Bioassay-guided isolation of glycoprotein SPG-56 from sweet potato Zhongshu-1 and its anti-colon cancer activity in vitro and in vivo

This study is aimed at separating and identifying a new glycoprotein from sweet potato (SPG) and detecting its anti-colon cancer bioactivity. The SPG-56 was obtained by water extraction, isoelectric precipitation, chromatography and electrophoresis. The compositions of sugar and protein in SPG-56 were identified with high performance liquid chromatography and amino acid analyzer, and the antitumor activities were explored using BALB/c nude mice and human colon cancer cells (HCT-116). Results showed that the molecular weight of SPG-56 is 56 KD. Relative sugar and protein contents of SPG-56 are 2.9% and 97.1%, comprising more than 6 types of sugars and 15 kinds of amino acids. Animal experiments showed that orally administrated SPG-56 could obviously suppress the tumor growth. Results from flow cytometry, western blotting and immunohistochemistry indicated that SPG-56 inhibits cancer by inducing apoptosis. These results suggest that SPG-56 would potentially delay the development of colon cancer.