Evaluation of the antioxidant potential of oregano leaves (Origanum vulgare L.) and their effect on the oxidative stability of ghee

Abstract

Antioxidants were extracted from oregano leaves (Origanum vulgare L.) using the solvents water, ethanol, methanol, acetone and diethyl ether. Although a higher extract yield was obtained with water, in general higher total phenolic and flavonoid content and better antioxidant activity were found in the extracts prepared using ethanol. The antioxidant potential of the ethanolic extract of oregano leaves in ghee during storage and frying was evaluated in comparison with the synthetic antioxidants butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). Three quality parameters, namely peroxide value (PV), free fatty acid (FFA) content and p-anisidine value (PAV), of ghee were analyzed. The PV, FFA content and PAV of control ghee samples increased significantly during storage and frying as compared to the ghee samples containing oregano extract (OGE), BHA or BHT. The frying period had a greater effect on changes in PV, FFA content and PAV of ghee than the storage period. Ghee samples with added 1.0% (w/w) OGE showed the least increase in PV, FFA content and PAV, which was comparable with samples with added 0.02% (w/w) BHA and BHT. The study revealed that oregano leaves could be a good natural source of antioxidants and can be used in ghee to retard oxidative deterioration during storage and frying.