A stable quinone identified in the reaction of carnosol, a major antioxidant in rosemary, with 2,2-diphenyl-1-picrylhydrazyl radical

Carnosol is known as a major antioxidant in rosemary (Rosmarinus officinalis L.). The reaction of carnosol with 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical was carried out and a novel product was identified as a quinine of carnosol, carnosylquinone. A mechanism for the carnosol-DPPH reaction is proposed.