Antipathogenic Activities and Chemical Composition of Cinnamomum osmophloeum and Cinnamomum zeylanicum Leaf Essential Oils

In this study, inhibitory activities of leaf essential oils from Cinnamomum osmophloeum and Cinnamomum zeylanicum and their major constituents (trans-cinnamaldehyde and eugenol) against Rhizoctonia solani were investigated. Furthermore, the relationship between the antipathogenic activity and the chemical structure of trans-cinnamaldehyde and eugenol is discussed. Results demonstrated that leaf essential oils and their major constituents from C. osmophloeum and C. zeylanicum had strong antipathogenic activities against R. solani. Results obtained from the chemical structure-antipathogenic activity relationship study suggested that trans-cinnamaldehyde or (E)-cinnamic acid with an aldehyde (-CHO) or an acid (-COOH) group, a conjugated double bond, and a Length of CH chain outside the ring affect their antipathogenic activity. Furthermore, the presence of the methyl moiety in the ortho position may have a considerable influence on the inhibitory action against R. solani. In addition, compounds with a free phenolic hydroxyl (-OH) group and a double bond at the C7 position of the phenylpropenes also exhibited potent antipathogenic activity.