NDGA 500MG. NDGA, CAS Number: 500-38-9, Molecular Formula: C18H22O4, Molecular Weight: 302. 4, Purity: greater than or equal to 97% by HPLC, Appearance: White to off-white solid, Synonym: Nordihydroguaiaretic Acid 4, 4'-(2, 3-dimethyl-1, 4-butanediyl)bis-1, 2-benzenediol, Size: 500MG