Structural determination of two active compounds that bind to the muscarinic M3 receptor in beer.
BACKGROUND
It is known that beer accelerates gastrointestinal motility in humans. Our previous studies showed that beer congener stimulates gastrointestinal motility by directly stimulating the muscarinic M3 receptor. Further, we isolated 2 active compounds (compounds A and B) from beer by liquid chromatography. The objective of the present study was to identify the 2 active compounds that bind to the muscarinic M3 receptor in beer.


METHODS
Structural analyses of the active compounds were performed by fast atom bombardment mass spectra, 1H-nuclear magnetic resonance (NMR), and 13C-NMR spectroscopy. Active compounds were chemically synthesized from p-coumaric acid and agmatine as starting materials. Binding activity to the muscarinic M3 receptor was used to confirm the activity of the synthetic compounds.


RESULTS
It was identified that 2 active compounds had the same structural characteristics: stereoisomers (cis-isomer and trans-isomer), molecular weight=550 and molecular formula=C28H38N8O4. Trans-isomer (compound B) was identified as the known substance hordatine A, a kind of phytoalexin in barley, and cis-isomer (compound A) was found to be a novel compound (tentatively referred to as aperidine). Both naturally present and chemically synthesized aperidine (compound A) and hordatine A (compound B) were demonstrated to have potent binding activities to the muscarinic M3 receptor.


CONCLUSIONS
The 2 active compounds isolated from beer, namely aperidine (compound A) and hordatine A (compound B), have structurally and functionally been identified as active entities of binding to the muscarinic M3 receptor.
Yamaji
Nahoko
N
Suntory Institute for Bioorganic Research, Osaka, Japan.
Yokoo
Yoshiaki
Y
Iwashita
Takashi
T
Nemoto
Asuka
A
Koike
Minako
M
Suwa
Yoshihide
Y
Wakimoto
Toshiyuki
T
Tsuji
Kuniro
K
Nukaya
Haruo
H
D000818:Animals; D001515:Beer / Q000032:analysis*; D001572:Benzofurans / Q000138:chemical synthesis / Q000302:isolation & purification* / Q000494:pharmacology; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D005769:Gastrointestinal Motility / Q000187:drug effects; D006146:Guanidines / Q000138:chemical synthesis / Q000302:isolation & purification* / Q000494:pharmacology; D009682:Magnetic Resonance Spectroscopy; D008970:Molecular Weight; D043587:Receptor, Muscarinic M3 / Q000187:drug effects*; D012717:Sesquiterpenes; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013729:Terpenes / Q000138:chemical synthesis / Q000302:isolation & purification* / Q000494:pharmacology; D000094162:Phytoalexins
D001572:Benzofurans; D006146:Guanidines; D043587:Receptor, Muscarinic M3; D012717:Sesquiterpenes; D013729:Terpenes; C528923:hordatine A; D000094162:Phytoalexins