Antioxidant activity of rosemary and sage extracts in rapeseed oil

Rosemary and sage leaves were extracted with hexane, acetone, ethyl acetate and ethanol. Yields of extracts and of carnosic acid contents were higher in solvents of medium polarity. Both carnosic acid and carnosol showed medi um activity in deodorized rapeseed oil, about the same as that of butylated hydroxyanisole. Carnosic acid was moderately more active than carnosol and the resulting oxidative stability of extracts was correlated with the cont ent of carnosic acid, but not with the content of carnosol. The antioxidant activity was about the same in rapeseed oil as in sunflower oil, but subst antially lower than that in lard. Antioxidant activities, expressed as prot ection factors, were higher under Schaal oven test conditions at 40 or 60C than when determined in Oxipres at 100C. The dependence of the concentratio n of antioxidants and the protection factor showed similar negative exponen tial relations in all tests.