Phylloquinone,

Chemical Name 2-Methyl-3-(3,7,11,1 5-tetramethvl-2-hexadecenvD-1,4-naphthalenedione Common Name Vitamin K, phytomeanadion, phylloquinone Structural Formula ... 

An example of a biological Friedel-Crafts reaction occurs during the biosynthesis of phylloquinone, or vitamin Kl( the human blood-clotting factor. Phylloquinone is formed by reaction of 1,4-dihydroxynaphthoic acid with phytyl diphosphate. Phytyl diphosphate first dissociates to a resonance-stabilized allylic carbocation, which then substitutes onto the aromatic ring in the typical way. Several further transformations lead to phylloquinone (Figure 16.10). 

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. 

K Phylloquinone, menaquinones Coenzyme in formation of y-carboxyglutamate in enzymes of blood clotting and bone matrix Impaired blood clotting, hemorrhagic disease... 

Although there are physiologically significant quantities of vitamin E (tocopherol) and vitamin K (phylloquinone) in black tea, their extractabil-ity is not adequately known.110... 

Reaction centers of bacteria contain polypeptides, bacteriochlorophylls, bacteriopheo-phytins, two quinines, and nonheme iron atom. In some bacterial species, both the quinones are ubiquinones, whereas in some others one of the quinones is menaquinone [37,39]. Depending on the bacterial species chloroplasts contain plastoquinone and phyl-loquinone. Structures of ubiquinone, menaquinone, and phylloquinone are provided in Figures 7.12 through 7.14, respectively. 

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... 

Hydroxylation ergotamine phenylalanine tyrosine norethisterone oestrone phenytoin phylloquinone... 

The vitamin K requirement is met from the diet (vitamin Ki) and microorganisms in the intestine (vitamin K2). The richest dietary source of vitamin K is green leafy vegetables but it is also present in meat and dairy produce. The structural formulae of vitamin Ki (phylloquinone) and vitamin K2 (menaquinone) are given in Figure 15.15. It was discovered in 1929 by Henrik Dam in Copenhagen, who discovered that it was necessary for the clotting... 

Vitamin K (phylloquinone) and similar substances with modified side chains are involved in carboxylating glutamate residues of coagulation factors in the liver (see p. 290). The form that acts as a cofactor for carboxylase is derived from the vitamin by enzymatic reduction. Vitamin K antagonists (e. g., coumarin derivatives) inhibit this reduction and consequently carboxylation as well. This fact is used to inhibit blood coagulation in prophylactic treatment against thrombosis. Vitamin K deficiency occurs only rarely, as the vitamin is formed by bacteria of the intestinal flora. 

This enzyme [EC 1.6.99.2] (also known as NAD(P)H quinone reductase, DT diaphorase, quinone reductase, azoreductase, phylloquinone reductase, and menadione reductase) catalyzes the reaction of NAD(P)H with an acceptor to produce NAD(P) and the reduced acceptor. This FAD-dependent enzyme is inhibited by dicoumarol. 

Among the vitamin K vitamers, only phylloquinone is accounted for routine food analysis. Furthermore infant formulas, both milk-based and soy protein-based, are supplemented with a synthetic preparation of phylloquinone (the only form admitted) [403], which usually contain about 10% of the biologically inactive ctT-isomer [497]. 

Vitamin K is traditionally extracted with solvents such as acetone or ethanol, followed by a sample clean-up, such as enzymatic hydrolysis [498,499], column chromatography [308], TEC [500,501], SPE [502,503], or a combination of them. Gao and Ackman [504] couple two different methods, an SPE purification, previously reported by Eerland and Sadowski [505], preceded by a modified enzymafic digestion from fhe original procedure of Bueno and Villalobos [506]. They observe fhaf SPE step is nol enough to purify the sample. Jacob and Elmadfa [507] report an extraction from food with different solvents (according to the type of food), the evaporation of these and re-dissolving in hexane to perform a simple LEE as the clean-up step using methanol/water. SFE has been successfully applied for phylloquinone extraction from powdered infant formulas [497]. 

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