Contact and fumigant actions of trans-cinnamaldehyde against wood-decay fungi evaluated by using solid-phase microextraction

Indigenous cinnamon (Cinnamomum osmophloeum) is an endemic tree in Taiwan. The leaf essential oil is rich in trans-cinnamaldehyde, and its excellent antifungal activity has been reported. Since trans-cinnamaldehyde is a volatile compound, it is here evaluated for whether it is more effective via fumigant action. This study illustrates the antifungal action of trans-cinnamaldehyde against wood-decay fungi. Two ways that trans-cinnamaldehyde inhibits the growth of fungi, namely direct contact and fumigation, were examined using the agar dilution method (AD) and the inverted paper disc method (IPD). In addition, the amount of trans-cinnamaldehyde vapor in the headspace of the Petri dish was quantified using solid-phase microextraction and GC–MS. Antifungal results showed that the antifungal indices observed in the IPD method were clearly higher than those in the AD method, indicating that trans-cinnamaldehyde vapor had stronger antifungal activity. Results from the quantitative analysis also revealed that the amounts of trans-cinnamaldehyde vapor measured by the IPD method were significantly greater than those by the AD method. Accordingly, with higher amount of trans-cinnamaldehyde evaporated, stronger antifungal activity was observed. It is clear that the antifungal action of trans-cinnamaldehyde was primarily attributed to fumigation instead of direct contact.