Spearmint hydrodistillation by-products: antioxidant activity and effects on lipid oxidation in sunflower and flaxseed oils.

In this study, spearmint hydrodistillation by-products (residual water and residual leaves material) were studied regarding their antioxidant potentials. Extraction of rosmarinic acid from the leaves to the residual water reached its maximum (7.04 g·l-1) at a distillation time of 150 min. The extracts obtained from residual water and residual leaves material were examined with several in vitro antioxidant activity-related assays including β-carotene bleaching activity, forced oxidation test and radical-scavenging activity to determine the antioxidative activities of extracts. Only residual water displayed dose-dependent antioxidative effects on β-carotene linoleate system with activity of 66 % at 1 g·l-1. The extracts added to the flaxseed and sunflower oils at the level of 1 g·l-1 exerted pro-oxidative effects on the oils in an accelerated test at 70 °C, whereas residual water had no observable positive or negative effects on the oxidation status of the oils. The results indicated that residual water and residual leaves material might be a candidate for enrichment and/or recovering of rosmarinic acid. [ABSTRACT FROM AUTHOR]