Specialization of Sesquiterpene Lactone Metabolites in <i>Liriodendron</i> Plant Defense

Tulip trees (<i>Liriodendron tulipifera</i> and <i>Liriodendron chinense</i>), members of the Magnolia family, are known for their distinctive morphology and ecological significance, but their chemical diversity remains understudied. In this study, we report the identification and characterization of an array of sesquiterpene lactones (SQLs) produced by <i>L. tulipifera</i>. Through comprehensive chemical analysis, including high-resolution mass spectrometry and nuclear magnetic resonance spectroscopy, we identified a series of STLs with distinct bioactivity profiles. Notably, one of these compounds exhibited antibacterial activity but was only present in <i>L. tulipifera</i>, being absent in <i>L. chinense</i>. Additionally, some STLs demonstrated significant deterrent effects on herbivory or increased mortality, supporting their role as chemical defenses against grazing organisms. These findings provide new insight into the ecological and chemical functions of <i>Liriodendron</i>, highlighting this group's capacity to produce complex bioactive metabolites that may have pharmaceutical and agricultural applications. Our results also suggest that sesquiterpene lactones could be central to the plant's adaptive strategies following evolutionary differentiation with species-specific production of certain metabolites. This work opens new avenues for the exploration of natural products with antimicrobial and herbivore-deterrent properties, with implications for both natural product chemistry and agrochemical lead development.