Influence of Ecological Conditions on the Phenolic Composition and Antioxidant Activity of Thymelaea hirsuta Extracts from Two Tunisian Regions

Abstract

Thymelaea hirsuta is a medicinal plant widely distributed in North Africa and traditionally used for the treatment of various diseases. This study aimed to investigate the phenolic composition and antioxidant potential of methanolic extracts obtained from the aerial parts of T. hirsuta collected from two ecologically distinct regions of Tunisia: Medenine (arid climate) and Mahdia (semi-arid climate). Plant materials were subjected to solvent extraction, and the resulting extracts were analyzed for total polyphenol and flavonoid contents using spectrophotometric methods. Antioxidant activity was evaluated in vitro using DPPH radical scavenging and ferric reducing antioxidant power (FRAP) assays. In addition, high-performance liquid chromatography (HPLC) was employed to characterize the phenolic profiles of the extracts.

The results revealed significant variations in phenolic and flavonoid contents depending on both the extraction method and the geographical origin of the plant material. Crude extracts exhibited higher concentrations of bioactive compounds compared with extracts obtained from dry powder. The crude extract from Mahdia showed the highest total polyphenol and flavonoid levels, whereas the Medenine extract displayed greater diversity in phenolic composition. All extracts demonstrated antioxidant activity, although their reducing power was lower than that of ascorbic acid. Notably, extracts from dry powder exhibited stronger radical scavenging capacity in the DPPH assay.

HPLC analysis revealed complex phenolic profiles with numerous detectable compounds, confirming that the antioxidant activity is likely due to synergistic effects among multiple constituents. Environmental stress associated with arid conditions appears to enhance the synthesis of secondary metabolites. Overall, T. hirsuta represents a promising natural source of phenolic antioxidants with potential applications in pharmaceutical, nutraceutical, and food industries.