To elucidate the sequence, origin and structure-activity relationship of antioxidant
peptides from sesame protein, sesame protein was hydrolysed by a dual-enzyme system
comprised alcalase and trypsin, then this hydrolysate was fractionated by ultrafiltration
and preparative HPLC. Subsequently, peptides in the high antioxidant activity fraction
were identified by nano liquid chromatography-electrospray ionization-tandem mass
spectrometry (Nano-LC-ESI-MS/MS), finally the structure-activity relationship of antioxidant
peptide with the strongest activity in the sesame peptides was illustrated by comparative
molecular field analysis (CoMFA). The results showed that seven novel antioxidant
peptides were discovered, their sequences were as follows, RDRHQKIG, TDRHQKLR, MNDRVNQGE,
RENIDKPSRA, SYPTECRMR, GGVPRSGEQEQQ and AGEQGFEYVTFR. The SYPTECRMR was the hydrolysate
of 2S albumin, the others derived from 11S globulin. The SYPTECRMR whose IC50 Values
of DPPH and ABTS were 0.105 mg/mL and 0.004 mg/mL respectively exhibited the highest
antioxidant activity among the seven sesame peptides. The active site of SYPTECRMR
tended to locate on Cys6 and Met8. A positive correlation between Cys6, Met8, the
bulky C-terminal amino acid residue (Arg9), the negative charged group around sulphur-containing
amino acids and the antioxidant activity of SYPTECRMR was observed from the CoMFA
model. The results presented herein suggested that sesame protein hydrolysates have
potential applications in functional food due to their high antioxidant activity,
the CoMFA model could provide insight into the structure-activity relationship of
antioxidant peptide, which is useful to screen, identify and design the novel antioxidant
peptide.