Abstract: In this paper, phytoglycogen (PG) was used as a carrier to load quercetin (Qu) to prepare phytoglycogen-quercetin (PG-Qu) complex. The solubility enhancing effect of PG-Qu complex on Qu was studied. The antioxidant activity of PG-Qu complex and its inhibition on cancer cells were investigated. Dynamic laser light scattering, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to analyze the particle size characteristics, morphology and molecular interaction of the complex. The results showed that PG was a high-efficiency carrier of Qu, and the formed PG-Qu complex significantly improved the apparent solubility of Qu (P < 0.05). The loading efficiency was related to the concentration of PG and Qu. Alkaline condition was beneficial to the loading of PG onto Qu. The presence of NaCl and acetate did not affect the formation of complexes. PG-Qu complex was prepared from 5 mg/mL PG solution and ethanol solution containing 6 mg/mL of Qu at pH 8 without phosphate, which could be lyophilized and reconstituted. When the PG concentration was 50 mg/mL, the solubility of Qu was 509.46 μg/mL, loading capacity 9.68 μg/mg, and loading efficiency 79.88%. Compared with free Qu, the total reducing power, hydroxyl radical scavenging capacity of PG-Qu complex and its inhibitory activity against MCF-7 and A549 cells were significantly improved. Both PG and PG-Qu complex had a smooth spherical structure; the average particle size of the complex was 68–72 nm, and the particle size distribution was uniform. The zeta potential of PG decreased from ?4.12 to ?10 mV after being loaded with Qu. Qu existed in the amorphous form in PG-Qu complex; hydrogen bonding is the main driving force for the interaction between Qu and PG. Therefore, PG is a highly efficient carrier and the preparation of PG-Qu complex is simple, which can significantly improve the apparent solubility, antioxidant activity and anticancer activity of Qu. The preparation of PG-Qu complex is expected to be an important way to maintain the biological effects of Qu and broaden its application in the food industry.

Key words: phytoglycogen (PG), quercetin (Qu), structural characterization, apparent solubility, antioxidant activity, inhibition of cancer cells