No, it does not appear to be true that hygrine is found in nightshades.
Cuscohygrine does occur in those plants yet it's precursor hygrine does not. How it then gets there without us being able to detect hygrine could be because it only occurs in very small concentrations or is produced and then quickly and wholly converted in to its cusco metabolite, or that it's produced through a different biosynthetic pathway.
Cuscohygrine does occur in those plants yet it's precursor hygrine does not. How it then gets there without us being able to detect hygrine could be because it only occurs in very small concentrations or is produced and then quickly and wholly converted in to its cusco metabolite, or that it's produced through a different biosynthetic pathway.