The formation of phenolic diterpenes in Rosmarinus officinalis L-under Mediterranean climate

The formation of phenolic diterpenes in the leaves of rosemary plants grown under Mediterranean climate was investigated. Low precipitation coincided with high solar radiation during the summer, resulting in water and light stress of the plants. The highest concentrations of the major diterpenes carnosic acid and carnosol were found during the winter and the lowest concentrations during the summer, which is likely to be the result of their enzymatic conversion in the presence of singlet oxygen. All other diterpenes followed different trends during the season. The concentration of carnosic acid increased with the relative water content of the leaf but decreased with increasing solar radiation and temperature. 11,12-di-O-Methylisorosmanol was found for the first time in rosemary leaves.