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 s tress of the plants. The highest concentrations of the major diterpenes car nosic acid and carnosol were found during the winter and the lowest concent rations during the summer, which is likely to be the result of their enzyma tic conversion in the presence of singlet oxygen. All other diterpenes foll owed different trends during the season. The concentration of carnosic acid increased with the relative water content of the leaf but decreased with i ncreasing solar radiation and temperature. 11,12-di-O-Methylisorosmanol was found for the first time in rosemary leaves.