Hound's-tongue contains four
consolidine), Echinatine (Indicine) and Heliosupine (an open diester pyrrolizidine alkaloid). The main pyrrolizidine alkaloid in Hound's-tongue is Heliosupine (aka Cynoglossophine), followed by
consolidine (a gluco-alkaloid, which hydrolyses to a sugar molecule and consolicine) which paralyses the CNS in cattle frogs and vertebrates. Large doses in cattle cause excessive thirst and palsy of the hind legs.
Cynoglossine, which is thrice as potent as consolidine, occurs in the roots, and has a paralytic effect similar to the action of
curarine (an alkaloid extracted from curare) on frog muscles.
Pyrrolizidine alkaloids are metabolically activated within the liver where they will alkylate both proteins and DNA molecules; they are therefore hepatotoxic causing liver damage, as well as mutagenic, teratogenic and carcinogenic. Substantial ingestion results in inhibition of neurons and paralysis.
The first two, Heliosupine and
Indicine, are used medicinally to relieve pain which they accomplish by depressing the Central Nervous System, but are potentially carcinogenic (see above paragraph). A related compound to indicine, indicine N-oxide, (where an oxygen atom is co-ordinate bonded to the shared ring nitrogen atom) is being tested as a drug against cancer.
[Your author is still searching for the structural formulae for cynoglossine, consolicin(e) and consolidin(e), which are all frequently stated as alkaloidal components of Hound's-tongue. Because none are forthcoming the Author can only assume that either they are the older names for more common alkaloids, or that they are unresolved mixtures of alkaloids. Most likely they are pyrrolizidine alkaloids, but that is just a guess].
But there is a solitary hint which your Author found which suggests Cynoglossine could be a trans-isomer of Heliosupine, where the bond upper-left has been swivelled upwards.
Hound's-tongue is poisonous to cattle, which can develop nervous symptoms and diarrhoea from which recovery is unlikely even given 3 months.
No relation to:
Hart's-tongue nor Adder's-tongue [plants of similar name, but differing family].