“…Usually, trolox or 1-naphthol are used as internal standards for the analysis of SCMs [150,151,154] . The CEHCs have been analyzed in rat and murine liver (α-, γ-, δ-CEHC [136,154] ), in rat plasma and in mice serum (γ-, δ-CEHC [136,141] ), as well as in human plasma and serum (α-, γ-, δ-CEHC [140,136,150,152,155] ), in human and mouse urine (α-, γ-, δ-CEHC [134][135][136]144,151,155,156] ) and in human and mouse feces (α-, γ-, δ-CEHC [136] ) as well as in rat bile (α-, γ-CEHC [149] ) and in vitro in A549 and HepG2 cells (γ-CEHC [140,141,144,137] ). Recently, two new metabolites, namely 12'-hydroxychromanol (12'-OH: γ-and δ-12'-OH) and 11'-hydroxychromanol (11'-OH: γ-and δ-11'-OH) have been identified using GC-MS in fecal pellets of mice fed a diet rich in γ-TOH [157] .…”