Conessine is a

steroid A steroid is a biologically active organic compound with four rings arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and a ...

alkaloid Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar ...

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 Members of the ...

, including ''

Holarrhena floribunda ''Holarrhena floribunda'', commonly known as the false rubber tree, conessi bark or kurchi bark, is a plant in the family Apocynaceae. Description ''Holarrhena floribunda'' grows as a shrub or tree up to tall, with a stem diameter of up to . It ...

'', '' Holarrhena antidysenterica'' and ''

Funtumia elastica ''Funtumia elastica'' (also known as the bush rubber tree or silkrubber) is a medium-sized African rubber tree with glossy leaves, milky sap, and long woody seedpods. The bark is used in the traditional medicine of tropical Africa. It is economi ...

''. 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 re ...

, 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 prevents solutes in the circulating blood from ''non-selectively'' crossing into the extracellular fluid of ...

penetration and high affinity for the adrenergic receptors.

References

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