Effects of olive oil and its fractions on oxidative stress and the liver's fatty acid composition in 2,4-Dichlorophenoxyacetic acid-treated rats

Abstract

Background: Olive oil's beneficial effects are not only related to its high content of oleic acid, but also to the antioxidant potential of its polyphenols. In this study, we assess the effects of virgin olive oil and its fractions on 2,4-D- induced oxidative damage in the liver of rats.

Methods: Male Wistar rats were randomly divided into eight groups of ten each: (C) a control group, (D) group that received 2,4-D (5 mg/kg b.w.), (D/EVOO) group treated with 2,4-D plus extra virgin olive oil, (D/OOHF) group that received 2,4-D plus hydrophilic fraction, (D/OOLF) group treated with 2,4-D plus lipophilic fraction, (EVOO) group that received only extra virgin olive oil, (OOHF) group given hydrophilic fraction and (OOLF) group treated with lipophilic fraction. These components were daily administered by gavage for 4 weeks.

Results: A significant liver damage was observed in rats treated with 2,4-D via increased serum levels of transaminases and alkaline phosphatase, hepatic lipid peroxidation and decreased hepatic antioxidant enzyme activities, namely, superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase. The liver's fatty acid composition was also significantly modified with 2,4-D exposure. However, extra virgin olive oil and hydrophilic fraction intake during 2,4-D treatment induced a significant increase in the antioxidant enzyme activities and a decrease in the conjugated dienes (CD) and thiobarbituric acid-reactive substances (TBARs) levels in the liver. The lipophilic fraction supplemented to 2,4-D- treated rats did not show any improvement in the liver oxidative status while a marked improvement was detected in the hepatic fatty acid composition of rats supplemented with olive oil and the two fractions.

Conclusion: We concluded that the protective effect of olive oil against oxidative damage induced by 2,4-D is mainly related to the antioxidant potential of its hydrophilic fraction.

Figure 1

Malondialdehyde (MDA) and conjugated dienes (CD) levels in liver of rat treated or not with 2,4-D under effects of supplemented extra virgin olive oil (EVOO) and its fractions (OOHF and OOLF). C: controls group, D: 2, 4-D treated group, D/EVOO: 2, 4-D + extra virgin olive oil, D/OOHF: 2, 4-D+ hydrophilic fraction, D/OOLF: 2,4-D+ lipophilic fraction, EVOO: extra virgin olive oil treated group alone, OOHF: group treated with hydrophilic fraction of olive oil, OOLF: group treated with lipophilic fraction of olive oil. Data are expressed as means ± SD (n = 10 rats per group). Comparison between groups was made using unpaired Student t test. * p < .05 vs 2,4-D group; § p < .05 vs control group.