21 CFR § 189.165 - Nordihydroguaiaretic acid (NDGA).
(a) Nordihydroguaiaretic acid is the chemical 4,4′-(2,3-dimethyltetramethylene) dipyrocatechol, C18H22O4. It occurs naturally in the resinous exudates of certain plants. The commercial product, which is synthesized, has been used as an antioxidant in foods.
(c) The analytical method used for detecting NDGA in food is in section 20.008(b) of the “Official Methods of Analysis of the AOAC INTERNATIONAL,” 13th Ed. (1980), which is incorporated by reference. Copies may be obtained from the AOAC INTERNATIONAL, 481 North Frederick Ave., suite 500, Gaithersburg, MD 20877, or may be examined at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.