Antihypertensive property of the peptic and chymotryptic hydrolysates derived from the crude protein extract of okra [Abelmoschus esculentus (L.) Moench] seeds

Bioactive peptides from okra seeds were successfully isolated, purified, and characterized for its antihypertensive properties. Okra seeds were decorticated, defatted, and suspended in 35 mM phosphate buffer (pH 7.6, with 0.4 M NaCl and 0.02% NaN3) to isolate the okra seed crude protein extract (OSCPE). The protein content of OSCPE was estimated to be 13.8 +/- 0.6 mg/mL. Sodium dodecyl sulfate-polyacrylamide-gel electrophoresis (SDS-PAGE) revealed six major polypeptide bands with molecular weights of 11, 13, 16, 18, 25, and 49 kDa. Bioactive peptides from OSCPE were released through separate enzymatic hydrolysis, using pepsin and a-chymotrypsin, from 0 min to 24 h of incubation. OSCPE was more resistant to enzymatic hydrolysis with a-chymotrypsin than pepsin. The 12-h hydrolysate from both enzymes exhibited the highest angiotensin I-converting enzyme (ACE) inhibitory activity. Both hydrolysates were fractionated through anion-exchange chromatography (IEX) using a DEAE-Sephacel column (1.6 cm x 5.0 cm). Fractions from prominent peaks were subjected to ACE inhibition assay. The 17th peptic IEX fraction and the 15th chymotryptic IEX fraction showed the highest ACE inhibitory activities of 68.68 +/- 2.91% and 71.89 +/- 7.77%, with IC50 values of 8.62 +/- 1.17 mu g/mL and 2.44 +/- 0.87 mu g/mL, respectively. Aside from sustaining an individual's daily protein requirements, okra seeds also have the potential to further improve health by releasing bioactive peptides that can alleviate hypertension. (c) All Rights Reserved