Chemical cleavage of fucoxanthin from Undaria pinnatifida and formation of apo-fucoxanthinones and apo-fucoxanthinals identified using LC-DAD-APCI-MS/MS.

As the most abundant carotenoid in nature, fucoxanthin is susceptible to oxidation under some conditions, forming cleavage products that possibly exhibit both positive and negative health effects in vitro and in vivo. Thus, to produce relatively high amounts of cleavage products, chemical oxidation of fucoxanthin was performed. Kinetic models for oxidation were probed and reaction products were identified. The results indicated that both potassium permanganate (KMnO4) and hypochlorous acid/hypochlorite (HClO/ClO(-)) treatment fitted a first-order kinetic model, while oxidation promoted by hydroxyl radical (OH) followed second-order kinetics. With the help of liquid chromatography-tandem mass spectrometry, a total of 14 apo-fucoxanthins were detected as predominant cleavage products, with structural and geometric isomers identified among them. Three apo-fucoxanthinones and eleven apo-fucoxanthinals, of which five were cis-apo-fucoxanthinals, were detected upon oxidation by the three oxidizing agents (KMnO4, HClO/ClO(-), and OH).