by the isomerisation of violaxanthin^" in the presence of acids, a react
. Carotenoids. Carotenoids; Carotenoids. 5 ANTHERAXANTHIN 191 Violaxanthin is formed together with antheraxanthin, though in somewhat poorer yield. It is a natural pigment of wide occurrence and has been repeatedly investigated within recent years. It will be described in detail on p. 193. d) Auroxanthin: CH, CH, CH3 CH, \/. C CH CH3 CH3 CH3 H3C CH=C CHg CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH C CHOH Auroxanthin The furanoid dioxide of zeaxanthin, auroxanthin, is a carotenoid occurring in blossoms. It can be obtained by the isomerisation of violaxanthin^" in the presence of acids, a reaction which proves its constitution. A detailed description of auroxanthin will be found on p. 196. 5. ANTHERAXANTHIN C40H56O3 In the course of investigations on the carotenoids of the anthers of Liliiim tigrinum, Karrer and Oswald''^ discovered a previously unknown phyto- xanthin which they termed antheraxanthin. Antheraxanthin occurs together with capsanthin and is found below the latter in the chromatogram. It shows an entirely hypophasic character in the partition test and its absorption spectrum differs very little from that of zeaxanthin. Karrer and Oswald deter- mined the molecular formula of the pigment, but were unable to establish the nature of the third oxygen atom. The constitution of antheraxanthin was elucidated later'^, when the pig- ment was identified with zeaxanthin mono-epoxide obtained by the oxidation of zeaxanthin with monoperphthalic acid. The two compounds could not be separated by chromatography on zinc carbonate and gave no mixed melting point depression. This partial synthesis established the constitution of anthera- xanthin (cf. p. 189). The formula is in agreement with the fact that the pigment absorbs 11 mols of hydrogen on catalytic hydrogenation'^. \V \V 0 CHq Cxlq CHq 0 H O \J /\ I I I I /\ CHj C-CH=CH-C=CHCH=CH-C=CHCH=CHCH=C-CH=CHCH=C-CH=CH-C CH^ HaC-C CHOH HOCH C \ / \^ / \^ Antheraxanthin CHj CH2 CH3 References p. 214— Please note that t
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