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Structures

Details



 

 

 

 

Vitamin K is a group name for a number of related compounds, which have in common a methylated naphthoquinone ring structure (see figure 1), and which vary in the aliphatic side chain attached at the 3-position.

 

Figure 1: Menadione (K3)

 

Phylloquinone (also known as vitamin K1) invariably contains in its side chain four isoprenid residues one of which is unsaturated (figure 2).

                                      

                

                   Figure 2: 2D structure of vitamin K1                                    3D structure of vitamin K1
                                                                                                            Designed by Dr. G Nicolaes


Menaquinones (known as vitamin K2) have side chains composed of a variable number of unsaturated isoprenoid residues; generally they are designated as MK-n, where n specifies the number of isoprenoids (Figure 3).

 

                                                             

             Figure 2: 2D structure of vitamin K2                       3D structure of Menaquinone-7
                   n stands for the number of                                                Designed by Dr. G Nicolaes
                        isoprenoid residues                                                                                                                 
                     

 
It is generally accepted that the naphthoquinone is the functional group, so that the mechanism of action is similar for all K-vitamins. Substantial differences may be expected, however, with respect to intestinal absorption, transport, tissue distribution, and bio-availability. These differences are caused by the different lipophilicity of the various side chains, and by the different food matrices in which they occur.