Determination of S-Adenosyl-L-methionine in Fruits by Capillary Electrophoresis

Introduction - S-adenosyl-L-methionine (SAM) plays an important role in many biochemical reactions in plants. It is mainly used as a methyl donor for methylation reactions, but it also participates in, for example, the biosynthesis of polyamines and the plant hormone ethylene. Objective - To develop a fast capillary electrophoresis technique to separate SAM in fruits and fruit juices without any pre-purification steps. Methodology - Four different extraction solutions and two extraction times were tested, of which 5% trichloroacetic acid (TCA) for 10 min was found most suited. A glycine : phosphate buffer (200 : 50 mm, pH 2.5) was found optimal to analyse SAM in TCA extracts. Analyses were preformed on different climacteric and non-climacteric fruits and fruit juices. The calibration curve was created in degraded tomato extract. The CE-method was compared with a more conventional HPLC method described in literature. Results - The CE technique made it possible to completely separate the S,S- and R,S-diastereoisomeric forms of SAM. The CE method proved to be very fast (20 min total running time instead of 42 min) and more sensitive (limit of detection of 0.5 mu m instead of 1 gm) compared with the conventional HPLC method. Conclusion - Fast measurements of SAM in fruits and juices are favoured by capillary electrophoresis in a 200 : 50 mM glycine : phosphate (pH 2.5) buffer system. Copyright (C) 2010 John Wiley & Sons, Ltd.