Retsyn

Retsyn is a trademarked name for a combination of copper gluconate and partially hydrogenated cottonseed oil, held by Cadbury Adams (a division of Cadbury Schweppes). It is an ingredient in Certs, Certs Cool Mint Drops, and Certs Power Mints.

According to a Pfizer FAQ Page, Retsyn, in addition to the flavor, is responsible for the efficacy of Certs against breath odors. The hydrogenated vegetable oil and the copper gluconate absorb odors in the mouth. The copper gluconate is also responsible for Retsyn's green color.