Preparation and Functional Exploration of Cysteine Peptides from Fresh Garlic Scales for Improving Bioavailability of Food Legume Iron and Zinc
Abstract Two γ-glutamyl-cysteine peptides (γ-GCPs), ( S C2 R C7)-γ- L -glutamyl- S -allyl- L -cysteine ( 1 ) and ( S C2 R C7)-γ- L -glutamyl- S -propyl- L -cysteine ( 2 ) were isolated from fresh garlic scales using ion-exchange chromatography and preparative HPLC. Their molecular structures were identified by HPLC-MS, CD, 1 H NMR, 13 C NMR, and specific rotation, and confirmed by using corresponding standard compounds. The influence of exogenously adding 1 and 2 on the bioavailability of iron and zinc from food legume was examined with soybean and mung bean, at the level of 0.01 mmol/5 g of legume respectively. The enhancing effect of the two γ-GCPs on bioavailability of iron was generally evidenced in the case of soybean (from 1.88% to 6.73% and 4.42%) and mung bean (from 2.52% to 12.04% and 9.38%). The two γ-GCPs similarly enhanced the bioavailability of zinc from the food legume, with the extent of increase in soybean ranging from 13.37% to 23.95% and 20.58%, and in mung bean from 15.98% to 28.44% and 27.05%. Obviously, both 1 and 2 had a promoting effect on the bioavailability of iron and zinc from food legumes. These findings are of practical value in a food-based strategy to enhance the bioavailability of trace minerals for human health.