Fast screening of the main phenolic acids with antioxidant properties in common spices using on-line HPLC/UV/DPPH radical scavenging assay

Abstract

Batch 1,1-diphenyl-2-picrylhydrazyl (DPPH˙) and on-line HPLC/UV/DPPH˙ radical scavenging assays were compared for the rapid screening of antioxidant properties of extracts of six Lamiaceae family spices, namely Origanum vulgare, Ocimum basilicum, Rosmarinus officinalis, Origanum majorana, Thymus vulgaris and Satureja hortensis. Generally, all spices showed good radical scavenging properties, which were in the following order: oregano > rosemary > savory ∼ thyme ∼ marjoram > basil. Rosmarinic acid and lithospermic acid B, as strong antioxidants, were identified according to their retention time, UV and mass spectra. Rosmarinic acid was found to be the main compound in all extracts and as it was measured by HPLC/UV/DPPH˙ it was responsible for more than 50% of the total extract radical scavenging capacity, except for oregano, when rosmarinic and lithospermic acid B were almost equally important radical scavengers. The highest amounts of rosmarinic and lithospermic acids were found in oregano extracts; lithospermic acid B was also found in reasonable concentrations in marjoram, savory and thyme extracts. Lithospermic acid B is reported as a constituent of marjoram, savory and thyme for the first time.