Evolution of the chemical composition of Ginkgo biloba external and internal leaf lipids through senescence and litter formation

External and internal lipids were analysed in fresh, senescent and litter l eaves of Ginkgo biloba to derive qualitative and quantitative information o n the changes that occur during the very early stages of diagenesis, and to identify potential biomarkers of the only living Ginkgoare. Analysis of fr esh leaves led to the identification of additional compounds, including sev eral series of phenolic constituents, and showed differences between the ex ternal and internal lipids (absence/presence of some components, relative a bundances and distributions of some series). Pronounced differences concern ed with the evolution of content (as wt.% of whole leaves) were observed be tween the internal lipids (regular decrease from fresh to senescent and to litter leaves) and the external lipids (no significant changes in content). Molecular studies showed variations in the relative abundances and distrib utions of most constituents of G, biloba leaf lipids which reflect differen t degrees of stability during the first stages of diagenesis. It also appea red that (i) the phenolic components and the co-occurrence of alpha -tocoph erol and nonacosan-10-ol could be useful biomarkers of G. biloba, and (ii) most of the internal lipids continue to be exported to the leaf surface whe re they are further degraded during senescence and litter formation. (C) 20 01 Elsevier Science Ltd. All rights reserved.