Rationale
Hepatocellular carcinoma (HCC) is a highly malignant disease for which the development of prospective or prognostic biomarkers is urgently required. Although metabolomics is widely used for biomarker discovery, there are some bottlenecks regarding the comprehensiveness of detected features, reproducibility of methods, and identification of metabolites. In addition, information on localization of metabolites in tumor tissue is needed for functional analysis. Here, we developed a wide‐polarity global metabolomics (G‐Met) method, identified HCC biomarkers in human liver samples by high‐definition mass spectrometry (HDMS), and demonstrated localization in cryosections using desorption electrospray ionization MS imaging (DESI‐MSI) analysis.
Methods
Metabolic profiling of tumor (n = 38) and nontumor (n = 72) regions in human livers of HCC was performed by an ultrahigh‐performance liquid chromatography quadrupole time‐of‐flight MS (UHPLC/QTOFMS) instrument equipped with a mixed‐mode column. The HCC biomarker candidates were extracted by multivariate analyses and identified by matching values of the collision cross section and their fragment ions on the mass spectra obtained by HDMS. Cryosections of HCC livers, which included both tumor and nontumor regions, were analyzed by DESI‐MSI.
Results
From the multivariate analysis, m/z 904.83 and m/z 874.79 were significantly high and low, respectively, in tumor samples and were identified as triglyceride (TG) 16:0/18:1(9Z)/20:1(11Z) and TG 16:0/18:1(9Z)/18:2(9Z,12Z) using the synthetic compounds. The TGs were clearly localized in the tumor or nontumor areas of the cryosection.
Conclusions
Novel biomarkers for HCC were identified by a comprehensive and reproducible G‐Met method with HDMS using a mixed‐mode column. The combination analysis of UHPLC/QTOFMS and DESI‐MSI revealed that the different molecular species of TGs were associated with tumor distribution and were useful for characterizing the progression of tumor cells and discovering prospective biomarkers.
A domino Michael/Michael reaction of 2‐(2‐formylethyl)naphthalene‐1,4‐dione and nitroalkene was catalyzed by diphenylprolinol silyl ether to afford functionalized spiro[cyclopentane‐1,2′(1′H)‐naphthalene] derivatives with four continuous stereocenters in good yields with excellent diastereo‐ and enantioselectivities.
The diarylprolinol‐mediated asymmetric direct cross‐aldol reaction of α,β‐unsaturated aldehyde as an electrophilic aldehyde was developed. The reaction becomes accelerated by an acid when a carbonyl group is introduced at the γ‐position of the α,β‐unsaturated aldehyde. Synthetically useful γ,δ‐unsaturated β‐hydroxy aldehydes were obtained with high anti‐selectivity and excellent enantioselectivity.
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