Frequently (and not so frequently) Asked Questions
BRIEF: I have a question reguarding sweet grass...
I have a question regarding "sweet grass" - hierochloe odorata.What is the concentration of coumarin in grass, and why did the FDA banned them from food additives.
Sweet vernal grass (Anthoxanthum oderatum) contains some nice-smelling compounds (coumarin and ortho-coumaric acid). These compounds can be converted to dicumarol under certain circumstances (such as the presence of Aspergillus fungi). dicumarol blocks the regeneration of the useful form or vitamin K, resulting in excessive bleeding. Coumarin itself, at high enough doses, can damage the liver, too. I don't know how much coumarin is in sweet vernal grass, but cattle have been poisoned by it in England and horses here in the US. More than 10 parts per million (ppm) dicumarol is thought by many to be enough to cause bleeding problems, and flavored liquors are supposed to have less than 5ppm coumarin. No coumarin may be added to food in this country (at least for the last 50 years), probably because of both the liver problem and the possibility of dicumarol formation. See pp294-297 of Cheeke's Natural Toxicants in Feeds, Forages and Poisonous Plants.