Abstract: Restrictions on the use of synthetic antioxidants are being imposed because of their toxic properties. The present study is the continuation of a program aimed at investigation on antioxidant activity of extracts from medicinal and aromatic plants and to identify alternative natural and safe sources of food antioxidant especially from plant origin. Henna is worldwide known as cosmetic agent with anticarcinogenic, anti- inflammatory, analagesic and antipyretic properties. The aim of present study is an attempt to evaluate the utilization of henna leaves extract as sources of natural antioxidants. Different solvents including methanol, ethanol, acetone, chloroform, hexane and water were used to prepare extracts of henna leaves. Attempts were also made to extract phenolic antioxidants of henna leaves using different solvents and by two different solvent extraction methods (solvent and ultrasound-assisted methods) with methanol and water. The effect of addition of henna leaves extracts on the stability of soybean oil was studied and the content total phenolic compounds in the extract was determined by spectrophotometric method according to the Folin -Ciocalteu and calculated as tannic acid equivalents. The plant material of the experiment (lawsonia inermis) was grown in Ke rman, Iran and collected in June 2004. Henna leaves extract as a natural antioxidant was evaluated during 16 days storage of refined soybean oil at 63°C. Peroxide Values (PV) and 2-thiobarbituric acid values were used as criteria to assess the antioxidant activity of henna leaves extract and were determined by official AOCS respectively. Two solvent (water and methanol) were used to prepare extract of Henna leaves. Water extract in comparison with the methanolic one had been more efficient. BHA and BHT at 200ppm and methanolic extract at 800ppm and 1400ppm had equal TBA and PV value in soybean oil. Also the antioxidant activity of water and methanolic extracts was determined by using the rancimat method (90,120,150°C) on refined soybean oil and compared with the induction period of synthetic antioxidants (BHA, BHT, TBHQ). The phenolic antioxidants of Henna leaves were extracted by two different solvent extraction methods (solvent and ultrasound-assisted method) with water and methanol. Sonication improved the total phenolic compounds of the extracts and shorter the extraction times. It was shown extraction method has significant effect on phenolic compound and antioxidant activity of Henna extract.

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