MOLECULE

Sitosterol

Beta-sitosterol, also known as sitosterol or harzol, belongs to the class of organic compounds known as stigmastanes and derivatives. These are sterol lipids with a structure based on the stigmastane skeleton, which consists of a cholestane moiety bearing an ethyl group at the carbon atom C24. Beta-sitosterol is widely distributed in the plant kingdom and is a main dietary phytosterol (a plant sterol) found in vegetable oils, nuts, avocados and prepared foods, such as salad dressings. Beta-sitosterol is one of the phytosterols known to occur in Cannabis sativa (PMID: 6991645). Phytopharmacological extracts, commonly derived from the South African star grass, Hypoxis rooperi, or from species of Pinus and Picea, contain mixtures of phytosterols, that includes Beta-sitosterol. However, these extracts also contain some sterols bonded with glucosides. While beta-sitosterol is the purported active constituent, beta-sitosterol-beta-D-glucoside is often detected. Thus, one or both metabolites may be the active components. Phytosterols, like cholesterol, contain double bonds that are susceptible to oxidation. Beta-sitosterol may have anti-carcinogenic and anti-atherogenic properties (PMID: 13129445, 11432711). Benign prostatic hyperplasia patients treated with beta-sitosterol, compared with placebo, had improved urinary symptom scores and flow measures (PMID: 10368239). Hyperandrogenic postmenopausal women, with higher risk of breast cancer because of their endocrine profiles, were placed on a plant food-based diet, to determine if eating a plant-based diet, rich in phytosterols, rather than animal-based diet, would have an increase in serum phytosterols. Compared to controls, women placed on the plant-based diet had increased serum phytosterols, particularly beta-sitosterol, suggesting that beta-sitosterol can be used as a biomarker of exposure in observational studies or as a compliance indicator in dietary intervention studies of cancer prevention (PMID: 14652381). Beta-sitosterol induces apoptosis and activates key caspases in MDA-MB-231 human breast cancer cells (PMID: 12579296). Although the exact mechanism of action of beta-sitosterols in the above studies is unknown, it may be related to cholesterol metabolism or anti-inflammatory effects (via interference with prostaglandin metabolism).