Allelopathic Effects of Compounds from the Ethanol Extract of Artemisia frigida on Five Invasive Alien Plants.

Invasive alien plants seriously threaten native plant biodiversity and agricultural production. The development of environmentally friendly agriculture requires sustainable weed control techniques to manage these invasive alien weeds. This study evaluated the allelopathic effects of ethanol extract from Artemisia frigida against five invasive alien plants (Ageratum conyzoides, Bidens pilosa, Ipomoea purpurea, Eclipta prostrata, and Amaranthus retroflexus). The main components in the extract were identified using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS), and we assessed their allelopathic effects on seed germination of the five species. The results showed that the ethanol extract of A. frigida completely inhibited seed germination of all five invasive plants at 5 g·L-1. Thirteen components were identified, among which 4-ethyloctanoic acid, cis-jasmone, and p-anisic acid exhibited significant inhibitory effects. Notably, 4-ethyloctanoic acid demonstrated broad-spectrum herbicidal activity. At 50 mg·L-1, it completely inhibited B. pilosa growth and had the strongest inhibitory effects on A. conyzoides and E. prostrata. This compound disrupted redox homeostasis and induced oxidative stress by modulating antioxidant enzyme activities, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). These findings indicate that 4-ethyloctanoic acid is the main allelochemical with herbicidal potential in A. frigida, providing a theoretical basis for developing novel herbicides and environmentally friendly control techniques for invasive alien plants.