Comparison on chemical, structural, thermal, functional and antioxidant properties of polysaccharides and phenolics co-extracted from mangosteen (Garcinia mangostana Linn) peels by different eco-friendly hybrid technologies

Abstract

This project aimed to compare the characteristics of the polysaccharides and phenolics simultaneously isolated from the peels of mangosteen using two hybrid methods: ultrasound-microwave (UMAE) and enzyme-ultrasound assisted extraction (EUAE). The polysaccharides extracted from mangosteen peels had dark brown to yellow color and rough surface with irregularly shaped particles, an accomplished purification of 92.5-94.8%, medium degree of esterification (48-53%), two molecular weights (0.12 to 2.42 x 105 Da and 11.66 to 13.24 x 105 Da), thermal profiles of two endothermic peaks and one exothermic peak, and monosaccharide profiles rich in arabinose, glucose, and galactose. However, UMAE polysaccharides possessed higher methoxyl content (6.4%), anhydrouronic acid content (69%), but lower solubility (69%), equivalent weight (540 g/mol), total phenolic content (25.9 mg gallic acid equivalent (GAE)/g dry weight (DW)), anthocyanin content (37.5 mg cyanidin-3-glucoside (C3G)/100 g DW), and antioxidant activity (24.9 mg Trolox equivalent (TE)/g DW) than EUAE ones (1.22%, 15%, 91%, 2300 g/mol, 42.1 mg GAE/g DW, 65.3 mg C3G/100 g DW, and 44.64 mg TE/g DW, respectively). Regarding the phenolics, both techniques produced the products with quite similar antioxidant properties in terms of total phenolics (222.7-230 mg GAE/g DW), total flavonoids (62-78 mg rutin equivalent/g DW), anthocyanin (95-108 mg C3G/100 g DW). However, EUAE phenolic extract exhibited higher α-mangostin, and γ-mangostin content (approximately 50% higher) than UMAE one, leading to its higher antioxidant activity. In conclusion, both extraction methods provide eco-friendly ways to obtain valuable products from mangosteen peels with potential health benefits and diverse applications.