Exceptional preservation of angiosperm markers in Miocene and Eocene ambers

The traditional organic geochemical view suggests that polar triterpenoids are degraded easily during fossilization of organic matter. For the first time, we show that dammarane-type tetracyclic polar triterpenoids are preserved in the geosphere. Hydroxydammarenone (20-hydroxy-24-dammaren-3-one), a typical constituent of extant Dipterocarpaceae (an angiosperm tree family) derived dammar resin, is preserved in Miocene amber. The oxidative products of hydroxydammarenone (i.e., 20,24-epoxy-25-hydroxydammaran-3-one, and hexakisnor-dammaran-3,20-dione) are found in both Miocene and Eocene ambers. The presence of hydroxydammarenone in Miocene amber clearly depicts that natural biotriterpenoid markers can be preserved in the geosphere for tens of millions of years. This result demonstrates that the dammarane-type oxygenated compounds, which are extensively used in archaeological studies, can also be utilized as diagnostic markers for paleochemosystematics.