Black Elderberry Press Cake as a Source of Bioactive Ingredients Using Green-Based Extraction Approaches

SIMPLE SUMMARY: Current practice in the management of fruit waste and by-products does not fully exploit waste potential, since fruit waste often contains valuable compounds that can be extracted and used in different industries. Black elderberry press cake is a by-product of the production of black elderberry juice that contains residual polyphenolic compounds with different bioactive potentials. The main focus of this research was to propose new streams to use black elderberry press cake, specifically to demonstrate the possibility of implementing green and safe technology in the food and pharmaceutical industries in order to enable more economical waste management, as well as to develop new technological lines that will increase economic growth. Our findings provide comprehensive approaches for treating anthocyanin-rich black elderberry press cake, which is highly correlated with antidiabetic potential, thereby enhancing its application for the development of novel food and herbal formulations. ABSTRACT: To study the efficiency of two green-based extraction techniques for the isolation of bioactive constituents from black elderberry press cake, changes in phenolic compounds and main anthocyanin contents were analyzed. Polyphenolic content was correlated with antioxidant and antidiabetic potential by radical-scavenging activity and monitoring of α-amylase inhibition. Black elderberry press-cake extracts were obtained by ultrasound-assisted (UAE) and microwave-assisted (MAE) extractions under different extraction conditions. High-performance liquid chromatography (HPLC) analysis revealed that cyanidin-3-sambubioside and cyanidin-3-glucoside were the principal anthocyanins in all the obtained extracts, with their content being highest in MAE obtained at 80 °C over 5 min. The same extract induced two-fold higher antioxidant activity (IC(50) 6.89 μg/mL) and α-amylase inhibitory potential (IC(50) 2.18 mg/mL) in comparison to UAE extracts. The main compositional differences between extracts obtained by the same extraction technique were assigned to the extraction temperature. A principal component analysis confirmed that the antidiabetic feature is to be attributed to the rich content of anthocyanins in black elderberry press cake. Our results indicate the great potential of underutilized black elderberry press cake for the development of novel food and herbal formulations due to notable anthocyanin contents highly correlated with antidiabetic activity.