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Cis and trans isomers of the vitamin menaquinone-7: which one is biologically significant?

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Recently, several studies have indicated that an adequate intake of menaquinone-7 (MK-7) offers numerous health benefits. However, the low availability of MK-7 in the diet necessitates the development of dietary supplements or functional food products to complement natural food sources and meet the daily intake requirements. Like most biological molecules, MK-7 can exist as geometric isomers that can occur in the cis, trans, and cis/trans forms; however, only the all-trans form is biologically significant. MK-7 is traditionally produced through bacterial fermentation, but various synthetic preparations have lately become available. The isomer composition in the final product is influenced by numerous factors, including the methods of production and purification, as well as particular environmental and storage conditions. The MK-7 profile obtained from the various production methods has not yet been elucidated, and the ideal method for the synthesis of the all-trans form of the vitamin is also debatable. Consequently, the quantification of the MK-7 profile of various products is necessary to develop an understanding of the factors that influence the proportion of isomers that are obtained in different preparations. Several possible methods exist for the quantification of MK-7 isomers, and of these, liquid chromatography in conjunction with mass spectrometry techniques appears to be the most promising. Evaluation of the isomer composition is an important consideration, as only the all-trans form sustains biological activity. Furthermore, knowledge of the prominent factors that influence the MK-7 composition may also enable their manipulation to obtain a more favorable MK-7 profile in the final product.
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MINI-REVIEW
Cis and trans isomers of the vitamin menaquinone-7: which one is
biologically significant?
Neha Lal
1
&Aydin Berenjian
1
Received: 14 November 2019 /Revised: 15 January 2020 /Accepted: 23 January 2020 /Published online: 3 February 2020
#Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract
Recently, several studies have indicated that an adequate intake of menaquinone-7 (MK-7) offers numerous health benefits.
However, the low availability of MK-7 in the diet necessitates the development of dietary supplements or functional food
products to complement natural food sources and meet the daily intake requirements. Like most biological molecules, MK-7
can exist as geometric isomers that can occur in the cis,trans,andcis/trans forms; however, only the all-trans form is biologically
significant. MK-7 is traditionally produced through bacterial fermentation, but various synthetic preparations have lately become
available. The isomer composition in the final product is influenced by numerous factors, including the methods of production
and purification, as well as particular environmental and storage conditions. The MK-7 profile obtained from the various
production methods has not yet been elucidated, and the ideal method for the synthesis of the all-trans form of the vitamin is
also debatable. Consequently, the quantification of the MK-7 profile of various products is necessary to develop an understanding
of the factors that influence the proportion of isomers that are obtained in different preparations. Several possible methods exist
for the quantification of MK-7 isomers, and of these, liquid chromatography in conjunction with mass spectrometry techniques
appears to be the most promising. Evaluation of the isomer composition is an important consideration, as only the all-trans form
sustains biological activity. Furthermore, knowledge of the prominent factors that influence the MK-7 composition may also
enable their manipulation to obtain a more favorable MK-7 profile in the final product.
Keywords Cis and trans isomers .MK-7 .Biological activity .Synthesis .Quantification
Introduction
Vitamin K collectively refers to a group of fat-soluble com-
pounds that contain a 2-methyl-1, 4-naphthoquinone moiety,
but differ in the structure of a lateral isoprenoid chain at the 3-
position (Sitkowski et al. 2018;Szterketal.2018b). Vitamin
K naturally exists in two forms, phylloquinone and a series of
menaquinones, both of which play an important role in hemo-
stasis (Berenjian et al. 2015; Beulens et al. 2013; Nannapaneni
et al. 2017; Szterk et al. 2018b). The major dietary source of
phylloquinone are green vegetables, whereas menaquinones
are primarily of microbial origin and are present in certain
animal products and fermented foods such as meat, beef liver,
eggs, natto, hard cheeses, curd, and sauerkraut (Berenjian
et al. 2013; Beulens et al. 2013; Szterk et al. 2018b; Vermeer
et al. 2018).
All differences in the properties of the various forms of
vitamin K are attributable to the length and degree of satura-
tion of the isoprenoid side chain (Beulens et al. 2013; Pucaj
et al. 2011; Sitkowski et al. 2018). Phylloquinone is a single
compound with a side chain comprising four isoprenoid resi-
dues, three of which are unsaturated (Beulens et al. 2013).
Whereas, menaquinones contain side chains of varying length
and degree of saturation, and can generally be represented in
the form MK-n, where n denotes the number of unsaturated
isoprenoid units in a chain, which is usually between four and
thirteen (Beulens et al. 2013;Dainesetal.2003;Szterketal.
2018b).
MK-7 is a class of menaquinones that can be synthesized
through both natural (bacterial fermentation) and chemical
means for a variety of applications, including functional foods
and dietary supplements (Berenjian et al. 2015; Southee et al.
2016; Szterk et al. 2018a; Szterk et al. 2018b; Walther et al.
2013). Lately, MK-7 has gained widespread interest in both
*Aydin Berenjian
aydin.berenjian@waikato.ac.nz
1
School of Engineering, Faculty of Science and Engineering, The
University of Waikato, Hamilton, New Zealand
Applied Microbiology and Biotechnology (2020) 104:27652776
https://doi.org/10.1007/s00253-020-10409-1
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... However, the administration of MK-4 is not reflected in an increased serum concentration [6]. By contrast, MK-7 is absorbed efficiently, which is reflected in increased serum MK-7 levels up to several days, thereby contributing to vitamin K status [6,21]. US Pharmacopeia monographs have been developed to establish quality standards for menaquinone-7 as a dietary ingredient at typically recommended levels [22]. ...
... US Pharmacopeia monographs have been developed to establish quality standards for menaquinone-7 as a dietary ingredient at typically recommended levels [22]. Although, there are cis, trans, and cis/trans isomers of MK-7, only the all-trans form is biologically active [21]. It can be produced naturally through fermentation, as in the case of natto, or by organic synthesis. ...
... In the process of organic synthesis of MK-7, cis/trans isomers can be produced at the same time. Thus, the potential for the different isomeric forms of MK-7 to have different cytotoxic or toxic properties is an important consideration [21,23]. Naturally derived MK-7 is Fig. 1 The biosynthesis pathways of menaquinone in isoforms from Bacillus subtilis, Saccharomyces cerevisiae and S. coelicolor [26,37,41]. ...
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Vitamin K2 (menaquinone, MK) is an essential lipid-soluble vitamin with critical roles in blood coagulation and bone metabolism. Chemically, the term vitamin K2 encompasses a group of small molecules that contain a common naphthoquinone head group and a polyisoprenyl side chain of variable length. Among them, menaquinone-7 (MK-7) is the most potent form. Here, the biosynthetic pathways of vitamin K2 and different types of MK produced by microorganisms are briefly introduced. Further, we provide a new aspect of MK-7 production, which shares a common naphthoquinone ring and polyisoprene biosynthesis pathway, by analyzing strategies for expanding the product spectrum. We review the findings of metabolic engineering strategies targeting the shikimate pathway, polyisoprene pathway, and menaquinone pathway, as well as membrane engineering, which provide comprehensive insights for enhancing the yield of MK-7. Finally, the current limitations and perspectives of microbial menaquinone production are also discussed. This article provides in-depth information on metabolic engineering strategies for vitamin K2 production by expanding the product spectrum.
... 4 Second, the form of MK-7 used was missing. 1 The highest quality MK-7 supplements contain ≤2% cis form 5 ; therefore, products with >98% of the trans form should be used and may be labeled "all trans. " 5 Third, in the early stages of aortic stenosis, endothelial damage and lipid deposition triggered an inflammatory response within the valve. 2 4 An inverse correlation was shown between several subtypes of vitamin K2 intake and risk of coronary heart disease. 4 A combination of vitamins K1 and K2 should be tested in a larger trial. ...
... However, many secondary metabolites with special structural segments tend to isomerise spontaneously until an equilibrium is formed. For examples, the isomerisation of a form of vitamin K, MK-7, which possesses cis and trans isomers, tend to occurs due to light exposure, purification techniques and storage conditions (Lal and Berenjian 2020). Amphiol, isolated from the culture broth of the fungus Pseudogymnoascus sp. ...
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A pair of new guaiane-type sesquiterpene tautomers (1) was isolated from rhizomes of Acorus calamus. Meanwhile, three pairs of known compounds, including a pair of dihydroflavone glycoside tautomers (2), a pair of 4-hydroxybenzoic acid ester glycoside tautomers (3), as well as a pair of secoiridoid glycoside tautomers (4) were isolated from fruits of Cornus officinalis. Their structures were elucidated by extensive spectroscopic and computational methods. Furthermore, the tautomeric mechanisms were discussed.
... The chemical structure of cis and trans MK-7 isomers (adapted from Lal and Berenjian[40]) ...
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Menaquinone-7 (MK-7) offers significant health benefits; however, only the all-trans form is biologically active. MK-7 produced through fermentation can occur as all-trans and cis isomers, and the therapeutic value of the resulting MK-7 is exclusively determined by the quantity of the all-trans isomer. Therefore, this study aimed to investigate the effect of the media composition on the isomer profile obtained from fermentation and determine the optimum media combination to increase the concentration of the all-trans isomer and diminish the production of cis MK-7. For this purpose, design of experiments (DOE) was used to screen the most effective nutrients, and a central composite face-centred design (CCF) was employed to optimise the media components. The optimum media consisted of 1% (w/v) glucose, 2% (w/v) yeast extract, 2% (w/v) soy peptone, 2% (w/v) tryptone, and 0.1% (w/v) CaCl2. This composition resulted in an average all-trans and cis isomer concentration of 36.366 mg/L and 1.225 mg/L, respectively. In addition, the optimised media enabled an all-trans isomer concentration 12.2-fold greater and a cis isomer concentration 2.9-fold less than the unoptimised media. This study was the first to consider the development of an optimised fermentation media to enhance the production of the bioactive isomer of MK-7 and minimise the concentration of the inactive isomer. Furthermore, this media is commercially promising, as it will improve the process productivity and reduce the costs associated with the industrial fermentation of the vitamin.
... Due to the identification of a high content of the cis/trans MK7 isomers in reference to all trans MK7 in some dietary supplements, 18 the determination of the biological activity as well as the toxicity of the cis/trans forms of MK7 is needed. 32 Since the vitamin K supplementation is essential to reach the recommended daily intake in certain conditions such as during developmental stages, CVD, and osteopenia, and, considering that the cis isomers have lower biological effects, the isomeric composition must be taken into consideration for the supplement formulation and its efficacy. ...
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Carboxylative enzymes are involved in many pathways and their regulation plays a crucial role in many of these pathways. In particular, γ‐glutamylcarboxylase (GGCX) converts glutamate residues (Glu) into γ‐carboxyglutamate (Gla) of the vitamin K‐dependent proteins (VKDPs) activating them. VKDPs include at least 17 proteins involved in processes such as blood coagulation, blood vessels calcification, and bone mineralization. VKDPs are activated by the reduced form of vitamin K, naturally occurring as vitamin K1 (phylloquinone) and K2 (menaquinones, MKs). Among these, MK7 is the most efficient in terms of bioavailability and biological effect. Similarly to other trans isomers, it is produced by natural fermentation or chemically in both trans and cis. However, the efficacy of the biological effect of the different isomers and the impact on humans are unknown. Our study assessed carboxylative efficacy of trans and cis MK7 and compared it with other vitamin K isomers, evaluating both the expression of residues of carboxylated Gla‐protein by western blot analysis and using a cell‐free system to determine the GGCX activity by HPLC. Trans MK7H2 showed a higher ability to carboxylate the 70 KDa GLA‐protein, previously inhibited in vitro by warfarin treatment. However, cis MK7 also induced a carboxylation activity albeit of a small extent. The data were confirmed chromatographically, in which a slight carboxylative activity of cis MK7H2 was demonstrated, comparable with both K1H2 and oxidized trans MK7 but less than trans MK7H2. For the first time, a difference of biological activity between cis and trans configuration of menaquinone‐7 has been reported.
... Microbial fermentation can also produce the final products more economically from inexpensive sources of energy, carbon, electrons, and trace nutrients [36]. Even though the chemical synthesized vitamin K can be made for high purity of all-trans vitamin K2 which has biological activity [37,38], it still has product safety concerns for use as a GRAS food supplement [39]. ...
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... Long-chain menaquinones can be produced naturally through biosynthesis, or by organic synthesis; the former is more favoured due to its non-toxic nature [12], and several bacteria have been reported to synthesize long-chain menaquinones. They are constituents of the bacterial cytoplasmic membrane, and act as an electron-delivery vector of the respiratory chain due to their ability to mediate electron transport between enzymes [13]. ...
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... Menaquinones (MK-n), the vitamin K 2 class of compounds with a 2-methyl-1,4-naphthoquinone moiety connected with n isoprenyl units, are crucially involved in diverse biological functions and insufficient levels of vitamin K result in diseases (Schurgers and Vermeer 2002;Halder et al. 2019;Sato et al. 2020;Farhadi Moghadam and Fereidoni 2020). Indeed, only the all-trans form of MK-7 is biological active (Lal et al. 2020). Recently, the acid-base and the redox properties of all-trans MK-4, -7, and -9 in 1, 2-dimyristoyl-snglycero-3-phosphocholine (DMPC) monolayers on mercury electrodes have been studied (Dharmaraj et al. 2020). ...
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The aim of this paper was to determine the chemical structure of cis/trans isomers of vitamin K2MK-7 found in dietary supplements. Vitamin K2MK-7 was extracted, along with contamination in the form of cis/trans isomers of menaquinone-7, from dietary supplements through tetrahydrofuran and then subjected to fractionation using the semi-preparative chromatography column with cholesteryl group phase (strong stereoselectivity for hydrophobic compounds). The obtained fractions of cis/trans isomers of menaquinone-7 underwent analysis with the use of multidimensional NMR methods optimized for maximum signal separation. NMR analysis made it possible to identify the first geometric isomer of (E,Z3,E2,ω)-menaquinone-7, which underwent NMR comparative analysis with a known “full trans” isomer. It was also possible to confirm the presence of other cis/trans isomers in menaquinone-7 in the collected fractions. Due to the fact that the other fractions indicate a mixture of at least two geometric isomers of menaquinone-7, it was not possible to conduct full structural identification.