Infusions of gamma irradiated Aloysia citrodora L. and Mentha x piperita L.: Effects on phenolic composition, cytotoxicity, antibacterial and virucidal activities

The incorporation of plants in industry requires high standards of hygiene, being the raw materials obligatorily decontaminated. Irradiation is increasingly applied as a decontamination technique in several countries. This work aimed to evaluate the effects of gamma radiation on the phenolic composition, cytotoxicity, virucidal and antimicrobial properties of Aloysia citrodora L. (lemon verbena) and Mentha x piperita L. (peppermint) infusions. Phenolic compounds profile was obtained by HPLC-DAD-ESI/MS and cytotoxicity was evaluated in human tumour and non-tumour cell lines; in virucidal efficacy, MNV-1 and HAdV-5 viral titers were determined by plaque assay in Raw264.7 and A549 cell lines, respectively; and the antibacterial potential was evaluated against Gram-negative and Gram-positive bacteria. Radiation treatment caused a significant increase in total phenolic compounds of both plants, while the virucidal efficacy was depend on the plant, the virus, and absorbed dose. S. aureus, with MIC and MBC values of 5 mg/mL, was the only bacteria sensible to the infusions of non-irradiated and 1 kGy irradiated lemon verbena and peppermint samples; gamma radiation appears to cause no alteration in the antibacterial potential of the studied plants. Peppermint infusion (irradiated at 10 kGy) showed the highest cytotoxic potential in all tumour cell lines.