Abstract
This study aims to map the total antioxidant capacity (TAC) of 50 Greek olive oil samples from the 2005-2006 season according to production region and cultivar and to compare the 2, 2’-azino-bis (3-ethylbenzo-thiazoline-6- sulfonic acid (ABTS), 2, 2-diphenyl-1-picrylhydrazyl radical (DPPH) and Folin-Ciocalteu tests for use with olive oil. Antioxidant capacities determined in the hydrophilic fraction range between 5.42 - 22.5 mM gallic acid Kg -1 olive oil for the ABTS method and 1.29 - 9.95 mM Kg -1 for the DPPH method while in total, olive oil TAC ranges between 77 - 177 mM Kg -1 as assessed by the DPPH method. The results of total phenol content range between 3.8 and 29.4 mM Kg -1 olive oil. Total phenol content correlates with total antioxidant capacity assessed in the hydrophilic fraction through the DPPH (r = 0.89) and the ABTS (r = 0.69) assays. The hydrophilic fraction DPPH values correlate significantly with the ABTS values (r = 0.81). However, the DPPH values for total olive oil correlate poorly with the ABTS assay, the Folin-Ciocalteu method and the DPPH assay in hydrophilic fraction. Although total phenolic content shows good correlation with ABTS and DPPH values and could serve as a useful indicator for olive oil antioxidant capacity, the use of a battery of tests contributes to better characterization of the antioxidant capacity of olive oil.
Highlights
Olive oil, which is the main lipid source in the Mediterranean diet, is obtained from the fruit of several cultivars of the olive tree Olea europea L
Gallic acid monohydrate was supplied from Riedel-de Haën. 2, 2-Diphenyl-1-picrylhydrazyl radical (DPPH), of 90% grade, 2, 2’-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), of 98% grade, and peroxidase (HRP), type II, 222 U mgϪ1, were obtained from Sigma
The gallic acid calibration curves used for transforming absorbance inhibition values (AI) to gallic acid equivalents (GAE, μM), for ABTS and DPPH assays, are: AIABTS x 102 ϭ (6.10Ϯ0.71) x GAE ϩ (6.2 Ϯ 4.0), r ϭ 0.997 and AIDPPH x 102 ϭ (6.78 Ϯ 0.31) x GAE ϩ (1.4 Ϯ 2.6), r ϭ 0.998
Summary
Olive oil, which is the main lipid source in the Mediterranean diet, is obtained from the fruit of several cultivars of the olive tree Olea europea L. Each cultivar exhibits specific physical and biochemical characteristics, providing oils with different compositions and properties. The composition of olive oil, and its sensorial characteristics, besides being strongly dependent on the cultivar, is influenced by several other factors like climatic and agronomic conditions, the time of harvest and agricultural practices. Extra virgin olive oil is a rich source of natural antioxidants such as tocopherols, carotenoids, sterols and phenolic compounds. Studies indicate that these phytochemicals, especially polyphenols, have high free-radical scavenging activity, which helps reduce the risk of chronic diseases, such as cardiovascular disease, cancer and age-related neuronal degeneration (Mascitelli et al, 2007). It is important to consume foods with high contents of antioxidants, such as virgin olive oil, to reduce the harmful effects of oxidative stress
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