Characterisation and antiproliferative effect of okra seed protein isolate on human cancer cell lines

Abstract

The increasing interest in plant-derived bioactive compounds has led to significant focus on okra seed protein isolate (OSPI) due to its notable nutritional and therapeutic properties. This research explores the structural and molecular characteristics of OSPI, aiming to assess its potential application as a nutraceutical in cancer therapy. A comprehensive amino acid profile showed that OSPI is rich in glutamic acid (14.46 g/100g), aspartic acid (7.56 g/100g), and arginine (9.42 g/100g), with a high proportion of hydrophobic (31.39 g/100g), and branched-chain amino acids (14.24 g/100g), known to support immune modulation and antitumour activity. Solubility analysis demonstrated peak protein solubility (91.86%) at pH 9, which is a critical factor affecting its functional efficacy. Molecular weight profiling indicated the presence of 7S and 11S globulin polypeptides, which are associated with encapsulation efficiency in nutraceutical development. Spectroscopic analysis, including FTIR and XRD, established the presence of α-helices and β-sheet structures, further supporting the protein’s conformational stability and amorphous nature, promoting bioavailability in pharmaceutical formulations. Particle size denoted monomodal distributions with the smallest size depicted at 0.144±0.10 µm, highlighting its suitability in drug delivery systems. The cytotoxic and antiproliferative effect of OSPI was evaluated using human cancer cell lines. In lung carcinoma cells (A549), OSPI reduced viability to 37.73% at 15 µg/mL and demonstrated a lower IC50 (21.80 µg/mL) than the standard chemotherapeutic agent camptothecin (524.85 µg/mL). Defatted okra flour (DOF) and OSPI significantly upregulated p53 levels with apoptotic induction against A549, as presented by Annexin V-binding. In hepatocellular carcinoma cells (Hep-G2), OSPI activated caspase-3/7, -8, and -9 at levels comparable to camptothecin, suggesting the initiation of both intrinsic and extrinsic apoptotic pathways. Furthermore, okra flour (OF) promoted reactive oxygen species (ROS) generation more effectively than camptothecin in A549 and Hep-G2 cells, reinforcing its potential oxidative stress-mediated apoptotic effects. These findings collectively underscore OSPI as a potential candidate for pharmaceutical and nutraceutical applications, particularly in cancer therapy. Its structural stability, solubility, and bioactive profile support its utilisation in the development of plant-based therapeutic interventions.