Isolation and characterisation of enzymatic hydrolysed peptides with antioxidant activities from green tender sorghum

Abstract

The antioxidant activities of bioactive peptides isolated from green tender sorghum (GTS) protein hydrolysate were determined using 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2’-azinobis-(3-ethyl-benzothiazoline-6-sulphonate) (ABTS), Fe2+ chelating activity and reducing power assay. Molecular mass and amino acids sequences of the purified peptides were identified using matrix assisted laser desorption ionization time-of-flight mass spectrometer (MALDI-TOF-MS/MS). Molecular weight distribution of the peptides from fractions F2B (875.5 Da) and F3A (858.5 Da) revealed higher antioxidant activity with 74.19% and 77.64% of inhibition, respectively. High performance liquid chromatography (HPLC) demonstrated hydrophobic amino acids content in green tender sorghum protein isolate (GTSPI), green tender sorghum protein hydrolysate (GTSPH) (>10 kDa), GTSPH (3–10 kDa) and GTSPH (<3 kDa) was found to be higher especially, 13.8, 74.5, 100.7 and 117.7 mg/g respectively, which contributed to higher degree of free radical inhibition. Oil holding capacity of GTSPI was 3.32 mL/g, while GTSPH exhibited only 1.13 mL/g. Purified peptides were identified in sub-fractions F2A (VPPSKLSP), F2B (VAITLTMK), F2C (GLLGKNFTSK), F2D (LDSCKDYVME), F2E (HQTSEFK), F3A (VSKSVLVK) and F3B (TSVEIITSSK) with ion table for identified peptide sequences. GTS Protein produced peptides with strong free radical scavenging capacity upon enzymatic hydrolysis and can be utilized to develop health related nutraceutical ingredients.