Polyphenols and antioxidant capacity of Bulgarian medicinal plants

Abstract

Extracts of 21 plants used in Bulgarian phytotherapy for the treatment of respiratory, gastrointestinal and other inflammatory disorders were screened in vitro for antioxidant activity and phenolic compounds content. Plant extracts were prepared as herbal teas following the ethnic use. The water-phase TEAC (Trolox equivalent antioxidant capacity) of the teas were compared to that of the famous tea-like beverages mate, rooibos and honeybush, and to that of green and black tea, well known for their high antioxidant potential. The content of total phenolics in the teas was determined spectrometrically according to the Folin-Ciocalteu procedure and calculated as quercetin equivalents (QE). Seven Bulgarian medicinal plants were with high phenolics content and antioxidant properties: Pulmonaria officinalis L. ( Boraginaceae) (TEAC 2.02 ± 0.14 mM/QE 673.39 ± 9.92 μM), Hypericum perforatum L. ( Hypericaceae) (TEAC 3.75 ± 0.14 mM/QE 881.93 ± 6.68 μM), Agrimonia eupatoria L. ( Rosaceae) (TEAC 3.76 ± 0.5 mM/QE 702.29 ± 6.82 μM), Origanum vulgare L. ( Lamiaceae) (TEAC 5.87 ± 0.2 mM/QE 1653.61 ± 11.52 μM) , Melissa officinalis L. ( Lamiaceae) (TEAC 4.06 ± 0.31 mM/QE 1370.09 ± 41.38 μM), Rubus sp. diversa ( Rosaceae) (TEAC 4.23 ± 0,12 mM/QE 608.95 ± 5.95 μM), Cotinus coggygria Scop. ( Anacardiaceae) (TEAC 7.05 ± 0.19 mM/QE 923.33 ± 14.19 μM). Therefore, Bulgarian herbs can be considered to be a rich source of water-soluble antioxidants and/or phenolic compounds as compared to studied foreign plants.