I'm no chemist, but according to wikipedia, cuscohygrine is found in belladona plants and it metabolizes into hygrine. So that could be what he's referring to?
I read the same wikipedia page and that statement is confusing if not incorrect. Hygrine is a not a metabolite of cuscohygrine, it's in fact the other way round: hygrine is the precursor and cuscohygrine is the metabolite.
The first reference on that page is "The role of hygrine in the biosynthesis of cuscohygrine and hyoscyamine"
stef25|1 year ago
The first reference on that page is "The role of hygrine in the biosynthesis of cuscohygrine and hyoscyamine"