THE CONSTITUTION AND SYNTHESIS OF VITAMIN K1

The Potential of Vitamin K as a Regulatory Factor of Bone Metabolism-A Review

Vitamin K (VK), a fat-soluble vitamin, is essential for the clotting of blood because of its role in the production of clotting factors in the liver. Moreover, researchers continue to explore the role of VK as an emerging novel bioactive molecule with the potential function of improving bone health. This review focuses on the effects of VK on bone health and related mechanisms, covering VK research history, homologous analogs, dietary sources, bioavailability, recommended intake, and deficiency. The information summarized here could contribute to the basic and clinical research on VK as a natural dietary additive and drug candidate for bone health. Future research is needed to extend the dietary VK database and explore the pharmacological safety of VK and factors affecting VK bioavailability to provide more support for the bone health benefits of VK through more clinical trials.

The Antifungal Activity of Naphthoquinones: An Integrative Review

Naphthoquinones are the most commonly occurring type of quinones in nature. They are a diverse family of secondary metabolites that occur naturally in plants, lichens and various microorganisms. This subgroup is constantly being expanded through the discovery of new natural products and by the synthesis of new compounds via innovative techniques. Interest in quinones and the search for new biological activities within the members of this class have intensified in recent years, as evidenced by the evaluation of the potential antimicrobial activities of quinones. Among fungi of medical interest, yeasts of the genus Candida are of extreme importance due to their high frequency of colonization and infection in humans. The objective of this review is to describe the development of naphthoquinones as antifungals for the treatment of Candida species and to note the most promising compounds. By using certain criteria for selection of publications, 68 reports involving both synthetic and natural naphthoquinones are discussed. The activities of a large number of substances were evaluated against Candida albicans as well as against 7 other species of the genus Candida. The results discussed in this review allowed the identification of 30 naphthoquinones with higher antifungal activities than those of the currently used drugs.

Nutrition and genetics: an expanding frontier

The age of molecular biology began in 1953 with the discovery of the structure of DNA. By 1961 the genetic code for the translation of the sequence of bases in DNA to amino acids in proteins was underway, and a model for the genetic regulation of protein synthesis was proposed. My interest in the genetic regulation of nutrient metabolism began in that year during my sabbatical leave in the laboratory of Sir Hans Krebs at Oxford University. In the present article, I describe 2 episodes in my career during which I used genetic concepts to explain a nutritional phenomenon; the first episode occurred before doing the experimental work, and the second occurred after the experimental work was completed. My first brainstorm, which occurred in 1961, was to investigate the hypothesis that all of the fat-soluble vitamins act by the regulation of a cluster of genes. Unfortunately, I selected vitamin K as my model and discovered that it is the only fat-soluble vitamin that does not work in full or in part by the regulation of a set of genes. In 1967 I undertook a second problem, which was to determine the mode of action of polyunsaturated fatty acids in lowering plasma lipid concentrations in humans. We discovered that linoleic acid reduced the storage and enhanced the oxidation of fatty acids. The genetic interpretation of this study has come only recently: polyunsaturated fats have been shown to down-regulate enzymes that accomplish storage of fatty acids and to up-regulate genes that enhance fatty acid oxidation.

Isoprenoid quinones as biomarkers of microbial populations in the environment

Isoprenoid quinones are lipid molecules present in all species of respiratory and photosynthetic microorganisms and exhibit marked structural variations depending upon the microbial taxon. Taking advantage of this, quinones have been used not only as chemotaxonomic markers in microbial systematics but also as good measures of microbial populations in the environment in terms of quantity, quality, and activity. Basically, this biomarker approach, called the quinone profile method, is applicable to all environmental samples from which an absolute amount of microbial biomass > or =10(9) cells can be collected. The quinone profile method allows good measurement of both fundamental and applied aspects of ecological and environmental microbiology. In particular, numerical cluster analyses of quinone profiles are useful for monitoring microbial population shifts in an ecosystem which is not amenable to conventional culture methods and molecular techniques. The combined use of molecular techniques and the quinone profile method in this research area should provide more accurate and reliable data regarding population dynamics and community structures.

The vitamin K dependent reaction

The vitamin K's are 2-methyl-1,4-naphthoquinones. The vitamin is required for the post-translational gamma-carboxylation of glutamyl residues in precursor polypeptides. The vitamin K step in this carboxylation, however, requires not the quinone but the hydroquinone plus oxygen. Thus, the vitamin K-dependent step is a "mixed function" oxidation requiring a reducing compound plus molecular oxygen to provide a form of oxidant (e.g., a free radical, a hydroperoxide) capable of abstracting a particular, slightly labile hydrogen from a glutamyl residue, leaving this position free to accept a carbon dioxide molecule. This oxidation appears similar to that of other mixed function oxidants such as cytochrome P450 plus oxygen, ascorbic acid (with traces of ferrous iron) plus oxygen, ferrous iron plus oxygen, and a number of other systems which function in a wide variety of oxidation. Inhibition by spin-trapping agents suggests a free radical step in the vitamin K hydroquinone-dependent reaction, similar to other mixed function oxidations.

VITAMIN K

During the decade following Dam's first observations on the hemorrhagic syndrome the combined efforts of several groups of investigators have solved many of the important problems connected with the new vitamin. Sources of vitamin K were discovered, methods of extraction and purification devised, the isolation effected, the structure of K(1) worked out and then verified by synthesis, and a promising start made on the therapeutic applications. In addition, simple water soluble compounds with antihemorrhagic properties have been supplied for clinical work. Preliminary results with these compounds are encouraging.