Query about Vitamin ##K_1## and ##K_2##

[Wrichik Basu]

I have a project at hand, the topic being vitamins and hormones.

While reading about Vitamin K on pubchem, I found that $K_1$ is the compound phytonadione, while my biology book mentions it to be phylloquinone. Similarly, $K_2$ is the compound menaquinone-2 as per pubchem, the the book says it's farnoquinone.

Now it turns out that phytonadione and phylloquinone are actually isomers, and the same is the case with menaquinone-2 and farnoquinone.

Can anyone confirm which is correct? Pubchem seems trustworthy, and so is the book.

 

[jim mcnamara]

$K_2$ is actually a whole family of menaquinone homologues - the form the compounds are stored in animal tissue. So it is not one single "flavor" of molecule, it is several that have differing numbers of isoprenoid moieties, different molecular weights, etc. $K_2$ is synthesized from $K_1$ for storage.

A lot the forms have varying names as well, menaquinone is standard. Worry a lot less about some arcane names (sometimes called a nomen confusum).
Realize that terms like vitamin D or vitamin K are dumping grounds for multiple kinds molecules.

https://pubchem.ncbi.nlm.nih.gov/compound/Menaquinone_7 - is but one $K_2$ - note carefully the long list of "chemical names", particularly the MK-n part. When in doubt search through the long list of chemical names to find what your book uses, if you think that is a major concern. Unless this is a college course and the person grading papers insists there is only one correct name. Just realize this is not always helpful to you the student.

 

[Wrichik Basu]

$K_2$ is actually a whole family of menaquinone homologues - the form the compounds are stored in animal tissue. So it is not one single "flavor" of molecule, it is several that have differing numbers of isoprenoid moieties, different molecular weights, etc.

Understood.

When in doubt search through the long list of chemical names to find what your book uses, if you think that is a major concern.

In that case, I'll write on only the ones mentioned in my book. Actually, the project was given in Chemistry. As a result, I am expected to write the molecular structure, and several other aspects of the vitamins. That's why I was asking which should be used, because I cannot go on writing on so many isomers. It's better if I stick to the book (though I'll remember what you said, and that has been added to my knowledge bank.)