Analytical Approaches for the Quantitation of Redox-active Pyridine Dinucleotides in Biological Matrices
Some of the main electron carriers in the metabolism are mono- or dinucleotides and they play crucial roles in maintaining a balanced redox homeostasis of cells, and in coupling many anabolic and catabolic reactions. Altered cellular redox status can be an indicator of various metabolic disorders such as obesity, the metabolic syndrome, or type 2 diabetes and of other pathological conditions, which involve oxidative stress, such as cardiovascular diseases. Adequate NAD+/NADH and NADP+/NADPH ratios are fundamental for normal cellular functions, thus accurate measurement of these pyridine dinucleotides is essential in biochemical research. Liquid chromatography coupled to tandem mass spectrometry has become the leading analytical technology in (targeted) state-of-the-art metabolic profiling. Main difficulties that hamper quantification of metabolites are chemical similarities, high polarity, and chemical and biological instability of the molecules to be measured. In this review, some critical steps of studying cellular redox status are described, in particular, different techniques of sample preparation and challenges in chromatographic separation.