Exploring 2-methyl-substituted vitamin K3 derivatives with potent inhibitory activity against the 3CL protease of SARS-CoV-2

Since the outbreak of the pandemic, various anti-SARS-CoV-2 drugs have been developed. In particular, 3CL protease (3C-like protease, 3CLpro) is an attractive drug target because it is an essential enzyme for viral multiplication and is present only in viruses, not in humans. To date, 3CLpro inhibitors against SARS-CoV-2 such as nirmatrelvir and ensitrelvir have been launched as oral drugs in Japan, but there is still no potent drug against SARS-CoV-2, due to issues of in vivo absorption and stability. Recently, vitamin K3 was reported to show inhibitory activity against 3CLpro of SARS-CoV-2, and the mechanism of action was predicted to be the formation of a covalent bond between the thiol group of cysteine 145, the active center of 3CLpro, and the C-3 position of vitamin K3. Therefore, we synthesized derivatives in which the 2-methyl group of the vitamin K3 was systematically converted to other substituents and examined their inhibitory activity against 3CLpro of SARS-CoV-2. The results showed that the compounds with the sulfide structure showed an approximately 4-fold increase in activity over vitamin K3. These results indicated the possibility of creating new inhibitors based on vitamin K3 and its derivatives.

Exploring Novel Vitamin K Derivatives with Anti-SARS-CoV-2 Activity

From our compound library of vitamin K derivatives, we found that some compounds exhibited anti-SARS-CoV-2 activity in VeroE6/TMPRSS2 cells. The common structure of these compounds was menaquinone-2 (MK-2) with either the m-methylphenyl or the 1-naphthyl group introduced at the end of the side chain. Therefore, new vitamin K derivatives having more potent anti-SARS-CoV-2 activity were explored by introducing various functional groups at the ω-position of the side chain. MK-2 derivatives with a purine moiety showed the most potent antiviral activity among the derivatives. We also found that their mechanism of action was the inhibition of RNA-dependent RNA polymerase (RdRp) of SARS-CoV-2. The chemical structures of our compounds were completely different from those of nucleic acid derivatives such as remdesivir and molnupiravir, clinically approved RdRp inhibitors for COVID-19 treatment, suggesting that our compounds may be effective against viruses resistant to these nucleic acid derivatives.

Activation of transient receptor potential channels is involved in reactive oxygen species (ROS)-dependent regulation of blood flow by (-)-epicatechin tetramer cinnamtannin A2

Intervention trials confirmed that blood flow-mediated dilatation increases significantly after intake of astringent (-)-epicatechin (EC) oligomers (procyanidins)-rich foods, but the mechanism remains unclear. We have previously found that procyanidins can activate the sympathetic nervous and subsequently increase blood flow. Here, we examined whether procyanidin-derived reactive oxygen species (ROS) activate transient receptor potential (TRP) channels in gastrointestinal sensory nerves and consequently induce sympathoexcitation. We evaluated the redox properties of EC and its tetramer cinntamtannin A2 (A2) at pH 5 or 7, mimicking plant vacuole or oral cavity/small intestine using a luminescent probe. At pH 5, A2 or EC showed O₂^･- scavenging ability, but they promoted O₂^･- generation at pH 7. We observed blood flow in rat cremaster arterioles using laser Doppler, a single oral dose of 10 µg/kg A2 markedly increased blood flow, while EC showed little activity. This change with A2 was significantly dampened by co-administration of adrenaline blocker, ROS scavenger N-acetyl-L-cysteine (NAC), TRP vanilloid 1, or ankyrin 1 antagonist. We also performed a docking simulation of EC or A2 with the binding site of a typical ligand for each TRP channel and calculated the respective binding affinities. The binding energies were notably higher for A2 than typical ligands, suggesting that A2 is less likely to bind to these sites. ROS produced at neutral pH following the orally administered A2 to the gastrointestinal tract could activate TRP channels, triggering sympathetic hyperactivation and causing hemodynamic changes.

Effect of lonidamine derivatives on the inhibition of transformed cell area expansion

Expansion of transformed cell area is regulated by the surrounding nontransformed cells. Lonidamine (LND) was recently found to regulate transformed cell area expansion through suppressing the cell motility of nontransformed cells; however, the structure-activity relationship between LND and this inhibitory activity has yet to be elucidated. We synthesized several LND derivatives and evaluated their inhibitory activity against the expansion of transformed cell area and found that the halogenation pattern on the benzene ring moiety, the carboxylic acid moiety, and the overall hydrophobicity of the molecule were correlated with inhibition activity. We also found that the localization of the tight junction protein, zonula occludens-1 (ZO-1), in nontransformed cells was significantly altered after treatment with the LND derivatives that displayed inhibitory activity. Further studies with LND derivatives and monitoring the localization of ZO-1 may help to develop more active compounds for suppressing transformed cell area expansion and lead to new anticancer treatments.

Naturally occurring UBIAD1 mutations differentially affect menaquinone biosynthesis and vitamin K-dependent carboxylation

UbiA prenyltransferase domain-containing protein-1 (UBIAD1) is responsible for the biosynthesis of menaquinone-4 (MK-4), a cofactor for extrahepatic carboxylation of vitamin K-dependent (VKD) proteins. Genetic variations of UBIAD1 are mainly associated with Schnyder corneal dystrophy (SCD), a disease characterized by abnormal accumulation of cholesterol in the cornea. Results from in vitro studies demonstrate that SCD-associated UBIAD1 mutations are defective in MK-4 biosynthesis. However, SCD patients do not exhibit typical phenotypes associated with defects of MK-4 or VKD carboxylation. Here, we coupled UBIAD1's biosynthetic activity of MK-4 with VKD carboxylation in HEK293 cells that stably express a chimeric VKD reporter protein. The endogenous Ubiad1 gene in these cells was knocked out by CRISPR-Cas9-mediated genome editing. The effect of UBIAD1 mutations on MK-4 biosynthesis and VKD carboxylation was evaluated in Ubiad1-deficient reporter cells by determining the production of MK-4 or by measuring the efficiency of reporter-protein carboxylation. Our results show that the hot-spot mutation N102S has a moderate impact on MK-4 biosynthesis (retained ˜ 82% activity) but does not affect VKD carboxylation. However, the G186R mutation significantly affected both MK-4 biosynthesis and VKD carboxylation. Other mutations exhibit varying degrees of effects on MK-4 biosynthesis and VKD carboxylation. These results are consistent with in vivo results obtained from gene knock-in mice and SCD patients. Our findings suggest that UBIAD1's MK-4 biosynthetic activity does not directly correlate with the phenotypes of SCD patients. The established cell-based assays in this study provide a powerful tool for the functional studies of UBIAD1 in a cellular milieu.

A novel vitamin K derived anticoagulant tolerant to genetic variations of vitamin K epoxide reductase

BACKGROUND

Vitamin K antagonists (VKAs), such as warfarin, have remained the cornerstone of oral anticoagulation therapy in the prevention and treatment of thromboembolism for more than half a century. They function by impairing the biosynthesis of vitamin K-dependent (VKD) clotting factors through the inhibition of vitamin K epoxide reductase (VKOR). The challenge of VKAs therapy is their narrow therapeutic index and highly variable dosing requirements, which are partially the result of genetic variations of VKOR.

OBJECTIVES

The goal of this study was to search for an improved VKA that is tolerant to the genetic variations of its target enzyme.

METHODS

A series of vitamin K derivatives with benzyl and related side-chain substitutions at the 3-position of 1,4-naphthoquinone were synthesized. The role of these compounds in VKD carboxylation was evaluated by mammalian cell-based assays and conventional in vitro activity assays.

RESULTS

Our results showed that replacing the phytyl side-chain with a methylene cyclooctatetraene (COT) moiety at the 3-position of vitamin K1 converted it from a substrate to an inhibitor for VKD carboxylation. Strikingly, this COT-vitamin K derivative displayed a similar inhibition potency in warfarin-resistant VKOR mutations whose warfarin resistance varied more than 400-fold. Further characterization of COT-vitamin K for the inhibition of VKD carboxylation suggested that this compound targets multiple enzymes in the vitamin K redox cycle. Importantly, the anticoagulation effect of COT-vitamin K can be rescued with high doses of vitamin K1 .

CONCLUSION

We discovered a vitamin K analogue that functions as a VKA and is tolerant to genetic variations in the target enzyme.

Development of Selective TGR5 Ligands Based on the 5,6,7,8-Tetrahydro-5,5,8,8-tetramethylnaphthalene Skeleton

TGR5, a G-protein-coupled receptor (GPCR), plays an important role in several physiological functions. TGR5 activation through bile acids induces an increase in energy expenditure. Therefore, synthetic TGR5 ligands could be useful for the treatment of obesity or dyslipidemia. In this study, we designed and synthesized a set of TGR5 ligands with a 5,6,7,8-tetrahydro-5,5,8,8-tetramethylnaphthalene (TMN) skeleton, and evaluated their TGR5 agonistic activity. We also investigated the selectivity of the synthesized compounds for TGR5 relative to the farnesoid X receptor (FXR) and retinoic acid receptor (RAR). Our results show that compound 4 b [N-(2-chlorophenyl)-5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenecarboxamide] exhibited potent TGR5 agonist activity with an IC₅₀ value of 8.4 nM without significant cytotoxicity. In addition, compound 4 b showed only slight agonistic activity toward FXR and RAR at 1 μM treatment. These data indicate that compound 4 b is a selective TGR5 agonist, and could be a promising therapeutic agent for dyslipidemia.

Study on structure-activity relationship of vitamin K derivatives: Conversion of the naphthoquinone part into another aromatic ring and evaluation of their neuronal differentiation-inducing activity

We synthesized novel vitamin K derivatives by converting the naphthoquinone group to benzene derivatives and benzoquinone. We evaluated their neuronal differentiation activities to investigate the effect of the quinone moiety on this process. We observed that the 1,4-quinone as well as the side chain part play important roles in neuronal differentiation. We also performed QSAR analysis to predict the compounds which would have higher differentiation activity.

Elucidation of the Interaction between Flavan-3-ols and Bovine Serum Albumin and Its Effect on Their In-Vitro Cytotoxicity

Flavan-3-ols (FLs), specifically catechin and its oligomer B-type procyanidins, are suggested to potently bind to bovine serum albumin (BSA). We examined the interaction between BSA and FLs by fluorescence quenching and found the following order of binding activities to BSA: cinnamtannin A2 (A2; tetramer) > procyanidin C1 (C1; trimer) ≈ procyanidin B2 (B2, dimer) > (−)epicatechin (EC, monomer). Docking simulations between BSA and each compound at the binding site showed that the calculated binding energies were consistent with the results of our experimental assay. FLs exerted cytotoxicity at 1000 μg/mL in F11 cell culture with fetal bovine serum containing BSA. In culture containing serum-free medium, FLs exhibited significant cell proliferation at 10⁻⁴ μg/mL and cytotoxicity was observed at concentrations greater than 10 μg/mL. Results of this study suggest that interactions between polyphenols and BSA should be taken into account when evaluating procyanidin in an in vitro cell culture system.

Eldecalcitol is more effective in promoting osteogenesis than alfacalcidol in Cyp27b1-knockout mice

Calcium (Ca) absorption from the intestinal tract is promoted by active vitamin D (1α,25D3). Vitamin D not only promotes Ca homeostasis, but it also inhibits bone resorption and promotes osteogenesis, thus playing a role in the maintenance of normal bone metabolism. Because 1α,25D3 plays an important role in osteogenesis, vitamin D formulations, such as alfacalcidol (ALF) and eldecalcitol (ELD), are used for treating osteoporosis. While it is known that, in contrast to ALF, ELD is an active ligand that directly acts on bone, the reason for its superior osteogenesis effects is unknown. Cyp27b1-knockout mice (Cyp27b1-/-mice) are congenitally deficient in 1α,25D3 and exhibit marked hypocalcemia and high parathyroid hormone levels, resulting in osteodystrophy involving bone hypocalcification and growth plate cartilage hypertrophy. However, because the vitamin D receptor is expressed normally in Cyp27b1-/-mice, they respond normally to 1α,25D3. Accordingly, in Cyp27b1-/-mice, the pharmacological effects of exogenously administered active vitamin D derivatives can be analyzed without being affected by 1α,25D3. We used Cyp27b1-/-mice to characterize and clarify the superior osteogenic effects of ELD on the bone in comparison with ALF. The results indicated that compared to ALF, ELD strongly induces ECaC2, calbindin-D9k, and CYP24A1 in the duodenum, promoting Ca absorption and decreasing the plasma concentration of 1α,25D3, resulting in improved osteogenesis. Because bone morphological measurements demonstrated that ELD has stronger effects on bone calcification, trabecular formation, and cancellous bone density than ALF, ELD appears to be a more effective therapeutic agent for treating postmenopausal osteoporosis, in which cancellous bone density decreases markedly. By using Cyp27b1-/-mice, this study was the first to succeed in clarifying the osteogenic effect of ELD without any influence of endogenous 1α,25D3. Furthermore, ELD more strongly enhanced bone mineralization, trabecular proliferation, and cancellous bone density than did ALF. Thus, ELD is expected to show an effect on postmenopausal osteoporosis, in which cancellous bone mineral density decreases markedly. In the future, this study may enable the development of next-generation active vitamin D derivatives with higher affinity for bone than ELD.

Comparison of the sympathetic stimulatory abilities of B-type procyanidins based on induction of uncoupling protein-1 in brown adipose tissue (BAT) and increased plasma catecholamine (CA) in mice

OBJECTIVES

We previously found that elevated energy expenditure following a single oral dose of flavan 3-ols (FL), a mixture of catechins and B type procyanidins, is caused by sympathetic nerve activation. In the present study, we compared the activity of the FL components (-)-epicatechin (EC; monomer), procyanidin B2 (B2; dimer), procyanidin C1 (C1; trimer), cinnamtannin A2 (A2; tetramer), and more than pentamer fraction (P5).

METHODS

Male ICR mice were treated with a single oral dose of FL, EC, B2, C1, A2, or P5. The animals were sacrificed and blood and brown adipose tissue (BAT) sampled. The plasma catecholamine (CA) levels and BAT uncoupling protein (UCP)-1 mRNA expression were determined.

RESULTS

A single dose of 10 mg/kg FL significantly increased plasma CA and UCP-1 mRNA levels. B2, C1, and A2, but not EC and P5 (all at 1 mg/kg), significantly increased plasma adrenaline levels. Plasma noradrenaline was significantly elevated by B2 and A2, but not by EC, C1, or P5. UCP-1 mRNA levels were significantly increased by C1 and P5. In the dose response study of A2, 10-3 mg/kg A2 increased UCP-1 mRNA levels significantly, but not 10-2 and 10-1 mg/kg A2. In addition, combination treatment with 10-1 mg/kg A2 and yohimbine, an α2 adrenalin blocker, remarkably increased UCP-1 mRNA levels.

CONCLUSION

These results suggest that FL and its components, except EC, increase UCP-1 mRNA and plasma CA with varying efficacy.

Synthesis of novel vitamin K derivatives with alkylated phenyl groups introduced at the ω-terminal side chain and evaluation of their neural differentiation activities

Vitamin K is an essential cofactor of γ-glutamylcarboxylase as related to blood coagulation and bone formation. Menaquinone-4, one of the vitamin K homologues, is biosynthesized in the body and has various biological activities such as being a ligand for steroid and xenobiotic receptors, protection of neuronal cells from oxidative stress, and so on. From this background, we focused on the role of menaquinone in the differentiation activity of progenitor cells into neuronal cells and we synthesized novel vitamin K derivatives with modification of the ω-terminal side chain. We report here new vitamin K analogues, which introduced an alkylated phenyl group at the ω-terminal side chain. These compounds exhibited potent differentiation activity as compared to control.

Substitution at the C-3 Position of Catechins Has an Influence on the Binding Affinities against Serum Albumin

It is known that catechins interact with the tryptophan (Trp) residue at the drug-binding site of serum albumin. In this study, we used catechin derivatives to investigate which position of the catechin structure strongly influences the binding affinity against bovine serum albumin (BSA) and human serum albumin (HSA). A docking simulation showed that (-)-epigallocatechin gallate (EGCg) interacted with both Trp residues of BSA (one at drug-binding site I and the other on the molecular surface), mainly by π-π stacking. Fluorescence analysis showed that EGCg and substituted EGCg caused a red shift of the peak wavelength of Trp similarly to warfarin (a drug-binding site I-specific compound), while 3-O-acyl-catechins caused a blue shift. To evaluate the binding affinities, the quenching constants were determined by the Stern-Volmer equation. A gallate ester at the C-3 position increased the quenching constants of the catechins. Against BSA, acyl substitution increased the quenching constant proportionally to the carbon chain lengths of the acyl group, whereas methyl substitution decreased the quenching constant. Against HSA, neither acyl nor methyl substitution affected the quenching constant. In conclusion, substitution at the C-3 position of catechins has an important influence on the binding affinity against serum albumin.

A single oral dose of flavan-3-ols enhances energy expenditure by sympathetic nerve stimulation in mice

Numerous clinical studies have found that ingestion of chocolate reduces the risk of metabolic syndrome, however, the mechanisms were remain unclear. We have reported that a single dose of a flavan-3-ol fraction derived from cocoa (FL) enhanced energy expenditure (EE) and increased the mRNA expression levels of uncoupling proteins (UCPs) and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), and the protein level of phosphorylated AMP-activated protein kinase (AMPK)α in tissues, along with plasma adrenaline level. In the present study, we examined whether the EE enhancing activity of FL is mediated by adrenergic effect using several adrenalin receptor (AR) blockers. In the first study, mice were butoxamine, as β2AR blocker, with vehicle or 10mg/kg FL orally. We found that pretreatment with butoxamine prevented the increases of EE, the mRNA expression of UCP-3, and phosphorylated AMPKα that were induced in the gastrocnemius muscle of mice by 10mg/kg FL. Secondly, mice were given SR52930, as β3AR blocker. Pretreatment with SR52930 prevented the increases of EE, the mRNA expression of UCP-3, and phosphorylated AMPKα that were induced in the gastrocnemius muscle of mice by 10mg/kg FL. Pretreatment with a combination of both blockers also reduced the increments in mRNA expression levels of UCPs and PGC-1α, however, phosphorylated AMPKα in skeletal muscle was rather increased. These results suggest that the ability of a single oral dose of FL to enhance metabolic activity is mediated by sympathetic nerve system (SNS).

A Single Oral Administration of Theaflavins Increases Energy Expenditure and the Expression of Metabolic Genes

Theaflavins are polyphenols found in black tea, whose physiological activities are not well understood. This study on mice evaluated the influence of a single oral administration of theaflavins on energy metabolism by monitoring the initial metabolic changess in skeletal muscle and brown adipose tissue (BAT). Oxygen consumption (VO2) and energy expenditure (EE) were increased significantly in mice treated with theaflavin rich fraction (TF) compared with the group administered vehicle alone. There was no difference in locomotor activity. Fasting mice were euthanized under anesthesia before and 2 and 5, 20-hr after treatment with TF or vehicle. The mRNA levels of uncoupling protein-1 (UCP-1) and peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) in BAT were increased significantly 2-hr after administration ofTF. The levels of UCP-3 and PGC-1α in the gastrocnemius muscle were increased significantly 2 and 5-hr after administration of TF. The concentration of phosphorylated AMP-activated protein kinase (AMPK) 1α was also increased significantly in the gastrocnemius 2 and 5-hr after treatment with TF. These results indicate that TF significantly enhances systemic energy expenditure, as evidenced by an increase in expression of metabolic genes.

Functional characterization of the vitamin K2 biosynthetic enzyme UBIAD1

UbiA prenyltransferase domain-containing protein 1 (UBIAD1) plays a significant role in vitamin K₂ (MK-4) synthesis. We investigated the enzymological properties of UBIAD1 using microsomal fractions from Sf9 cells expressing UBIAD1 by analysing MK-4 biosynthetic activity. With regard to UBIAD1 enzyme reaction conditions, highest MK-4 synthetic activity was demonstrated under basic conditions at a pH between 8.5 and 9.0, with a DTT ≥0.1 mM. In addition, we found that geranyl pyrophosphate and farnesyl pyrophosphate were also recognized as a side-chain source and served as a substrate for prenylation. Furthermore, lipophilic statins were found to directly inhibit the enzymatic activity of UBIAD1. We analysed the aminoacid sequences homologies across the menA and UbiA families to identify conserved structural features of UBIAD1 proteins and focused on four highly conserved domains. We prepared protein mutants deficient in the four conserved domains to evaluate enzyme activity. Because no enzyme activity was detected in the mutants deficient in the UBIAD1 conserved domains, these four domains were considered to play an essential role in enzymatic activity. We also measured enzyme activities using point mutants of the highly conserved aminoacids in these domains to elucidate their respective functions. We found that the conserved domain I is a substrate recognition site that undergoes a structural change after substrate binding. The conserved domain II is a redox domain site containing a CxxC motif. The conserved domain III is a hinge region important as a catalytic site for the UBIAD1 enzyme. The conserved domain IV is a binding site for Mg²⁺/isoprenyl side-chain. In this study, we provide a molecular mapping of the enzymological properties of UBIAD1.

YY1 positively regulates human UBIAD1 expression

Vitamin K is involved in bone formation and blood coagulation. Natural vitamin K compounds are composed of the plant form phylloquinone (vitamin K1) and a series of bacterial menaquionones (MK-n; vitamin K2). Menadione (vitamin K3) is an artificial vitamin K compound. MK-4 contains 4-isoprenyl as a side group in the 2-methyl-1,4-naphthoquinone common structure and has various bioactivities. UbiA prenyltransferase domain containing 1 (UBIAD1 or TERE1) is the menaquinone-4 biosynthetic enzyme. UBIAD1 transcript expression significantly decreases in patients with prostate carcinoma and overexpressing UBIAD1 inhibits proliferation of a tumour cell line. UBIAD1 mRNA expression is ubiquitous in mouse tissues, and higher UBIAD1 mRNA expression levels are detected in the brain, heart, kidneys and pancreas. Several functions of UBIAD1 have been reported; however, regulation of the human UBIAD1 gene has not been elucidated. Here we report cloning and characterisation of the human UBIAD1 promoter. A 5' rapid amplification of cDNA ends analysis revealed that the main transcriptional start site was 306 nucleotides upstream of the translation initiation codon. Deletion and mutation analyses revealed the functional importance of the YY1 consensus motif. Electrophoretic gel mobility shift and chromatin immunoprecipitation assays demonstrated that YY1 binds the UBIAD1 promoter in vitro and in vivo. In addition, YY1 small interfering RNA decreased endogenous UBIAD1 mRNA expression and UBIAD1 conversion activity. These results suggest that YY1 up-regulates UBIAD1 expression and UBIAD1 conversion activity through the UBIAD1 promoter.

Vitamin K2 biosynthetic enzyme, UBIAD1 is essential for embryonic development of mice

UbiA prenyltransferase domain containing 1 (UBIAD1) is a novel vitamin K₂ biosynthetic enzyme screened and identified from the human genome database. UBIAD1 has recently been shown to catalyse the biosynthesis of Coenzyme Q10 (CoQ10) in zebrafish and human cells. To investigate the function of UBIAD1 in vivo, we attempted to generate mice lacking Ubiad1, a homolog of human UBIAD1, by gene targeting. Ubiad1-deficient (Ubiad1^−/−) mouse embryos failed to survive beyond embryonic day 7.5, exhibiting small-sized body and gastrulation arrest. Ubiad1^−/− embryonic stem (ES) cells failed to synthesize vitamin K₂ but were able to synthesize CoQ9, similar to wild-type ES cells. Ubiad1^+/− mice developed normally, exhibiting normal growth and fertility. Vitamin K₂ tissue levels and synthesis activity were approximately half of those in the wild-type, whereas CoQ9 tissue levels and synthesis activity were similar to those in the wild-type. Similarly, UBIAD1 expression and vitamin K₂ synthesis activity of mouse embryonic fibroblasts prepared from Ubiad1^+/− E15.5 embryos were approximately half of those in the wild-type, whereas CoQ9 levels and synthesis activity were similar to those in the wild-type. Ubiad1^−/− mouse embryos failed to be rescued, but their embryonic lifespans were extended to term by oral administration of MK-4 or CoQ10 to pregnant Ubiad1^+/− mice. These results suggest that UBIAD1 is responsible for vitamin K₂ synthesis but may not be responsible for CoQ9 synthesis in mice. We propose that UBIAD1 plays a pivotal role in embryonic development by synthesizing vitamin K₂, but may have additional functions beyond the biosynthesis of vitamin K₂.

[Structure-activity relationship of novel vitamin K analogues as steroid and xenobiotic receptor (SXR) agonists]

Vitamin K2 is a ligand for a nuclear receptor, steroid and xenobiotic receptor (SXR), that induces the gene expressions of CYP3A4. We synthesized new vitamin K analogues with the same isoprene side chains symmetrically introduced at the 2 and 3 positions of 1,4-naphthoquinone and vitamin K2 analogues with hydroxyl or phenyl groups at the ω-terminal of the side chain. The upregulation of SXR-mediated transcription of the target gene by the analogues was dependent on the length of the side chain and the hydrophobicity of the ω-terminal residues. Phenyl analogue menaquinone-3 was as active as the known SXR ligand rifampicin.

Cytochrome P450-dependent catabolism of vitamin K: ω-hydroxylation catalyzed by human CYP4F2 and CYP4F11

Vitamin K plays an essential role in many biological processes including blood clotting, maintenance of bone health, and inhibition of arterial calcification. A menaquinone form of vitamin K, MK4, is increasingly recognized for its key roles in mitochondrial electron transport, as a ligand for the nuclear receptor SXR, which controls the expression of genes involved in transport and metabolism of endo- and xenobiotics, and as a pharmacotherapeutic in the treatment of osteoporosis. Although cytochrome P450 (CYP) 4F2 activity is recognized as an important determinant of phylloquinone (K1) metabolism, the enzymes involved in menaquinone catabolism have not been studied previously. CYP4F2 and CYP4F11 were expressed and purified and found to be equally efficient as in vitro catalysts of MK4 ω-hydroxylation. CYP4F2, but not CYP4F11, catalyzed sequential metabolism of MK4 to the ω-acid without apparent release of the intermediate aldehyde. The ω-alcohol could also be metabolized to the acid by microsomal NAD(+)-dependent alcohol and aldehyde dehydrogenases. LC-MS/MS analysis of trypsinized human liver microsomes (using a surrogate peptide approach) revealed the mean concentrations of CYP4F2 and CYP4F11 to be 14.3 and 8.4 pmol/mg protein, respectively. Microsomal MK4 ω-hydroxylation activities correlated with the CYP4F2 V433M genotype but not the CYP4F11 D446N genotype. Collectively, these data expand the lexicon of vitamin K ω-hydroxylases to include the 'orphan' P450 CYP4F11 and identify a common variant, CYP4F2 (rs2108622), as a major pharmacogenetic variable influencing MK4 catabolism.

Menadione (vitamin K3) is a catabolic product of oral phylloquinone (vitamin K1) in the intestine and a circulating precursor of tissue menaquinone-4 (vitamin K2) in rats

Mice have the ability to convert dietary phylloquinone (vitamin K1) into menaquinone-4 (vitamin K2) and store the latter in tissues. A prenyltransferase enzyme, UbiA prenyltransferase domain-containing 1 (UBIAD1), is involved in this conversion. There is evidence that UBIAD1 has a weak side chain cleavage activity for phylloquinone but a strong prenylation activity for menadione (vitamin K3), which has long been postulated as an intermediate in this conversion. Further evidence indicates that when intravenously administered in mice phylloquinone can enter into tissues but is not converted further to menaquinone-4. These findings raise the question whether phylloquinone is absorbed and delivered to tissues in its original form and converted to menaquinone-4 or whether it is converted to menadione in the intestine followed by delivery of menadione to tissues and subsequent conversion to menaquinone-4. To answer this question, we conducted cannulation experiments using stable isotope tracer technology in rats. We confirmed that the second pathway is correct on the basis of structural assignments and measurements of phylloquinone-derived menadione using high resolution MS analysis and a bioassay using recombinant UBIAD1 protein. Furthermore, high resolution MS and (1)H NMR analyses of the product generated from the incubation of menadione with recombinant UBIAD1 revealed that the hydroquinone, but not the quinone form of menadione, was an intermediate of the conversion. Taken together, these results provide unequivocal evidence that menadione is a catabolic product of oral phylloquinone and a major source of tissue menaquinone-4.

Structure-activity relationship of novel menaquinone-4 analogues: modification of the side chain affects their biological activities

We synthesized new vitamin K analogues with demethylation or reduction of the double bonds of the side chain of menaquinone-4 (MK-4) and evaluated their SXR-mediated transcriptional activity as well as the extent of their conversion to MK-4. The results indicated that the analogue with the methyl group deleted at the 7' site of the side chain part affected conversion activity to MK-4. In contrast, a decrease in the number of the double bonds in the side chain moiety appeared to decrease the SXR-mediated transcriptional activity.

Synthesis of new vitamin K analogues as steroid and xenobiotic receptor (SXR) agonists: insights into the biological role of the side chain part of vitamin K

Vitamin K(2) has been demonstrated to induce gene expression related to bone formation through a nuclear steroid and xenobiotic receptor (SXR). We synthesized new vitamin K analogues with the same isoprene side chains symmetrically introduced at the 2 and 3 positions of 1,4-naphthoquinone and evaluated the transcriptional activity of the target gene. The transcriptional activity was related to the length of the side chain which allowed optimal interaction with ligand-binding domain of SXR.

Synthesis of novel vitamin K2 analogues with modification at the ω-terminal position and their biological evaluation as potent steroid and xenobiotic receptor (SXR) agonists

Vitamin K(2) is a ligand for a nuclear receptor, steroid and xenobiotic receptor (SXR), that induces the gene expressions of CYP3A4. We synthesized vitamin K(2) analogues with hydroxyl or phenyl groups at the ω-terminal of the side chain. The up-regulation of SXR-mediated transcription of the target gene by the analogues was dependent on the length of the side chain and the hydrophobicity of the ω-terminal residues. Phenyl analogue menaquinone-3 was as active as the known SXR ligand rifampicin.

Efficient synthesis and biological evaluation of demethyl geranylgeranoic acid derivatives

Synthetic retinoids have generated in the fields of dermatology and oncology due to their potent anti-proliferative and differentiation activities. We efficiently synthesized different demethyl geranylgeranoic acid (GGA) analogs, and evaluated their biological activities. Among the demethyl analogs synthesized, 3-demethyl derivative exhibited the highest anti-proliferative activity in HL-60 cells. In addition, a 3-demethyl derivative induced apoptosis more potently than 9Z-retinoic acid. These activities were due to the high binding affinity of 3-demethyl derivative for retinoid receptors. We found that, in a conjugated polyene system combined with a methyl substituent, the position of the methyl played an important role in the regulation of gene transcription and apoptosis-inducing activity. These results provided useful information on the structure-activity relationships of GGA derivatives that function as acyclic retinoic acid analogs. This information is likely to be useful in the development of new anti-cancer drugs.

Elucidation of the mechanism producing menaquinone-4 in osteoblastic cells

Vitamin K is an essential nutrient and a cofactor for the carboxylation of specific glutamyl residues of proteins to gamma-glutamyl residues, which activates osteocalcin related to bone formation. Among vitamin K homologues, menaquinone-4 (MK-4) is the most active biologically, up-regulating the gene expression of bone markers, and thus has been clinically used in the treatment of osteoporosis in Japan. Recently, we confirmed that MK-4 was converted from dietary phylloquinone (PK), and then accumulated in various tissues at high concentrations. This system should play an important role in biological functions including bone formation, however, the pathway by which MK-4 is converted remains unclear. In this study, we studied the mechanism of MK-4's conversion with chemical techniques using deuterated analogues.

Vitamin K content of foods and dietary vitamin K intake in Japanese young women

Several reports indicate an important role for vitamin K in bone health as well as blood coagulation. However, the current Adequate Intakes (AI) might not be sufficient for the maintenance of bone health. To obtain a closer estimate of dietary intake of phylloquinone (PK) and menaquinones (MKs), PK, MK-4 and MK-7 contents in food samples (58 food items) were determined by an improved high-performance liquid chromatography method. Next, we assessed dietary vitamin K intake in young women living in eastern Japan using vitamin K contents measured here and the Standard Tables of Food Composition in Japan. PK was widely distributed in green vegetables and algae, and high amounts were found in spinach and broccoli (raw, 498 and 307 microg/100 g wet weight, respectively). Although MK-4 was widely distributed in animal products, overall MK-4 content was lower than PK. MK-7 was observed characteristically in fermented soybean products such as natto (939 microg/100 g). The mean total vitamin K intake of all subjects (using data from this study and Japanese food composition tables) was about 230 microg/d and 94% of participants met the AI of vitamin K for women aged 18-29 y in Japan, 60 microg/d. The contributions of PK, MK-4 and MK-7 to total vitamin K intake were 67.7, 7.3 and 24.9%, respectively. PK from vegetables and algae and MK-7 from pulses (including fermented soybean foods) were the major contributors to the total vitamin K intake of young women living in eastern Japan.

Low plasma phylloquinone concentration is associated with high incidence of vertebral fracture in Japanese women

It has been reported that vitamin K supplementation effectively prevents fractures and sustains bone mineral density in osteoporosis. However, there are only limited reported data concerning the association between vitamin K nutritional status and bone mineral density (BMD) or fractures in Japan. The objectives were to evaluate the association between plasma phylloquinone (K1) or menaquinone (MK-4 and MK-7) concentration and BMD or fracture in Japanese women prospectively. A total of 379 healthy women aged 30-88 years (mean age, 63.0 years) were consecutively enrolled. Plasma K1, MK-4, MK-7, and serum undercarboxylated osteocalcin (ucOC) concentrations, BMD, and incidence of vertebral fractures were evaluated. In stepwise multiple linear regression analyses, L2-4 BMD and a bone turnover marker, log K1, concentrations were independently correlated with vertebral fracture incidence. When subjects were divided into low and high K1 groups by plasma K1 concentration, the incidence of vertebral fracture in the low K1 group (14.4%) was significantly higher than that in the high K1 group (4.2%), and its age-adjusted RR was 3.58 (95% CI, 3.26-3.93). L2-4 BMD was not different between the two groups. These results suggest that subjects with vitamin K1 insufficiency in bone have increased susceptibility for vertebral fracture independently from BMD.

Conversion of phylloquinone (Vitamin K1) into menaquinone-4 (Vitamin K2) in mice: two possible routes for menaquinone-4 accumulation in cerebra of mice

There are two forms of naturally occurring vitamin K, phylloquinone and the menaquinones. Phylloquinone (vitamin K(1)) is a major type (>90%) of dietary vitamin K, but its concentrations in animal tissues are remarkably low compared with those of the menaquinones, especially menaquinone-4 (vitamin K(2)), the major form (>90%) of vitamin K in tissues. Despite this great difference, the origin of tissue menaquinone-4 has yet to be exclusively defined. It is postulated that phylloquinone is converted into menaquinone-4 and accumulates in extrahepatic tissues. To clarify this, phylloquinone with a deuterium-labeled 2-methyl-1,4-naphthoquinone ring was given orally to mice, and cerebra were collected for D NMR and liquid chromatography-tandem mass spectrometry analyses. We identified the labeled menaquinone-4 that was converted from the given phylloquinone, and this conversion occurred following an oral or enteral administration, but not parenteral or intracerebroventricular administration. By the oral route, the phylloquinone with the deuterium-labeled side chain in addition to the labeled 2-methyl-1,4-naphthoquinone was clearly converted into a labeled menaquinone-4 with a non-deuterium-labeled side chain, implying that phylloquinone was converted into menaquinone-4 via integral side-chain removal. The conversion also occurred in cerebral slice cultures and primary cultures. Deuterium-labeled menadione was consistently converted into the labeled menaquinone-4 with all of the administration routes and the culture conditions tested. Our results suggest that cerebral menaquinone-4 originates from phylloquinone intake and that there are two routes of accumulation, one is the release of menadione from phylloquinone in the intestine followed by the prenylation of menadione into menaquinone-4 in tissues, and another is cleavage and prenylation within the cerebrum.

Quantification of fat-soluble vitamins in human breast milk by liquid chromatography-tandem mass spectrometry

Sensitive quantification method for fat-soluble vitamins in human breast milk by liquid chromatography-tandem mass spectrometry was developed. Vitamins A, D and E were extracted from 10.0 mL of breast milk after saponifying by basic condition. Vitamin K derivatives were extracted from 3.0 mL of breast milk after lipase treatment. The corresponding stable isotope-labeled compounds were used as internal standards. For the determination of vitamin D compounds, derivatization with a Cookson-type reagent was performed. All fat-soluble vitamins were determined by liquid chromatography-tandem mass spectrometry in the positive ion mode. The detection limits of all analytes were 1-250 pg per 50 microL. The recoveries of fat-soluble vitamins were 91-105%. Inter-assay CV values of each vitamin were 1.9-11.9%. The mean concentrations of retinol, vitamin D3, 25-hydroxyvitamin D3, alpha-tocopherol, phylloquinone and menaquinone-4 were 0.455 microg/mL, 0.088 ng/mL, 0.081 ng/mL, 5.087 microg/mL, 3.771 ng/mL, and 1.795 ng/mL, respectively (n=82). This method makes possible to determine fat-soluble vitamins with a wide range of polarities in human breast milk. The assay may be useful for large-scale studies.

Efficient synthesis and biological evaluation of ω-oxygenated analogues of vitamin K2: Study of modification and structure–activity relationship of vitamin K2 metabolites

Novel omega-oxygenated vitamin K2 analogues, which are candidates for metabolites of vitamin K2 homologues, were efficiently synthesized and their apoptosis-inducing activity was evaluated. We revealed that some of those analogues were biologically active and the side-chain part played an important role in apoptosis-inducing activity. Our results can provide useful information to develop the structure-activity relationship of vitamin K2 analogues for new drugs based on vitamin K.

Biological activities of 2alpha-substituted analogues of 1alpha,25-dihydroxyvitamin D3 in transcriptional regulation and human promyelocytic leukemia (HL-60) cell proliferation and differentiation

Biological activities of 2alpha-substituted 1alpha,25-dihydroxyvitamin D3 analogues were evaluated in vitro. Their binding affinity was examined with calf thymus cytosolic vitamin D receptor (VDR) and rat plasma vitamin D-binding protein (DBP). In addition, the transcriptional activity of the analogues was measured using a rat 25-hydroxyvitamin D3-24-hydroxylase gene promoter, a human osteocalcin gene promoter, and VDR-GAL4 system. This study investigated the biological activities of 2alpha-substituted analogues in comparison with 2beta-substitued analogues at the molecular level, with regard to the structural differences of alkyl, hydroxyalkyl, hydroxyalkoxy substituents at the 2-position of 1alpha,25-dihydroxyvitamin D3.

Synthesis and biological evaluation of several structural analogs of 2-arachidonoylglycerol, an endogenous cannabinoid receptor ligand

2-Arachidonoylglycerol (2-AG (1)) is an endogenous ligand for the cannabinoid receptors (CB1 and CB2). There is growing evidence that 2-arachidonoylglycerol plays important physiological and pathophysiological roles in various mammalian tissues and cells, though the details remain to be clarified. In this study, we synthesized several remarkable analogs of 2-arachidonoylglycerol, closely related in chemical structure to 2-arachidonoylglycerol: an analog containing an isomer of arachidonic acid with migrated olefins (2-AGA118 (3)), an analog containing a one-carbon shortened fatty acyl moiety (2-AGA113 (4)), an analog containing an one-carbon elongated fatty acyl moiety (2-AGA114 (5)), a hydroxy group-containing analog (2-AGA105 (6)), a ketone group-containing analog (2-AGA109 (7)), and a methylene-linked analog (2-AGA104 (8)). We evaluated their biological activities as cannabinoid receptor agonists using NG108-15 cells which express the CB1 receptor and HL-60 cells which express the CB2 receptor. Notably, these structural analogs of 2-arachidonoylglycerol exhibited only weak agonistic activities toward either the CB1 receptor or the CB2 receptor, which is in good contrast to 2-arachidonoylglycerol which acted as a full agonist at these cannabinoid receptors. These results clearly indicate that the structure of 2-arachidonoylglycerol is strictly recognized by the cannabinoid receptors (CB1 and CB2) and provide further evidence that the cannabinoid receptors are primarily the intrinsic receptors for 2-arachidonoylglycerol.

Probing a water channel near the A-ring of receptor-bound 1 alpha,25-dihydroxyvitamin D3 with selected 2 alpha-substituted analogues

The crystal structure of the vitamin D receptor (VDR) in complex with 1 alpha,25(OH)2D3 revealed the presence of several water molecules near the A-ring linking the ligand C-2 position to the protein surface. Here, we report the crystal structures of the human VDR ligand binding domain bound to selected C-2 alpha substituted analogues, namely, methyl, propyl, propoxy, hydroxypropyl, and hydroxypropoxy. These specific replacements do not modify the structure of the protein or the ligand, but with the exception of the methyl substituent, all analogues affect the presence and/or the location of the above water molecules. The integrity of the channel interactions and specific C-2 alpha analogue directed additional interactions correlate with the binding affinity of the ligands. In contrast, the resulting loss or gain of H-bonds does not reflect the magnitude of HL60 cell differentiation. Our overall findings highlight a rational approach to the design of more potent ligands by building in features revealed in the crystal structures.

[Prevention of osteoporosis by foods and dietary supplements. Vitamin D and bone metabolism]

Vitamin D is an essential nutrient for maintenance of calcium homeostasis. In case of vitamin D deficiency, low vitamin D production rate in skin, insufficient metabolic activation of vitamin D, reduction of bone mass, and osteoporosis would be induced. In the last year, "Dietary Reference Intakes for Japanese, 2005" was published by Ministry of Health, Labour, and Welfare, Japan. This reference was based on the concept of the dietary reference intake (DRIs). The parameter for the assessment of vitamin D nutrition status was defined on the basis of the plasma levels of 25-hydroxyvitamin D, and established as "adequate intake" in the reference. The dietary vitamin D intake for prevention of osteoporosis will be more important according to the progress of examination of dietary vitamin D intake in Japanese.

Comparative uptake, metabolism, and utilization of menaquinone-4 and phylloquinone in human cultured cell lines

It is generally accepted that the availability of vitamin K in vivo depends on its homologues, the biological activities of which would differ among organs. To test this hypothesis, we examined the uptake, metabolism, and utilization of menaquinone-4 (MK-4) and phylloquinone (PK) using 18O-labeled compounds in two cultured human cell lines (HepG2 and MG-63). Lipid extracts were prepared from the cells and media after 1, 3, and 6h of incubation. The detection of the vitamin K analogues (18O-, 16O-quinone, and epoxide forms) was carried out with LC-APCI-MS/MS as previously reported. The 18O of vitamin K was replaced with atmospheric 16O2 during the formation of vitamin K epoxide with a carboxylative catalytic reaction. As a result, a significant difference was observed between MK-4 and PK in the amounts taken up into the cells. The 18O-labeled MK-4 was rapidly and remarkably well absorbed into the cells and metabolized to the epoxide form via a hydroquinone form as compared to the 18O-labeled PK. The difference in uptake of MK-4 and PK was not affected by treatment with warfarin although the metabolism of both compounds was markedly inhibited. This methodology should be utilized to clarify some of the actions of vitamin K in target cells and facilitate the development of new vitamin K drugs.

Vitamin K status of healthy Japanese women: age-related vitamin K requirement for gamma-carboxylation of osteocalcin

BACKGROUND

Vitamin K deficiency is associated with low bone mineral density and increased risk of bone fracture. Phylloquinone (K1) and menaquinone 4 (MK-4) and 7 (MK-7) are generally observed in human plasma; however, data are limited on their circulating concentrations and their associations with bone metabolism or with gamma-carboxylation of the osteocalcin molecule.

OBJECTIVES

The objectives were to measure the circulating concentrations of K1, MK-4, and MK-7 in women and to ascertain whether each form of vitamin K is significantly associated with bone metabolism.

DESIGN

Plasma concentrations of K1, MK-4, MK-7, undercarboxylated osteocalcin (ucOC; measured by using the new electrochemiluminescence immunoassay), intact osteocalcin (iOC), calcium, and phosphorus; bone-derived alkaline phosphatase activity; and concentrations of urinary creatinine, N-terminal telopeptide, and deoxypyridinoline were measured in healthy women (n = 396).

RESULTS

On average, MK-7 and MK-4 were the highest and lowest, respectively, of the 3 vitamers in all age groups. K1 and MK-7 correlated inversely with ucOC, but associations between nutritional basal concentration of MK-4 and ucOC were not observed. Multiple regression analysis indicated that not only K1 and MK-7 concentrations but also age were independently correlated with ucOC concentration and the ratio of ucOC to iOC. The plasma K1 or MK-7 concentration required to minimize the ucOC concentration was highest in the group aged > or =70 y, and it decreased progressively for each of the younger age groups.

CONCLUSIONS

The definite role of ucOC remains unclear. However, if submaximal gamma-carboxylation is related to the prevention of fracture or bone mineral loss, circulating vitamin K concentrations in elderly people should be kept higher than those in young people.

Method for the determination of vitamin K homologues in human plasma using high-performance liquid chromatography-tandem mass spectrometry

We report here the development of a precise and sensitive method for the determination of vitamin K homologues including phylloquinone (PK), menaquinone-4 (MK-4), and menaquinone-7 (MK-7) in human plasma using HPLC-tandem mass-mass spectrometry with atmospheric pressure chemical ionization (LC-APCI-MS/MS). The method involves the use of stable isotope (18)O-labeled internal standard compounds, which were synthesized in our laboratory, and the selection of a precursor and product ion with a MS/MS multiple reaction monitoring method. The average intraassay and interassay variation values for PK, MK-4, and MK-7 were <10%. Average spiked recoveries from authentic compounds added to normal human plasma samples for PK, MK-4, and MK-7 were 98-102%. Mean plasma concentrations of PK, MK-4, and MK-7 from healthy subjects (n = 20) were 1.22 +/-0.57, 0.39 +/- 0.46, and 6.37 +/- 7.45 ng/mL, respectively. We conclude that this novel LC-APCI-MS/MS method should be useful for the evaluation of vitamin K status in postmenopausal women and elderly subjects and provides useful information for the treatment and prevention of osteoporosis with vitamin K.

Determination of 25-Hydroxyvitamin D in Human Plasma Using High-Performance Liquid Chromatography−Tandem Mass Spectrometry

We report here the development of a precise and sensitive method to determine 25-hydroxyvitamin D (25-OH-D(2)/ -D(3)) in human plasma using high-performance liquid chromatography-tandem mass-mass spectrometry with atmospheric pressure chemical ionization (LC-APCI-MS/MS). The method involves the use of deuterated 25-OH-D(3) as an internal standard compound for 25-OH-D(2)/-D(3), which was synthesized in our laboratory, and the selection of a precursor and product ion with a MS/MS multiple reaction monitoring method. The average intraassay and interassay variation values (relative standard deviation) were 5.7 and 2.5%, respectively, for 25-OH-D(3) and 4.5 and 5.1%, respectively, for 25-OH-D(2). The average spiked recoveries from authentic compounds added to normal human plasma samples for 25-OH-D(3) and 25-OH-D(2) were 103.8 and 98.8%, respectively. Mean plasma concentrations of 25-OH-D(3) and 25-OH-D(2) in healthy subjects were 20.5 and 0.4 ng/mL, respectively. We conclude that this novel LC-APCI-MS/MS method would be useful for the evaluation of the vitamin D status in postmenopausal women and elderly subjects and provide useful information in the diagnosis of vitamin D insufficiency/deficiency, as well as for the treatment and prevention of osteoporosis with vitamin D.

METABOLISM OF 2α-PROPOXY-1α,25-DIHYDROXYVITAMIN D3AND 2α-(3-HYDROXYPROPOXY)-1α,25-DIHYDROXYVITAMIN D3BY HUMAN CYP27A1 AND CYP24A1

Recently, we demonstrated that some A-ring-modified vitamin D3 analogs had unique biological activity. Of these analogs, 2alpha-propoxy-1alpha,25(OH)2D3 (C3O1) and 2alpha-(3-hydroxypropoxy)-1alpha,25(OH)2D3 (O2C3) were examined for metabolism by CYP27A1 and CYP24A1. Surprisingly, CYP27A1 catalyzed the conversion from C3O1 to O2C3, which has 3 times more affinity for vitamin D receptor than C3O1. Thus, the conversion from C3O1 to O2C3 by CYP27A1 is considered to be a metabolic activation process. Five metabolites were detected in the metabolism of C3O1 and O2C3 by human CYP24A1 including both C-23 and C-24 oxidation pathways. On the other hand, three metabolites of the C-24 oxidation pathway were detected in their metabolism by rat CYP24A1, indicating a species-based difference in the CYP24A1-dependent metabolism of C3O1 and O2C3 between humans and rats. Kinetic analysis revealed that the Km and kcat values of human CYP24A1 for O2C3 are, respectively, approximately 16 times more and 3 times less than those for 1alpha,25(OH)2D3. Thus, the catalytic efficiency, kcat/Km, of human CYP24A1 for O2C3 is only 2% of 1alpha,25(OH)2D3. These results and a high calcium effect of C3O1 and O2C3 in animal experiments using rats suggest that C3O1 and O2C3 are promising for clinical treatment of osteoporosis.

Determination of plasma Vitamin K by high-performance liquid chromatography with fluorescence detection using Vitamin K analogs as internal standards

A HPLC fluorescence determination method for Vitamin K derivatives (Vitamin K(1), phylloquinone, PK and K(2), menaquinones, MK-4 and MK-7) using post-column reduction and internal standards was developed. Selectivity and reproducibility were increased by optimized chromatography conditions and satisfactory precision and accuracy were attained by using synthetic internal standards. After addition of internal standards to plasma samples, lipids were extracted with ethanol and hexane. Chromatography was performed by isocratic reverse phase separation on a C18 column. Vitamin K derivatives were detected at 430 nm with excitation at 320 nm for MK-4 and 240 nm for PK and MK-7. The detection limits for MK-4, PK and MK-7 were 4, 2 and 4 pg, respectively. The recoveries of MK-4, PK and MK-7 were greater than 92% and the inter- and intra-assay R.S.D. values were 5.7-9.2% for MK-4, 4.9-9.6% for PK and 6.3-19.3% for MK-7. The data showed good correlation between proposed method and LC-APCI/MS method for MK-4 (R(2)=0.988), PK (R(2)=0.979) and MK-7 (R(2)=0.986). The method allows the determination of Vitamin K for evaluating their clinical and nutritional status.

Design and Efficient Synthesis of 2α-(ω-Hydroxyalkoxy)-1α,25-dihydroxyvitamin D3 Analogues, Including 2-epi-ED-71 and Their 20-Epimers with HL-60 Cell Differentiation Activity

A concise and efficient synthetic approach to 2 alpha-(omega-hydroxyalkoxy)-1 alpha,25-dihydroxyvitamin D(3) (4a-c), including 2-epi-ED-71, was developed starting from D-glucose as a chiral template for the construction of the 2 alpha-modified A-ring precursors (11a-c). It was found that the best ligand for the bovine thymus vitamin D receptor (VDR) in this series is 4b, which has 1.8 times greater binding affinity for the bovine thymus VDR than that of the natural hormone 1. Interestingly, potency in the induction of HL-60 cell differentiation for 4a-c was almost the same or weaker than that of 1 despite the strong binding affinity for the VDR. Next, we were interested in the "double modification"of 1 based on 4a-c with C20-epimerization, affording 2 alpha-(omega-hydroxyalkoxy)-20-epi-1 alpha,25-dihydroxyvitamin D(3) (20-epi-4a-c). All three 2 alpha-substituted 20-epi analogues of 1 (20-epi-4a-c) exhibited stronger binding affinities for the VDR, and their conformations in the ligand binding domain of VDR were analyzed by molecular modeling. Double-modified analogues of 20-epi-4a-c showed marked HL-60 cell differentiation activity, and 20-epi-4a possesses an activity 58-fold higher than that of the natural hormone 1.