Biosynthesis and Accumulation of Rosmarinic Acid in Plant Cell Cultures

Abstract

Rosmarinic acid (RA), an ester of caffeic acid and 3,4-dihydroxyphenyllactic acid, is a natural compound occurring in many species of the Lamiaceae and Boraginaceae. It therefore also occurs in a number of well-known medicinal plants and spices. The biological activities of RA are described as antibacterial, antioxidative, antiviral and antiinflammatory; RA therefore contributes to the pharmacological and food-preserving qualities of these plants. Cell cultures of Coleus blumei can accumulate up to 20% of the cell dry weight as RA, when the culture medium is supplemented with high sucrose concentrations. The biosynthesis and accumulation of RA has been investigated in cell cultures of Coleus blumei and other RA-containing plants. The precursors phenylalanine and tyrosine are transformed to rosmarinic acid by eight enzymatic steps catalyzed by soluble enzymes and membrane-bound cytochrome P-450 monooxygenases. RA is stored in the vacuole and transported across the tonoplast by a carrier protein. The regulation of RA biosynthesis and accumulation on the enzyme as well as the gene level is studied in the model system Coleus blumei.