Rosmarinic acid

Rosmarinic acid is a natural phenol antioxidant carboxylic acid found in many Lamiaceae herbs used commonly as culinary herbs such as lemon balm, rosemary, oregano, sage, thyme and peppermint. Chemically, rosmarinic acid is an ester of caffeic acid with 3,4-dihydroxyphenyl lactic acid. It is a red-orange powder that is slightly soluble in water, but well soluble in most organic solvents.

Natural occurrences
Rosmarinic acid and a rosmarinic acid 3′-O-β-D-glucoside can be found in Anthoceros agrestis, a hornwort (Anthocerotophyta).

Biological importance
Because of the antioxidant activity of Lamiaceaeous herbs in laboratory test models they have been suggested to have beneficial effects in humans. Rosmarinic acid has a number of interesting biological activities, e.g. antiviral, antibacterial, antiinflammatory and antioxidant. It is also a potential anxiolytic as it acts as a GABA transaminase inhibitor. The presence of rosmarinic acid in medicinal plants, herbs and spices has beneficial and health promoting effects. In plants, rosmarinic acid is supposed to act as a preformed constitutively accumulated defense compound.

Metabolism
Rosmarinic acid is known to undergo metabolism in humans and rats to methylated rosmarinic acid, coumaric acid, ferulic acid and caffeic acid.. However, unconjugated rosmarinic acid and its metabolites remain in the bloodstream of rats for enough time to reach the brain and decrease acetylcholineterase activity, which is useful in the treatment of Alzheimer's disease. Rosmarinic acid may be transported in the bloodstream bound to human serum albumin and lysozyme.