Class of tetracyclic compounds derived from steroids
For the drug with trade name Sterane, see
Prednisolone. For the parent compound which steranes are derivatives of, see
Gonane.
Steranes constitute a class of
tetracyclictriterpanes derived from
steroids or
sterols via
diagenetic and
catagenetic degradation, such as
hydrogenation. They are found in sediments and sedimentary rocks in nature.[1] Steranes are derivatives of
gonane, the steroid nucleus which is also called "cyclopentanoperhydrophenanthrene".[2] They have an
androstane skeleton with a side chain at the C-17 carbon. The sterane structure constitutes the core of all sterols. Steranes are widely used as
biomarkers for the presence of
eukaryotes in past ecosystems because steroids are nearly exclusively produced by eukaryotes.[3] In particular,
cholestanes are diagenetic products of cholesterol in
animals, while stigmastanes are diagenetic products of
stigmasterols in
algae and
land plants.[1] However, some bacteria are now known to produce sterols and it is inferred that the ultimate origin of sterol biosynthesis is in bacteria.[4] Sterols are produced via protosterols that are direct cyclization compounds of
squalene by the catalysis of
oxidosqualene cyclase.[4] All known sterols in eukaryotes are enzymatically extensively modified from protosterols, while organisms that only produce protosterols are not known. The oldest record of modified steranes are in sedimentary rocks deposited ca. 720–820 million years ago.[5] In contrast, diagenetic products of protosterols (called protostanes and cyclosteranes) are widely distributed in older
Proterozoic rocks and imply the presence of extinct proto-eukaryotes and/or sterol-producing bacteria before the evolution of crown-group eukaryotes.[6]
Steranes may be rearranged to diasteranes during
diagenesis (C-27 to C-30, rearrangement at C-18 and C-19, no R at C-24).
Oils from
clastic source rocks tend to be rich in diasteranes.
^"About biomarkers". The Summons Lab, Massachusetts Institute of Technology (MIT). November 2006. Archived from
the original on 24 April 2020. Retrieved 8 October 2009.