Rosmarinic acid is a polyphenol found in many plants, especially in high concentrations in oregano, rosemary, lemon balm, sage and marjoram. It is one of the aroma compounds in these plants.

Rosmarinic acid has strong anti-oxidant activity.
The antioxidant activity of rosmarinic acid is stronger than that of vitamin E. Rosmarinic acid helps to prevent cell damage caused by free radicals, thereby reducing the risk for cancer and atherosclerosis.

Rosmarinic acid is also used for food preservation. In Japan the perilla extracts, rich in rosmarinic acid, is used the garnish and improve the shelf life of fresh seafood.