When trees of the genera Aquilaria and Gyrinops (from the Thymelaeaceae family) are injured, they produce a black resinous deposit called agarwood, which is sought after because of its fragrance and medicinal properties. As natural agarwood sources are depleted and collection from the wild is restricted, artificial agarwood has been developed. Furthermore, the quality of commercial agarwood is determined through subjective evaluation by human experts, and standard quality controls are lacking. In this study, we evaluated the effects of chemical injury treatments using plant hormones (salicylic acid, methyl jasmonate, and ethylene), which have attracted attention in the production of artificial agarwood. Resin-deposited areas on the treated branches were quantified using image analysis as an objective quality indicator. In addition, the yield of 2-(2-phenylethyl)chromones (2PECs), which are essential fragrance compounds in high-quality agarwood, was quantified. Treatment with salicylic acid or methyl jasmonate resulted in resin-deposited areas more than double those of the control, with enhanced 2PEC content, such as oxidoagarochromone A, B, and C, and agarotetrol. Additionally, treatment of wood with over-the-counter medicines containing salicylic acid resulted in a dramatic increase in the resin-deposited area and 2PEC content. Furthermore, the total oxidoagarochromone A, B, and C content was positively correlated with the resin-deposited area in the six months treatment samples. This is the first study to quantitatively demonstrate the effect of plant hormones on the agarwood resin-deposited area and 2PEC content, especially oxidoagarochromone A, B, and C, and agarotetrol, simultaneously, and is expected to contribute to further development of artificial agarwood production, quality evaluation methods, and elucidation of the resin deposition process.
