Analytical Sciences

Applicability of the DPPH Assay for Evaluating the Antioxidant Capacity of Food Additives – Inter-laboratory Evaluation Study –

Tomoko SHIMAMURA,*1 Yoshihiro SUMIKURA,*1 Takeshi YAMAZAKI,*2,*3 Atsuko TADA,*2 Takehiro KASHIWAGI,*1 Hiroya ISHIKAWA,*4 Toshiro MATSUI,*5 Naoki SUGIMOTO,*2 Hiroshi AKIYAMA,*2 and Hiroyuki UKEDA*1

*1 Faculty of Agriculture, Kochi University, Monobe B-200, Nankoku, Kochi 783-8502, Japan
*2 National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo 158-8501, Japan
*3 Faculty of Human Life Sciences, Jissen Women’s University, 4-1-1 Osakaue, Hino, Tokyo 191-8510, Japan
*4 International College of Arts and Sciences, Fukuoka Women’s University, 1-1-1 Kasumigaoka, Higashi, Fukuoka 813-8529, Japan
*5 Faculty of Agriculture, Graduated School of Kyushu University, 6-10-1 Hakozaki, Higashi, Fukuoka 812-8581, Japan

An inter-laboratory evaluation study was conducted in order to evaluate the antioxidant capacity of food additives by using a 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. Four antioxidants used as existing food additives (i.e., tea extract, grape seed extract, enju extract, and d-α-tocopherol) and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) were used as analytical samples, and 14 laboratories participated in this study. The repeatability relative standard deviation (RSD_r) of the IC₅₀ of Trolox, four antioxidants, and the Trolox equivalent antioxidant capacity (TEAC) were 1.8 – 2.2%, 2.2 – 2.9%, and 2.1 – 2.5%, respectively. Thus, the proposed DPPH assay showed good performance within the same laboratory. The reproducibility relative standard deviation (RSD_R) of IC₅₀ of Trolox, four antioxidants, and TEAC were 4.0 – 7.9%, 6.0 – 11%, and 3.7 – 9.3%, respectively. The RSD_R/RSD_r values of TEAC were lower than, or nearly equal to, those of IC₅₀ of the four antioxidants, suggesting that the use of TEAC was effective for reducing the variance among the laboratories. These results showed that the proposed DPPH assay could be used as a standard method to evaluate the antioxidant capacity of food additives.

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