Keywords: bis-γ-Glu-Cys; bis-γ-glutamyl-cystine; Cys; cysteine; Cys-bis-Gly; cystinyl-bis-glycine; Cys-Gly; cysteinyl-glycine; E. canadensis; Elodea canadensis Michx; ECystine/2Cys; reduction potential of cysteine; EGSSG/2GSH; reduction potential of glutathione;