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N. lappacheum and N. mutabile seed are alternative sources of bioactive peptides.Peptides produced using the enzymes exhibited α-amylase inhibitory activity.A high number of novel peptides were identified using the bioinformatics approach.The mechanism of the inhibitory activity was investigated.The potential of N. lappacheum and N. mutabile seed as a source of α-amylase inhibitor peptides was explored based on the local traditional practice of using the seed. Different gastro-digestive enzymes (i.e. pepsin or chymotrypsin) or a sequential digestion were used to extract the peptides. The effects of digestion time and enzyme to substrate (E:S) ratio on the α-amylase inhibitory activity were investigated. Results showed that chymotrypsin was effective in producing the inhibitor peptides from rambutan seed protein at E:S ratio 1:20 for 1h, whereas pepsin was more effective for pulasan seed protein under the same condition. A total of 20 and 31 novel inhibitor peptides were identified, respectively. These peptides could bind with the subsites of α-amylase (i.e. Trp58, Trp59, Tyr62, Asp96, Arg195, Asp197, Glu233, His299, Asp300, and His305) and formed a sliding barrier that preventing the formation of enzyme/substrate intermediate leading to lower α-amylase activity.