Assessment of Phytochemical Content, Polyphenolic Composition, Antioxidant and Antibacterial Screening of Selected Traditional Medicinal Plants from Tunisia

Medicinal and aromatic plants are valuable sources of bioactive metabolites and used in various industries such as food and pharmaceutical. In the present investigation the biochemical composition, antioxidant activity and the antimicrobial activity of the different extracts from seven medicinal plants, namely Foeniculum vulgare (Mill.), Lavandula multifida (L.) L., Periploca laevigata Aiton, Thymus algeriensis Boiss. & Reut., Clematis flammula L., Globularia vulgaris L., and Asphodelus tenuifolius Cav. were assessed. The results indicated significant differences in these bioactive components between plant species. Lavandula multifida (L.) exhibited the highest levels of polyphenols, flavonoids, and tannins (143.5 mg GAE/g DR, 68.2 mg RE/g DR, 42.5 mg CE/g DR, respectively) among the studied extracts. Furthermore, antioxidant activities of the extracts were assessed through various assays, revealing Lavandula multifida (L.) as the most potent antioxidant source. High-performance liquid chromatography (HPLC) analysis reveals distinct profiles of phenolic compounds and flavonoids in each plant. Total antioxidant capacity, DPPH radical scavenging, ABTS•+ radical scavenging, and ferric reductive power, were used to determine the antioxidant ability of the different extracts from the selected medicinal plants. Despite the high antioxidant potential, the extracts showed lower efficacy compared to standard antioxidants. Antimicrobial testing demonstrated significant antibacterial activity, particularly with Lavandula multifida, against various pathogenic strains, suggesting their potential as natural antimicrobial agents with a maximum zone of inhibition against E. coli ATCC 25922, E. coli ATCC 25922/3, P. aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923, Serratia marcescens ATCC 13880. Principal component analysis (PCA) and hierarchical clustering further elucidate the relationships among the plant species based on their phytochemical content and biological activities.