Oxidative stability of sunflower oil supplemented with carnosic acid compared with synthetic antioxidants during accelerated storage

In vitro antioxidant activities and protective effects in stabilising sunflower oil of three rosemary extracts high in carnosic acid (CA) were tested. The CA contents (w/w) of the extracts were 24.9% (CA25), 60.5% (CA60) and 98.3% (CA98). Total phenolic contents of CA25 and CA60 were (3.58 ± 0.026 g/100 g) and (8.20 ± 0.027 g/100 g), (3.91 ± 0.029 g/100 g) and (8.10 ± 0.056 g/100 g) expressed in gallic acid and catechin equivalents, respectively. Reducing power of CA and other antioxidants at 0.5 mg/ml followed the order of l-ascorbic acid > CA98 > TBHQ > BHA > CA60 > BHT > CA25. The IC₅₀ values in the DPPH assay obtained for CA25, CA60, CA98, BHA, BHT and TBHQ were 0.30 ± 0.002, 0.20 ± 0.003, 0.12 ± 0.002, 0.19 ± 0.002, 0.42 ± 0.010, and 0.09 ± 0.001 mg/ml, respectively.