Characterization of secondary metabolite compounds correlated with the seasons in Artemisia princeps var. orientalis (Pamp.) H. Hara leaves using direct sample injection and gas chromatography–mass spectrometry: contribution to phytotoxicity

Leaves from a natural population of Artemisia princeps var. orientalis (Pamp.) H. Hara were collected monthly from April through October and characterized for composition of secondary metabolite compounds and their phytotoxic effects on seed germination and seedling growth of Achyranthes japonica and Lactuca sativa. The compounds were identified using gas chromatography/mass spectrometry (GC/MS) coupled with a solvent-free solid injector (SFSI). GC/MS analyses of all samples revealed qualitative variability in the composition of secondary metabolites. The greatest number of compounds was identified in July (56) followed by September (30) and April (24), and the lowest number was found in June (2) and August (2). Among 92 compounds, the major compounds were various terpenes (23) (mono-, sesqui, di-, and tri-terpenes) followed by heterocyclic compounds (18) and hydrocarbons (14). The higher the concentration of the secondary metabolites, the lower the seed germination and seedling growth of A. japonica and L. sativa. Plant samples collected in July and August were most detrimental. Taken together, variability in the secondary metabolites compounds of A. princeps var. orientalis was verified during different seasons, and the compounds were successfully identified by a combination of SFSI and GC/MS. Notably, the antimicrobial and antioxidative effects were inconsistent throughout the various seasons