Antioxidant activity and phenolic content of water extracts of Borago officinalis L: influence of plant part and cooking procedures

Abstract

Borage (Borago officinalis L.) water extracts were prepared from raw stems and leaves and from cooked (boiled and steamed) stems. Antioxidant activity (AA) was determined by ABTS and DPPH after their respective calibration with Trolox as standard and expressing results of both assays as µg Trolox/g fresh plant. Also total phenolic compounds (TPC) were determined for each extract. Values for DPPH and ABTS in leaf extracts were similar and approximately 3.5 fold the values obtained for stem extracts. The high antioxidant activity of leaf extracts might be attributed to the high amount of phenolic compounds (2.36 mg GAE/g fresh plant for leaves and 0.57 mg GAE/g fresh plant for stems). Boiling significantly decreased antioxidant activity (51-52 % decrease) and total phenolic compounds (67 % decrease). Steaming caused no significant effect on the antioxidant activity values, whereas total phenolic compounds showed approximately half of the decrease found for boiling (35 %). Borage water extracts, and particularly, those of their by-products (leaves) showed great antioxidant activity, that could potentially be used for different applications in food industry.