Antioxidant Activity of Chemical Components from Sage (Salvia officinalis L.) and Thyme (Thymus vulgaris L.) Measured by the Oil Stability Index Method

A new abietane diterpenoid, 12- O -methyl carnosol ( 2 ), was isolated from the leaves of sage ( Salvia officinalis L.), together with 11 abietane diterpenoids, 3 apianane terpenoids, 1 anthraquinone, and 8 flavonoids. Antioxidant activity of these compounds along with 4 flavonoids isolated from thyme ( Thymus vulgaris L.) was evaluated by the oil stability index method using a model substrate oil including methyl linoleate in silicone oil at 90 °C. Carnosol, rosmanol, epirosmanol, isorosmanol, galdosol, and carnosic acid exhibited remarkably strong activity, which was comparable to that of α-tocopherol. The activity of miltirone, atuntzensin A, luteolin, 7- O -methyl luteolin, and eupafolin was comparable to that of butylated hydroxytoluene. The activity of these compounds was mainly due to the presence of ortho -dihydroxy groups. The 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity of these compounds showed the similar result. Keywords: Salvia officinalis L.; sage; Thymus vulgaris L.; thyme; 12- O -methyl carnosol; apianane terpenoid; abietane diterpenoid; flavonoid; antioxidative activity; oil stability index; OSI; DPPH radical scavenging activity