White Willow (Salix alba) (Salix alba)

White Willow (Salix alba) bark contains the key bioactive glycoside salicin at approximately 0.5–10% dry weight (highly variable by species, age, and plant part), which is hydrolyzed in the gut to saligenin and glucose, then oxidized to salicylic acid (bioavailability moderate; salicin absorption occurs in the small intestine with hepatic conversion). Polyphenolic compounds include tannins (catechins, condensed tannins) at roughly 8–20% dry weight, flavonoids (luteolin, apigenin, naringenin glycosides) at approximately 1–3%, and phenolic acids (p-coumaric acid, ferulic acid) at trace to low concentrations. Tremulacin and populin (additional salicylate esters) are present at variable levels. Macronutrient content is negligible in typical bark extract use (predominantly fiber/cellulose structurally). Micronutrients include trace minerals such as calcium, potassium, and magnesium in minor amounts not nutritionally significant at therapeutic doses. Tannin content may reduce bioavailability of co-administered minerals and proteins through chelation and precipitation. Polyphenol bioavailability is generally low due to poor intestinal absorption and extensive hepatic first-pass metabolism. Standardized extracts are typically normalized to 15% salicin content for consistency in traditional preparations.