Effect of Enzymatic Hydrolysis on the Antioxidant Properties of Alcoholic Extracts of Oilseed Cakes

The aim of the present study is to compare changes in the total phenolic, flavonoid and reducing sugar content and antioxidant activity of alcoholic extracts of Oenothera biennis, Borago officinalis and Nigella sativa oilseed cakes before and after enzymatic hydrolysis. Extraction with ethanol and hydrolysis with different commercially available glycosidases: a-amylase, beta-glucosidase, beta-glucanase and their combinations in a ratio of 1:1:1 were investigated. Total phenolic, flavonoid and reducing sugar content, iron-chelating activity and antioxidant activity according to DPPH and ABTS tests were measured in non-hydrolysed extracts and compared with the results obtained for the extracts after the application of in-mobilised enzymes. As a result, the hydrolysed extracts had a higher phenolic and reducing sugar content as well as higher iron-chelating and antioxidant activities. Total phenolic content of Oenothera biennis, Borago officinalis and Nigel la sativa oilseed cake extracts after enzymatic hydrolysis was higher in comparison with non-hydrolysed extracts, i.e. 2 times (for the enzyme combination), and 1.5 and 2 times (for beta-glucanase) (p<0.05), respectively. The best results in increasing the flavonoid and sugar content as well as in iron-chelating activity were obtained after enzymatic hydrolysis of oilseed cake extracts by beta-glucanase. Oilseed cake extracts after hydrolysis with an enzyme combination in a ratio of 1:1:1 had the highest increase in antioxidant activity.