Role of phytochemicals present in Azadirachta indica leaves extracts in controlling toxigenic fungi and inhibition of aflatoxins biosynthesis

The present study assesses the bioactive compounds, antifungal activities and anti-aflatoxigenic properties of neem leaves-based extracts in various solvent (methanol, ethanol, chloroform and ethyl acetate) against aflatoxins biosynthesis molds (Aspergillus flavus and Aspergillus parasiticus) at dosage of 75, 50, 25 and 5 mg/mL. The Gas-Chromatography (GC) and Mass Spectroscopy (MS) screening exposed that each extract possessed divese bioactive compositions. The methanol extract was found the dominant bioactive compounds were 3-hydroxy-hexadecanoic acid (20.70%), octadecanoic acid methyl ester (21.20%) and 9,12-octadecadienoic acid methyl ester (28.62%). The ethanol extracts contained high levels of 4 H-pyran-4-one derivatives (6.99%), tetradecanoic acid (23.64%) and arabino-hex-1-enitol (25.12%), while the chloroform extract was rich in (Z)-2-decenal (12.47%), 2,3-butanedione monooxime (14.19%) and nonanal (18.35%). The ethyl acetate extrac displayed relatively lesser quantifications of ketones and fatty acids. All neem leaves extracts significantly (p < 0.05) controlled fungal mycelium growth and aflatoxins sysntheis in a concentration-dependent way. At 75 mg/mL the mycelial dry weight of Aspergillus flavus reduced to 190 ± 0.3 mg (ethyl acetate), 160 ± 0.2 mg (chloroform), 80 ± 0.1 mg (methanol) and 70 ± 0.6 mg (ethanol), corresponding to inhibition of 56.8%, 63.6%, 81.8% and 84.1% respectively. Likewise, Aspergillus parasiticus biomass reduced to 170 ± 0.5 mg, 120 ± 0.2 mg, 75 ± 0.6 mg and 60 ± 0.4 mg, coreesponding to 60.6%,72.2%, 82.6% and 86.1% inhibition, respectively. Aflatoxins inhibition was alos uppermost in the ethanol extract, whwere aflatoxin (B1) was decreased by 89.3% in Aspergillus flavus and 90.7% in Aspergillus parasiticus, linked with ethyl acetate (57.1% and 62.2%), chloroform (63.4% and 68.5%) and methanol (81.3% and 82.4%). The collective occurrence of lactones derivatives, phenolics, aldehydes and fatty acids probable payed synergistically to the experimental activities. Generally, the ethanol and methanol neem leaves extracts revealed the highest antifungal and anti-aflatoxigenic activities, supportive the possible application of neem leaves bioactive metabolites as non-synthetic substitute for controlling toxigenic molds in feed and food systems.