We hold no sourced statement of where this molecule comes from biologically. It is a recorded absence, not a claim that the origin is mysterious or that nobody knows it. The value stays Unknown until a citable source supplies one, even where the chemistry makes a reasonable guess available.

Why it matters here

This is one of the fields on this site recorded as not on file rather than left blank. A blank looks like an oversight and invites the reader to fill it in from the surrounding text, whereas Unknown states plainly that the gap is ours.

Also called

• unknown
• unspecified

The alias unspecified resolves here too, although in ordinary use the two differ: unspecified suggests a source that declined to say, unknown suggests nobody recorded it. This domain does not distinguish them.

Compounds carrying this term

None on file yet. This term is in the controlled vocabulary but no compound record currently uses it — which is a statement about our coverage, not about the term.

See also

• Synthetic — Molecular Origin
• Recombinant — Molecular Origin
• Human Endogenous — Molecular Origin