Determination of nucleotides, nucleosides and their transformation products in Cordyceps by ion-pairing reversed-phase liquid chromatography-mass spectrometry

An ion-pairing reversed-phase liquid chromatography-mass spectrometry (IP-RP-LC-MS) was developed for the determination of nucleotides, nucleosides and their transformation products in Cordyceps. Perfluorinated carboxylic acid, namely pentadecafluorooctanoic acid (PDFOA, 0.25 mM), was used as volatile ion-paring agent and a reversed-phase column (Agilent ZORBAX SB-Aq column) was used for the separation of three nucleotides namely uridine-5'-monophosphate (UMP, 0.638-10.200 mu g/mL), adenosine-5'-monophosphate (AMP, 0.24-7.80 mu g/mL) and guanosine-5'-monophosphate (GMP, 0.42-13.50 mu g/mL), seven nucleosides including adenosine (0.55-8.85 mu g/mL), guanosine (0.42-6.75 mu g/mL), uridine (0.33-10.50 mu g/mL), inosine (0.21-6.60 mu g/mL), cytidine (0.48-15.30 mu g/mL), thymidine (0.20-6.30 mu g/mL) and cordycepin (0.09-1.50 mu g/mL), as well as six nucleobases, adenine (0.22-6.90 mu g/mL), guanine (0.26-4.20 mu g/mL), uracil (0.38-12.15 mu g/mL), hypoxanthine (0.13-4.20 mu g/mL), cytosine (0.39-12.45 mu g/mL) and thymine (0.26-8.25 mu g/mL) with 5-chlorocytosine arabinoside as the internal standard. The overall LODs and LOQs were between 0.01-0.16 mu g/mL and 0.04-0.41 mu g/mL for the 16 analytes, respectively. The contents of 16 investigated compounds in natural and cultured Cordyceps were also determined and compared after validation of the developed IP-RP-LC-MS method. The transformations of nucleotides and nucleosides in Cordyceps were evaluated based on the quantification of the investigated compounds in three extracts, including boiling water extraction (BWE), 24 h ambient temperature water immersion (ATWE) and 56 h ATWE extracts. Two transformation pathways including UMP -> uridine -> uracil and GMP -> guanosine -> guanine were proposed in both natural Cordyceps sinensis and cultured Cordyceps militaris. The pathway of AMP -> adenosine -> inosine -> hypoxanthine was proposed in natural C. sinensis, while AMP -> adenosine -> adenine in cultured C. militaris. However, the transformation of nucleotides and nucleosides was not found in commercial cultured C. sinensis. (C) 2010 Elsevier B.V. All rights reserved.