Lipid peroxidation inhibition capacity of decoctions prepared from gamma irradiated medicinal plants traditionally used in Portugal

Due to the renewed interest and the growing use of medicinal plants, it is of great importance to study how their properties are affected by different post-harvest technologies to assure its quality and safety. Among the non-thermal physical technologies available to sanitize plant products, the irradiation treatment with gamma-rays emerges in an exceptional position. Meanwhile, there is a growing scientific interest in irradiation-induced modifications on the bioactive properties of treated products [1,2]. Therefore, two highly quoted medicinal plants traditionally used in Portugal were selected for this study. Both species, Malva neglecta Wallr. and Tuberaria lignosa (Sweet) Samp., are commonly prepared in decoctions for externai and topical use due to its disinfectant and anti-inflammatoty properties [3]; nevertheless, the effect of gamma irradiation on its bioactivity remained unknown until now. In this study, the effect of lowdose gamma irradiation on the lipid peroxidation inhibition capacity of these species was investigated. The plant material was sustainable wild harvested in the Northeast region of Portugal, lyophilised and then exposed to 1 kGy of gamma-rays in a cobalt-60 chamber. Nonirradiated samples followed ali the experiment. The lipid peroxidation inhibition capacity was evatuated in decoctions, prepared according to folk redpes/formulations from irradiated and non-irradiated samples, through the TBARS (thiobarbituric acid reactive substances) formation inhibition and p-carotene bleaching inhibition assays. T. lignosa decoctions revealed higher bioactivity than the M. neglecta ones. For T. lignosa, the TBARS formation inhibition capacity was maintained and the beta-carotene bleaching inhibition capacity improved with the irradiation treatment, while M. neglecta revealed opposite results. This study confirms the suitability of low dose gamma irradiation to maintain or improve the lipid peroxidation inhibition capacity of the treated plants. Even so, further studies are of interest to evaluate the effects on other quality parameters.