Ozonation of triterpenoids: Implications for early diagenesis of biomarkers in oxic environments

► Transformation of triterpenoids during ozonation has been investigated. ► Various transformation products of β-amyrin and lupenone have been identified. ► No transformation product was detected for friedelin. ► Ozonation of β-amyrin proceeds via epoxydation, oxidation and ring-C opening reaction. ► Reaction of lupenone consists of de-alkylation, hydroxylation, epoxydation, oxidation.