Antifungal activity of Liriodenine from Michelia formosana heartwood against wood-rotting fungi

Wood-rotting fungi lead to great economic losses of lignocellulosic materials. The influence of extractives on the decay resistance of Michelia formosana wood and the antifungal activities of heartwood extract and its constituent against wood-rotting fungi were evaluated. Results revealed that extractives had a strong influence on the decay resistance of M. formosana heartwood. The unextracted heartwood block was resistant to fungi, while the extracted heartwood block was not. Antifungal activities of ethanolic extract from heartwood were assessed; results revealed that the ethanolic extract possessed good antifungal activity against wood-rotting fungi. The ethanolic extract was further separated into four fractions including n-hexane-soluble fraction, ethyl acetate-soluble fraction, n-butanol-soluble fraction, and water-soluble fraction. Among these fractions, the n-hexane-soluble fraction exhibited the best antifungal ability. An alkaloid, liriodenine, was isolated from the active n-hexane-soluble fraction. IC₅₀ values of liriodenine against the white-rot fungi Lenzites betulina and Trametes versicolor were 0.76 and 3.50 μg/mL, respectively. IC₅₀ values of liriodenine against the brown-rot fungi Laetiporus sulphureus, Gloeophyllum trabeum, and Fomitopsis pinicola were all lower than 2.0 μg/mL. Results indicated that liriodenine exhibited a broad spectrum of antifungal activity and great potential to develop as an environmentally benign fungicide for the preservation of lignocellulosic materials.