Abstract: Objective: The metabolite compositions and antioxidant activity were considered to select a suitable drying method for ziziphi spinosae fructus. Methods: The impact of three commonly used drying methods, i.e., freeze drying, sun drying and hot air drying, on the metabolite composition and antioxidant activity of ziziphi spinosae sarcocarp was investigated using 1H nuclear magnetic resonance (NMR) combined with multivariate statistical analysis (MSA) and partial least square regression (PLSR). Results: A total of 32 metabolites were identified in the 1H NMR spectrum. MSA and PLSR analysis showed that the contents of total flavonoids, sugars (xylose and β-glucose), amino acids (arginine, glycine, and L-aspartic acid) and choline in the freeze dried samples remained at higher levels. It also had the strongest 1,1-diphenyl-2-picrylhydrazyl radical scavenging capacity. The sun dried samples retained the contents of polysaccharides, L-proline and dimethylamine to the maximum extent and had stronger for 2,2’-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) radical cation scavenging capacity. The hot-air dried samples had the highest total phenolic content, and also retained higher contents of L-methionine, 3-hydroxybutyric acid, zizyphus saponin II, α-glucose, fructose and betaine. Conclusion: Freeze drying is the most suitable method for ziziphi spinosae sarcocarp to retain the antioxidant activity and reduce the drying time greatly.

Key words: ziziphi spinosae sarcocarp, drying methods, 1H nuclear magnetic resonance, multivariate statistical analysis, antioxidant activities