Antioxidant, antibacterial, and α-glucosidase inhibition potential of three Allium species (Amaryllidaceae) from Iran

Abstract

Introduction: Wild species of the genus Allium have high potential for use as medicine due to their essential secondary metabolites with antioxidant activity. This study explored the antioxidant, antibacterial, and α-glucosidase inhibition activities of three Allium species: Allium tripedale, Allium hooshidaryae, and Allium stipitatum. Methods: The antioxidant potentials of the plant methanol extracts were evaluated using the ferric reducing antioxidant power (FRAP) and the 2,2-diphenyl-1picrylhydrazil (DPPH) radical scavenging test. Total phenolic content (TPC), total flavonoid content (TFC) and α-glucosidase inhibition were also evaluated. Antibacterial assessments were done employing disk diffusion and microdilution methods to determine inhibition zone and minimum inhibitory concentration (MIC), respectively against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa. Results: Allium hooshidaryae displayed high TPC (70.24 ± 0.0039 mg gallic acid equivalent/g extract), while A. tripedale had the highest TFC (87 ± 0.013 mg Quercetin equivalent/g extract). A. hooshidaryae showed superior antioxidant capacity (DPPH IC50: 724.4 ± 0.31 µg/mL; FRAP: 36.87 mg ascorbic acid equivalent/g extract) and stronger α-glucosidase inhibition (IC50 = 2.59 mg/mL vs. 4.33 mg/mL for A. tripedale and 6.41 mg/mL for A. stipitatum). Qualitative tests confirmed phenolic, flavonoid, and glycoside compounds in all three species. A. stipitatum uniquely contained saponin and tannin. A. hooshidaryae and A. stipitatum inhibited the bacterial strains effectively, especially at the higher concentration (400 µg/mL). A. stipitatum showed inhibition against all strains, particularly against S. aureus (MIC: 12.5 µg/mL). Conclusion: This study highlights the antidiabetic and antibacterial potential of three Allium species, emphasizing their values as rich sources of bioactive compounds.