Vitamin D3 (Cholecalciferol)

Vitamin D₃ (cholecalciferol) is a fat-soluble secosteroid hormone.

• It is produced in the skin upon exposure to ultraviolet-B radiation.
• It can also be obtained from certain foods and supplements.
• Its primary physiological role is to maintain calcium-phosphate homeostasis.
• This supports bone mineralization and skeletal health.

• Vitamin D₃ (cholecalciferol) is a sterol-like molecule with the IUPAC name (3S,5Z,7E)-9,10-sec-cholesta-5,7-diene-3-ol.
• Molecular formula: C₂₇H₄₄O
• Molecular weight: 384.64 g mol⁻¹
• Its structure consists of:
  • A broken B-ring (secosteroid)
  • A 3-β-hydroxyl group
  • A conjugated diene (C5–C6 and C7–C8)
  • A side chain (C-19 carbon) ending in a saturated alkyl chain.
• The molecule is highly lipophilic (logP ≈ 8).
• It is insoluble in water but soluble in organic solvents and lipid matrices, which underlies its absorption with dietary fat.
• The 3-hydroxyl group is the key functional group for VDR binding after conversion to the active 1α-hydroxylated form.

• Vitamin D₃ is primarily derived from lanolin (wool wax) of sheep.
  • The precursor 7-dehydrocholesterol is extracted, purified, and UV-irradiated to produce cholecalciferol.
• Alternative sources include fish oil and lichen (the latter for vegan-friendly products).
• Most commercial supplements are synthesized via photochemical conversion of 7-dehydrocholesterol to cholecalciferol, followed by purification steps (e.g., chromatography) to achieve >98 % purity.
• Quality considerations include:
  • Verification of potency (via HPLC)
  • Absence of heavy metals or residual solvents
  • Stability (protect from light and heat)
• Third-party testing (e.g., USP, NSF) helps assure consistency, especially for high-dose formulations.