Antioxidant properties and phytotoxic activity of five Eucalyptus leaves extract

Eucalyptus species, which have long been renowned for their impressive stature and aromatic foliage, are the focus of the current study, which focuses on five methanolic extracts of eucalyptus species cultivated in Tunisia. The liquid chromatography-mass spectrometry (LC/MS) analysis identified 21 phenolic compounds, with quinic acid being the major component among all samples. Furthermore, cluster analysis classified the species into three distinct groups based on their phenolic composition. Total phenolic content varied among species, with Eucalyptus lehmannii exhibiting the highest levels (252 +/- 1.16 mg GAE/g DW), while Eucalyptus lesouefii showed the highest flavonoid content (137.25 +/- 1.12 QE/g DW). Therefore, antioxidant assays showed that E. lehmannii has the greatest ability to scavenge radicals with EC50 values of 89.93 +/- 1.55 mu g/mL for 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays and 218.51 +/- 1.43 mu g/mL for 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. As for the phytotoxic activity, all extracts appear to be effective in reducing the germination rates and the seedling growth of Sinapis arvensis and Trifolium campestre seeds, yet E. lesouefii exhibited the highest effect with a total inhibition at the highest concentrations (0.3%). These findings are of great interest for sustainable applications.