Phenolic composition and antioxidant activity of industrial cork by-products

•The phenolic composition of two by-products from the Quercus suber L. cork industry, was investigated by HPLC–MS.•The phenolic composition of cork was also analyzed for comparative purposes.•Sixteen and thirteen phenolic compounds were identified in cork powder and black condensate, respectively.•DPPH radical scavenging activity of cork powder and black condensate extracts has been first reported in this work.•Our results contribute for the valorization of cork industry by-products. The phenolic composition of cork powder and black condensate, two by-products from the cork industry, was investigated by the first time using high-performance liquid chromatography-multi-stage mass spectrometry (HPLC–MSn). The same methodology of extraction was applied to cork, for comparative purposes. Eighteen phenolic compounds were identified in cork, five of them are reported for the first time as its constituents. Sixteen and thirteen phenolic compounds were identified as cork powder and black condensate components, respectively, with only one compound of each residue published before as its constituent. The antioxidant activity of the extracts was evaluated, being, to our knowledge, the first study concerning the antioxidant activity of these cork residues. The extracts present an antioxidant activity higher than BHT, with black condensate showing the lowest IC50 value. These results, together with the phenolic content values, demonstrate the high potential of these residues as source of high value compounds.