Preliminary evaluation of storax and its constituents: Fungal decay, mold and termite resistance

Abstract

Essential oils and their derivatives might be one of the promising preserving agents to prevent fungal decay and termite/insect attack in wood since such compounds have a long history of safe usage as antimicrobial agents in various industries. Considerable research has focused on utilizing bioactive essential oils and wood extractives based on green technologies to develop environmentally friendly wood preservatives. This study evaluated biological activities of storax from Liquidambar orientalis tree, some storax constituents and commercial styrax against wood-decaying fungi, mold fungi, and termites in laboratory conditions. Scots pine sapwood specimens were treated with various concentrations of styrax, storax and storax constituents i.e. cinnamyl acetate, cinnamyl alcohol and ethyl cinnamate. Treated specimens were subjected to leaching followed by soil block decay tests using two brown rot and two white rot fungi. Specimens were also subjected to two different laboratory termite resistance tests based on the standards methods by the American Society for Testing and Materials (ASTM) and Japanese Industrial Standards (JIS). Inhibitory effects of the compounds were evaluated in vitro against Basidiomycetes, mold, and staining fungi. Treated wood specimens were also tested for mold growth. The storax constituents, storax and styrax did not inhibit fungal decay by the brown rot fungi. The constituents and storax-treated specimens resulted in mostly “moderate resistance” to fungal decay by the white rot fungi based on the ASTM D2017 classification. Styrax only was effective against the Basidiomycetes fungi in vitro tests; however, the mold and staining fungi tested were not completely inhibited. Natural storax at the concentration level of 0.5% inhibited all fungi except Trametes versicolor and Ceratocystis pilifera. Cinnamyl alcohol inhibited fungal growth with the exception of Aspergillus niger. In mold tests, complete inhibition was not observed for any of the test fungi; however, cinnamyl alcohol reduced mold growth considerably on treated wood specimens. Cinnamyl alcohol was also effective against termites in unleached specimens; however, styrax and natural storax at the concentration level of 10% reduced wood consumption in treated specimens.