In order to explore snow chrysanthemum polysaccharides (SCPs) as functional food ingredients and natural antioxidants for industrial applications, both microwave-assisted extraction (MAE) and ultrasonic-assisted extraction (UAE) were firstly optimized for the extraction of SCPs. Furthermore, the effects of conventional hot water extraction, UAE, and MAE on the chemical structures and antioxidant activities of SCPs were investigated. The maximum extraction yields of SCPs extracted by UAE (4.13 ± 0.24%) and MAE (4.26 ± 0.21%) were achieved at the optimized extraction parameters as follows: ultrasound amplitude (68%) and microwave power (500 W), ultrasound extraction time (21 min) and microwave extraction time (6.5 min), and ratio of liquid to raw material (42.0 mL/g for UAE and 59.0 mL/g for MAE). In addition, different extraction methods significantly affected the contents of uronic acids, the molecular weights, the molar ratio of constituent monosaccharides, and the degree of esterification of SCPs. SCPs exhibited remarkable DPPH (IC₅₀ ≤ 1.702 mg/mL), ABTS (IC₅₀ ≤ 1.121 mg/mL), and nitric oxide (IC₅₀ ≤ 0.277 mg/mL) radical scavenging activities, as well as reducing power (≥ 80.17 ± 4.8 μg Trolox/mg), which suggested that SCPs might be one of the major contributors toward the antioxidant activities of snow chrysanthemum tea. The high antioxidant activities (DPPH, IC₅₀ = 0.693 mg/mL; ABTS, IC₅₀ = 0.299 mg/mL; nitric oxide, IC₅₀ = 0.105 mg/mL; and reducing power, 127.79 ± 2.57 μg Trolox/mg) observed in SCP-M extracted by the MAE method might be partially attributed to its low molecular weight and high content of unmethylated galacturonic acids. Results suggested that the MAE method could be an efficient technique for the extraction of SCPs with high antioxidant activity, and SCPs could be further explored as natural antioxidants for industrial application.

In order to evaluate effects of extraction techniques on the physicochemical characteristics and antioxidant activities of kiwifruit polysaccharides (KPS), and further explore KPS as functional food ingredients, both microwave-assisted extraction (MAE) and ultrasonic-assisted extraction (UAE) were optimized for the extraction of KPS. Furthermore, the physicochemical structures and antioxidant activities of KPS extracted by different techniques were investigated. The optimal extraction conditions of UAE and MAE for the extraction of KPS were obtained by response surface methodology. Different extraction techniques significantly affected the contents of uronic acids, molecular weights, molar ratios of constituent monosaccharides, and the degree of esterification of KPS. Results showed that KPS exhibited remarkable DPPH and ABTS radical scavenging activities, and reducing power. The high antioxidant activities observed in KPS extracted by the MAE method (KPS-M) might be partially attributed to its low molecular weight and high content of unmethylated galacturonic acid. Results suggested that the MAE method could be a good potential technique for the extraction of KPS with high antioxidant activity, and KPS could be further explored as functional food ingredients.

In order to explore Cassia seed polysaccharides (CSPs) as natural antioxidants for application in the functional-food industry, microwave-assisted extraction (MAE) was optimized for the extraction of CSPs by using a response surface methodology. Furthermore, the chemical structures and antioxidant activities of CSPs extracted by MAE and hot water extraction were investigated and compared. The maximum extraction yield of CSPs extracted by MAE (8.02 ± 0.19%) was obtained at the optimized extraction parameters as follows: microwave power (415 W), extraction time (7.0 min), and ratio of water to raw material (51 mL/g). Additionally, the contents of the uronic acids, molecular weight, ratio of constituent monosaccharides, intrinsic viscosities, and degrees of esterification of CSPs were significantly affected by the MAE method. Moreover, CSPs exhibited remarkable 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) ABTS, 2,2-diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl DPPH, nitric oxide, and hydroxyl radical scavenging activities as well as reducing power. The high antioxidant activities observed in CSPs extracted by MAE could be partially attributed to its low molecular weights and high content of unmethylated galacturonic acid. Results indicate that the MAE method could be an efficient technique for the extraction of CSPs with high antioxidant activity, and CSPs could be further explored as functional food ingredients.

Seven extraction methods, including hot water extraction (HWE), pressurized water extraction (PWE), ultrasound-assisted extraction, microwave-assisted extraction, ultrasound-assisted enzymatic extraction, high-speed shearing homogenization extraction, and ultrasound-microwave-assisted extraction, were utilized to extract polyphenolic-protein-polysaccharide complexes (PPPs) from Hovenia dulcis. Next, their physicochemical properties and in vitro antioxidant activities, antiglycation effects, and inhibition activities on α-glucosidase and α-amylase were studied and compared. The findings from this study indicate that various extraction processes exhibit notable influences on the physicochemical properties and in vitro bioactivities of PPPs. Extraction yields, contents of polyphenolics and flavonoids, apparent viscosities, molecular weights, molar ratios of monosaccharide compositions, and ratios of amino acid compositions in PPPs varied in different extraction methods. Furthermore, 13 phenolic compounds in PPPs, including rutin, myricitrin, myricetin, quercetin, kaempferol, protocatechuic acid, gallocatechin, p-hydroxybenzoic acid, ampelopsin, quercetin-7,4′-diglucoside, dihydroquercetin, 5-methylmyricetin, and naringenin, were identified. The relatively strong in vitro antioxidant activities, antiglycation effects, and inhibition activities on α-glucosidase and α-amylase were determined in both PPP-W and PPP-P obtained by HWE and PWE, respectively. The high content of total polyphenolics may be one of the main contributors to their in vitro bioactivities. The findings have shown that the PWE method can be an appropriate method to prepare PPPs with strong bioactivities for application in the functional food industry.