Antifungal and anti-aflatoxigenic activity of <i>Heliopsis longipes</i> roots and affinin/spilanthol against <i>Aspergillus parasiticus</i> by downregulating the expression of <i>alf</i>D and <i>afl</i>R genes of the aflatoxins biosynthetic pathway

Abstract

In the present study, ethanolic extract from <i>Heliopsis longipes</i> roots and affinin/spilanthol against <i>Aspergillus parasiticus</i> growth and aflatoxins production were studied in relation to the expression of <i>afl</i>D and <i>afl</i>R, two key genes of aflatoxins biosynthetic pathway. Phytochemical analysis of the ethanolic extract by GC-EIMS identified affinin/spilanthol (7.84 ± 0.27 mg g^-1) as the most abundant compounds in <i>H. longipes</i> roots. The antifungal and anti-aflatoxigenic assays showed that affinin/spilanthol at 300 µg mL^-1 produced the higher inhibition of radial growth (95%), as well as, the higher aflatoxins production inhibition (61%) in comparison to <i>H. longipes</i> roots (87% and 48%, respectively). qRT-PCR revealed that the expression of <i>afl</i>D and <i>afl</i>R genes showed a higher downregulation in affinin/spilanthol at 300 µg mL^-1. The expression ratio of <i>alf</i>D was suppressed by affinin/spilanthol in 79% and <i>afl</i>R in 84%, while, a lower expression ratio suppressed by <i>H. longipes</i> was obtained, <i>alf</i>D (55%) and <i>afl</i>R (59%). Affinin/spilanthol possesses higher antifungal and anti-aflatoxigenic activity against <i>A. parasiticus</i> rather than <i>H. longipes</i> roots, and this anti-aflaxotigenic activity occurring via downregulation of the <i>afl</i>D and <i>afl</i>R genes. Thus, <i>H. longipes</i> roots and affinin/spilanthol can be considered potent antifungal agents against aflatoxigenic fungus, especially, affinin/spilanthol.