Preparation, Digestive Stability and Biological Activity Evaluation of Goji (Lycium barbarum L.) Leaves Flavonoids Microcapsules

Goji (Lycium barbarum L.) leaves flavonoid microcapsules (M-LBLF) were prepared using gelatin and carboxymethyl cellulose sodium (CMC) as wall materials, and the stability and biological activities were investigated. The preparation process of M-LBLF was optimized through response surface methodology. The stability of the product was detected using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis and in vitro simulated digestion. The biological activity of the product was evaluated through free radical scavenging and enzyme activity inhibition experiments. Results showed that, the optimal process conditions for M-LBLF were a core to wall ratio of 1:3.86, a wall material concentration of 1.15%, a stirring temperature of 45 ℃, and an embedding rate of 84.21%. SEM observation showed that most of the surface of the microcapsule particles was smooth, the structure of the capsule wall remained intact, and there were no signs of rupture on the wall material. FT-IR spectra showed a shift in C=O at 1594 cm−1 in Lycium barbarum leaves flavonoids (LBLF), suggesting an electrostatic interaction between LBLF and CMC. XRD spectra showed that due to microencapsulation, the amorphous structure of the product was partially transformed into a crystalline state, resulting in slight changes in the diffraction peak intensity of M-LBLF and LBLF. Thermogravimetric analysis found that microencapsulation improved the high-temperature decomposition, playing a protective role for LBLF. In vitro simulated digestion and antioxidant activity experiments showed that microencapsulation improved the stability of LBLF and retained good antioxidant activity during digestion. In addition, the equations were fitted by multiple linear regression to obtain the semi-inhibitory mass concentration (IC50) of the microcapsules against pancreatic lipase (2.2004±0.03 mg/mL) and against α-amylase (2.188±0.02 mg/mL), suggesting that M-LBLF was able to inhibit both pancreatic lipase activity and α-amylase activity, which suggested that it had the potential to regulate the glycolipid metabolism activity. This research would provide a foundation for improving the stability of flavonoids extracted from goji leaves and developing the related nutritional and health foods.