Natural durability of Sextonia rubra, an Amazonian tree species: description and origin
Sextonia rubra is a tropical tree species belonging to Lauraceae family. In French Guiana, its long lasting heartwood is largely exploited for different purposes including house construction, and furniture making. Decay tests have confirmed S. rubra natural durability, and led us to discover some variability. Rubrynolide and rubrenolide, which are two majors metabolites isolated from the heartwood of S. rubra, exhibit potent antifungal and termiticidal activities that result in the exceptiona l natural durability of this species heartwood. Interestingly, we have also described and isolated acylated precursors of these two secondary metabolites from the sapwood. Although the constitutions and total synthesis of rubrynolide and rubrenolide have been comprehensively described in literature, little is known about their origin and fate in the context of the heartwood formation process. HPLC was thus used to investigate the repartition of rubrenolide and rubrynolide as well as the acylated precursors in sapwood and heartwood of S. rubra, leading to propose that the biotransformation of the precursors into rubrenolide and rubrynolide occurs at the transition zone between sapwood and heartwood. Finally, 13 trees were sampled from natural populations char acterized by different growth dynamics evaluated through dendrometric parameters, tree architecture description and bark desquamation. Our aim was to study the influence of life history traits on S. rubra heartwood formation from a chemical quantitative and qualitative (LC MS analysis) point of view. We observed significant variations concerning sapwood and heartwood extraction yields depending on the trees, as well as a noticeable variability of the heartwood chemical signature.