- Assessment of the contribution of NAD(P)H-dependent quinone oxidoreductase 1 (NQO1) to the reduction of vitamin K in wild-type and NQO1-deficient mice
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NQO1 [NAD(P)H quinone oxidoreductase 1; also known as DT-diaphorase] is a cytosolic enzyme that catalyses the twoelectron reduction of various quinones including vitamin K. The enzyme may play a role in vitamin K metabolism by reducing vitamin K to vitamin K hydroquinone for utilization in the post-translational γ-glutamyl carboxylation reactions required by several proteins involved in blood coagulation. The aim of the present study was to assess the contribution of NQO1 to vitamin K reduction and haemostasis in an in vivo model. We examined the contribution of NQO1 to haemostasis by examining survival rates in mice poisoned with the anticoagulant warfarin. Supraphysiological amounts of vitamin K sufficiently reversed the effects of warfarin in both wild-type and NQO1-deficient mice. Additionally, vitamin K reductase activities distinct from VKOR (vitamin K epoxide reductase) and NQO1 were measured in vitro from both wild-type and NQO1-defecient mice. The results of the present study suggest that NQO1 does not play a major role in the production of vitamin K hydroquinone and supports the existence of multiple vitamin K reduction pathways. The properties of a NAD(P)H-dependent vitamin K reductase different from NQO1 are described.
- Ingram, Brian O.,Turbyfill, Jared L.,Bledsoe, Peggy J.,Jaiswal, Anil K.,Stafford, Darrel W.
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- Prodrugs for systemic bioreductive activation-independent delivery of phyllohydroquinone, an active form of phylloquinone (vitamin K1) 1: Preparation and in vitro evaluation
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With the aim of overcoming the delivery problems (water-solubility and bioreductive activation problems) of phyllohydroquinone (PKH), an active form of phylloquinone (PK, vitamin K1), the N,N-dimethylglycine esters of phyllohydroquinone (1-mono, 1; 4-mono, 2; and 1,4-bis, 3) have been synthesized and assessed in vitro as a prodrug for the systemic bioreductive activation-independent delivery of PKH. The hydrochloride salts of the esters were found to be quite soluble in water. Hydrolysis of the esters in rat liver S9 fraction, rat plasma and phosphate buffer, pH 7.4, at 37 °C, was kinetically studied in the presence and absence of an esterase inhibitor. The hydrolysis was catalyzed by esterases located in rat liver and rat plasma and quantitatively yielded PKH. The enzymatic cleavage and the vitamin K- dependent carboxylation activity of the esters in the rat liver microsome preparation at pH 7.2 and 25°C were studied. The regeneration of PKH from the esters was catalyzed by carboxylesterases located in the rat liver microsome, and the order was as follows: 1>3>2. The carboxylation was stimulated by selected ester 1 in the absence of dithiothreitol, an activator of the vitamin K cycle. The carboxylation activity of 1 was strongly inhibited in the presence of eserine, a carboxylesterase inhibitor. Compound 1 could also stimulate carboxylase under warfarin-poisoning conditions, where the vitamin K cycle was strongly inhibited. These results indicated that these highly water-soluble and liver-esterase hydrolyzable ester derivatives of PKH are potential candidates for parenteral prodrugs which can thus achieve the systemic bioreductive activation-independent delivery of PKH.
- Takata, Jiro,Karube, Yoshiharu,Matsunaga, Kazuhisa,Hanada, Mitsunobu,Hidaka, Ryoji,Matsushima, Yoshikazu
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- Method for synthesizing vitamin K1
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The invention relates to a method for synthesizing vitamin K1, relating to the technical field of synthesis of organic matters. The method comprises the following steps: reducing 2-methyl1,4-naphthoquinone to 2-methyl-1,4-naphthalenediol in certain solvents by virtue of a reducing agent under certain conditions, then adding phytol, reacting by using an appropriate catalyst under certain conditions to synthesize 2-methyl3-phytyl1,4-naphthalenediol, then oxidizing the 2-methyl3-phytyl1,4-naphthalenediol by using an appropriate oxidizing agent to obtain vitamin K1, and decompressing and concentrating to obtain the vitamin K1. According to the method for synthesizing the vitamin K1, the 2-methyl1,4-naphthoquinone is used as a raw material, and the hydroxyl groups are not required to be protected, so that the method has the characteristics of simple process, moderate reaction conditions, high productivity, high product purity and high yield; moreover, the method is low in production cost and very suitable for industrialized production.
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- Detection and quantification of vitamin K1 quinol in leaf tissues
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Phylloquinone (2-methyl-3-phytyl-1,4-naphthoquinone; vitamin K1) is vital to plants. It is responsible for the one-electron transfer at the A1 site of photosystem I, a process that involves turnover between the quinone and semi-quinone forms of phylloquinone. Using HPLC coupled with fluorometric detection to analyze Arabidopsis leaf extracts, we detected a third redox form of phylloquinone corresponding to its fully reduced - quinol-naphthoquinone ring (PhQH2). A method was developed to quantify PhQH2 and its corresponding oxidized quinone (PhQ) counterpart in a single HPLC run. PhQH2 was found in leaves of all dicotyledonous and monocotyledonous species tested, but not in fruits or in tubers. Its level correlated with that of PhQ, and represented 5-10% of total leaf phylloquinone. Analysis of purified pea chloroplasts showed that these organelles accounted for the bulk of PhQH2. The respective pool sizes of PhQH2 and PhQ were remarkably stable throughout the development of Arabidopsis green leaves. On the other hand, in Arabidopsis and tomato senescing leaves, PhQH2 was found to increase at the expense of PhQ, and represented 25-35% of the total pool of phylloquinone. Arabidopsis leaves exposed to light contained lower level of PhQH2 than those kept in the dark. These data indicate that PhQH2 does not originate from the photochemical reduction of PhQ, and point to a hitherto unsuspected function of phylloquinone in plants. The putative origin of PhQH2 and its recycling into PhQ are discussed.
- Oostende, Chloe van,Widhalm, Joshua R.,Basset, Gilles J.C.
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p. 2457 - 2462
(2008/12/22)
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