engleski

Are volatile isolates containing glucosinolate breakdown products overlooked in testing the activity against mycotoxigenic Penicillium verrucosum?

Moulds that cause food spoilage are a huge problem in the food industry, especially mycotoxin- producing moulds, which pose a major health risk to food consumers. Penicillium verrucosum is one of the major producers of ochratoxin A (OTA) in food. International Agency for Research on Cancer (IARC) classifies OTA as a nephrotoxic, neurotoxic, hepatoxic, teratogenic, genotoxic, immunotoxic, embryotoxic, and carcinogenic toxin. Traditionally, mould growth and OTA production in foods have been controlled by the use of various chemical additives, but nowadays there is an increasing demand from consumers to avoid chemical food additives, which has prompted researchers to search for new safe and biodegradable preservatives. Many studies indicate that essential oils (EOs) and volatile isolates (VIs) rich in low molecular weight phenolic and terpenoid compounds are promising alternative antifungal agents, but there haven’t been many studies showing the antifungal activity of EOs and VIs rich in glucosinolate breakdown products, such as isothiocyanates, nitriles, epithionitriles, and thiocyanates. For that purpose, the antifungal activity of nasturtium (Tropaeolum majus L.) VI was tested. The nasturtium seeds powder was subjected to microwave hydrodiffusion and gravity (MHG) for 15 min at a power of 500 W using an ETHOS X device, and further hydrodistillated with Clevenger system for 2.5 hours to obtain a VI. The chemical composition of nasturtium VI was determined by GC-MS/MS, while the minimal inhibitory concentrations (MIC) of nasturtium VI and its pure compounds (benzyl isothiocyanate, 2- phenylacetonitrile) against P. verrucosum were determined by microdilution method. GC-MS/MS analysis revealed that nasturtium VI was mainly composed of benzyl isothiocyanate (54.35%), and 2- phenylacetonitrile (37%). Among these compounds, nasturtium VI was the most effective with MIC value of 0.05 mg/mL. Excellent antifungal activity was also found for pure benzyl isothiocyanate with MIC value of 0.10 mg/mL, while pure 2- phenylacetonitrile was 8 fold lower with MIC value of 0.8 mg/mL. For comparison, Jeršek et al. (2014) found that oregano EO, mainly composed of phenolic compounds thymol (4.5%) and carvacrol (53.4%), had a MIC of 1.09 mg/mL. The most potent of these compounds was thymol with a MIC of 0.12 mg/mL, while carvacrol had a MIC of 0.38 mg/mL. Thus, it can be concluded that nasturtium VI, which is rich in glucosinolate breakdown products (benzyl isothiocyanate, 2-phenylacetonitrile), has ca. 20 times better antifungal activity against P. verrucosum than oregano EO. It can be assumed that isothiocyanates are the main compounds that confer excellent antifungal activity to nasturtium VI. This result indicates that VIs rich in glucosinolate breakdown products, which are not typically used in mould control studies, are a promising alternative to phenol-rich EOs. Isothiocyanates are lipophilic and therefore can react with membrane-bound enzymes, inhibit fungal growth and cause cell death. In addition, benzyl isothiocyanate is known for its inhibitory effect on mycotoxin production, such as AME, AOH, ALT and TEN (Wang et al., 2020). Therefore, it is necessary to determine the effect of nasturtium VI, benzyl isothiocyanate and 2-phenylacetonitrile on mycotoxin production of P. verrucosum. It is also important to test synergism between the glucosinolate breakdown products in the further studies.

penicillium verrucosum ; antifungal activity ; nasturtium volatile isolate ; benzyl isothiocyanate ; 2-phenylacetonirile

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