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To the Editor: In their study of cocoa intake and blood pressure, Dr Taubert and colleagues¹ concluded that the reduction of diastolic and systolic blood pressure caused by dark chocolate intake was due to increased formation of S-nitrosoglutathione. Many biochemical markers were measured in the study using commercially available assays or reported methods. However, we are not aware of reports of the analytical performance of the liquid chromatography tandem mass spectrometry method used for the measurement of plasma S-nitrosoglutathione. This is potentially an important problem for research involving S-nitrosothiols, for which the reported concentrations in biological fluids has a 3–order magnitude range.²

We are also unaware of previous reports of achieving measurement (with a lower limit of detection of 0.1 nmol/L) of such low plasma baseline levels of S-nitrosoglutathione (0.33 nmol/L) by liquid chromatography tandem mass spectrometry.^2-3 Such methods require full validation to avoid analytical errors; . . . [Full Text of this Article]

Dimitrios Tsikas, PhD
tsikas.dimitros@mh-hannover.de
Institute of Clinical Pharmacology
Hannover Medical School
Hannover, Germany

Ranieri Rossi, PhD
Department of Evolutionary Biology
Laboratory of Pharmacology and Toxicology
University of Siena
Siena, Italy

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Cocoa Intake and Blood Pressure—Reply
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