Optimization and component identification of ultrasound-assisted extraction of functional compounds from waste blackberry (Rubus fruticosus Pollich) seeds.

Abstract

Blackberry seeds, as a by-product of processing, have potential bioactive substances and activities. A response surface method was used to determine the optimal conditions of blackberry seed extracts (BSEs) with high 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity by ultrasound-assisted extraction (UAE). The composition and antioxidant capacity of BSEs were further analyzed. The optimal conditions were material-to-liquid ratio of 0.07 g mL-1, ethanol concentration of 56%, extraction temperature of 39 °C and ultrasonic power of 260 W. Using these conditions, the extraction yield and total polysaccharide, phenolic and anthocyanin contents in BSEs were 0.062 g g-1 and 633.91, 36.21 and 3.07 mg g-1, respectively. The Fourier transform infrared spectra of BSEs exhibited characteristic peaks associated with polysaccharide absorption. The antioxidant capacity, DPPH and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity, and ferric reducing antioxidant power of BSEs were 1533.19, 1021.93 and 1093.38 mmol Trolox equivalent g-1, respectively. The delphinidin-3-O-glucoside, paeoniflorin-3-O-glucoside and cyanidin-3-O-arabinoside contents in BSEs were 3.05,12.76 and 1895.90 ± 3.45 μg g-1. Five polyphenols including gallic acid, coumaric acid, ferulic acid, catechin and caffeic acid were identified and quantified in BSEs with its contents at 8850.43, 5053.26, 4984.65, 1846.91 and 192.40 μg g-1. These results provide a method for preparing BSE containing functional components such as polysaccharides, phenols and anthocyanins through UAE, and BSEs have potential application in food industries. © 2024 Society of Chemical Industry.