ARS | Publication request: Antioxidant Activities of Lipophilic Extracts of Forty Foods Using Lipophilic Oxygen Radical Absorbance Capacity (Orac(fl)-Lipo) Assay

Submitted to: Journal of Federation of American Societies for Experimental Biology
Publication Type: Abstract
Publication Acceptance Date: January 10, 2003
Publication Date: March 17, 2003
Citation: WU, X., PRIOR, R.L. ANTIOXIDANT ACTIVITIES OF LIPOPHILIC EXTRACTS OF FORTY FOODS USING LIPOPHILIC OXYGEN RADICAL ABSORBANCE CAPACITY (ORAC(FL)-LIPO) ASSAY. JOURNAL OF FEDERATION OF AMERICAN SOCIETIES FOR EXPERIMENTAL BIOLOGY. 2003. v. 17(5). p. A1115. Abstract No. 694.10.

Interpretive Summary: Dietary antioxidants, when ingested, can protect cells in the body from oxidative damage. There are numerous antioxidants in foods which can be classified as being with soluble in water or soluble in fat. Up until this point there has not been a method to measure total fat soluble antioxidants in foods. In these studies, methods were developed to extract and measure total fat soluble antioxidant capacity in foods, so that both water soluble and fat soluble antioxidant capacity could be assessed. Antioxidant capacity was measured by using the Oxygen Radical Absorbance Capacity Assay. Compared to the water soluble antioxidant capacity, the fat soluble antioxidant capacity is relatively low. The fat soluble ORAC values from 40 foods ranged from 1.00±0.06 to 31.23±0.22 units which were defined as micromoles of Trolox Equivalents (TE)/g dry weight, whereas water soluble ORAC values ranged from 7.34±0.85 to 568.0±14.2 'mol TE/g dry weight. The percentage of fat soluble ORAC in total ORAC value ranged from 0.59% to 39.51%. These results demonstrate, however, that measures of total antioxidant capacity of foods needs to include measures of both the water and lipid soluble antioxidant in order to have an accurate total for a given food sample. These methods are being used to develop a database of antioxidant capacity of common foods, which will be useful in future studies of the effect of diet on the prevention of diseases such as cancer and cardiovascular disease.

Technical Abstract: Lipophilic components of forty foods were extracted by Hexane-CH2Cl2 (1:1). The antioxidant activities of these extracts were evaluated by means of Lipophilic Oxygen Radical Absorbance Capacity (L-ORAC(FL)) Assay, which used randomly methylated ß-cyclodextrin as a solubility enhancer. Hydrophilic components of these foods were extracted by AWA (acetone: water: acetic acid = 70:29.5:0.5, v/v) after lipophilic extraction. Their ORAC values were measured by Oxygen Radical Absorbance Capacity (H-ORAC(FL)) Assay. Compared to the hydrophilic ORAC values, lipophilic ORAC values are low. The lipophilic ORAC values of all 40 extracts range from 1.00±0.06 to 31.23±0.22 'molTE/g (n=2) dry weight, whereas hydrophilic ORAC values are from 7.34±0.85 to 567.99±14.22 'molTE/g (n=2) dry weight. The sum of lipophlic and hydrophilic ORAC value was regarded as total ORAC value for a given sample. Then percentage of lipophlic ORAC in total ORAC value ranged from 0.59% to 39.51%. Furthermore, 4 representative samples (cashew, strawberry, lettuce and avocado) were chosen to be extracted directly by AWA. Their ORAC values are similar to that obtained for hydrophilic values following lipophilic extraction, but lower than the sum of lipophilic and hydrophilic ORAC value. From this point, we conclude that in order to get an accurate total ORAC value of a given food sample, both lipophilic and hydrophilic fractions needs to be measured.