Pseudaconitine

Pseudaconitine, also known as nepaline (C36H51NO12), is an extremely toxic alkaloid found in high quantities in the roots of Aconitum ferox, also known as Indian Monkshood, which belongs to the family Ranunculaceae. The plant is found in East Asia, including the Himalayas.

History
Pseudaconitine was discovered in 1878 by Wright and Luff. They isolated a highly toxic alkaloid from the roots of the plant Aconitum ferox and called it pseudaconitine. The poison is also called bikh, bish, or nabee.

Toxicity and mechanism
Pseudaconitine is a moderate inhibitor of the enzyme acetylcholinesterase. This enzyme breaks down the neurotransmitter acetylcholine through hydrolysis. Inhibition of this enzyme causes a constant stimulation of the postsynaptic membrane by the neurotransmitter which it cannot cancel. This accumulation of acetylcholine may thus lead to the constant stimulation of the muscles, glands and central nervous system. Furthermore, it appears the substance in small quantities also causes a tingling effect on the tongue, lips and skin.

Structure and reactivity
Pseudaconitine is a diterpene alkaloid, with the chemical formula C36H51NO12. The crystal melts at 202 °C and is moderately soluble in water, but more so in alcohol. This shows that it is a lipophilic substance. When heated in the dry state, it undergoes pyrolysis and pyropseudaconitine (C34H47O10N) is formed. This does not have the same tingling effect as pseudaconitine.