Abstract

The aim of the present study was to evaluate antioxidative effects of water and ether extracts of Iranian Urtica dioica, during its pre and post flowering on vegetable oil during storage. Different concentration of water and ether extracts (0, 200, 400, 600, 800 and 1000 ppm) and β-Hydroxy toluene (BHT; 200 ppm) were added to sunflower oil emulsion in the presence of cupric ions and incubated for 7 days at 60°C. Peroxide values (PVs) and thiobarbituric acid reacting substances (TBARS) levels were measured each day up to day seven. Furthermore, antioxidant capacity of the extracts was determined using DPPH and β-Carotene linoleic acid methods. Values were compared among groups in each incubation time points using 1-way ANOVA. Results showed that DPPH and β-Carotene-linoleic acid assay findings on the U. dioica extracts were comparable to those found for BHT. Furthermore, in all incubation time points, U. dioica extracts lowered PVs and TBARS levels significantly when compared with the control (p<0.001). In this respect, the water extract was more potent than the ether extract. In addition, antioxidant properties of the water extracts in post flowering stage were similar to those of BHT in the same concentration (200 ppm). It seems that water extract of the post flowering U. dioica is a potent antioxidant for oil and oily products.

Key words: Urtica dioica, antioxidant activity, sunflower oil emulsion, extract.