ORIGIN AND EARLY DIAGENESIS OF ARBORINONE ISOARBORINOL IN SEDIMENTS OF A HIGHLY PRODUCTIVE FRESH-WATER LAKE

This paper reports on the presence of arborinone, isoarborinol and som e of their early diagenetic degradation products in a tropical lake. I soarborinol and arborinone, two 3-oxygenated pentacyclic triterpenes w hose origin was initially ascribed to higher plants, were found to be highly abundant in Lake Valencia (Venezuela) surface sediments. The pr imarily autochthonous origin of the organic matter in sediments from t his hypereutrophic lake seems to indicate a microbial source for these compounds, as previously suggested by other authors. The structures o f two novel tetracyclic aliphatic alkene degradation products of arbor inone:isoarborinol are also proposed, and sediment core profiles for b oth parent and degradation products are discussed.