Evaluation of ornamental/exotic plant extracts as natural preservative methodology against termites and fungi

Abstract

The present work investigated new sustainable opportunities for wood protection against xylophagous organisms (cellulolytic fungi and termites) based on the use of natural bioactive compounds present in Milicia excelsa wood and Nerium oleander bark. To achieve this, solid–liquid extractions by ethanol were carried out, obtaining extraction yields of 5.47 ± 0.78% for the extract of M. excelsa and 21.88 ± 0.53% for N. oleander. Gas chromatography coupled with mass spectrometry analyses were carried out to evaluate the chemical composition of both extracts, showing interesting compounds with biological activity such as pyrogallol, 4-acetylresorcinol, karanjin and scopoletin. Likewise, an evaluation of the cellulolytic capacity of different wood-isolated fungi (Aspergillus flavus, Penicillium chrysogenum, Trichoderma longibrachiatum, Mucor circinelloides and Mucor fragilis) was carried out through two screenings, based on their growth rate in carboxymethyl cellulose agar media, and their cellulose-degrading ability via filter paper rupture, being T. longibrachiatum the fungus with the highest growth rate in both substrates. Finally, a protective treatment for pine wood (Pinus sp.) was designed by using the ethanolic extracts separately and combined, respectively, against T. longibrachiatum and Reticulitermes grassei, comparing in both cases the biotic damage with a control. The results demonstrated that the impregnation significantly reduced T. longibrachiatum biomass consumption by over 70% for all treatments. Additionally, the M. excelsa impregnation notably decreased termite activity, with a 81% reduction in the long-term assays.