Abstract:
Plants produce various types of terpenoids that play an important role in the interaction of the plant with its environments. The last two decades have seen considerable progress in elucidating plant terpenoid biosynthetic pathways at the gene and enzyme levels. However, the biosynthetic evolution of these natural products remains poorly understood. We have addressed this knowledge gap by demonstrating the geological preservation of a bioactive angiosperm metabolite. Specifically, we report the presence of 20,24-epoxy-25 hydroxy dammaran-3-ol, an oxidative product of dammarenediol, from 54 Ma old dipterocarp-derived dammar resins. Other dammarane-type triterpenoids such as 20,24-epoxy-25-hydroxydammaran-3-one and hexakisnor-dammaran-3,20-dione were also present in the solvent extracts of the fossilized resins. Dammarenediol is the main precursor of several ginsenosides which have many pharmacological effects. It's occurrence in early Eocene sediments unequivocally demonstrates that plants from this period had produced the enzyme dammarenediol cyclase that catalyzes the cyclization of 2,3-oxidosqualene into dammarenediol. This study opens new avenues for research into evolution of important plant metabolites in deep-time. (C) 2016 Elsevier B.V. All rights reserved.