Extraction of Polyphenols from Unripe Banana Peels via Response Surface Methodology and Analysis of In Vitro Bioactive Properties

Abstract

Banana peels are rich in phytochemicals, including tannins, phenolic compounds, flavonoids, glycosides, saponins, and terpenoids. This study focused on the use of unripe banana peels of Musa × paradisiaca var. Monthan for the extraction of total phenolic content (TPC) and total flavonoid content (TFC). Three independent variables (solid‒solvent ratio, ethanol concentration, and extraction time) were selected for optimizing the ultrasound-assisted extraction of the TPC and TFC via response surface methodology. The banana peel extract presented a maximum TPC and TFC of 68.2 mg GAE/g and 15.4 QE/g, respectively, when extracted under the following extraction conditions: a 6% solid‒solvent ratio, 50% ethanol, and 40 min extraction time. Banana peels showed 75.4±2.1% inhibition in the DPPH assay and 59.9±1.1% inhibition in the ABTS assay at a concentration of 100 µg/mL. Banana peels presented significant enzyme inhibitor activity. The IC₅₀ values of the α-amylase and α-glucosidase inhibitory activities of the peel extract were 7.4±0.2 mg/mL and 9.5±0.09 mg/mL, respectively. Banana peel extract suppressed the synthesis of proinflammatory cytokines such as IFN-γ, IL-1α, TNF-α, and IL-6 and upregulated the synthesis of anti-inflammatory cytokines (IL-13 and IL-10). Banana peel can be utilized for its anti-inflammatory, antioxidant, and antidiabetic activities.