a survey of the effect of licorice plant extract on aflr gene expression and aflatoxin production in aspergillus parasiticus via real-time pcr

objective: aflatoxin is important in the food industry, in animal husbandry and the medical area; there are enormous negative economic impacts due to this toxin. numerous studies have researched extracts and plant compounds with the intent to reduce the growth of aflatoxin-producing organisms, inhibit toxin production and suppress the major toxin encoded genes (i.e., aflr) in these organisms. licorice is an important plant in traditional medicine that possesses numerous antimicrobial activities. there is no report regarding the effects of licorice or its mechanism of action on the aflatoxin-producing aspergillus species. the present study focuses on the inhibitory effects of licorice extract on aflr gene expression and the growth and survival of aspergillus parasiticus (a. parasiticus). methods: after the culture of a. parasiticus in toxin-inducer medium, we measured the minimal inhibitory concentration (mic) for licorice extract. the aflatoxin concentration in the control and treated media was determined by hplc. after harvesting the fungi from the toxin-inducing medium, its mrna was extracted and cdna synthesized by universal primers. the quantitative change in the aflr expression was analyzed via real-time pcr. statistical analysis was performed by spss (v16). results: the production of fungal mycelium decreased with increasing concentrations of licorice extract. the highest inhibitory concentration observed was 500 mg/ml of the extract. hplc analyses revealed that the 10 mg/ml concentration of licorice extract inhibited toxin production by 99.9%. at this concentration, aflr gene expression was suppressed up to 40% as documented by quantitative rt-pcr analysis. conclusion: overall we concluded that the licorice extract could inhibit the aflr gene expression and consequently the aflatoxin production efficiently in the a. parasiticus.