Bioactivity of blackberry (Rubus fruticosus L.) pomace: Polyphenol content, radical scavenging, antimicrobial and antitumor activity

A large volume of industrial waste of biological origin is produced annually worldwide, causing a serious disposal problem even though it is a huge source of beneficial compounds which may be used for their high nutritional and bioactive properties. The bio-potential of blackberry pomace (waste) obtained after juice separation from the Čačanska bestrna and Thornfree cultivars was evaluated. Higher amounts of total and monomeric anthocyanins, total phenolics, and total flavonoids were found in Thornfree pomace extract and demonstrated stronger 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (2.12 mmol TEAC g-1) than Čačanska bestrna pomace extract (1.03 mmol TEAC g-1). Both extracts highly increased apoptosis/necrosis ratios in all investigated cell lines. The highest cell growth inhibition effects (EC50=52.5 - 64.7 μg mL-1) and the highest increase of apoptosis (AI=12.2) were obtained in breast adenocarcinoma cell line. Both blackberry pomace extracts inhibited the growth of all tested microorganisms. In the reference and wild bacterial strains MIC and MBC/MFC were achieved in the 0.39-25 mg mL-1 and 0.78-25 mg mL-1 range, respectively. Blackberry cultivar pomaces are rich source of phytochemicals with significant health promoting properties that could be further utilized as beneficial food ingredients.