Gas chromatographic determination of S-alk(en)ylcysteine sulfoxides

A new GC method for determination of S-alk(en)ylcysteine sulfoxides, import ant secondary metabolites occurring in many plant genera, has been develope d. The method is based on isolation of the amino acid fraction by ion-excha nge chromatography followed by derivatization with ethyl chloroformate at a mbient temperature and reduction of derivatized S-alk(en)ylcysteine sulfoxi des by sodium iodide. The main advantages of the new method are its high se nsitivity, excellent resolution capability, accuracy and reliability, as we ll as the possibility to identify unknown compounds by means of GC-MS. The content of alliin and other S-alk(en)ylcysteine sulfoxides was determined i n nine different samples of garlic (Allium sativum L.) originating from the Czech Republic, France, and China. The total content of S-alk(en)ylcystein e sulfoxide pool ranged between 0.53 and 1.3% fresh weight, with S-allylcys teine sulfoxide (alliin) being predominant. A novel S-alkylcysteine derivat ive, S-ethylcysteine sulfoxide (ethiin), not previously reported to occur i n Allium species, was found in some of the samples examined. (C) 1999 Elsev ier Science B.V. All rights reserved.