Infusions from Thymus vulgaris L. treated at different gamma radiation doses: effects on antioxidant activity and phenolic composition

The use of ionizing radiation dates back to many years ago, and is accredited for application in different foods with several purposes. It has been increasingly used in many countries for the treatment of aromatic plants. Thymus vulgaris L. (thyme) is a plant commonly used by food, pharmaceutical and cosmetic industries representing a natural source of several bioactives such as phenolic compounds. The aim of this work was to evaluate the effects of gamma radiation on the antioxidant activity (measured through the free radical scavenging activity, reducing power and lipid peroxidation inhibition) and phenolic compounds profile (obtained by HPLC-DAD-ESI/MS) of infusions prepared from irradiated thyme. The results showed that gamma irradiation at the dose of 10 kGy improved the free radical scavenging activity, reducing power and lipid peroxidation inhibition capacity of the studied infusions, while increasing significantly the concentrations of methyleriodictyol-O-pentosylhexoside, luteolin-7-O-glucoside, eriodictyol and total flavonoids content. Thus, gamma radiation could be considered as a suitable treatment to be used in Thymus vulgaris L., herein validated for its bioactive parameters.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) and FEDER under Programe PT2020 for financial support to CIMO (UID/AGR/00690/2013), LSRE (Project UID/EQU/50020/2013), C2TN (RECI/AAG-TEC/0400/2012), L. Barros (SFRH/BPD/107855/2015) and R.C. Calhelha (SFRH/BPD/ BPD/68344/2010) grants. The authors are also grateful to Ministry of Agriculture, Portugal (Project AROMAP - PRODER/FEADER/EU), for financial support of the work and E. Pereira grant, and to Pragmático Aroma Lda company for providing the “MaisErvas - Aromáticas e Medicinais” samples