Extraction, hydrolysis and partial characterization of soluble proteins from commercially available roasted watermelon seeds with potential α-amylase

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Bachelor of Science in Biochemistry




Commercially available roasted watermelong seeds (butong pakwan) were used to as sources of soluble proteins and peptides with potential α-amylase inhibitory properties. Soluble proteins from defatted watermelon seed meal were extracted with phosphate buffer saline (pH 7) and precipitated via ammonium sulfate precipitation at 99% saturation, followed by dialysis. Soluble protein contents obtained 0.90 mg/mL for crude extract (CE), 0.47 mg/mL for crude protein (CP), and 0.79 mg/mL for the dialysed cruide protein (DCP). Sequential peptic hydrolysis at acidic pH of CE and DCP at 2h and 4h afforded hydrolysates with α-amylase inhibitory properties via in vitro starch-iodine colorimetric assay. Denaturing gel electrophoretic profiles of CE and DCP showed protein bands with approximate molecular weights ranging from 14 kDa to 33 kDa and 27 kDa to 58 kDa, respectively. α-Amylase inhibitory activities of soluble protein hydrolysates were generally higher than the protein samples and was observed highest in the hydrolysis products of DCP upon 4-h incubation with pepsin. An increasing trend in α-amylase inhibitory potential was observed when hydrolysis period was increased from 2h to 4h and it was notable that the dialysed crude protein showed inhibitory activity higher than the crude extract indicating the innate bioactivity of the watermelon seed soluble proteins obtained in this study.

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