Water-soluble polysaccharides from agro-industrial by-products: Functional and biological properties

• Determination of chemical composition of water-soluble polysaccharides isolated from the by-products of almond and pistachio juices processing.
• Determination of functional properties of these water-soluble polysaccharides.
• Evaluation of antioxidant and antihypertensive activities of almond and pistachio water-soluble polysaccharides.

Water-soluble polysaccharides were isolated from almond (AWSP) and pistachio (PWSP) juice processing by-products. Their chemical and physical characteristics were determined using NMR and Infrared spectroscopic analysis. The complexities of the spectra reflected the heterogeneity of these polysaccharides. The ACE inhibitory activities (IC50 AWSP = 2.81 mg mL−1 and IC50 PWSP = 2.59 mg mL−1) and antioxidant properties of AWSP and PWSP were investigated based on the DPPH radical-scavenging capacity assay (IC50 AWSP = 2.87 mg mL−1 and IC50 PWSP = 1.61 mg mL−1). Reducing power, β-carotene bleaching inhibition (IC50AWSP = 4.46 mg mL−1 and IC50 PWSP = 3.39 mg mL−1), and ferrous chelating assays (IC50 AWSP = 0.22 mg mL−1 and IC50 PWSP = 0.19 mg mL−1) were also performed. The findings revealed that water-soluble polysaccharides exhibited antioxidant and antihypertensive activities. AWSP and PWSP showed excellent interfacial concentration-dependent properties. Overall, the results suggested that both AWSP and PWSP are promising sources of natural antioxidants and ACE inhibitory agents and could, therefore, be used as alternative additives in food, pharmaceutical and cosmetic preparations.