Phytochemical Analysis of Flavonoids and Antimicrobial Efficacy of Certain Libyan Medicinal Plants
Keywords:
Libyan medicinal plants, Flavonoids, Antimicrobial activity, Thymus capitatus, Retama raetam, Artemisia herba-alba, HPLC-DADAbstract
The escalating prevalence of antimicrobial resistance (AMR) has necessitated a global search for novel therapeutic agents derived from natural sources. Libyan folk medicine has long utilized indigenous flora for treating infectious diseases, yet these plants remain largely uncharacterized by modern phytochemical and pharmacological standards. This study aims to bridge this gap by conducting a comprehensive phytochemical analysis, with a specific focus on flavonoid profiling, and evaluating the antimicrobial efficacy of three selected Libyan medicinal plants: Retama raetam, Thymus capitatus, and Artemisia herba-alba. Plant samples were collected from the Al-Jabal Al-Akhdar region, and crude extracts were prepared using maceration with 80% ethanol. Total flavonoid content (TFC) was quantified via a colorimetric aluminum chloride assay, while individual flavonoid compounds were identified using High-Performance Liquid Chromatography coupled with Diode-Array Detection (HPLC-DAD). The antimicrobial activity was assessed against a panel of standard pathogenic strains, including Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853), and Candida albicans (ATCC 10231), using the agar well diffusion method and broth microdilution to determine Minimum Inhibitory Concentrations (MICs). The results revealed that T. capitatus exhibited the highest TFC (125.3 ± 4.2 mg QE/g extract), followed by A. herba-alba (98.7 ± 3.1 mg QE/g) and R. raetam (56.2 ± 2.5 mg QE/g). HPLC-DAD analysis identified quercetin, apigenin, and luteolin as the predominant flavonoids across the samples. The antimicrobial assays demonstrated that T. capitatus extract possessed the most potent activity, producing significant inhibition zones against S. aureus (22.5 ± 1.1 mm) and C. albicans (19.8 ± 0.9 mm), with MIC values of 0.39 mg/mL and 0.78 mg/mL, respectively. A. herba-alba showed notable efficacy against Gram-negative bacteria, particularly E. coli. Statistical analysis revealed a significant positive correlation (p < 0.01) between TFC and antimicrobial activity, suggesting that flavonoids are key contributors to the observed effects. This study provides scientific validation for the traditional use of these Libyan plants and identifies T. capitatus as a promising source of flavonoid-based antimicrobial agents. Future research should focus on isolating active compounds, elucidating their mechanisms of action, and evaluating their synergistic potential with conventional antibiotics.
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