Isolation and characterization of anti-inflammatory peptides derived from trypsin hydrolysis of microalgae protein (<i>Synechococcus</i>sp. VDW)

Abstract

The Synechococcus sp. VDW peptides were prepared by trypsin digestion, which was then purified by ultrafiltration with molecular weight cut off membranes of 10, 5 and 3 kDa. Among the fractions, the MW <3 kDa fraction exhibited high levels of inhibitory activity toward the NO radical scavenging activities with IC50 values of 34.51 ± 9.8 μg/mL. The MW <3 kDa fraction was purified by reversed-phase HPLC to yield four fractions. The 30–40 min sub-fraction with maximum NO radical scavenging activity (77.50 ± 0.55%) was selected for further analysis by Q-TOF ESI mass spectrometry. Five isolated peptides with amino acid sequences of AILQSYSAGKTK; 1,265.69 Da, ALNKTHLIQTK; 1,265.74 Da, LLVHAPVK; 875.55 Da, IPDAHPVK; 875.48 Da, and VVVLRDGAVQQLGTPR; 1,706.97 Da were identified. The MW <3 kDa fraction showed no cytotoxicity toward RAW264.7 macrophage cells. Quantitative RT-PCR results showed that the MW <3 kDa fraction reduced gene expression of pro-inflammatory cytokines iNOS, TNF-α, COX-2, and IL-6. The peptides isolated from the MW <3 kDa fractions represent potential model peptides to develop natural anti-inflammation food-grade ingredients, drugs, and cosmetic products.