The Journal of Phytopharmacology 2025; 14(3):170-176 DOI:10.31254/phyto.2025.14307

Research Article

Extraction, isolation, and antimicrobial evaluation of bioactive compounds from the ethanolic extract of Allium cepa L.

Dickson Aboagye¹ , Caleb Ofori Bandoh¹ , Kingsley Ofolikwei Quaye¹ , Josephine Frimpomaa Oppong¹ , Justice Yao Akakpo¹ , Emmanuel Ogwoh Chisom¹ , Kelvin Amankwah Sarfo¹ , Prince Nartey-Addy Amoyaw¹

Dickson Aboagye,Caleb Ofori Bandoh,Kingsley Ofolikwei Quaye,Josephine Frimpomaa Oppong,Justice Yao Akakpo,Emmanuel Ogwoh Chisom,Kelvin Amankwah Sarfo,Prince Nartey-Addy Amoyaw

1. Department of Pharmaceutical Sciences, School of Pharmacy, Central University, Accra, Ghana

*Author to whom correspondence should be addressed.

Received: 5th May, 2025 / Accepted: 12th July, 2025 / Published : 31st July, 2025

Abstract

Background: Allium cepa (onion) is a widely cultivated plant, known for its rich phytochemical composition and diverse medicinal properties. As global antibiotic resistance continues to rise, there is an increasing interest in exploring natural sources, such as medicinal plants, for the discovery of novel bioactive compounds. This study investigated the extraction, isolation, and antimicrobial activity of chemical constituents from the ethanolic extract of Allium cepa. Aims and Objectives: This study aimed to extract and isolate bioactive compounds from the ethanolic extract of Allium cepa and evaluate their antimicrobial activities against Escherichia coli and Staphylococcus aureus. Materials and Methods: Fresh Allium cepa bulbs were obtained from Aburi, Ghana. A total of 316 g of dried powdered bulbs were extracted via cold maceration using 95% ethanol and 5% water. The extract was filtered and concentrated using a rotary evaporator, and then analyzed by TLC, revealing three spots (Rf: 0.29, 0.33, and 0.5). Further purification using flash column chromatography and HPLC yielded the pure compound AC (Rf = 0.5). Compound AC’s antimicrobial activity was evaluated using the micro broth dilution method against E. coli and S. aureus, using ciprofloxacin and clindamycin as controls. Results: Phytochemical screening of the crude extract confirmed the presence of alkaloids, tannins, flavonoids, quercetin, and saponins. TLC analysis of the crude extract yielded three spots, and flash chromatography isolated AC with Rf = 0.5. The isolated compound, AC, had a melting point of 317°C and was soluble in DMSO and methanol. The MIC values of compound AC were 0.5 mg/mL against S. aureus and 3.91 mg/mL against E. coli, which are comparable to standard antibiotics such as ciprofloxacin (MICs:< 0.1 mg/mL and <0.1 mg/mL respectively) and clindamycin (MICs: <0.1 mg/mL and <0.5 mg/mL respectively). Conclusion: The ethanolic extract of Allium cepa contained bioactive compounds with significant antimicrobial activity, particularly against S. aureus. The isolated compound AC showed promising results, supported by TLC, flash chromatography, HPLC, and MIC determination.