Coumarin

Coumarin is a fragrant flavour constituent of many foods, notably cinnamon, where it contributes sweet, hay-like, vanilla-adjacent notes. Also known chemically as 2-hydroxycinnamic acid lactone, it has been investigated for cytotoxicity and anticancer activity, but it is toxic in excess, with high doses causing liver damage in susceptible individuals. Food regulators therefore limit coumarin levels, particularly in cinnamon-flavoured bakery, confectionery, and beverages, and the rules distinguish cassia cinnamon (Cinnamomum cassia), which is high in coumarin, from true Ceylon cinnamon, which contains far less.