Toxicity Assessment of Secondary Metabolites Extract from Clitocybe nuda as Natural Food Antimicrobial

Introduction: Clitocybe nuda is an edible mushroom which shows promise to be developed as novel natural food antimicrobials due to various antimicrobial components found in its secondary metabolites extract in recent years. This antimicrobial of secondary metabolites extract has several advantages such as naturally occurred compounds, against broad spectrum of foodborne pathogens, high water solubility, wide pH range, good thermal stability and low cost. However, currently there is no toxicity information available about this secondary metabolites extract from C. nuda. 

Purpose: To assess the toxicity effects of the secondary metabolites extract from C. nuda using in vitro toxicity testing methods.  

Methods: The cytotoxic effect of the secondary metabolites extract was investigated with cytotoxicity assay using both animal and human cell lines. The acute oral LD₅₀ values were also estimated based on an established prediction model. Besides, genotoxic effects of this secondary metabolites extract were evaluated with two standard in vitro genotoxicity assays: bacteria reverse mutation assay and cytokinesis-blocked micronucleus cytome assay. Moreover, the potential influences of heat treatment to the secondary metabolites extract toxicity were also investigated. 

Results: The estimated acute oral LD₅₀ values of this secondary metabolites extract are higher than the threshold value of 2,000 mg/kg body weight, which can be classified as non-toxic according to the state-of-the-art recommendation. Also, there are no significant differences (P<0.05) between this secondary metabolites extract and controls for all of the genotoxic biomarkers examined in both bacteria and human hepatoma cells. Results from this study indicate that the secondary metabolites extract from C. nuda is not genotoxic and might also be properly classified as non-acute-oral-toxic. 

Significance: Results from this study can help to prove the safety of the secondary metabolites extract from C. nuda to be added into foods as a novel natural antimicrobial.