Aflatoxin B1-reduction of Aspergillus flavus by three medicinal plants (Lamiaceae)

Aflatoxin B1 (AFB1) is one of the most hazardous mycotoxins for humans and livestock that essentially produced by Aspergillus flavus and A. parasiticus in wide variety of natural substrates such as grains, nuts, food products, etc. Natural sources such as plants and microbes can reduce AFB1-contamination from substrate. In this study, the ability of essential oils (EOs) and various extraction solvents (ethanol, ethanol70% and water extracts) of three medicinal plants (Thymus daenensis, Satureja khozistanica and Satureja macrosiphonia) was investigated for reducing A. flavus growth and it's AFB1-content in the liquid culture by use of HPTLC and HPLC analysis. Interestingly, both T. daenensis and S. khozistanica EOs at 375 mg/l as well as their ethanol extracts at 4000 mg/l could completely inhibit Aspergillus growth. In general, ethanol and ethanol70% extracts of all three plants at 2000 mg/l as well as their EOs at 125 mg/l inhibited (51-87%) AFB1-production and exhibited stronger anti-AFB1-biosyntesis activity than aqueous extract. On the contrary, EOs, ethanol and ehanol70% extracts of the plants couldn't significantly degrade AFB1-contamination whereas their aqueous extracts could significantly degrade AFB1-content. The aqueous extract of T. daenensis (AET) at concentration of 2000 mg/l resulted in reduction of 97% AFB1-level, while those extracted of S. khozistanica and S. macrosiphonia reduced 6-15% AFB1-content. The destractive-AFB1 differed from standard AFB1 chemically, and lost a fluorescence property. In general, EOs and ethanol extracts of both T. daenensis and S. khozistanica considerably inhibited A. flavus growth as well as AFB1-biosynthesis while aqueous extracts of T. daenensis showed strong AFB1-degradation activity and introduced as a new promising candidate for degrading AFB1.

► Thymus daenensis and Satureja khozistanica reduce AFB1-level of Aspergillus flavus. ► Essential oils and ethanol extracts of both plants inhibit A. flavus growth. ► Essential oils and ethanol extracts of both plants inhibit AFB1-biosynthesis. ► Aqueous extract of T. daenensis destructs AFB1 strongly. ► The destructive AFB1 differs from aflatoxins chemically and loses a fluorescence property.