Inhibitory effects of natural spices extracts on Aspergillus growth and aflatoxin synthesis

Aflatoxins are naturally occurring toxic metabolites produced by many Aspergillus particularly Aspergillus flavus and Aspergillus parasiticus in food and feed products. These toxins are hepatotoxic and mutagenic causing severe health disorders including hepatitis and hepatocellular carcinoma (HCC). Various physical and chemical strategies have been introduced to control the growth and aflatoxin production. However, due to safety concerns and potent toxicity of chemicals, researchers are seeking for cost-effective and non-toxic alternates of plant origins to prevent deterioration of grain crops. The aim of this study was to check the effect of natural spices products such as aniseed, black cumin, black pepper, cardamom and turmeric extracts on the growth of pathogenic strains and their ability to produce aflatoxin contamination. Antifungal activity of spices including black cumin, turmeric, black pepper, cardamom and aniseed were performed against aflatoxigenic strain of Aspergillus parasiticus. Water soluble extracts of these spices were prepared, agar diffusion assay was performed and zone of inhibition was measured after applying different concentrations of extracts against the above strain. Subsequently, aflatoxin inhibition assay was performed by inoculating sub-inhibitory concentrations of these extracts with aflatoxigenic strain in Czapek Dox liquid medium. After incubation, thin layer chromatography (TLC) was performed to detect and quantify aflatoxins. All extracts have shown concentration dependent antifungal activity and best results were obtained with cardamom which was active even at 0.005% concentration. In addition, it was also observed that the synthesis of toxin was inhibited by all extracts and maximum activity at the concentration of 0.00025% was shown by black cumin, black pepper and aniseed. Our study showed that these extracts are effective to control aflatoxigenic strains of Aspergillus and aflatoxin contamination and may be considered as an alternative to control post-harvest fungal diseases.