Valorization of fruit processing by-products: free, esterified, and insoluble bound phytochemical extraction from cherry (Prunus avium) tissues and their biological activities

Abstract

Fruit processing by-products having limited utilization and no commercial value are generated in high amounts. However, they are rich in phytochemicals with high nutritional value. Therefore, different techniques and applications including extractions, purifications, and fermentations have been evolved for the recovery of these phytochemicals into high value-added products. Similarly, free (F), esterified (E) and insoluble-bound (B) phenolic fractions of sweet cherry processing by-products including stalk, pulp, seed, and leaf were extracted and the potential of these extracts as a source of natural biological compounds were investigated in this study. Total contents of phenolic (TPC), flavonoid (TFC), and hydrolysable tannin compounds (HTC) were analyzed. Individual phenolics were identified and quantified using liquid chromatography–electrospray ionization–tandem mass spectrometry (LC–ESI–MS/MS). The biological activity of these phytochemicals was determined in terms of antioxidant (DPPH, ABTS, FRAP, and CUPRAC), antidiabetic, and antimicrobial activity. TPC, TFC, and HTC were highly found in F phenolic fractions. Nine phenolic compounds were quantified, most notably in the F phenolic fractions. The enzyme inhibition activity against α-glucosidase (5.88 mg/mL) and α-amylase (0.46 mg/mL) of the E phenolic fractions of seed were significantly higher (p < 0.05) than those of F and B extracts. F fractions of stalk had remarkable antimicrobial activity against selected microorganisms except for Escherichia coli. Two uncorrelated principal components explaining 84.51% of the total variance helped to classify sweet cherry tissues. The results clearly showed that F, E, and B phenolics with their biological properties could be suitable food additives or supplements for enrichment agents in the different formulations.