Antifungal Potential of Ethanol Leaf Extract of Bitter Leaf (Vernonia Amygdalina L) Against Dioscorea rotundata (White Yam) Spoilage Fungi Antifungal Potential of Ethanol Leaf Extract of Vernonia Amygdalina Against Dioscorea rotundata

Abstract

Dioscorea rotundata is one of the most cherished yam varieties, but it is unfortunately highly susceptible to fungal infection, posing a significant threat to food security. Efforts to address this issue with conventional fungicides have worsened the situation by compromising food safety. This study aimed to assess the potential of Vernonia amygdalina extract to protect yam tubers against fungal attack. Freshly harvested leaves of Vernonia amygdalina (bitter leaf) from a household garden were processed into a fine powder. Exactly 500 g of Vernonia amygdalina ethanol leaf extract (VAELE) was macerated in 1,000 mL of 70% ethanol for 72 hours before being filtered. The resulting filtrate was concentrated using a rotary evaporator. Microbial procedures and analyses, such as fungal isolation, identification, anti-fungal sensitivity bioassay, minimum inhibitory concentration (MIC), and minimum fungicidal concentration, were performed using standard procedures. Fungal presence was most pronounced on the 6^th (45.0 × 10⁶) and 7^th spots (55.0 × 10⁶ CFU/g) SYTS. However, the 5th spoiled yam tuber spot (SYTS) manifested the least fungal load of 3.0 × 10⁶ CFU/g. Aspergillus niger recorded the highest occurrence (34.42%), whereas Fusarium oxysporum had the lowest (14.75%). The anti-fungal activity of VAELE was dose-dependent, with the most pronounced activity observed at 300 mg/mL. The minimum inhibitory concentration (MIC) was established at 75 mg/mL against all fungal isolates (A. niger, A. flavus, P. chrysogenum, and F. oxysporum). Fungicidal activity of VAELE was established at 300 and 150 mg/mL. In conclusion, it can be deduced from this study that Vernonia amygdalina ethanol leaf extract can impede or kill A. niger, A. flavus, P. chrysogenum, and F. oxysporum depending on the concentration applied.