Thymus pulegioides L. is widespread in Europe and its aerial parts are used in culinary, as condiments, and in traditional medicine to treat gastro-intestinal and respiratory infections. However, data on the detailed composition of its extracts still needs further investigation as compared to that of essential oils.
This work aims to give a detailed composition of T. pulegioides phenolic compounds obtained by two extraction methods (decoction and repeated hydro-ethanolic extraction (HE)) and to assess their anti-oxidant activity. Total phenolic, total flavonoids and ortho-diphenols contents were evaluated using colorimetric methods. For phenolic compounds profile characterization and quantification, extracts were analyzed by HPLC-DAD-ESI-MSn (negative mode). Three colorimetric in vitro methods were used to assess antiradical activity of extracts against: ABTS•, OH• and NO• radicals.
Results indicate that, HE extract was richer than decoctions in total phenolics (56.11±5.6 vs. 26.12±0.91 mg CAE/g dry plant), total flavonoids (61.75±12.58 vs. 37.23±1.29 mg CE/g) and ortho-diphenols (24.7±1.63 vs. 14.95±0.57 CAE/g). Phenolic profile of both extracts was characterized by the presence of rosmarinic acid as major compound (8.53±1.56 and 32.51±3.58 mg/ g dry plant, in decoction and HE, respectively), eriodictyol derivatives, luteolin hexuronide, chrysoeriol hexoside and caffeic acid. HE extract was rich in phenolics, presenting compounds not detected in decoction (e.g. salvianolic acid I). HE extracts presented a 2-fold higher ABTS• radical scavenging activity than decoction. However, decoction had higher OH• radical inhibition in site specific assay. Overall, studied extracts had moderate antiradical activity against OH• and NO• radicals comparing to other Thymus species.
In conclusion, these data show that T. pulegioides could be considered as potential source for functional ingredients for food and pharmaceutical industries.
Keywords: Hydro-ethanolic, decoction, phenolic compounds, NO radicals, hydroxyl radicals
Acknowledgements to: UTAD-Botanical-Garden, to FCT (grant to M.T.(PD/BD/52563/2014)), INTERACT-project–NORTE-01-0145-FEDER-000017 (ISAC), co-financed by ERDF through NORTE2020.