Conessine

Conessine is a steroid alkaloid found in a number of plant species from the Apocynaceae family, including Holarrhena floribunda, Holarrhena antidysenterica and Funtumia elastica. It acts as a histamine antagonist, selective for the H₃ subtype (with an affinity of pK_i = 8.27; K_i = ~5 nM). It was also found to have long CNS clearance times, high blood-brain barrier penetration and high affinity for the adrenergic receptors.