Characterization and antitumor activity of protein hydrolysates from Arthrospira platensis ( Spirulina platensis) using two-step hydrolysis.

In this study, Arthrospira platensis proteins were hydrolyzed using sequential digestion with alcalase/papain. Gel filtration chromatography was used to separate hydrolysates and five fractions D1-D5 were obtained. D1 showed the strongest antitumor effects on MCF-7 and HepG-2 cells, with the IC values of <31.25 and 49.36 μg mL, respectively. Subsequently, three small peptides with antitumor activities, including AGGASLLLLR, LAGHVGVR, and KFLVLCLR, were identified. The truncated peptide LCLR exhibited better activity than its parent peptide KFLVLCLR, with the inhibition rate of >60 % on MCF-7 and HepG-2 cells, but little cytotoxicity on L-O2 cells (∼6 %), at 500 μg mL. Moreover, D1 was confirmed to inhibit solid tumor growth in HepG-2-bearing nude mice, with the best inhibition achieved at day 11, up to 39.75 % at the dosage of 200 mg kg day. Taken together, the identified peptides possessed potent antitumor activities but low cytotoxicity on normal cells and could be used as nutraceuticals and pharmaceuticals. [ABSTRACT FROM AUTHOR]