Phenolic diterpene and α-tocopherol contents in leaf extracts of 60 Salvia species

BACKGROUND: Carnosic acid and carnosol, the two major phenolic diterpenes present in rosemary and sage extracts, have received attention in food science and biomedicine because of their potent antioxidant properties. In plants, these compounds have been identified as being present in some species of the family Lamiaceae, but there is still little information about their distribution within the plant kingdom. The aim of the present study was to gain a better understanding of the occurrence of these compounds within leaf extracts of the genus Salvia and also to examine to what extent leaf senescence may influence their accumulation in relation to that of alpha-tocopherol (vitamin E). RESULTS: Methanolic leaf extracts of 60 species of the genus Salvia were tested for the presence of carnosic acid and carnosol. These two diterpenes were detected in 48 and 27 species respectively. In contrast, alpha-tocopherol was present in all species examined. Leaf senescence in Salvia officinalis resulted in alpha-tocopherol increases by up to 5.5-fold, while carnosic acid and carnosol increased by up to IS and 290% respectively. Isorosmanol, an oxidation product of carnosic acid, increased by up to 2.1-fold in senescing leaves. CONCLUSION: It was found that, while alpha-tocopherol is ubiquitous in the genus Salvia, phenolic diterpenes are present in several but not all species. It was also shown that leaf senescence may increase the yield of both phenolic diterpenes and alpha-tocopherol in sage extracts. (c) 2008 Society of Chemical Industry