Plant Sterols (Phytosterols)
Cardiovascular Health
Overview
- Plant sterols, also called phytosterols, are a group of naturally occurring, plant‑derived sterols and stanols that structurally resemble cholesterol.
- The primary purpose of dietary phytosterols is to modulate lipid metabolism, most notably by reducing intestinal absorption of dietary cholesterol, thereby supporting cardiovascular health.
Chemistry
- Phytosterols are tetracyclic triterpenoid alcohols (C27–C29) with a characteristic cyclopentanoperhydrophenanthrene nucleus, a side‑chain at C‑17, and a methyl group at C‑24.
- The most abundant member, β‑sitosterol, has the formula C₂₉H₅₀O and the IUPAC name (3β,24R)-Stigmast-5-en-3-ol.
- Other common phytosterols include campesterol (C₂₈H₄₈O) and stigmasterol (C₂₉H₄₈O).
- They are highly lipophilic (log P ≈ 7–8) and poorly soluble in water but readily dissolve in oils and lipid membranes.
- Their structural similarity to cholesterol (identical sterol nucleus) underlies their competitive absorption, while the additional ethyl or methyl groups at C‑24 confer a slightly larger steric bulk, reducing membrane permeability and favoring excretion.
Sources & Quality
- Commercial phytosterols are extracted primarily from plant oils (e.g., soybean, corn, and canola) and wheat germ by solvent extraction (hexane or supercritical CO₂) followed by crystallization or chromatography to enrich the sterol fraction.
- Tall oil (a by‑product of the pulp and paper industry) is another industrial source, especially for β‑sitosterol.
- Proprietary processes may use enzymatic esterification to improve solubility in food matrices.
- For supplements, the phytosterol content is expressed as “total phytosterols” (including free sterols and sterol esters).
- High‑quality products are ≥ 90 % purity, free of heavy metals, pesticides, and trans‑fat contaminants.
- Standardized extracts must comply with pharmaco‑peia specifications (e.g., USP, European Pharmacopeia) and be tested for oxidative stability (e.g., peroxide value) to ensure efficacy and safety.
Where to Buy Plant Sterols (Phytosterols)
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