Harmane and harmalan are bioactive components of classical clonidine-displacing substance.
Elucidation of the structure of the endogenous ligand(s) for imidazoline binding sites, clonidine-displacing substance (CDS), has been a major goal for many years. Crude CDS from bovine lung was purified by reverse-phase high-pressure liquid chromatography. Electrospray mass spectrometry (ESMS) and nuclear magnetic resonance ((1)H NMR) analysis revealed the presence of L-tryptophan and 1-carboxy-1-methyltetrahydro-beta-carboline in the active CDS extract. Competition radioligand binding studies, however, failed to show displacement of specific [(3)H]clonidine binding to rat brain membranes for either compound. Further purification of the bovine lung extract allowed the isolation of the beta-carbolines harmane and harmalan as confirmed by ESMS, (1)H NMR, and comparison with synthetic standards. Both compounds exhibited a high (nanomolar) affinity for both type 1 and type 2 imidazoline binding sites, and the synthetic standards were shown to coelute with the active classical CDS extracts. We therefore propose that the beta-carbolines harmane and harmalan represent active components of classical CDS. The identification of these compounds will allow us to establish clear physiological roles for CDS.
Parker
Christine A
CA
Psychopharmacology Unit, University of Bristol, UK.
Anderson
Neil J
NJ
Robinson
Emma S J
ES
Price
Rhiannon
R
Tyacke
Robin J
RJ
Husbands
Stephen M
SM
Dillon
Michael P
MP
Eglen
Richard M
RM
Hudson
Alan L
AL
Nutt
David J
DJ
Crump
Matthew P
MP
Crosby
John
J
D000818:Animals; D002243:Carbolines / Q000737:chemistry / Q000378:metabolism*; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D003000:Clonidine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D006247:Harmine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D008168:Lung / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization
D002243:Carbolines; D006247:Harmine; C045323:harmalan; C005010:harman; C055140:clonidine-displacing substance; D003000:Clonidine