Fucoxanthin-hemiketal

Chlorophyll-a Pheophytin-a Pyropheophitin- a Pheophorbide-a Pyropheophorobide-a Isofucoxanthin-dehydrate Fucoxanthin dehydrate Fucoxanthin-hemiketal Isofucoxanthin dehydrate pheophorbide a ester Isofucoxanthin dehydrate pheophorbide a ester Isofucoxanthin dehydrate pyropheophorbide a ester 23.5 26.4 28.1 5.0 6.9 10.7 12.0 6.4 24.4 22.9 25.4... 

The striking colour change observed upon treatment of the yellow deacetylated fucoxanthin hemiketal (43) with acid, providing the blue oxonium ion (10, )imax 690 nm), followed by reversion to the yellow fucoxanthinol hemiketal (43) by treatment with base is illustrated in Fig. 18. The hemiketals exhibit characteristic fragmentation pattern by EIMS. 

Fig. (17). Formation of blue oxonium ions via cyclic hemiketals upon treatment of fucoxanthin (42) with strong acid, and conversion of the blue oxonium ion to yellow hemiketal with base Reprinted with permission from [10], Copyright 1994 Acta Chemica Scandinavica.

---