HPLC-DAD and HPLC-MS/MS Analyzes of Phenolic Compounds, Antioxidant and Antibacterial Activities of the Methanol Extract of Atractylis caespitosa Desf

The Asteraceae family are known for their diverse pharmacological activities, such as hepatoprotective, antioxidant, antibacterial, and anti-inflammatory effects. This study aimed to investigate the phenolic compounds composition, antioxidant, and antibacterial activities of the aqueous-methanol extract of the aerial parts of Atractylis caespitosa Desf., a plant species from the Asteraceae family. This species is used in conventional medicine to treat various ailments across different regions of Algeria. The phenolic compounds were analyzed using a newly developed High-Performance Liquid Chromatography coupled with Diode Array Detection (HPLC-DAD) and High-Performance Liquid Chromatography-Tandem Mass Spectrometry (HPLC-MS/MS) techniques. The antioxidant activity was assessed using the 2,2-diphenyl-1- picryl hydrazyl (DPPH) radical scavenging and the Ferric Reducing Antioxidant Power (FRAP) assays. Antibacterial activity was evaluated against notable pathogenic bacterial strains using the disk diffusion method. Through area normalization, 13 phenolic compounds were identified from the HPLC-DAD analysis of Atractylis caespitosa aerial parts with rosmarinic acid being the predominant compound at a concentration of 36.662 ppm. Additionally, 5 phenolic compounds were detected through the HPLC-MS/MS analysis, with gentisic acid being the most abundant at a concentration of 8.492 µg/g. The extract exhibited significant antioxidant activity with IC50 of 366.65 ± 1.25 µg/mL in the DPPH assay. The extract showed notable antibacterial activity, particularly against Pseudomonas aeruginosa and Escherichia coli, with the extract showing the lowest Minimum Inhibitory Concentration (MIC) of 2.5 mg/mL against both bacterial strains. The present findings pave the way for further exploration of Atractylis caespitosa.