Mechanisms of cholesterol and saturated fatty acid lowering by Quillaja saponaria extract, studied by in vitro digestion model

Abstract

Quillaja saponin extracts are known to reduce plasma cholesterol levels in humans. Here we study the mechanism of this effect with Quillaja Dry saponin extract (QD). In vitro model of triglyceride lipolysis is used to quantify the effect of QD on the solubilization of cholesterol and of the lipolysis products (fatty acids and monoglycerides) in the dietary mixed micelles (DMM). We found that QD extract decreases significantly both the cholesterol (from 80% to 20%) and saturated fatty acids (SFA, from 70% to 10%) solubilised in DMM. Series of dedicated experiments prove that QD may act by two mechanisms: (1) direct precipitation of cholesterol and (2) displacement of cholesterol from the DMM. Both mechanisms lead to increased cholesterol precipitation and, thus, render cholesterol bio-inaccessible. We prove also that the saponin molecules are not the active component of QD, because highly purified Quillaja extract with very similar saponin composition does not exhibit cholesterol-lowering or SFA-lowering effect. The effect of QD extract on cholesterol solubilisation is most probably caused by the high-molecular weight polyphenol molecules, present in this extract. The reduced SFA solubilisation is caused by Ca(2+) ions of relatively high concentration (1.25 wt%), also present in QD extract, which precipitate the fatty acids into calcium soaps.

Lowering of cholesterol bioaccessibility and serum concentrations by saponins: in vitro and in vivo studies

“…In previous studies, we found that QD also acts by inducing cholesterol precipitation. 25 Comparing the effects of the two extracts at similar saponin weight concentrations, one sees that QD is more efficient than SAP in decreasing cholesterol bioaccessibility. The mechanisms that govern the effect of saponins on the solubilization of cholesterol in DMM are discussed in section 4.1.…”

“…2973) and EU (E999) and is used as an emulsifier and a foamer in several food technologies; (2) it is known to lower serum cholesterol in rats 10 and to induce cholesterol precipitation in vitro. 25 Therefore, the main purpose of the experiments with QD was to serve as a positive control, thus validating the used in vitro and in vivo methods. On the other hand, there are no reports of the effect of SAP on cholesterol and SFA, neither in vitro nor in vivo.…”

Hypolipidemic Effect of the Autoclaved Extract Prepared from Pea (<i>Pisum sativum</i> L.) Pods In Vivo and In Vitro

“…Dietary fibers, specifically SDF and polyphenol, have been reported to precipitate cholesterol and bile salt (26,(32)(33)(34). In this study, AE adsorbed cholesterol micelles in vitro.…”

Recent Advances and Applications of Plant-Based Bioactive Saponins in Colloidal Multiphase Food Systems

“…Saponins exhibit a wide range of biological activities, such as hypocholesterolemic, hypoglycemic, hepatoprotective, hemolytic, immunomodulatory, antiviral, anti-inflammatory and antitumor activities [ 15 , 16 ]. Many of these activities are usually associated with the interactions of saponins with the lipids of biological membranes, such as cholesterol and phospholipids [ 37 , 38 , 39 , 40 , 41 , 42 ]. Numerous studies have demonstrated the ability of saponins to inhibit cholesterol absorption and to decrease serum and liver cholesterol [ 43 , 44 ].…”

“…Numerous studies have demonstrated the ability of saponins to inhibit cholesterol absorption and to decrease serum and liver cholesterol [ 43 , 44 ]. Vinarova et al recently studied the effect of six saponin extracts on the bioaccessibility of cholesterol and saturated fatty acids by using in vitro digestion model and in vivo animal studies [ 37 , 38 ]. They found that the saponin extracts (Quillaja Dry and Sapindin) can decrease cholesterol bioaccessibility up to 44%, and the main mechanism of cholesterol-lowering effect is the displacement of cholesterol from the dietary mixed micelles, which can lead to the direct precipitation of cholesterol that cannot pass through the mucus layer of the intestine.…”