In the present work, polysaccharides were extracted from coffee residue (CRP) using hot water and ultrasound-assisted extraction methods. Experimental results showed that both CRP had similar monosaccharide compositions (mannose and galactose), they presented also typical IR spectra characteristic of polysaccharides. CRP-U uronic acid content (6.28 ± 0.93%) was significantly (P < 0.05) higher than that of CRP-H (4.86 ± 0.07%). The ACE inhibitory activities (IC50 CRP-H = 0.2 mg/mL and IC50 CRP-U = 0.15 mg/mL) and antioxidant capacities of both CRP were assessed via different methods, including DPPH radical-scavenging activity assay (IC50 CRP-H = 0.08 mg/mL and IC50 CRP-U = 0.053 mg/mL), reducing power (RP0.5 CRP-H = 1.1 mg/mL and RP0.5 CRP-U = 0.8 mg/mL), and β-carotene bleaching inhibition assay (IC50 CRP-H = 4.65 mg/mL and IC50 CRP-U = 5.59 mg/mL). Those polysaccharides did not show any hemolytic activity towards erythrocytes.
Coffee residue is the major coffee industry residue with an international generation of 6 million tons annually. Taking into account this huge quantity produced worldwide, the reutilization of this residue is a pertinent subject. Results indicated that coffee residue can be used to generate high value-added products, thus offering a valuable source of polysaccharides for application in wide range of biotechnological and functional food applications.