EFFECT OF EXTRACTION CONDITIONS ON PHENOLIC COMPOUNDS FROM BLACKBERRY LEAVES EXTRACTS

Blackberry leaves have been used as a tea substituent in many herbal mixtures. Medicinal properties of this plant material are related to a high level of components with antioxidant activity, such as phenolic compounds. The aim of the research was to evaluate the effect of different extraction conditions on the content of phenolic compounds and antioxidant activity of blackberry leaves extracts. In this study, blackberry leaves extracts were produced by an aqueous extraction procedure. Different extraction conditions: water temperature (40 and 80 degrees C) and extraction time (15 and 30 min) were investigated. The blackberry leaves extract prepared by applying higher temperature (80 degrees C) and longer time (30 minutes) was characterized by the highest contents of total phenolic compounds (1534.15 mg gallic acid equivalents L-1), flavonoids (715 mg quercetin equivalents L-1) and flavan-3-ols (28.21 mg (+)-catechin L-1). Also, this extract expressed the highest antioxidant activity in terms of the ferric reducing ability of plasma (27.33 mmol Trolox equivalents L-1) and generation of 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (1.47 mmol Trolox equivalents L-1). The obtained results indicated that the produced extracts are a rich source of phenolic compounds with high antioxidant activity. Among investigated conditions, the use of water heated to higher temperature (80 degrees C) during prolonged time (30 min) is the most optimal procedure for the extraction of phenolic compounds with antioxidant activity from blackberry leaves. Further research is needed to determine the exact phenolic profile and their bioavailability, as well as to develop new functional food ingredients or nutraceuticals containing blackberry leaves extracts.