Seasonal Variation in Chemical Constituents and Bioactivity of Ageratina adenophora.

Ageratina adenophora (A. adenophora) is a globally invasive plant with strong ecological adaptability. To elucidate its adaptive chemical basis and seasonal dynamics of bioactive constituents, this study used gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS) to analyze volatile oils and ethanol extracts from the aerial tissues of A. adenophora across four seasons. Partial least squares-discriminant analysis (PLS-DA) was applied to link seasonal metabolites with antioxidant and antibacterial activities. Essential oils contained monoterpenes and sesquiterpenes, peaking in summer (0.18%) and lowest in winter (0.08%). Monoterpenes dominated spring (28.67%), oxygenated sesquiterpenes autumn (40.81%). Major metabolites included three monoterpenes (o-cymene, (+)-4-carene, α-phellandrene) and four sesquiterpenes (α-bisabolol, germacrene D, aristolone, cubenol). Ethanol extracts had fluctuating phenolics, flavonoids, and tannins; flavonoids/tannins peaked in spring, phenolics in summer. Summer samples showed the strongest antioxidant activity, autumn extracts optimal antimicrobial efficacy. PLS-DA screened key active compounds: oil-borne α-terpinolene, α-cadinol, and extract rosmarinic acid, rutin, which dominate dual bioactivities. This study clarifies seasonal composition-bioactivity correlations in A. adenophora, supporting research on its invasion mechanisms and resource exploitation.