Rehmannia glutinosa

Rehmannia glutinosa (family Orobanchaceae) is a perennial herb native to East Asia. Its tuberous root has been used for centuries in Traditional Chinese Medicine. Modern supplements employ extracts of the dried root (often called “shǔdi”) to influence endocrine, metabolic, and neuro‑protective pathways, making it a popular adaptogenic and “tonic” ingredient.

• Catalpol: The principal bioactive iridoid, catalpol, has the molecular formula C₁₅H₂₂O₉ and an IUPAC name (1S,4aR,5R,6R,7S,8R,8aS)-1‑hydroxy‑5‑(hydroxymethyl)‑6‑(hydroxymethyl)‑7‑(hydroxymethyl)‑8‑(hydroxymethyl)‑1,4a,8‑trihydroxy‑2,3‑dihydro‑1,4‑dihydro‑2‑oxabicyclo[4.1.0]hept‑5‑yl β‑D‑glucopyranoside.
• Iridoid Structure: Rehmannioside A (C₂₀H₂₈O₁₁) and other iridoids share a cyclopentanoid‑pyran skeleton with multiple hydroxyl groups, conferring high polarity and water solubility.
• Other Compounds: The plant also contains phenolic acids (e.g., caffeic acid, ferulic acid) and high‑molecular‑weight polysaccharides (≈10‑30 kDa) that contribute to its immunomodulatory profile.
• Standardization: The extract’s standardized content is usually expressed as “% iridoid glycosides” measured by HPLC‑UV.

• Cultivation: Rehmannia glutinosa is cultivated primarily in the Henan, Shanxi, and Liaoning provinces of China, where the climate and soil (loamy, slightly acidic) optimize root growth.
• Harvest: Harvest occurs in late autumn when iridoid concentrations peak.
• Processing: The dried root is either air‑dried or low-temperature‑oven‑dried, then ground and extracted with water or 30‑50 % ethanol; the resulting liquid is spray‑dried to yield a powdered extract.
• Quality Control: High‑quality supplements are standardized to ≥30 % iridoid glycosides and are verified by HPLC fingerprinting.
• Testing: Quality control includes heavy‑metal testing (Pb < 5 ppm), pesticide screening, and microbial limits (≤10⁴ CFU/g).
• Preferred Practices: Organic or GMP‑certified farms are preferred to minimize contaminants and ensure consistent phytochemical profiles.