Chemical characterization and multifunctional bioactivities of red kidney bean (Phaseolus vulgaris L.)

Kidney bean protein isolate (KPI) was extracted from red kidney bean (Phaseolus vulgaris L.) and evaluated for its bioactive properties. KPI showed a balanced amino acid composition and typical protein secondary structures confirmed by FTIR. KPI exhibited a typical U-shaped solubility profile, with lowest solubility near isoelectric point (pH 4-5), and improved solubility under acidic and alkaline conditions. Antioxidant assays demonstrated strong concentration-dependent activity. DPPH scavenging increased from 45.71% at 50 μg/mL to 87.57% at 1000 μg/mL, while ferric reducing power rose from 0.443 to 1.691 within the same range, although both values remained lower than TBHQ. Cytotoxicity assays revealed selective effects, with HepG2 liver cancer cells being most sensitive (IC₅₀ = 199.14 μg/mL), while PC3 prostate (IC₅₀ = 668.51 μg/mL) and Caco-2 colorectal (IC₅₀ = 757.94 μg/mL) cells were less responsive. These findings highlight KPI as a nutritionally valuable protein with notable antioxidants and moderate anticancer potential, especially against hepatocellular carcinoma, supporting its application in functional foods and nutraceuticals.