The Effect of Boiled Oil (Olive Oil Produced Using Boiled Olive Fruits) on the Rat's Liver
Authors: Janakat Sana , Alzu'bi Taghreed , Subih Hadeel 
Published: February 2025

Aims

This research aims to investigate the reduced hepatoprotective effect of virgin olive oil if olive fruits are boiled before being pressed. The hepatoprotective activity of virgin olive oil with boiled oil is also determined whether boiled oil still exhibits hepatoprotective activity in the rat’s liver.

Background

The Olive tree (Olea European L) is the most cultivated fruit tree, and olive oil is one of the main products in Jordan. The hepatoprotective activity of virgin olive oil (VOO) was earlier attributed to phenolic compounds' antioxidant activity. In some villages in Northern Jordan, villagers boil olive fruits in tap water for 10 minutes and sundry them for two weeks before oil extraction to enhance the colour and obtain an intense taste. Moreover, the locals claim that this oil has healing properties and refer to this oil as “boiled oil”.

Methods

Forty-two male Wistar albino rats were divided into six groups of 7 rats/group. Corn oil was used as a negative control. The positive control groups were fed corn oil, virgin olive oil, or “boiled oil” in addition to 3 g/Kg body weight of paracetamol (acetaminophen, N-acetyl- P -aminophenol) as a hepatotoxin on the penultimate day. The experimental groups were fed virgin olive oil (VOO) and boiled oil only. All groups were fed 7.5 ml/kg/day for 21 days. On the slaughter day, the rats were anaesthetised with ether, and blood samples were collected via heart puncture, then liver function tests, alanine aminotransferase (ALT), aspartate aminotransferase (AST), and bilirubin, were conducted. The liver was excised, washed, paper toweled and weighed to calculate the liver weight/body weight ratio (LW/BW ratio).

Results

Virgin olive oil decreased ALT significantly (p<0.05) from (108.42 ± 3.79 U/L) in the corn oil group to ((26.86 ± 8.22 U/L) in the VOO group and (71.50 ± 5.13 U/L) in the boiled group. VOO and boiled oil also affected AST similarly. AST decreased significantly from (117.07 ± 2.13 U/L) in the corn oil group to (41.16 ± 1.61 U/L) in the VOO group and (66.35 ± 4.78 U/L) in the boiled oil group. Bilirubin also decreased significantly from (0.86 ± 0.12 mg/dl) in the control group to (0.27 ± 0.02 mg/dl) in the VOO group and (0.62 ± 0.02) mg/dl) boiled oil group. Liver weight/ body weight ratio also decreased from (3.67 ± 0.10%) to (3.50 ± 0.09%) using VOO and to (3.88 ± 0.038%) using boiled oil. All positive control groups (receiving paracetamol) showed a significant increase (p<0.05) in all parameters compared with their negative controls. Moreover, VOO with paracetamol decreased ALT significantly (p<0.05) from (191.06 ± 4.23 U/L) in the corn oil group to ((70.17±17.89U/L) in the VOO group and (110.50 ± 18.69U/L) in the boiled group. AST decreased significantly from (208.94 ± 4.68U/L) in the corn oil group to (74.58 ± 3.87 U/L) in the VOO group and (116.48 ± 15.73 U/L) in the boiled oil group. Bilirubin decreased significantly from (1.65 ± 0.10 mg/dl) in the control group to (0.57±0.04 mg/dl) in the VOO group and (0.90 ± 0.08mg/dl) in the boiled oil group. LW/BW ratio also decreased from (3.76 ± 0.15%) to (3.61 ± 0.12%) using VOO and to (3.93 ± 0.12%) using boiled oil.

Conclusion

Boiling olive fruits before pressing (boiled oil) decrease hepatoprotective activity compared to VOO, but is not completely diminished.