Silydianin

Silydianin is a pure flavonolignan compound (C₂₅H₂₂O₁₀, molecular weight ~482.44 g/mol), not a food ingredient, and therefore carries no conventional macronutrient or micronutrient profile (zero protein, fat, carbohydrate, fiber, or caloric value in its isolated form). It is one of the minor constituents of silymarin, the standardized extract from milk thistle (Silybum marianum) seeds, typically comprising approximately 5–10% of the total silymarin complex by weight, compared to silybin which dominates at ~50–70%. As a bioactive compound, silydianin contains a phenylchromane skeleton with multiple hydroxyl groups conferring its antioxidant capacity. Oral bioavailability of silydianin, like other flavonolignans, is generally low due to limited aqueous solubility, first-pass hepatic metabolism, and poor intestinal absorption; studies on the broader silymarin complex suggest systemic bioavailability of individual flavonolignans typically falls below 1–5% from standard formulations, with phospholipid complexes (e.g., Siliphos) improving absorption by up to 4–5 fold. No standalone pharmacokinetic data specific to isolated silydianin in humans is currently published. In commercial milk thistle extracts standardized to 70–80% silymarin, silydianin concentration is estimated at roughly 35–80 mg per 1,000 mg extract. No dietary reference intakes (DRIs) or established daily values exist for silydianin.