Cholinergic properties of soy.
OBJECTIVE
Soybeans have been shown to have numerous health benefits, but the underlying mechanisms are poorly understood. The aim of this study was to characterize some pharmacologic properties of active substances in aqueous soy extract.


METHODS
The pharmacologic actions of the extract were tested by measuring mechanical activity of isolated guinea-pig ileum in an organ bath.


RESULTS
The ileum contracted in response to soy extract in a concentration-dependent manner. This response was unaffected by the nerve blocker tetrodotoxin (10(-6) M) but was completely inhibited by atropine (10(-9) M), indicating an action via muscarinic receptors on the muscle. In the presence of the M(3) muscarinic antagonist 1,1-dimethyl-4-diphenylacetoxypiperidinium iodide and to a lesser extent in the presence of the M(2) muscarinic antagonist 11-([2-[(diethylamino)methyl]-1-piperidinyl]acetyl)-5,11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepine-6-one, the response was decreased. When acetylcholine (ACh) esterase inhibitors were added to the medium before the addition of soy extract, the response to the extract was potentiated. Preincubation of the extract with exogenous ACh esterase reduced its activity. The response to choline, ACh, and phosphorylcholine was also tested, and none of these substances accurately replicated the response to soy extract. However, some qualitative similarities were observed between the effect of choline and ACh to that of the extract.


CONCLUSIONS
These results indicate the presence of an ACh-like substance in soy. Due to the abundance and importance of muscarinic receptors, the presence of a cholinergic substance in soy could have numerous implications. The role of this substance in the beneficial effect of soy on various body systems merits further investigation.
Roeytenberg
Annina
A
Department of Surgery, Hadassah University Hospital, Mount Scopus, Jerusalem, Israel.
Cohen
Tzeela
T
Freund
Herbert R
HR
Hanani
Menachem
M
D000818:Animals; D018678:Cholinergic Agents / Q000494:pharmacology*; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D007082:Ileum; D018727:Muscarinic Antagonists / Q000494:pharmacology*; D009924:Organ Culture Techniques; D010936:Plant Extracts / Q000494:pharmacology*; D043585:Receptor, Muscarinic M2; D043587:Receptor, Muscarinic M3; D011950:Receptors, Cholinergic / Q000187:drug effects / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*; D013025:Glycine max / Q000737:chemistry*
D018678:Cholinergic Agents; D002800:Cholinesterase Inhibitors; D018727:Muscarinic Antagonists; D010936:Plant Extracts; D043585:Receptor, Muscarinic M2; D043587:Receptor, Muscarinic M3; D011950:Receptors, Cholinergic; D011976:Receptors, Muscarinic