Phylloquinones vitamin

Figure 16.10 Biosynthesis of phylloquinone (vitamin K-j) from 1,4-dihydroxynaphthoic acid. The key step that joins the 20-carbon phytyl side chain to the aromatic ring is a Friedel-Crafts-like electrophilic substitution reaction.

Phylloquinones (vitamin Kl, produced by plants) and menaquinones-n (MK-n, vitamin K2)... 

Vitamin K represents two groups of substances named phylloquinones (vitamin Kl produced by plants) and menaquinones-n (MK-n vitamin K2). Menaquinones are synthesized by bacteria, using repeated 5-carbon units in the molecules side chain, n stands for the number of 5-carbon units. Interestingly, MK-4 is synthesized only in small amounts by bacteria but can be produced by animals (including humans) from phylloquinones and is found in a number of organs. For an overview see [1, 2],... 

As the above mentioned studies with high supplementation dosages exemplarily show, there is no known toxicity for phylloquinone (vitamin Kl), although allergic reactions are possible. This is NOT true for menadione (vitamin K3) that can interfere with glutathione, a natural antioxidant, resulting in oxidative stress and cell membrane damage. Injections of menadione in infants led to jaundice and hemolytic anemia and therefore should not be used for the treatment of vitamin K deficiency. 

Phylloquinone (vitamin Kl) is the form of vitamin K synthetized by mainly green leafy vegetables and such also appears in plant oils (soybean, cottonseed, canola, olive). Both are good sources for a daily supply, although the need of such a supply is still under discussion. Table 1 shows some good sources and their content of vitamin Kl. 

Snyder and Rapoport photolysed phylloquinone (vitamin K-l, 82) in cyclohexane solution with the surface exposed to atmospheric oxygen and moisture. This system was adopted on the assumption that the in vivo photo-oxidation would occur with the hydrocarbon side-chain dissolved in a lipid layer, but the polar naphthoquinone moiety would be in contact with water. Under the... 

Vitamin K activity is associated with several quinones, including phylloquinone (vitamin Kj), menadione (vitamin K3), and a variety of menaquinones (vitamin K2). These quinones promote the synthesis of proteins that are involved in the coagulation of blood. These proteins include prothrombin, factor VII (proconvertin), factor IX (plasma thromboplastin), and factor X (Stuart factor). A detailed discussion of blood coagulation is found in Chapter 22. The vitamin K quinones are obtained from three major sources. Vitamin K is present in vari-... 

Booth SL, Sadowski JA, Pennington JAT. Phylloquinone (vitamin Kl) content of foods in the U.S. Food and Drug Administration s total diet study. J Agric Food Chem 1995 43 1574-1579. 

The protein complex of T. elongatus consists of 12 subunits that contain 96 Chi a and 22 carotenoid molecules, 3 [4Fe4S] centres and 2 phylloquinone (vitamin K,) molecules (for molecular structures see Fig. 2). The cofactors of the ET chain are arranged in two branches as pairs of molecules related by a pseudo-C2 axis. After light excitation an electron is donated from the primary donor P700, a pair of chlorophylls, to monomeric chlorophyll a (acceptor A0), phylloquinone (A() and the 3 iron-sulfur centres (F , Oa and B). It has been controversially discussed in the literature whether both highly symmetric pigment branches are... 

Radical pairs of phylloquinone (vitamin Ki) were produced by reaction with A1C13 or by photochemical reaction at 77 K.40 The dipolar splitting (D) of 19 0.5 mT for the photochemically produced radical pair corresponds to a point dipole distance of 5.3 A, which is attributed to a solvent-separated radical pair. For radical pairs generated with A1C13, D --= 11.2 + 0.5 mT (r = 6.3 A), which is consistent with the distance between two phylloquinone radicals coordinated to an Al3+ ion.40... 

The structure of vitamin K is characterized by methylnaphthoquinone rings with a side chain at position 3. It exists naturally in two forms phylloquinone (vitamin Kt 6.13) occurs only in plants, while menaquinones (vitamin K2 6.14) are a family of compounds with a side chain consisting of between 1 and 14 isoprene units. Menaquinones are synthesized only by bacteria (which inhabit the human gastrointestinal tract and thus provide some of the vitamin K required by the body). Menadione (vitamin K3 6.15) is a synthetic compound with vitamin K activity. Unlike Kj and K2, menadione is water soluble and is not active until it is alkylated in vivo. 

Haroon, Y., Shearer, M. J., Rahim, S., Gunn, W. G., Mcenery, G. and Barkhan, P. 1982. The content of phylloquinone (vitamin Kd in human milk, cows milk and infant formula foods determined by high-performance liquid chromatography. J. Nutr. 112, 1105-1117. 

Two forms of vitamin K exist in nature. Phylloquinone (vitamin K,) is a specific vitamer synthesized by green plants in the chloroplasts menaquinones (vitamin K2) are a series of structural analogs that are synthesized by bacteria. 

JP Langenberg, UR Tjaden, EM de Vogel, DI Langerak. Determination of phylloquinone (vitamin K,) in raw and processed vegetables using reversed phase HPLC with electrofluorometric detection. Acta Alimentaria 15 187-198, 1986. 

SL Booth, KW Davidson, JA Sadowski. Evaluation of an HPLC method for the determination of phylloquinone (vitamin K,) in various food matrices. J Agric Food Chem 42 295-300, 1994. 

F Zonta, B Stancher. Quantitative analysis of phylloquinone (vitamin K,) in soy bean oils by high-performance liquid chromatography. J Chromat 329 257-263, 1985. 

M Careri, A Mangia, P Manini, N Taboni. Determination of phylloquinone (vitamin K,) by high performance liquid chromatography with UV detection and with particle beam-mass spectrometry. Fre-senius J Anal Chem 355 48-56, 1996. 

The structures of ubiquinone, menaquinone (vitamin K2), plastoquinone, and phylloquinone (vitamin K ). Purple photosynthetic bacteria contain ubiquinone, menaquinone, or both, depending on the bacterial species chloroplasts contain plastoquinone and phylloquinone. 

The Z scheme. [(Mn)4 = a complex of four Mn atoms bound to the reaction center of photosystem II Yz = tyrosine side chain Phe a = pheophytin a QA and Qb = two molecules of plastoquinone Cyt b/f= cytochrome hf,f complex PC = plastocyanin Chi a = chlorophyll a Q = phylloquinone (vitamin K,) Fe-Sx, Fe-SA, and Fe-SB = iron-sulfur centers in the reaction center of photosystem I FD = ferredoxin FP = flavoprotein (ferredoxin-NADP oxidoreductase).] The sequence of electron transfer through Fe-SA and Fe-SB is not yet clear. 

On the reducing site of photosystem I, the initial electron acceptor appears to be a molecule of chlorophyll a (see fig. 15.17). The second acceptor probably is a quinone, phylloquinone (vitamin K, fig. 15.10). In these respects, photosystem I resembles photosystem II and purple photosynthetic bacteria, which use pheophytin a or bac-teriopheophytin a followed by a quinone. From this point on, photosystem I is different its next electron carriers consist of iron-sulfur proteins instead of additional quinones. 

Menadione (vitamin K3),phylloquinone (vitamin Kj), and ascorbate (vitamin C) have been used to donate electrons to cytochrome c. For example, ascorbate is oxidized to dehydroascorbate as it uses its electrons to reduce cytochrome c directly. The dehydroascorbate is quickly reduced to ascorbate in the mitochondrion by NADH or FADH2. Menadione appears to improve cellular phosphate metabolism and to enhance electron transfer after a respiratory Complex I block. 

Bolton-Smith CPR, Fenton ST, Harrington DJ, and Shearer MJ (2000) Compilation of a provisional UK database for the phylloquinone (vitamin Ki) content of foods. British Journal of Nutrition 83, 389-99. 

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