Vitamin K
Cardiovascular Health
Overview
- Vitamin K refers to a group of fat-soluble, quinone-derived compounds (primarily phylloquinone (K₁) and menaquinones (K₂)) that act as essential cofactors for γ-glutamyl carboxylase enzymes.
- Their principal biological role is to enable the post-translational γ-carboxylation of specific glutamate residues in proteins.
- This modification is essential for calcium binding and thus for normal blood clotting, bone mineralization, and vascular health.
Chemistry
- Vitamin K1 (phylloquinone) is 2-methyl-3-(3′-hydroxy-4′-methyl-2′-(3-oxobutyl)-phenyl)-1,4-naphthoquinone, with molecular formula C₃₁H₄₆O₂ and a molecular weight of 450.7 g/mol.
- Its structure comprises a 2-methyl-1,4-naphthoquinone core with a phytyl side-chain (a 20-carbon saturated, branched hydrocarbon) at the 3-position, conferring lipophilicity.
- Menaquinones (K₂) differ by the length and saturation of the isoprenoid side chain (e.g., MK-4 has four isoprene units; MK-7 has seven).
- The quinone ring undergoes redox cycling between quinone, hydroquinone, and epoxide forms during the carboxylation cycle.
- The high degree of unsaturation in the side chain influences tissue distribution and half-life; MK-7’s longer chain yields a plasma half-life of 2–3 days versus 1 hour for K₁.
Sources & Quality
- Natural dietary sources include leafy green vegetables (e.g., kale, spinach) for phylloquinone and fermented foods (e.g., natto, hard cheeses) for menaquinones, especially MK-7.
- Commercial supplements are derived from two main processes:
- Extraction: phylloquinone is extracted from plant material using solvent-based methods (e.g., ethanol, supercritical CO₂) and purified by chromatography.
- Fermentation: MK-7 is produced by bacterial fermentation (e.g., Bacillus subtilis or Bacillus natto) followed by purification.
- Synthetic routes exist but are less common due to cost and regulatory scrutiny.
- Quality considerations include verification of the specific K-form, absence of heavy metals, and compliance with pharmaco-peptide standards (e.g., USP, EFSA).
- Look for third-party testing (e.g., USP Verified, NSF) to ensure potency, purity, and correct labeling of the vitamin K isoform.
Where to Buy Vitamin K
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