Identification of antifungal compounds in konjac flying powder and assessment against wood decay fungi

Abstract Public concern for the environment has stimulated the development of natural wood preservatives. The antifungal activity of konjac (Amorphophallus konjac K. Koch) flying powder (a by-product produced during mechanical processing of konjac flour) ethanol extracts was evaluated against wood decay fungi in poplar (Populus nigra L.). Compounds associated with antifungal activity in the extracts were isolated and purified by silica gel column chromatography. The antifungal active fractions were identified by ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS). The ethanol extracts showed better activity against the brown-rot fungus, Gloeophyllum trabeum (Pers.: Fr.) Murr. than the white-rot fungus, Trametes versicolor (L. ex Fr.) Quel. in poplar. The antifungal active fractions were mainly composed of organic acids and plant essential oils. Salicylic acid, 2,4,6-trichlorophenol, vanillin and cinnamaldehyde were present in the active fractions. These compounds showed high efficacy against both fungi in poplar. The results indicate that konjac extracts have potential as natural wood protectants and suggested that some fractions of konjak flying powder may be useful for protecting wood against fungal attack.