Calcifediol
[CAS# 63283-36-3]

Identification

• Classification: API >> Vitamins and minerals >> Vitamin AD drugs
• Name: Calcifediol
• Synonyms: (5Z,7E)-9,10-Secocholesta-5,7,10(19)-triene-3b,25-diol monohydrate; 25-Hydroxycholecalciferol monohydrate; 25-OHD3; 25-Hydroxyvitamin D3 monohydrate
• Molecular Formula: C₂₇H₄₄O₂.H₂O
• Molecular Weight: 418.65
• CAS Registry Number: 63283-36-3
• EC Number: 621-370-5
• SMILES: C[C@H](CCCC(C)(C)O)[C@H]1CC[C@@H]2[C@@]1(CCC/C2=CC=C/3C[C@H](CCC3=C)O)C.O

Properties

• Solubility: DMSO 72 mg/mL, Water 70 mg/mL (Expl.)

Safety Data

• Hazard Symbols: GHS06;GHS08 Danger
• Risk Statements: H301-H301-H311-H330-H372
• Safety Statements: P260-P262-P264-P270-P271-P280-P284-P301+P316-P302+P352-P304+P340-P316-P319-P320-P321-P330-P361+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Acute toxicity	Acute Tox.	2	H310
Acute toxicity	Acute Tox.	2	H300
Acute toxicity	Acute Tox.	1	H330
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413
Reproductive toxicity	Repr.	2	H361
Acute toxicity	Acute Tox.	4	H302
Acute toxicity	Acute Tox.	1	H300
Skin irritation	Skin Irrit.	2	H315
Acute toxicity	Acute Tox.	1	H310
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Acute toxicity	Acute Tox.	2	H330

• Transport Information: UN 2811

Discovery and Applications

Calcifediol, with the molecular formula C₂₇H₄₄O₂ and CAS number 19356-17-3, is a naturally occurring vitamin D metabolite, also known as 25-hydroxyvitamin D3 or 25(OH)D3. It is the primary circulating form of vitamin D in the human body, serving as a biomarker for vitamin D status and a precursor to the active hormone calcitriol. Its discovery and applications are well-documented in the literature, rooted in the study of vitamin D metabolism and its role in calcium homeostasis and bone health.

The discovery of calcifediol emerged from research in the mid-20th century to elucidate the metabolic pathway of vitamin D. In the 1960s, scientists, including Hector DeLuca and colleagues at the University of Wisconsin, identified calcifediol as the major circulating metabolite of cholecalciferol (vitamin D3), formed by hepatic hydroxylation. Using radiolabeled vitamin D3, they demonstrated that the liver enzyme 25-hydroxylase (CYP2R1) converts cholecalciferol to 25-hydroxyvitamin D3, which was isolated and characterized by 1968. This breakthrough clarified the two-step activation process of vitamin D, with calcifediol as the intermediate that is further hydroxylated in the kidneys to calcitriol (1,25-dihydroxyvitamin D3). The discovery addressed the need to understand vitamin D’s role in preventing rickets, osteoporosis, and other metabolic disorders, building on advances in chromatography, mass spectrometry, and enzymatic studies. Calcifediol’s identification led to its use in clinical diagnostics and therapeutics by the 1970s.

Synthetically, calcifediol is produced from cholecalciferol, which is derived from 7-dehydrocholesterol extracted from lanolin or fish oil. The key step involves enzymatic or chemical 25-hydroxylation. In industrial processes, cholecalciferol is subjected to biomimetic hydroxylation using cytochrome P450 enzymes or chemical oxidation with reagents like selenium dioxide or manganese oxide, selectively introducing the hydroxyl group at the 25-position of the side chain. The reaction is followed by purification via high-performance liquid chromatography to yield calcifediol as a white crystalline powder. Alternatively, calcifediol can be isolated from animal liver extracts, but synthetic methods are preferred for scalability and purity. These processes rely on established protocols in steroid chemistry and enzymatic catalysis, ensuring high stereospecificity and yield.

The primary application of calcifediol is in clinical medicine for the treatment and prevention of vitamin D deficiency and related disorders. As a therapeutic agent, it is used to manage conditions such as osteoporosis, osteomalacia, hypoparathyroidism, and chronic kidney disease, where impaired renal 1-hydroxylation limits calcitriol production. Calcifediol is administered orally or via injection, offering advantages over cholecalciferol due to its higher potency and faster onset of action, as it bypasses hepatic 25-hydroxylation. It raises serum 25-hydroxyvitamin D levels more effectively, supporting calcium absorption and bone mineralization. In diagnostics, calcifediol levels in blood are measured via immunoassays or liquid chromatography-tandem mass spectrometry to assess vitamin D status, with levels below 20 ng/mL indicating deficiency. It is also used in research to study vitamin D metabolism, receptor interactions, and non-skeletal effects, including immune modulation and cancer prevention.

In academic research, calcifediol is investigated for its role in the vitamin D endocrine system, particularly the regulation of 25-hydroxylase and 1-alpha-hydroxylase enzymes. Its pharmacokinetics and binding to vitamin D-binding protein are studied to optimize dosing regimens. The compound’s significance lies in its dual role as a therapeutic agent and diagnostic marker, reflecting progress in vitamin D research and steroid biochemistry. By enabling effective management of vitamin D-related disorders, calcifediol has become a cornerstone in endocrinology and clinical nutrition.

References

2024. Efficacy and Safety of Weekly Calcifediol Formulations (75 and 100 µg) in Subjects with Vitamin D Deficiency: A Phase II/III Randomised Trial. Nutrients, 16(22).
DOI: 10.3390/nu16223796

2024. Native vitamin D in CKD and renal transplantation: meaning and rationale for its supplementation. Journal of Nephrology, 37(7).
DOI: 10.1007/s40620-024-02055-x

1987. Hyperparathyroidism and Low Serum Osteocalcin Despite Vitamin D Replacement in Primary Biliary Cirrhosis. The Journal of Clinical Endocrinology and Metabolism, 64(5).
DOI: 10.1210/jcem-64-5-873