Contribution of the main polyphenols of Thymus mastichina subsp. mastichina to its antioxidant properties

• The different polyphenols seem to contribute in a different way to the antioxidant capacity of Thymus mastichina L.
• Some populations showed high intra-population variability while others showed a similar composition among individual plants.
• T. mastichina L. could be an interesting source of natural antioxidants.

The antioxidant activity and phenol content of 14 populations of Thymus mastichina grown in an experimental plot, was analyzed by DPPH, FRAP and Folin-Ciocalteu method to define their antioxidant activity. Polyphenols were analyzed by HPLC-DAD and the relationship between polyphenols and antioxidant capacity was established. Populations means for DPPH activity ranges were 44–98 mg TE/g DW while FRAP antioxidant capacity was 52–115 mg TE/g DW. Total phenol content ranged between 11 and 38 mg of CAE/g DW for the different populations. The polyphenols identified were: chlorogenic acid, caffeic acid, rosmarinic acid, luteolin glucoside and luteolin. The main polyphenols were rosmarinic acid, ranging from 1.7 to 43 mg/g DW, one unidentified polyphenol designated as Peak 3 (0.53–15 LE eq mg/g) and luteolin glucoside ranging from 0.96 to 19 LE eq mg/g. Rosmarinic acid contributed mainly to the FRAP antioxidant capacity and to the total phenols, while peak 3 contributed mainly to the DPPH assay. Luteolin, chlorogenic acid and caffeic acid had a range of 0–2.7, 0.07–2.2, 0–0.46 mg/g DW, respectively. The study showed high intra-populations variability and above all high inter-populations variability. The Carrocera population had the highest antioxidant activity and amount of phenols and it could be selected for its content.