Mohammad Ali Ebrahimzadeh1,
Mehdi Gharekhani2,
Mohammad Ghorbani2 
,
Pegah Dargany2
For correspondence:- Mohammad Ghorbani Email: moghorbani@yahoo.com Tel:+981513543081
Received: 13 January 2014 Revised: 10 November 2014 Published: 30 January 2015
Citation: Ebrahimzadeh MA, Gharekhani M, Ghorbani M, Dargany P. Effect of extract of aerial parts of Urtica dioica (Urticaceae) on the stability of soybean oil. Trop J Pharm Res 2015; 14(1):125-131 doi: 10.4314/tjpr.v14i1.18
© 2015 The authors.
This is an Open Access article that uses a funding model which does not charge readers or their institutions for access and distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0) and the Budapest Open Access Initiative (http://www.budapestopenaccessinitiative.org/read), which permit unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited..
Purpose: To evaluate the effectiveness of Urtica. dioica (Urticaceae) extract as a natural antioxidant and compare with the most commonly used synthetic antioxidants, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT).
Methods: Three different U. dioica extracts, viz, chloroform, methanol (80 %) and water extracts, were prepared. The antioxidant activity of the extracts were evaluated by 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical scavenging and soybean oil models. Varying concentrations of the extracts (200, 500 and 800 ppm), BHA and BHT (100 and 200 ppm) were separately added to soybean oil and stored in the oven (60±1 °C) for 25 days. Peroxide and thiobarbituric acid (TBA) values were measured at various heating periods for the oil samples. Total phenolic and flavonoid contents of the extracts were determined using Folin–Ciocalteu and aluminium chloride methods, respectively, while the aerial parts of the plant were also phytochemically screened.
Results: Analysis of the chemical composition of U. dioica aerial parts showed they contain crude proteins (21.78 %±0.11), crude lipids (1.66 %±0.03), total soluble carbohydrates (37.19 %±0.21), crude fibers (19.62 %±0.14) and ash (19.75 %±0.17). The aqueous extract contained the highest level of total phenolic contents (7.89 ±0.38, mg g-1 of powder) while the choroform extract contained the highest level of flavonoid contents (15.40 ±0.53 mg g-1 powder). The half-maximal concentration (IC50) values for chloroform, methanol (80 %) and aqueous extracts in respect of DPPH radical scavenging activity were 77.53±0.99, 199.71±1.02 and 159.88±1.57 μg ml-1, respectively. Mixing soybean oil with 200 - 800 ppm of extract decreased oil oxidation and formation rate of TBA reacting substances at a level that is almost equivalent to the synthetic antioxidant, BHT, at a concentration of 200 ppm.
Conclusion: These findings demonstrate that mixing soybean oil with U. dioica extract can improve the quality of the oil during frying process.
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