Antioxidant abietane diterpenoids from Salvia barrelieri

The root extract of endemic Algerian Salvia species Salvia barrelieri Ettling and its diterpenoids were investigated for potential antioxidant activity. From its acetone extract, a new natural abietane diterpenoid 7-oxoroyleanone-12-methyl ether (1) and six known diterpenoids 7α-acetoxyroyleanone-12-methyl ether (2), royleanone (3), horminone (4), 7-acetylhorminone (5), cryptojaponol (6) and inuroyleanol (7) were isolated, and their structures were elucidated by spectroscopic means. Among the diterpenoids, the new diterpenoid 7-oxoroyleanone-12-methyl ether (1) showed highest superoxide anion scavenging activity while inuroyleanol (7) showed both the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity and inhibition of lipid peroxidation in β-carotene–linoleic acid system. These findings indicate that S. barrelieri extract as well as isolated abietane diterpenes, particularly inuroyleanol are promising antioxidants which can be used as food additives.