β-Cyclodextrins as sustained-release carriers for natural wood preservatives

Abstract

Natural preservatives for wood protection have gained increasing attention due to their intrinsic antimicrobial properties, renewability, and lower impact on the environment. We report a study on the use of β-cyclodextrin (βCD) derivatives as sustained-release carriers of allyl isothiocyanate (AITC), as a model natural preservative compound. The formation of AITC inclusion complex in βCDs is qualitatively confirmed by FT-IR and the maximum inclusion yield is estimated to be 39%. Impregnation of wood with the water-borne βCD-AITC complexes allows penetration and even distribution of the preservative in the lumen and possibly in the cell walls. The efficacy of the βCD-AITC complexes as wood preservatives of southern yellow pine is examined by the AWPA E10-16 standard. Compared with the water-treated and AITC-treated wood, βCD-AITC-treated wood exhibits decrease in mass loss from 45% to 25% and no visible cell wall damage after exposure to brown and white rot fungi. The results indicate that βCD suppresses the premature leaching of otherwise volatile AITC and suggests a novel approach of application of volatile or water-immiscible natural preservatives for wood protection.