Origin and early diagenesis of arborinone/isoarborinol in sediments of a highly productive freshwater lake

This paper reports on the presence of arborinone, isoarborinol and some of their early diagenetic degradation products in a tropial lake. Isoarborinol and arborinne, two 3-oxygenated pentacyclic triterpenes whose origin was initially ascribed to higher plants, were found to be highly abundant in Lake Valencia (Venezuela) surface sediments. The primarily autochthonous origin of the organic matter in sediments from this hypereutrophic lake seems to indicate a microbial source for these compounds, as previously suggested by other authors. The structures of two novel tetracyclic aliphatic alkene degradation products of arborinone/isoarborinol are also proposed, and sediment core profiles for both parent and degradation products are discussed.