Gas Chromatographic Determination of Nordihydroguaiaretic Acid in Larrea Divaricata

A glc analysis method utilizing a flame ionization detector was developed to determine nordihydroguaiaretic acid (NDGA). Lyophilized samples of an aqueous extract from leaves of L. divaricata were reconstituted in water at a concentration of 50 mg/ml. A 100 mcl aliquot of this solution had 50 mcl of the internal standard solution, p,p'-biphenol (0.4 mg/ml in methanol) added followed by extraction with benzene:isopropyl alcohol (98:2), evaporation, and trimethylsilylation with N,O-bis-(trimethylsilyl)-acetamide. Glc analysis was accomplished using a 10% OV-101 on 80/100 Gas Chrom Q column. Accuracy and precision for the glc method was demonstrated over the range of anticipated concentration of NDGA in the L. divaricata leaves. The content of NDGA present in the leaves was found to be 1.6%.