Antioxidant and Anti-inflammatory Activities of Bean (Phaseolus vulgaris L.) Hulls

Hulls obtained by mechanical abrasive dehulling from four bean cultivars were extracted with two solvents, aqueous (70%) acetone and water, and the extracts evaluated for antioxidant and anti-inflammatory activities in relation to their phenolic contents. Total phenolic content and antioxidant activity of bean hulls, measured using oxygen radical absorbance capacity (ORAC) values, were 6−8-fold those of corresponding whole beans. Aqueous acetone (70%) extracted over twice the amount of total phenolics from hulls that exhibited significantly higher antioxidant and stronger inhibitory effect on both cyclooxygenases, COX-1 and COX-2, than water. Acetone extract of black bean hull exhibited strong COX-1 (IC50 = 1.2 μg/mL) and COX-2 (IC50 = 38 μg/mL) inhibitory effects, even outperforming aspirin. Bean hull water extracts were stronger inhibitors of lipoxygenase, 15-LOX, than corresponding acetone extracts. Anti-inflammatory activity of bean hulls was dependent on their phenolic content and antioxidant activity that were significantly affected by cultivar and extracting solvent.