Organic compound found in plants and derived from the amino acid phenylalanine. It creates the fragrance in fresh-mowed hay. More than 300 coumarins have been identified from natural sources, especially green plants. However, simple coumarins are potent antioxidants.
References for this information:
Journal of Natural Products, September 2001, issue 9, pages 1238–1240
Chemistry and Physics of Lipids, December 1999, issues 1-2, pages 125–135
General Pharmacology, June 1996, issue 4, pages 713–722