Identification of an Epoxide Metabolite of Lycopene in Human Plasma Using 13C-Labeling and QTOF-MS - PubMed (original) (raw)

Identification of an Epoxide Metabolite of Lycopene in Human Plasma Using 13C-Labeling and QTOF-MS

Morgan J Cichon et al. Metabolites. 2018.

Abstract

The carotenoid lycopene is a bioactive component of tomatoes and is hypothesized to reduce risk of several chronic diseases, such as prostate cancer. The metabolism of lycopene is only beginning to be understood and some studies suggest that metabolites of lycopene may be partially responsible for bioactivity associated with the parent compound. The detection and characterization of these compounds in vivo is an important step in understanding lycopene bioactivity. The metabolism of lycopene likely involves both chemical and enzymatic oxidation. While numerous lycopene metabolites have been proposed, few have actually been identified in vivo following lycopene intake. Here, LC-QTOF-MS was used along with 13C-labeling to investigate the post-prandial oxidative metabolism of lycopene in human plasma. Previously reported aldehyde cleavage products were not detected, but a lycopene 1,2-epoxide was identified as a new candidate oxidative metabolite.

Keywords: lycopene; mass spectrometry; metabolite; stable isotopes.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1

Figure 1

Mass spectra of the 13C-labeled lycopene (A) and lycopene epoxide (B) detected with the IROA ClusterFinder software.

Figure 2

Figure 2

Representative extracted ion chromatogram of the lycopene epoxide (m/z 592.58) in plasma with the corresponding mass spectrum of the peak.

Figure 3

Figure 3

UV-Vis spectra of _all-trans_-lycopene (A) and the lycopene epoxide (B).

Figure 4

Figure 4

Average appearance of the 13C-lycopene epoxide metabolite (A) and the 13C-lycopene parent (B) in the plasma of subjects (±SEM) with insets zoomed to the first 24 h. (13C-lycopene data have been previously published [18] and are visualized here for comparison purposes.).

Figure 5

Figure 5

Mass spectrum comparing the isotope distributions for native (unlabeled) lycopene and the 13C-labeled lycopene in a representative plasma sample.

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