Methyl Jasmonate Elicitation Enhances the Biosynthesis of Coumarin Derivatives in Phlojodicarpus sibiricus

Coumarins are most abundant phenolic compounds of Phlojodicarpus sibiricus Koso-Pol., a medicinally valuable Apiaceous plant that, owing to declining natural populations, is currently of limited availability. In this study, we observed a 3.25-fold increase in the total coumarin content in the leaves of P. sibiricus on day 4 after treatment with 1 mM methyl jasmonate (MeJA). Additionally, the effect of exogenous 0–2 mM MeJA on the phenolic composition was evaluated through metabolite profiling using high-performance liquid chromatography with photodiode array and ion trap-time-of-flight mass spectrometry (HPLC–PDA–IT–TOF–MS). The phenolic chemodiversity increased from untreated plants to those treated with 1 mM MeJA, resulting in a total of 73 identified compounds. These included simple coumarins such as umbelliferone and peucedanol derivatives, pyranocoumarins (including lomatin and khellactone derivatives), phenylpropanoids, and flavonoids, with coumarins being the predominant compounds. The content of coumarins changed considerably after treatment with 1 mM MeJA, showing nearly a three-fold increase in key components such as d-laserpitin (3112.7 μg/g versus 1027.6 μg/g in 0 mM MeJA), dihydrosamidin (2465.6 μg/g vs. 820.5 μg/g in 0 mM MeJA), and praeroside II (3277.0 μg/g vs. 1053.8 μg/g in 0 mM MeJA). In addition to the MeJA-induced accumulation of coumarins, there was a considerable increase in the activity of key coumarin biosynthetic enzymes, including phenylalanine ammonia-lyase, cinnamic acid 4-hydroxylase, 4‑coumarate: CoA ligase, and tyrosine ammonia lyase. These findings suggest that MeJA stimulates phenylpropanoid metabolism in P. sibiricus leaves, enhancing the accumulation of pyranocoumarins, which could serve as valuable targets for further research into coumarin biosynthesis and bioactive compound production.