Evaluation of the Inhibitory Activity of Aqueous and Alcoholic Extracts of Onion (Allium cepa L.) Scale Leaves Against Some Fungi Belonging to the Genera Aspergillus, Penicillium, and Mucor in Tripoli Markets, Libya

Abstract

This study aimed to isolate and identify the fungal species responsible for the spoilage of onion bulbs (Allium cepa L.) and to evaluate the inhibitory potential of aqueous and alcoholic extracts of onion scale leaves as biological alternatives for fungal control. A total of 40 onion samples (20 red and 20 yellow) were collected from local markets in Tripoli, Libya, during the 2024-2025 period. Three scale leaf layers from each bulb were examined, and fungi were isolated on Potato Dextrose Agar (PDA).The results revealed significant fungal diversity and variation in the number of isolates between the two onion types; yellow onions recorded 72 isolates compared to 47 isolates for red onions. The identified genera included Aspergillus, Mucor, and Penicillium, with Aspergillus being the most dominant, exceeding a 60% frequency rate. Statistical analysis using the Mann-Whitney U test confirmed significant differences (P-value < 0.05) in fungal distribution, proving greater susceptibility in yellow onions. Inhibitory Activity, Antifungal efficacy tests at concentrations of 3, 5, and 7 mg/mL showed that the alcoholic extract of red onion was superior against Aspergillus spp., achieving a 92.47% inhibition rate. Meanwhile, the alcoholic extract of yellow onion recorded the highest inhibition against Penicillium spp. at 77.13%. Conclusion, the study confirms the higher efficiency of alcoholic extracts compared to aqueous ones in extracting active compounds such as phenols and anthocyanins. These findings suggest promising prospects for using these extracts in post-harvest crop protection to reduce economic losses and improve the quality and safety of onion crops in the Libyan local markets.