Menthol (DL-Menthol) is an organic compound made synthetically or obtained from peppermint or mint oils with flavoring and local anesthetic properties.

High levels of the major DL-Menthol metabolite, menthol-glucuronide, was observed in the urine of smokers of either menthol or non-menthol cigarettes. The fact that a significant inverse correlation was observed between the levels of urinary menthol-glucuronide and NNAL-N-glucuronide, a major detoxification metabolite of the tobacco carcinogen, NNK, suggests that menthol may be inhibiting the clearance of this important tobacco carcinogen.