Function, Application and Detection of Plant Sterols

What are plant sterols?

Plant sterols belong to sterols with plant active ingredients, which are important components of plant cells. Its molecule contains 28-29 carbon atoms, and the hydroxyl group at the C-3 position is an important active group, which can be combined with carboxylic acid to form plant sterol ester and has better lipid solubility and biological activity than sterol.

Derivatives of plant sterols include two major classes of sterols and sterol esters. There are a variety of controllable enzymatic esterified plant sterols, including both free and esterified types. Free plant sterols are most abundant in various oil seeds and less abundant in fruits. Esterified plant sterols are most abundant in cereals.

There are many types of plant sterols, and more than 40 plant sterols have been identified from plants. The most common plant sterols include glutasterol, glutathione, rape sterol and soy sterol, and there are more than 250 plant sterol derivatives, such as glutathione ferulic acid and soy sterol ferulic acid esters.

Functions of plant sterols

1. Affect cholesterol metabolism

Studies have found that dietary intake of 2 g of plant sterols per day reduces low-density lipid cholesterol (LDL-C) concentrations by approximately 10%. With increased intake of plant sterols, cholesterol absorption rates as well as serum cholesterol levels can be reduced. Supplementation with plant sterols and sterols results in lower blood levels of total cholesterol (TC) and LDL-C, while no changes are observed in high-density lipoprotein cholesterol (HDL-C) and triglyceride (TG) levels.

2. Antioxidant effect

The antioxidant properties of plant sterols are closely related to their anti-cardiovascular effects and anti-cancer effects. Mustard plant sterols and plant sterol vanillate have high antioxidant properties. The antioxidant properties of glutathione increase with its content. The antioxidant properties may be related to the conversion of sterols into sterolenes through dehydration at the 1 and 2 bond positions.

β-sitosterol can inhibit superoxide anion and scavenge hydroxyl radical. Adding 0.08% plant sterol in oil and grease can minimize the oxidation of oil and grease. Its antioxidant ability increases with the increase in concentration, especially when combined with vitamin E or other antioxidant drugs, the antioxidant effect can be synergistic to produce a stronger superimposed effect.

3. Hormone-like effects

Plant sterol has a high affinity for the adrenal glands, liver, testes and ovaries, the tissues where steroid hormones are synthesized. It can be used as a precursor of steroid hormones to synthesize steroid hormones.

4. Anti-inflammatory and antipyretic effects

β-sitosterol has a stronger anti-inflammatory effect similar to that of corticosteroids such as hydrocortisone and prednisone. Soy sterols, cyclic mucosterols and spinach sterols have obvious anti-inflammatory and antipyretic effects, and there are no side effects of traditional anti-inflammatory and antipyretic drugs, so they can be used as auxiliary anti-inflammatory drugs.

5. Other effects

The role of plant sterol also includes its use (i) as a preventive agent of liver dysfunction; (ii) as an immunomodulatory factor, stimulating the proliferation of lymphocytes and T cells; (iii) inhibiting the occurrence and development of breast cancer, gastric cancer and intestinal cancer in the body; (iv) promoting the expression of human prostate stromal cell growth factor and enhancing the activity of protein kinase, etc.

Applications of plant sterols

Clinical medicine: β-sitosterol can be used to treat hypercholesterolemia and hypertriglyceridemia.

Drug synthesis: Plant sterols can be used to synthesize sterol hormones that regulate water, protein, sugar and salt metabolism, a feature that can be used to make almost all steroids such as hypertension drugs and oral contraceptives.

Healthy food: Plant sterols are widely used in food preparation as functional active ingredients for the prevention of cardiovascular diseases.

Livestock breeding: Adding plant sterols to the diet can improve the feed conversion efficiency of broiler, the production performance of weaned piglets and reduce the feed to meat ratio. Supplementation of a certain amount of plant sterols in prelactation cows can increase milk production and improve milk composition, so that milk fat rate, milk protein rate and non-fat solids can be increased, while body cell count and milk urea nitrogen content have different degrees of reduction. At the same time, it can balance energy and protein intake and improve the milk production performance of dairy cows.

Figure 1. The overall effect of plant sterols (Kopylov et al.,2021).

Detection of plant sterols

Creative Proteomics is primarily based on liquid phase mass spectrometry (LC-MS) technology, using Thermo Scientific's U3000 fast liquid chromatography for sample separation and Thermo Scientific™ Q Exactive™ for sample identification for efficient and accurate detection of plant sterols. In addition, detection can also be performed by high performance liquid chromatography (HPLC) or gas phase mass spectrometry (GC-MS).

Reference:

1. Kopylov, A. T., Malsagova, K. A., Stepanov, A. A., & Kaysheva, A. L. (2021). Diversity of Plant Sterols Metabolism: The Impact on Human Health, Sport, and Accumulation of Contaminating Sterols. Nutrients, 13(5), 1623.