Ultrasound and Microwave-Assisted Extraction of Blackberry (Rubus fruticosus L.) Pomace: Analysis of Chemical Properties and Anticancer Activity

Blackberries are seasonal berries that are processed into various products leaving a large amount of residues after processing, and therefore the most effective ways of utilising the residues need to be evaluated. The aim of this study was to determine the effect of different extraction methods on the chemical content of blackberry pomace extracts from different cultivars and their effect on the viability of the Caco-2 colorectal adenocarcinoma cell line and CCD-18Co normal colon fibroblast cancer cells. Blackberry pomace from berries of the cultivars 'Polar', 'Orkan', and 'Brzezina' was extracted by ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE) and a combination of these two extraction methods (MAE+UAE). The phenolic profile and the amount of organic acids and sugars were detected by HPLC. The spectrophotometric method was used to determine the amount of total phenolics, total flavonoids, and total anthocyanins. The cytotoxicity of the extracts was measured by the MTT assay. The chemical content of the extracts depends on the blackberry cultivar, the extraction method, and its interaction. Only the DPPH antioxidant activity did not depend on these factors and had no statistically significant differences between the different extracts. The extracts at a concentration of 5.0% increased the growth of both cancer cells, while the extracts at 1% and 2.5%, depending on the cultivar, reduced the growth of these cells. The MAE and UAE extracts of the 'Orkan' cultivar at concentrations of 1%, 1.5%, 2%, and 2.5% best inhibited the viability of Caco-2 cells. The extracts inhibited the growth of the Caco-2 cell line better than CCD-18Co normal colon fibroblasts.