Conessine is a steroidal alkaloid found in a number of plant species from the family

Apocynaceae Apocynaceae (, from '' Apocynum'', Greek for "dog-away") is a family of flowering plants that includes trees, shrubs, herbs, stem succulents, and vines, commonly known as the dogbane family, because some taxa were used as dog poison. Notable mem ...

, including '' Holarrhena floribunda'', '' Holarrhena antidysenterica'' and '' Funtumia elastica''. It acts as a

histamine antagonist Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. Typically, people take antihistamines as an inexpensive, generic (not patented) drug that can be bought without a prescription and provides r ...

, 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 The blood–brain barrier (BBB) is a highly selective semipermeable membrane, semipermeable border of endothelium, endothelial cells that regulates the transfer of solutes and chemicals between the circulatory system and the central nervous system ...

penetration and high affinity for the adrenergic receptors.

References

{{pharm-stub Alkaloids found in Apocynaceae H3 receptor antagonists Steroidal alkaloids