Inhibitory Effect of Essential Oils on Aspergillus ochraceus Growth and Ochratoxin A Production

Abstract

Ochratoxin A (OTA) is a mycotoxin which is a common contaminant in grains during storage. Aspergillus ochraceus is the most common producer of OTA. Essential oils play a crucial role as a biocontrol in the reduction of fungal contamination. Essential oils namely natural cinnamaldehyde, cinnamon oil, synthetic cinnamaldehyde, Litsea citrate oil, citral, eugenol, peppermint, eucalyptus, anise and camphor oils, were tested for their efficacy against A. ochraceus growth and OTA production by fumigation and contact assays. Natural cinnamaldehyde proved to be the most effective against A. ochraceus when compared to other oils. Complete fungal growth inhibition was obtained at 150–250 µL/L with fumigation and 250–500 µL/L with contact assays for cinnamon oil, natural and synthetic cinnamaldehyde, L. citrate oil and citral. Essential oils had an impact on the ergosterol biosynthesis and OTA production. Complete inhibition of ergosterol biosynthesis was observed at ≥100 µg/mL of natural cinnamaldehyde and at 200 µg/mL of citral, but total inhibition was not observed at 200 µg/mL of eugenol. But, citral and eugenol could inhibit the OTA production at ≥75 µg/mL and ≥150 µg/mL respectively, while natural cinnamaldehyde couldn’t fully inhibit OTA production at ≤200 µg/mL. The inhibition of OTA by natural cinnamaldehyde is mainly due to the reduction in fungal biomass. However, citral and eugenol could significant inhibit the OTA biosynthetic pathway. Also, we observed that cinnamaldehyde was converted to cinnamic alcohol by A. ochraceus, suggesting that the antimicrobial activity of cinnamaldehyde was mainly attributed to its carbonyl aldehyde group. The study concludes that natural cinnamaldehyde, citral and eugenol could be potential biocontrol agents against OTA contamination in storage grains.

Natural Occurrence of Ochratoxin A Contamination in Commercial Spices in Tehran

“…In contrast with these results, Hua and coworkers (23) reported that the essential oil of cinnamon inhibits the growth of A. ochraceus and OTA production. In a related study, Ferreira (24) found that turmeric has inhibitory effect on mycotoxin production.…”

Ochratoxin A in black pepper, white pepper and clove sold in Yaoundé (Cameroon) markets: contamination levels and consumers’ practices increasing health risk

“…The absence of OTA noticed in clove samples could be related to the antifungal activity of this spice. Mostafa et al (1990) and Hua et al (2014) observed the inhibitory effect of clove on fungal growth and OTA production. The absence of OTA in clove has also been reported by Karan et al (2005) in clove sold at Belgrade, Serbia.…”

Inhibitory Effect of Essential Oils on Growth and Ochratoxin a Production by Penicillium Species

“…The fungitoxicity of oil extracted from caraway (Carum carvi) against A. flavus and A. parasiticus was also reported by Soher (1999). Hua et al (2014) have reported the inhibition of A. ochraceus, A. flavus, A. parasiticus and F. moniliforme by the essential oil of thyme, cinnamon, anise spearmint and basil oil at 3000 ppm. Cinnamon oil was also reported to be fungistatic against mycotoxigenic fungi studied by Mukherjee and Nandi (1994) and found the useful in protecting concentration to the extent of 97% OTA and 75% of the biomass production by P. nordicum.…”

“…In recent times, considerable interest in the essential oils as in the prevention of mycotoxins in foods and feeds has been witnessed (Hua et al, 2014). Basil oil inhibited the growth of the F. verticillioides, F. oxysporum, F. proliferatum and F. subglutinans (Kocic-Tanackov et al, 2013).…”