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 ...

alkaloid Alkaloids are a class of basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Th ...

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 antidysenterica ''Wrightia antidysenterica'', the coral swirl or tellicherry bark, is a flowering plant in the genus ''Wrightia''. ''Wrightia antidysenterica'' is sometimes confused with the species ''Holarrhena pubescens ''Holarrhena pubescens'' is a species ...

'' 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 ...

, 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.

References

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