Rosmarinic acid

Rosmarinic acid is a chemical compound found in a variety of plants. It was found to exhibit photoprotective effect against ultraviolet C (UVC) damage when examined "in vitro". 
History.
Rosmarinic acid was first isolated and characterized in 1958 by the Italian chemists M. L. Scarpatti and G. Oriente from rosemary ("Rosmarinus officinalis").
Chemistry.
Chemically, rosmarinic acid is a caffeic acid ester of 3-(3,4-dihydroxyphenyl)lactic acid.
Natural occurrences.
Rosmarinic acid accumulation is shown in hornworts, in the fern family Blechnaceae and in species of several orders of mono- and dicotyledonous angiosperms.
It is found most notably in many Lamiaceae (dicotyledons in the order Lamiales), especially in the subfamily Nepetoideae. It is found in species used commonly as culinary herbs such as "Ocimum basilicum" (basil), "Ocimum tenuiflorum" (holy basil), "Melissa officinalis" (lemon balm), "Rosmarinus officinalis" (rosemary), "Origanum majorana" (marjoram), "Salvia officinalis" (sage), thyme and peppermint. It is also found in plants in the family Marantaceae (monocotyledons in the order Zingiberales) such as species in the genera "Maranta" ("Maranta leuconeura", "Maranta depressa") and "Thalia" ("Thalia geniculata").
Rosmarinic acid and the derivative rosmarinic acid 3′-"O"-β--glucoside can be found in "Anthoceros agrestis", a hornwort (Anthocerotophyta).
Biosynthesis.
The biosyntheses of rosmarinic acid uses 4-coumaroyl-CoA from the general phenylpropanoid pathway as hydroxycinnamoyl donor. The hydroxycinnamoyl acceptor substrate comes from the shikimate pathway: shikimic acid, quinic acid and 3,4-dihydroxyphenyllactic acid derived from -tyrosine. Thus, chemically, rosmarinic acid is an ester of caffeic acid with 3,4-dihydroxyphenyllactic acid, but biologically, it is formed from 4-coumaroyl-4'-hydroxyphenyllactate. Rosmarinate synthase is an enzyme that uses caffeoyl-CoA and 3,4-dihydroxyphenyllactic acid to produce CoA and rosmarinate. Hydroxyphenylpyruvate reductase is also an enzyme involved in this biosynthesis.