Structural characteristics of a low molecular weight velvet antler protein and the anti-tumor activity on S180 tumor-bearing mice

Velvet antler is a traditional Chinese medicine with various pharmacological values, which is an important raw material for traditional Chinese medicinal wine. Nevertheless, the chemical compositions and bioactivities of velvet antler residue used for making medicinal wine are rarely reported, leading to a waste of resources. In this study, a velvet antler protein (VA-pro) was extracted from velvet antler residue by simulating the gastrointestinal digestion, and its composition, structural characteristics and in vivo anti-tumor activities were determined and investigated. VA-pro possessed high purity with a relatively low molecular weight as 22.589 kDa under HPLC, one- and two-dimensional electrophoresis, and it contained high contents of Pro, Gly, Glu and Ala. Besides, the secondary structure of VA-pro was dominated by β-turn and β-sheet, and VA-pro possessed similar protein sequence, isoelectric point and amino acid compositions to hypothetical protein G4228_020061. The in vivo results substantiated that VA-pro could improve the body weights and immune organ indices, increase the expressions of sera cytokines and regulate the distributions of T and B lymphocytes subsets in peripheral blood of S180 tumor-bearing mice. Furthermore, VA-pro could effectively inhibit solid S180 tumors growth by inducing S phase cell cycle arrest mediated through mitochondria. To summarize, our study provided theoretical support that VA-pro had the potential to be used as an immunopotentiator in immunocompromised or cancer-bearing hosts.