Isolation and Characterization of the Total Protein in 'Lakatan' Banana (Musa acuminata Colla) with Bioactive Peptides Exhibiting Antioxidative and Antihypertensive Activities

Hypertension is a leading cause of disease burden in developing countries. Leading factors are obesity, increased cholesterol levels, and long-term oxidative stress. Since commercially available drugs for cardiovascular diseases such as antioxidants and ACE receptor blockers are expensive, preventive cheaper alternatives derived from foods are sought after. Lakatan, one of the most abundant and cheap food sources in the Philippines has been proven to have antioxidant and antihypertensive properties but studies exploring the proteins and bioactive peptides responsible for its health benefits are very limited. In this study, proteins from Lakatan (Musa acuminata Colla) have been studied to understand the components of banana that gives its health benefits. In silico analysis was done to determine the presence of bioactive peptides. Results showed that a 14.697 kDa lectin may release antioxidative and antihypertensive peptides upon digestion. Isolation of the crude/total protein of "Lakatan" banana (Musa acuminata) flesh was done using 500 mM Tris-CI, pH 8.0, 100 mM KCI, 2% polyvinylpolypyrrolidone (PVPP). The protein concentration of the crude/total protein was determined using Lowry assay and results showed a value equal to 0.865 mg/mL +/- 0.052 mg/mL. The crude/total protein was subjected to proteolytic digestion using pepsin, trypsin, chymotrypsin, and thermolysin as enzymes for 3-, 12-, and 24 - hours digestion time. Using densitometric analysis, complete digestion has occurred after 24 hours of digestion time. The crude/total proteins and digests were subjected to antioxidative assay using 2,2-diphenyll-picrylhydrazyl (DPPH) and spectrophotometric Angiotensin-Converting Enzyme (ACE) inhibition assay. Results of the DPPH assay showed the highest antioxidative activity of 54.00% from the undigested crude/total proteins. Among the different digests, the 12 h digest (38.60%) had the highest antioxidative activity. Results of the ACE assay showed the highest inhibition (43.03%) after 24 h digestion time. These study shows that Lakatan has the potential to be a cheap source of antioxidants and antihypertensive functional food which can be further explored for drug discovery and development.