Ethanol extracts of saw palmetto contain the indirectly acting sympathomimetic: tyramine.
BACKGROUND
To identify the bioactive components of saw palmetto ethanol extracts that affect contractility in the rat prostate gland.


METHODS
A commercially available saw palmetto ethanol extract was lyophilized then subjected to fractionation using silica gel column chromatography. Composition of fractions was assessed by proton nuclear magnetic resonance ((1)H NMR) spectroscopy and mass spectrometry (MS). Contractile activity of these fractions was evaluated pharmacologically using isolated preparations of rat prostate gland and compared to the activity of crude ethanol extract.


RESULTS
Saw palmetto ethanol extract caused contractions of the rat prostate gland which were consistent with indirectly acting sympathomimetic activity. Fractions resulting from chromatography produced contractions of isolated rat prostates that were similar in magnitude to the contractions produced by the crude extracts. Analysis of NMR and mass spectra revealed that this bioactivity was due to tyramine in the active fraction.


CONCLUSIONS
Tyramine is present in saw palmetto ethanol extracts and causes indirect α(1)-adrenoceptor mediated contractions via the release of noradrenaline from sympathetic neurons. This has clinical implications, as tyramine interacts with MAO inhibitors to cause hypertensive crisis.
Chua
Thiam
T
Medicinal Chemistry and Drug Action, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia.
Simpson
Jamie S
JS
Ventura
Sabatino
S
D000818:Animals; D000431:Ethanol / Q000737:chemistry; D008297:Male; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000187:drug effects*; D010936:Plant Extracts / Q000494:pharmacology*; D011467:Prostate / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D028024:Serenoa; D013566:Sympathomimetics / Q000494:pharmacology*; D014439:Tyramine / Q000494:pharmacology*
D010936:Plant Extracts; D013566:Sympathomimetics; D000431:Ethanol; C040972:saw palmetto extract; D014439:Tyramine