7-hydroxycoumarins are also natural metabolites in the body that play important roles in the metabolism of ethanol, chemotherapeutic drugs, acetaminophen, anabolic steroids, and other hepatotoxic drugs [ref 12]. Indeed, measurement of concentrations of 4-methylumbelliferyl glucuronide (a metabolic product of 4-methylumbelliferone) is a common assay for determining the level of toxicity of liver-toxic drugs [ref 13].