Abstract

ROJAS -LLANES, Jennifer Pilar; MARTINEZ, Jairo René  and  STASHENKO, Elena E. CONTENT OF PHENOLIC COMPOUNDS AND ANTIOXIDANT CAPACITY OF BLACKBERRY (Rubus glaucus Benth) EXTRACTS OBTAINED UNDER DIFFERENT CONDITIONS. Vitae [online]. 2014, vol.21, n.3, pp.218-227. ISSN 0121-4004.

Background: Blackberry contains phenolic compounds that contribute to their antioxidant capacity. The most common method used to isolate these substances is the conventional solvent extraction, which can be assisted by ultrasound in order to increase the content of extracted analyte. Objectives: Determining the conditions of solvent type and concentration, and ultrasound-assisted extraction time, under which the highest content of phenolic compounds and antioxidant capacity are obtained, in Andean blackberry (Rubus glaucus Benth) extracts. To compare the antioxidant capacity of blackberry extracts with those of reference antioxidants, such as di-tert-butylhydroxytoluene (BHT) and a-tocopherol. Methods: Three experimental designs, of two factors with three levels, were done to provide the data for the analysis of variance. Variables were the acetone, ethanol or methanol concentration in water and the duration of ultrasound-assisted extraction. The response variables were the total content of phenolic compounds, which was determined with the Folin-Ciocalteu reagent and the antioxidant capacity, measured by ORAC (oxygen radical absorbance capacity) assay. The correlation coefficient between the two response variables was calculated. The blackberry extracts' antioxidant capacity, obtained under isolation conditions inferred as optimal was compared with those of BHT and a-tocopherol. Results: Extracts obtained with an aqueous solution of 31% acetone (v/v), performing ultrasound-assisted extraction for 100 min, showed the highest content of phenolic compounds (30 ± 1 mg gallic acid/g dry blackberry), and antioxidant capacity (273 ± 6 μmol Trolox^®/g dry blackberry). The correlation coefficient between the total phenolic compounds content and antioxidant capacity was 0.92. Blackberry extracts presented higher antioxidant capacity than BHT and a-tocopherol. Conclusions: Under optimum conditions of extraction, the aqueous solutions of acetone afforded the highest content of phenolic compounds and highest antioxidant capacity value. There was a linear relationship between the two response variables analyzed. Blackberry extracts, under the improved conditions found, presented higher antioxidant capacity than the reference compounds analyzed.

Keywords : Andean blackberry; phenolic compounds; antioxidant capacity; ORAC; ultrasound.

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