Microbial alteration of 17α(H)-hopanes in Madagascar asphalts: removal of C-10 methyl group and ring opening |
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Authors: | Jürgen Rullkötter Detlef Wendisch |
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Institution: | Institute of Petroleum and Organic Geochemistry (ICH-5) Kernforschungsanlage Jülich GmbH D-5170 Jülich 1, Federal Republic of Germany;Bayer AG, Research and Development Division, D-5090 Leverkusen, Federal Republic of Germany |
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Abstract: | The detailed investigation of the saturated hydrocarbon fractions of two biodegraded asphalts from the Morondava Basin, Madagascar, and the comparison with a related non-biodegraded asphaltic oil revealed new information on the compositional alteration of reservoired hydrocarbons due to biodegradation. A nuclear-demethylated 17α(H)-hopane was isolated from one of the asphalts and the preferred structure is suggested to be 25-nor-17α(H)-hopane. In addition to a homologous series of 25-nor-17α(H)-hopanes and 25-normoretanes a series of tetracyclic triterpanes was detected. These are thought to be derived from 17α(H)-hopanes by ring C opening. Steranes in the biodegraded asphalts were found to be altered but not completely removed. |
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