Evaluation of the effects of radiation on the chemical composition and bioactivity of the plants used in the pharmaceutical and/or food industries

Abstract

Medicinal plants and their extracts or isolated compounds have various applications, especially as food additives and as health promoters, as nutraceuticals and ingredients in formulations of functional foods, for pharmaceutical and food industries. However, medicinal plants may be contaminated by soil, water, air and powder, not only during the growth process but also during harvest and drying. Microbial contaminations reduce their quality and shelf life and pose a threat to public health, as they may involve the presence of pathogenic bacteria. Irradiation is a simple, modern and clean physical non-thermal method of processing that allows significant reduction in the microbial load, which is being increasingly applied as a feasible technology for different purposes: disinfestation, decontamination, sterilization or shelf-life extension of food products. It is authorized in several countries, including the European Union (Directive 1999/2/EC). In the present work, the feasibility of using gamma and e-beam (EB) radiation for preservation and decontamination of several aromatic and medicinal dried plants was evaluated, verifying that the main physico-chemical characteristics and relevant molecules were, in general, satisfactorily preserved, as also microbiological safety. The nutritional value was determined by official methodologies for food analysis; free sugars were analysed by HPLC-RI, fatty acids by GC-FID, organic acids by UFLC-DAD, tocopherols by HPLC-fluorescence, and phenolic compounds by HPLC-DAD-ESI/MS. The antioxidant properties were evaluated through free radicals scavenging activity, reducing power and inhibition of lipid peroxidation in brain homogenates assays. Cytotoxic properties were tested in tumor (MCF-7, NCI-H460, HeLa and HepG2) and non-tumor (PLP2) cell lines. Mycotoxin levels were determined by HPLC-fluorescence after immunoaffinity column (IAC) cleanup. Irradiation proved to produce heterogeneous effects on chemical, nutritional and bioactive variables, preserving or degrading molecules, and also increasing the bioavailability of some compounds. The preservation of sensible compounds over time (12 to 18 months) was not observed equally in all species submitted to irradiation, however, in general, EB stood out as the best processing option for the studied materials.