(P03-063-23) The Polyphenol Profile, Antioxidant Capacity and α-Glucosidase Activity Inhibition Potential of Broad Bean Hull Extract and Its Fractions

Objectives: Broad bean (Vicia faba) is a widely consumed legume with significant nutritional benefits due to its nutrient profile. The seed coat (broad bean hull, BBH) is a secondary product of processing that is rich in fibre and polyphenols. To investigate the health benefits of BBH, we assessed its polyphenolic composition, antioxidant potential, and in vitro α-glucosidase inhibition activity.

Methods: The BBH extract was prepared using 50% ACN and 0.1% formic acid (ACNE extract, ACNE). The ACNE was fractionated by liquid chromatography into unbound, bound (acetone), and ethanol fractions using ethanolic gradient elusions and 75% acetone. Polyphenolic composition was determined by LC-MS. Antioxidant properties of the fractions were tested by ferric reducing ability of plasma (FRAP). The α-glucosidase inhibition activity of ACNE and acetone fraction were assessed spectrophotometrically by measuring the production of p-nitrophenol from p-nitrophenyl-α-D-glucophranoside at 405 nm.

Results: The acetone fraction contained significantly more total flavonoids (22899.8 ± 305.3 ng/mg) than others (p < 0.05) (13225.8 ± 499.4, 2467.8 ± 81.6, 15883.8 ± 888.7 ng/mg of ACNE, unbound and ethanol fractions respectively). Non-flavonoid polyphenols in the ethanol fraction (2732.7 ± 109.8 ng/mg) were significantly higher (p < 0.05) than others (1804.8 ± 70.4, 229.3 ±9.1 and 1564.4 ± 139.5 ng/mg of ACNE, unbound and acetone fractions respectively). Total flavonoids were positively associated with FRAP activity (r=0.959, p=0.041). However, FRAP activities of ACNE, ethanol and acetone fractions were similar (12272.5 ± 761.8, 12736.4 ± 1041.7 and 12997.6 ± 243.1 µM FeSO₄ equivalent respectively, p >0.05) suggesting potential synergistic effects between polyphenol groups. The IC₅₀ of ACNE and acetone fraction were 0.55 and 0.66 µg GAE/ml respectively. They reached maximum inhibition (97%) at a concentration of 12.9 µg GAE/ml, while the maximum inhibition observed with the inhibitor control (acarbose) only reached up to 75%. There was a significant dose-response effect (p < 0.001) of both samples.

Conclusions: Flavonoids are the principal polyphenolic compounds in ACNE of BBH. The study showed that BBH has good antioxidant and α-glucosidase activity inhibition with potential anti-diabetic properties.

Funding Sources: The work was funded by the Scottish Government (RESAS).