Lycopene chemical oxidation

Carotenoid oxidation products were not only formed from the parent molecules in order to elucidate structure, they were also obtained by partial or total synthesis or by direct oxidation of carotenoid precursors. Thus, apo-8 -lycopenal was synthesized in 1966 more recently, the ozonide of canthaxanthin was obtained by chemical oxidation of canthaxanthin. ... 

We developed and applied two oxidation methods to lycopene and p-carotene. The first chemical oxidation method was performed in biphasic medium using the potassium permanganate hydrophilic oxidant. Cetyltrimethylammoniumbromide was the phase transfer agent used to achieve contact of the hydrophilic oxidant with the lycopene lipophilic carotenoid dissolved in methylene chloride/toluene (50/50, v/v). 

Carotenoids are a class of lipophilic compounds with a polyisoprenoid structure. Most carotenoids contain a series of conjugated double bonds, which are sensitive to oxidative modification and cis-trans isomerization. There are six major carotenoids (ji-carotenc, a-carotene, lycopene, P-cryptoxanthin, lutein, and zeaxanthin) that can be routinely found in human plasma and tissues. Among them, p-carotene has been the most extensively studied. More recently, lycopene has attracted considerable attention due to its association with a decreased risk of certain chronic diseases, including cancers. Considerable efforts have been expended in order to identify its biological and physiochemical properties. Relative to P-carotene, lycopene has the same molecular mass and chemical formula, yet lycopene is an open-polyene chain lacking the P-ionone ring structure. While the metabolism of P-carotene has been extensively studied, the metabolism of lycopene remains poorly understood. 

FIGURE 20.1 Schematic illustration of lycopene metabolic pathway by CM02. (a) 5-cis Lycopene and 13-cis lycopene are preferentially cleaved by CM02 at 9, 10 -double bond. The cleavage product, apo-lO -lycopenal, can be further oxidized to apo-lO -lycopenol or reduced to apo-lO -lycopenoic acid, depending on the presence of NAD+ or NADH. (b) Chemical structures of apo-lO -lycopenoic acid, acyclo-retinoic acid, and all-frans retinoic acid. (Adapted from Hu, K.Q. et al., J. Biol. Chem., 281, 19327, 2006. With permission.)... 

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