Norsesquiterpenes from Lolium perenne and Their Replacement Control of an Invasive Plant, Ageratina adenophora, Through Allelopathy

<i>Lolium perenne</i> (Poaceae), a perennial forage, has high economic and nutritional value. It is often used as a replacement control for some invasive plants, as it has achieved good ecological and economic effects. However, its control effects, allelochemicals, allelopathic effects, release pathways, and contents are still unclear in the process of <i>L. perenne</i> replacement control of an invasive plant, <i>Ageratina adenophora</i> (Asteraceae). Therefore, it is necessary to reveal the mechanism of <i>L. perenne</i> replacement control of <i>A. adenophora</i> from the perspective of allelopathy. In this study, <i>L. perenne</i> could effectively inhibit the growth of <i>A. adenophora</i> in the competition assay. In addition, seven norsesquiterpenes (<b>1</b>-<b>7</b>) were isolated and identified from the whole plant of <i>L. perenne</i>, and most of the compounds exhibited potent allelopathic effects on the growth of <i>A. adenophora</i> and one model plant (<i>Lactuca sativa</i>, Asteraceae). Moreover, some active compounds were released into the environment through root secretion and rainwater leaching, and their contents were determined by UPLC-MS/MS (Ultra Performance Liquid Chromatography Tandem Mass Spectrometry). Our results elucidated the allelopathic mechanism of <i>L. perenne</i>'s replacement control, <i>A. adenophora</i>, and provided a theoretical basis for the development of norsesquiterpenes from <i>L. perenne</i>.