Phenolic Composition and In Vitro Allelopathic Potential of Inula graveolens Extracts

Abstract

Inula graveolens (L.) Desf. is an aromatic plant that grows naturally in the wild. Several studies have shown that this species is rich in bioactive compounds, including phenols, terpenoids, tannins, and flavonoids. In this context, the present study aimed to investigate the allelopathic potential of aqueous, methanol, and ethanol extracts of I. graveolens against wheat (Triticum aestivum L.) and several ecologically significant invasive plant species. The phytochemical composition of the plant was analyzed by LC-MS/MS method using a Shimadzu Nexera model ultra-high-performance liquid chromatograph (UHPLC), enabling quantitative evaluation of 56 phytochemicals. Based on the HPLC results, chlorogenic acid (8.444 mg/g extract), quinic acid (1.702 mg/g), and gentisic acid (1.183 mg/g) were identified as the predominant constituents in the methanol extract of the plant. In allelopathy experiments, aqueous extracts of I. graveolens (1%, 3%, 5%, 10%, and 20%) and methanol and ethanol extracts (150, 300, 600 ppm) were tested for their biological activity against Triticum aestivum L., Amaranthus palmeri S. Watson, and Cephalaria syriaca (L.) Schrad., Ipomoea purpurea (L.) Roth, and Vaccaria pyramidata Medik. The extracts demonstrated significant inhibitory effects on both seed germination and biomass production of the test species.