Effects of Selected Plant Extracts and Leaf Ashes on Aspergillus flavus Growth and Aflatoxin B1 Production in Maize Grains

Abstract

Synthetic fungicides used against aflatoxigenic fungi have negative health and environmental impacts. Plant-based alternatives offer safer, biodegradable options. This study evaluated the in vitro and in vivo antifungal activity of ethanolic extracts from leaves and leaf ashes of five medicinal plants (Trichilia emetica, Sclerocarya birrea, Tabernaemontana elegans, Combretum molle, and Securidaca longepedunculata) against Aspergillus flavus and aflatoxin B1 (AFB1) production in maize grains. Antifungal activity was tested at 2.5–10.0 mg mL⁻¹ using mycelial growth inhibition in vitro and on stored maize grains (in vivo). AFB1 was extracted with 80% methanol and detected by thin layer chromatography. Phytochemical screening revealed alkaloids, flavonoids, phenols, and cardiac glycosides in most extracts, while terpenoids were absent in leaf ashes. T. elegans leaf ash, S. birrea leaf, and S. birrea leaf ash showed 100% in vitro inhibition at 2.5 mg mL⁻¹ (MIC = 2.5 mg mL⁻¹). However, in vivo, only T. elegans leaf ash exhibited strong activity (93.3% inhibition at 7.5–10.0 mg mL⁻¹), while most extracts failed to inhibit fungal growth on maize grains. AFB1 was completely suppressed by T. elegans leaf ash at all concentrations (5.0–10.0 mg mL⁻¹), and by S. birrea leaf, S. birrea leaf ash, and S. longepedunculata root at 10.0 mg mL⁻¹. The superior performance of T. elegans leaf ash is likely due to retained bioactive alkaloids combined with alkaline and hygroscopic properties. This extract represents a promising eco-friendly alternative to synthetic fungicides for aflatoxin control in stored maize