Preparation And Functional Exploration Of Cysteine Derivatives From Garlic For Improving Bioavailability Of Food Crops Iron And Zinc

Most of organic sulfides in garlic belong to cysteine derivatives,which are S-substituted cysteine species,cysteine sulfoxides and ?-glutamyl-cysteine peptides.The healthy biological effects of garlic are attributed to its organosulfur compounds,including those with a sulfydryl or S-substituted moiety in their structures.?-Glutamyl-cysteine peptides(?-GCPs)differ from poorly water-soluble alliin and fat-soluble allicin on structure and function,which are integral parts in the thiol transport chain in Allium.These dipeptides accord with the structure characteristics of phytochelatin,leading to chelate many mineral elements safely and steady.Five cysteine derivatives,(RC7)-S-allyl-L-cysteine(1),(RC7)-S-allyl-L-cysteine sulfoxide(2),(SC2RC7)-?-L-glutamyl-S-allyl-L-cysteine(3)and(SC2RC7)-?-L-glutamyl-S-propyl-L-cysteine(5)were isolated from garlic bulbs using ion-exchange chromatography and preparative HPLC.Theirmolecular structures were identified by HPLC-MS,CD,1H NMR,13C NMR,and specific rotation,and confirmed by using corresponding standard compounds.To determine the effect of these cysteine derivatives on bioavailability of iron and zinc from the major grain crops such as soybean,mung bean and millet,a simulate intestinal gastrointestinal digestion procedure was established with invitro method.The mechanism for improving bioavailability of food crops iron and zinc was revealed and discussed.The results are as followed:The influence of exogenously adding 1,2 and 3 on the bioavailability of iron and zinc from food crops was examined with soybean,mung bean and millet,compared with Cys,GSH and EDTA at the molar ratio of 1:1 to the iron/zinc in the food crops respectively.The enhancing effect of the three cysteine derivatives on bioavailability of iron was generally evidenced in the case of soybean(from 1.52%to 2.96%,2.00%and 3.38%),mung bean(from 1.91%to 2.56%,2.35%and 8.18%)and millet(from 7.68%to 9.13%,8.76%and 12.32%),and bioavailability of zinc in the case of soybean(from 10.83%to 18.16%,14.13%and 19.12%),mung bean(from 20.52%to 23.34%,28.45%and 32.44%)and millet(from 4.79%to 6.03%,5.69%and 6.92%).Obviously,all of three cysteine derivatives(1,2 and 3)had a promoting effect on the bioavailability of iron and zinc from food crops.The two cysteine derivatives(1 and 2)similarly enhanced the bioavailability of zinc from the food crops with GSH.The influence of exogenously adding 3 on the bioavailability of iron and zinc was better than 1 and 2.These findings are of practical value in a food-based strategy to enhance the bioavailability of trace minerals for human health.The paper also discussed the mechanism of cysteine derivatives for improving the bioavailability of iron and zinc,including the effect of cysteine derivatives variety on bioavailability,the effect of iron and zinc existence state(solution state)on bioavailability,the effect of chelating ability with iron and zinc,the effect of cooked processing to food crops,the effect of anti-nutritional compounds,and the influence between zinc,iron and calcium,and revealed the mechanism for improving the bioavailability of zinc and iron.In the study we explores the biological activity of GSAC,including iron and zinc ion-chelating activity,decreased glycation activity,antioxidant activity,scavenging activity of DPPH free radicals.On the basis of the reveal of the biological activity of GSAC,the mechanism for improving bioavailability of food crops iron and zinc was proposed.