ANTIOXIDANT ACTIVITY AND PHENOLIC CONTENT OF WATER EXTRACTS OF BORAGO OFFICINALIS L.: INFLUENCE OF PLANT PART AND COOKING PROCEDURE

Water extracts of borage (Borago officinalis L.) 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 the results of both assays are expressed as mu g Trolox/g fresh plant. Total phenolic compounds (TPC) were also determined for each extract. The DPPH and ABTS values in leaf extracts were similar and approximately 3.5 times higher than 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 the antioxidant activity (51-52% decrease) and total phenolic compounds (67% decrease). Steaming had no significant effect on the antioxidant activity values, whereas the total phenolic compound values showed approximately half of the decrease found for boiling (35%). Borage water extracts, particularly those of their by-products (leaves), showed high antioxidant activity, that could potentially be used for different applications in the food industry.