Fucoxanthin-3-acetate

Fig. 116. Layer polyamide (perlon)-cellulose (80 + 20) solvent petrol ether (BP 100—120° C)-butanone-methanol (78 + 11 + 11). Substances a eschscholtz-xanthin b capsorubin c capsanthin (in 1) zeaxanthin d (in 2 and 3) fucoxanthin e lutein / fucoxanthin acetate g lutein monoacetate h cryptoxanthin i by-product from acetylation oi f k lutein diacetate. Applied ia + c + d + 26+c + d 9 + A 36 + c + d + e+ / + [42]...

Structure of various terpenoid piant pigments (a) fucoxanthin, (b) (i-carotene, and (c) xanthophyll. OAc = acetate. 

Fucoxanthin and its metabolites Egg yolk Normal phase, Silica gel column Acetone hexane gradient Normal phase, Silica gel column Hexane, Dichlormethane, 2-Propanol and Ethyl-diisopropylamine (90.9 7 3 0.1 v/v/v/v) isocratic Reverse phase, C18 column Methanol and Water (67 33 v/v) isocratic Bonded nitrile column Hexane, Isopropyl acetate, Acetone, Methanol (76 17 7 0.1 v/v/v/v) isocratic Strand et al., 1998... 

Stereomutation of all-trans-fucoxanthin [(3S,5.R,6S,3 S,5 R,6, R)-5,6-epoxy-3,3, 5 -trihydroxy-6, 7 -didehydro-5,6,7,8,5, 6 -hexahydro-/3,/3-caroten-8-one 3 -acetate (41)], which has R axial chirality, gave three main isomers.24 Two of these were identified as mono unhindered cis-isomers, and the third, from H n.m.r. data etc., is considered to be the allenic isomer in which the chiral axis is S. 

Saponification of the extracts is generally desirable to remove unwanted lipid materials. However, this step is omitted in the isolation of carotenol esters, since these are hydrolyzed by this procedure. It is also omitted in the isolation of carotenoids such as fucoxanthin and peridinin, which are alkali-labile. If acetone has been used in the initial extraction, it is essential that all traces be removed before saponification. The general procedure used involves dissolving the total lipid fraction in an alcoholic (ethanol or methanol) solution of potassium hydroxide. The mixture is then either heated for a short period of time while kept in the dark, or left in the dark at room temperature for 12-16 h. There has been considerable discussion of the merits of these two procedures. Which method is used is dependent on the nature of the samples being analyzed and the requirements of the analysis (Davies, 1976 Liaaen-Jensen, 1971). After saponification, water is added, and neutral lipids (the unsaponifiable fraction) are extracted with diethyl ether or hexane. Acidic carotenoids remain in the alkaline phase and are extracted with diethyl ether or hexane after acidification with acetic acid. The unsaponifiable fraction usually contains sterols as well as carotenoids. If desired, sterol contaminants can be removed by precipitation from cold (- 10°C) petroleum ether or by precipitation of these compounds as their digitonides. 

Fucoxanthin (40) in a series of reactions involving lithium aluminium hydride reduction of the keto and acetate function to fucoxanthinol, allylic dehydration and subsequent epoxide rearrangement in acidic chloroform of fucoxanthinol to the epimeric fucochromes and further reaction with lithium aluminium hydride under forcing conditions, finally provided zeaxanthin (26) (22, 26). 

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