Understanding the Relationship of Bile Acid Binding Capacity, Phenolic Compounds and Their Bioaccessibility of Selected Vegetables

Abstract

Vegetables with bile acid capacity provide multiple benefits to human health, including reducing plasma cholesterol levels, controlling blood sugar in type 2 diabetic patients, and preventing colon cancer. The in vitro bile acid binding capacities of Brussels sprouts, green kale, red kale, red cabbage, and red leaf lettuce were tested and their dietary fiber content was analyzed. Green kale was used for further studies to explore the optimal dose for bile acid binding, the effect of bile acid composition on the binding capacity, the influence of minimal processing on the bile acid binding capacity, the interaction of bioactive compounds with bile acids, and the impact of bile acids on the bioaccessibility of kale polyphenols.

The in vitro digestion was conducted in three phases that simulated oral, gastric, and intestinal digestion. Bile acids were incubated with vegetables in the intestinal digestion phase. Kale had the greater bile acid binding capacity compared with Brussels sprouts, red cabbage, and red leaf lettuce. In the experiment testing the effect of different bile acid compositions on bile acid binding capacity, kale showed a similar binding capacity for the bile acid composition simulating that found in healthy females and males with gallstones, but it bound less bile acids when the composition simulated the bile acid pool of type-2 diabetic males. The type-2 diabetic male patient model was used to explore bile acid binding capacity in response to different doses of kale. The results suggested that the optimal dose of kale was 1.8 g, which bound 81.8% of the added bile acid. Microwaving and steaming significantly improved kale’s in vitro bile acid binding capacity.

To study the interaction between bile acids and different bioactive compounds in kale, polyphenols were separated from the fiber-rich kale tissue, and both of these were incubated with bile acids. We found that the fiber-rich tissue in kale was the main component that binds bile acids. Similar in vitro digestions both with and without bile acids suggested that bile acids improved the bioaccessibility of quercetin and the total identified polyphenols in kale. Therefore, bile acids can be bound by fiber rich tissues in the kale and have some interactions with kale polyphenols.