Abstract
Conifer plant Pinus densiflora predominates in the catchment of the Pond Shibu-ike in Matsumoto City, Nagano Prefecture, Japan. P. densiflora can supply leaf resins to the sediments in the pond. In this study, we analyzed lipids in P. densiflora leaves, forest soils, and Pond Shibu-ike sediments to understand early diagenetic processes of the abietane-type diterpenoids. P. densiflora leaves contained abietane-type precursors such as dehydroabietic acid, which might be altered to several diterpenoids in forest soils and lacustrine sediments. A great amount of compounds, of which molecular weight was 258 or 272, were detected in the litter layer of forest soil. They might be mixtures of intermediates of diterpenoid hydrocarbons derived from P. densiflora. They disappeared completely in the humic layer underlying forest soils presumably due to microbial degradation. On the other hand, aromatic and dehydro-type abietanes were identified in the Pond Shibu-ike sediment, and must be produced by early diagenetic processes from dehydroabietic acid, which was confirmed to be present in P. densiflora leaves samples. It is suggested that aromatic abietanes such as retene were produced by aromatization of abietane-type diterpenoids in lacustrine sediments.
