The heartwood of Prosopis juliflora is resistant to fungal attack caused by different brown and white rot fungi. This durability due to the presence of high amounts of extractives decreases after extraction of these latter ones with different solvents. Heartwood extractives were effective in inhibiting the growth of the fungi. Depending on the concentration used, development of the fungal mycelium on the treated medium started after a more or less important inhibition period, suggesting that the extractives present rather fungistatic than fungicidal properties. Chemical characterization of extractives of P. juliflora was investigated by 1H NMR and GC-MS techniques to understand their contribution to heartwood durability. Results show that heartwood extractives contain mainly (-)-mesquitol possessing important antioxidant properties, which can be at the origin of durability to fungi. Durability of heartwood was also investigated towards Macrotermes natalensis, a subterranean termite commonly found in Kenya, on extracted or unextracted wood blocks. Weight losses on solvent extracted wood exposed to termites are higher than for the unextracted samples suggesting that heartwood resistance of P. juliflora heartwood to Macrotermes natalensis is associated to the presence of extractives. No-choice tests realized with filter papers impregnated with different amounts of extractives caused important termites mortality. Biological resistance of P. juliflora wood against termites and fungi seems therefore associated to the presence of extractives.

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