Bioactivity of Juniperus communis essential oil and post-distillation waste: assessment of selective toxicity against food contaminants

Abstract

Previously chemically characterized Juniperus communis essential oil (EO) and post-distillation waste (PDW) were tested for cytotoxicity and antimicrobial activity against food contaminants. Microdilution assay showed that PDW induced moderate antifungal (minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values, ranging between 0.118-0.900 mg mL-1), and an antibacterial effect against Listeria monocytogenes (MIC and minimum bactericidal concentration (MBC) were 0.39 and 0.74 mg mL-1, respectively). Combinations of EO/PDW with selected antibiotics induced synergistic antilisterial activity in the checkerboard assay. The MTT assay determined that cytotoxicity against colon cancer cells was high for the EO but negligible for PDW (IC50 values were 0.087-0.106 and 1.450-6.840 mg mL-1, respectively). The selectivity indices indicated high selectivity of PDW against tested fungi and L. monocytogenes. In the adhesion-inhibition assay, PDW reduced in vitro adhesion of L. monocytogenes to colon cells (29-62% of inhibition). In conclusion, PDW exhibited an antimicrobial effect against important food spoilage and poisoning fungi and L. monocytogenes, and also reduced in vitro adhesion of L. monocytogenes to colon cells. The results indicate that J. communis PDW could be considered as natural preservative against food spoilage and poisonous fungi, and as an adjuvant to conventional therapy of listeriosis.