Effect of e-beam irradiation on the extractability of bioactive compounds from lettuce: evaluation of the extracts’ stability during frozen storage

The use of electron beam irradiation (low energy e-beam–LEEB, and high energy e-beam–HEEB) of lettuce and the storage at – 80 °C of the prepared extracts was evaluated to study their stability during storage by assessing phenolic and flavonoid contents, and antioxidant, antimicrobial, antidiabetic and antiproliferative activities. The general results demonstrated that irradiation with LEEB at 4 kGy improved the content of phenolic (18.9 ± 0.6 mg GAE/g dw) and flavonoid (32 ± 2 mg CAE/g dw) compounds from lettuce ethanolic extracts stored up to 28 days. Furthermore, Autumn seemed to be the best harvest season to obtain extracts with higher bioactive content. No antimicrobial activity was found for all the prepared extracts. The 28 days stored aqueous extracts from lettuces presented higher α-glucosidase inhibition (72 ± 3 % inhibition) indicating potential antidiabetic activity. Moreover, these extracts also demonstrated higher antiproliferative activity against A549 lung tumour cells. These findings suggested the possibility of exploring ethanolic extracts from irradiated lettuces as food supplements, and the aqueous extracts as antitumor and antidiabetic agents. • Phytochemical composition, bioactivities of e-beam treated lettuce were evaluated. • The stability of prepared extracts during 28 days storage at - 80 °C was assessed. • LEEB enhanced the phytochemical content and antioxidant activity of lettuce. • Irradiated lettuce aqueous extracts showed antidiabetic and antiproliferative effects.