A Highly Sensitive SPE Derivatization-UHPLC-MS Approach for Quantitative Profiling of Carotenoid-Derived Dialdehydes from Vegetables

Abstract

Oxidative cleavage of carotenoids leads to dialdehydes (diapocarotenoids, DIALs) in addition to the widely known apocarotenoids. DIALs are biologically active compounds that presumably impact human health and play different roles in plant development and carotenoid metabolism. However, detection of DIALs in plants is challenging due to their instability, low abundance, and poor ionization efficiency in mass spectrometry. Here, we developed a solid-phase extraction and derivatization protocol coupled with ultrahigh performance liquid chromatography-mass spectrometry for quantitative profiling of DIALs. Our method significantly enhances the sensitivity of DIAL detection with a detection limit of 0.05 pg/mg of dried food materials, allowing unambiguous profiling of 30 endogenous DIALs with C₅ to C₂₄ from vegetables. Our work provides a new and efficient approach for determining the content of DIALs from various complex matrices, paving the way for uncovering the functions of DIALs in human health and plant growth and development.

Keywords: UHPLC−MS; diapocarotenoids SPE; diapocarotenoids chemical derivatization; diapocarotenoids profiling; food diapocarotenoids.

Figure 1

Structures of representative carotenoid-derived DIALs.

Figure 2

MS/MS spectra of T3-derivatized 5 (A), 8 (B), and 11 (C) standards. Insets: extracted ion chromatograms (EICs) and proposed cleavages of T3-derivatized DIALs.

Figure 3

Effect of the SPE purification on the detection of T3- derivatized DIALs. (A) Optimal SPE purification procedure. (B) Total ions chromatograms (TICs) of tomato samples with (blue) and without (red) SPE purification (top) and EICs of representative endogenous T3-derivatized DIALs with (blue) and without (red) SPE purification (bottom).

Figure 4

Identification of DIALs from tomato fruits by using UHPLC−MS: (A) EICs of 30 endogenous T3-derivatized DIALs from tomato; (B) high-resolution MS/MS spectra of representative endogenous T3-derivatized DIALs with NCE of 20 eV.

Figure 5

Quantitative method validation with tomato samples: (A) intra- (n = 5) and interday (n = 9) precision; (B) correlation between the added and determined amount of 4 and 5 in tomato samples. n = 3 in each level. Mean ± SD.

Figure 6

Quantitation of DIALs from vegetables. n = 4 in each group (n = 3 for tomato). Mean ± SD.