Single-laboratory validated method for determination of nordihydroguaiaretic acid in chaparral-containing dietary supplements.
Nordihydroguaiaretic acid (NDGA) occurs naturally in chaparral (Larrea tridentate Coville), a plant which commonly grows in the Southwest United States and has been used for medicinal purposes by Native Americans indigenous to that region. In addition to its traditional use as a tea, manufacturers of dietary supplements have marketed chaparral-containing products in a variety of formulations. Because of the hepatotoxicity of NDGA, and its occurrence in regulated products, we have developed a method for the determination of NDGA in dietary supplements and have tested this method in several dietary supplement formulations. Products were extracted with 80% methanol, filtered, and analyzed by high-performance liquid chromatography. NDGA was detected and determined with both a diode array detector and negative-ion electrospray. Fragmentation in the triple-quadrupole mass spectrometer was obtained by collisional activation of the [M-H](-) ion. Collisional activation produced sufficient fragmentation to provide unambiguous identification. Lack of a stable isotope labeled internal standard has led us to compare quantitations based on UV detection with quantitations based on tandem mass spectrometry (MS/MS). Presence of NDGA was confirmed in several dietary supplement products. Quantitative results from the 2 detection methods were comparable for most products. The limit of quantitation using MS/MS was lower and fewer interferences were observed, although UV detection provided better linearity.
Gay
Martha L
ML
U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, HFS-707, 5100 Paint Branch Pkwy, College Park, MD 20770, USA. Martha.Gay@fda.hhs.gov
Musser
Steven M
SM
D002851:Chromatography, High Pressure Liquid / Q000379:methods; D019587:Dietary Supplements / Q000032:analysis* / Q000592:standards; D005504:Food Analysis / Q000379:methods* / Q000592:standards; D007202:Indicators and Reagents; D032442:Larrea / Q000737:chemistry*; D009637:Masoprocol / Q000032:analysis* / Q000592:standards; D012015:Reference Standards; D015203:Reproducibility of Results; D012996:Solutions; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D013056:Spectrophotometry, Ultraviolet; D053719:Tandem Mass Spectrometry / Q000379:methods
D007202:Indicators and Reagents; D012996:Solutions; D009637:Masoprocol