Extraction, characterization, and bioactivity of soluble dietary fiber from Physalis alkekengi L. calyx

Physalis alkekengi L. is one of the most popular berries in the world, and its calyx is rich in nutrients. Still, the study of soluble dietary fiber (SDF) from Physalis alkekengi L. calyx (PC) has not been reported. This study aimed to extract Physalis alkekengi L. calyx soluble dietary fiber (PCSDF), and the optimal extraction process was investigated using response surface methodology. After ultrasonic pretreatment, the yield of PCSDF reached 8.74 ± 0.17% under the conditions of liquid-solid ratio of 30 mL/g, thermostable α-amylase concentration of 2000 U/mL, dispase concentration of 20,000 U/mL, amyloglucosidase concentration of 40,000 U/mL. For the first time, PCSDF was characterized by UV spectroscopy, infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis, and the composition of the monosaccharides, namely mannose, glucuronic acid, rhamnose, galacturonic acid, glucose, galactose, xylose, arabinose and fucose, was identified by HPLC. For antioxidant activity, the half inhibitory concentration (IC₅₀) against DPPH, ABTS⁺, ·OH, and ·O₂⁻radicals were 3.67, 2.96, 5.45, and 2.90 mg/mL, respectively, and there was a specific Fe³⁺ reducing capacity. In terms of hypoglycemic feature, the IC₅₀ values for the inhibitory ability of α-glucosidase and α-amylase were 1.20 and 9.21 mg/mL, respectively. For lipid-lowering potential, the IC₅₀ value for pancreatic lipase inhibitory ability for lipid-lowering was 16.95 mg/mL. This paper fills the research gap of PCSDF and provides a basis for further evaluation of PCSDF using in vivo studies.

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