Supercritical carbon dioxide extraction of antioxidants from rosemary (Rosmarinus officinalis) leaves for use in edible vegetable oils.

Abstract

Supercritical extraction was employed to produce rosemary (Rosmarinus officinalis L.) extracts with different composition and antioxidant activity. CO₂ was utilized as supercritical solvent and diverse extraction conditions (temperature, pressure, amount of cosolvent and fractionation scheme) were applied. The extracts with higher antioxidant content were selected to study their capability as natural antioxidant of several commercial edible vegetable oils. Linseed oil (LO), grape seed oil (GO) and sesame oil (SO) were oxidized under Rancimat conditions in presence of 0, 100, 200 and 300 mg/kg of selected extracts. Antioxidant activity index (AAI) was estimated as the ratio of induction time in presence of extracts to induction time in absence of extract. Induction time in absence of extracts was 3.3, 7.9 and 23.4 h for LO, GO and SO, respectively. Regardless of these different susceptibilities, the highest AAI for the three oils was obtained for the extract with the highest antioxidant-enrichment (33.25% carnosic acid plus carnosol) and added at the highest level (300 mg/kg). However, at such conditions, the AAI was significantly higher (p<0.001) for LO (3.5), followed by SO (2.2) and the poorest value was for GO (1.1). Therefore, the magnitude of the AAI depended on the antioxidant-enrichment of the extracts, the level of addition within the oils, but also on the own individual oils.