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Menadione is an Intermediate in the Phylloquinone to Menaquinone‐4 Conversion
Author(s) -
Rajabi Ala Al,
Peterson James W.,
Booth Sarah L.,
Choi SangWoon,
Fu Xueyan
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.218.6
Subject(s) - menadione , chemistry , side chain , chromatography , biochemistry , enzyme , organic chemistry , polymer
Objective Phylloquinone (PK; MW 451) is converted into menaquinone‐4 (MK‐4; MW 445) via side‐ chain removal. Direct evidence that menadione (MD; MW 172), the naphthoquinone ring without the side chain, is the conversion intermediate is lacking. Methods Following a 14 day PK‐deficient diet, male Fischer 344 rats (8‐mo; n=15) were fed deuterium‐labeled (‐d) collard greens as source of 1.5 mg PK‐d [MW 459–463 (64% of total)] per kg diet for 0 (control), 1 and 7 days. Results Using LC/MS, PK‐d and MK‐4‐d (MW 446–449) were detected in tissues after 1 and 7 days. The liver contains PK‐d (209.7±111.8 pmol/g on day 7) but no MK‐4‐d; in contrast, the salivary gland and brain contained MK‐4‐d (757.2±111.8 and 38.6±8.3 pmol/g, respectively on day 7) but no PK‐d. MK‐4‐d carried the d‐label on the naphthoquinone ring, but not on the side chain, confirming the need for side chain removal for its formation. Using LC/MS, unconjugated MD‐d (MW 173–174) was detected in urine. Using LC‐MS/MS, unconjugated MD‐d was detected in serum of rats (n=4/5 at day 1; n= 3/5 at day 7). There was no detected PK‐d, MK‐4‐d, or MD‐d in the controls. Conclusions This is the first time unconjugated MD in biological materials has been detected. This is the first direct evidence that MD is an intermediate in the PK to MK‐4 conversion. Future studies are required to determine the function of this conversion. Grant Funding Source : USDA Cooperative Agreement 58‐1950‐7‐707 and National Institutes of Health DK069341