Profiles of S-alk(en)ylcysteine sulfoxides in various garlic genotypes

The contents of major S-alk(en)ylcysteine sulfoxides (namely alliin, methiin and isoalliin) were determined in a set of 58 various garlic genotypes (22 flowering plant morphotypes, 14 semi bolting plants and 22 scape absent morphotype plants), representing the garlic collection of the Allium gene bank in the Czech Republic. The plants were cultivated in four successive years (2005-2008) and analysed immediately after harvest and subsequently after eight weeks of storage at 5°C. The total content of the three cysteine derivatives in fresh samples varied considerably between 3.35 mg/g fresh weigh and 12.77 mg/g fresh weight, with the mean of 7.50 mg/g fresh weight and the average relative proportions of alliin/methiin/isoalliin of 83/16/1. Upon 8-week storage at 5°C, the average total amount of S-alk(en)ylcysteine sulfoxides increased by 30% to 9.75 mg/g fresh weight, with the alliin/methiin/isoalliin ratio changing to 82/14/4. The data obtained were statistically evaluated using linear discrimination analysis to distinguish the differences between the years of harvest, between freshly harvested and stored samples, and between the individual morphotypes. While the year-to-year differences between the samples were statistically not very significant, the fresh and stored samples as well as the individual garlic morphotypes differed considerably in S-alk(en)ylcysteine sulfoxide content. Our results indicate that the content of S-alk(en)ylcysteine sulfoxides primarily depends on various genetic factors and post-harvest storage conditions, whereas the climatic conditions during the growth (e.g. temperature, irrigation) influence their level to a lesser extent. Various implications for the food and pharmaceutical industries are discussed.