Identification and Quantification of Apo-lycopenals in Fruits, Vegetables, and Human Plasma

Abstract

Research has suggested that lycopene may be metabolized by eccentric cleavage, catalyzed by β-carotene oxygenase 2 (BCO2), resulting in the generation of apo-lycopenals. Apo-6′-lycopenal and apo-8′-lycopenal have been reported previously in raw tomato. We now show that several other apolycopenals are also present in raw and processed foods, as well as in human plasma. Apo-lycopenal standards were prepared by in vitro oxidation of lycopene, and a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method using atmospheric pressure chemical ionization in negative mode was developed to separate and detect the apo-6′-, 8′-, 10′-, 12′-, 14′-, and 15′-lycopenal products formed in the reaction.Hexane/acetone extracts of raw tomato, red grapefruit, watermelon, and processed tomato products were analyzed, as well as plasma of individuals who had consumed tomato juice for eight weeks. Apo-6′-, 8′-, 10′-, 12′-, and 14′-lycopenals were detected and quantified in all food products tested, as well as plasma. The sum of apo-lycopenals was 6.5 µg/100 g 'Roma' tomato, 73.4 µg/100 g tomato paste, and 1.9 nmol/L of plasma. We conclude that several apo-lycopenals, in addition to apo-6′-and 8′-lycopenal, are present in lycopene containing foods. In addition, the presence of apo-lycopenals in plasma may derive from the absorption of apo-lycopenals directly from food and/or human metabolism.

Carotenoid metabolism in mammals, including man: formation, occurrence, and function of apocarotenoids

“…Recently, in addition to apo-6 ′ -and 8 ′ -lycopenal, apo-10 ′ -, 12 ′ -, and 14 ′ -lycopenals were found in both raw and processed food products ( 86 ) ( Fig. 3 ).…”

Accumulation of Paprika Carotenoids in Human Plasma and Erythrocytes

“…Recently, several oxidative metabolites of lutein, zeaxanthin, and lycopene have been found in humans and other mammals. Lutein undergoes oxidation to ε, ε-carotene-3,3 -dione via 3-hydoxy-β, ε-caroten-3 -one 26 29 , while lycopene is converted to cyclolycopene-5,6-diols and several apolycopeneals 29,30 . These carotenoids are found at very low levels 50 pmol/mL in human plasma 27,28,30 .…”

“…Lutein undergoes oxidation to ε, ε-carotene-3,3 -dione via 3-hydoxy-β, ε-caroten-3 -one 26 29 , while lycopene is converted to cyclolycopene-5,6-diols and several apolycopeneals 29,30 . These carotenoids are found at very low levels 50 pmol/mL in human plasma 27,28,30 . Interestingly, conversion of capsanthin to capsanthone appeared to be more active compared with similar conversion reported for lutein, zeaxanthin, and lycopene.…”

Metabolomics of carotenoids: The challenges and prospects – A review

“…In this context, the possible formation of lycopene metabolites, also known as lycopenoids are discussed. Studies have claimed the presence of lycopene metabolites in serum and tissues at physiologically significant levels in contrast to retinoids (Nikki Ford & Erdman, 2012;Kopec et al, 2010). This shows that the lycopene metabolites may be biologically active, hence it is interesting to elucidate further the metabolites in humans and animals.…”

“…Consequently, Gajic, Zaripheh, Sun, and Erdman (2006) have determined the existence of apo-8 0 -and apo-12 0 -lycopenal as well as other polar metabolites of lycopene in rats. Kopec et al (2010) have shown a series of apo-lycopenals formation in human plasma and concluded, metabolites are formed either by enzymatic or chemical oxidative cleavage.…”