Biogeneration and chemical properties of pure thiosulfinates and propanethial-S-oxide representative of Allium spp

The inclusion of garlic, onion and other Alliums in diets has long been espoused to promote an array of health benefits. Thiosulfinates and propanethial- S-oxide (PTSO) are the major organosulfur compounds in freshly minced Allium tissues; they are also intermediates in the formation of other organosulfur compounds in processed tissue derivatives of Allium spp.; A model reaction system was developed for generating pure thiosulfinates and PTSO using an isolated alliinase (EC 4.4.1.4) and isolated or synthetic alk(en)yl-L-cysteine sulfoxides (ACSO). Reaction yields were 30–60%, and organosulfur reaction products were extracted into CHCl₃ and analyzed by HPLC. A pure thiosulfinate or PTSO was derived from a single ACSO, and a preparation containing a mixture of four thiosulfinate species was derived from reaction mixtures employing binary ACSO substrate systems. Identities of homologous thiosulfinates and PTSO were confirmed by 1H NMR. This biogeneration system was used as a preparative tool for yielding pure thiosulfinates and PTSO to facilitate the study of chemical and potentially biological properties of this group of compounds.; Thiosulfinate decay could be fitted to first-order processes over the pH range of 1.2–9.0 and at 20–80°C. The pH dependence of thiosulfinate stability in descending order was: pH 4.5–5.5 > pH 1.2 > pH 6.5–7.5 > pH 8.0–9.0 in the presence of 0.1 M Tris. Thiosulfinates with longer and saturated alk(en)yl groups were generally more stable than those with shorter and unsaturated alk(en)yl groups. Thiosulfinates underwent alkyl-exchange reactions at pH 8–9 without net loss of total thiosulfinate levels within 60—90 min at 20°C.; A kinetic modeling approach was applied to dynamic reaction mixtures to account for the observed reactivity and profile of organosulfur products that may occur in Allium preparations. This approach employed a semi-quantitative accounting of both the evolution and fate of organosulfur species generated in enzymic and postenzymatic phases of reactions. Such a kinetic characterization should be useful in exploiting this biogenerating system to prepare organosulfur product mixtures of controlled composition for evaluating biological activities.