Inhibitory effect of <i>Capsicum chinense</i> and <i>Piper nigrum</i> fruits, capsaicin and piperine on aflatoxins production in <i>Aspergillus parasiticus</i> by downregulating the expression of <i>afl</i>D, <i>afl</i>M, <i>afl</i>R, and <i>afl</i>S genes of aflatoxins biosynthetic pathway

Abstract

Aflatoxins produced by <i>Aspergillus parasiticus</i> are toxic and carcinogenic metabolites. The biosynthesis of this mycotoxins is a complex process and involves at least 30 genes clustered within an approximately 82 kB gene cluster. In the present study, the effect of <i>Capsicum chinense</i> and <i>Piper nigrum</i> fruits on <i>Aspergillus parasiticus</i> growth and aflatoxin production were studied in relation to the expression of <i>afl</i>D, <i>afl</i>M, <i>afl</i>R, and <i>afl</i>S four; key genes of aflatoxins biosynthesis pathway. GC-EIMS analysis identified capsaicin (66,107 µg g^-1) and piperine (1,138 µg g^-1) as the most abundant compounds in <i>C. chinense</i> and <i>P. nigrum</i> fruits, respectively. The antifungal and anti-aflatoxigenic assays showed that <i>C. chinense, P. nigrum,</i> capsaicin, and piperine inhibited <i>A. parasiticus</i> growth and aflatoxins production in a dose-dependent manner. The piperine at 300 µg mL^-1 produced higher radial growth inhibition (89%) and aflatoxin production inhibition (69%). The expression of aflatoxin biosynthetic genes was evaluated by quantitative real-time PCR (qRT-PCR) and revealed that aflatoxin inhibition occurring via downregulating the <i>afl</i>S and <i>afl</i>R, and subsequently <i>afl</i>D and <i>afl</i>M genes. These results will improve our understanding of the mechanism of aflatoxin regulation by <i>C. chinense, P. nigrum,</i> capsaicin, and piperine, and provides a reference for further study.