Assessment of Phenolic Content, Saponin Content, and Antioxidant Activities in Gray, Red, and White Adzuki Bean Germplasm: A Multivariate Analysis

Assessment of Phenolic Content, Saponin Content, and Antioxidant Activities in Gray, Red, and White Adzuki Bean Germplasm: A Multivariate Analysis

Seed color is controlled by several genes and is a key trait in determining the metabolite content and biological activities of legume genotypes. In this study, 296 adzuki bean accessions, including 159 grey, 99 red, and 38 white adzuki beans, were grown in Korea. Variations in total phenolic content (TPC), total saponin content (TSC), DPPH• scavenging activity, ABTS•+ scavenging activity, and ferric reducing antioxidant power (FRAP) were assessed and were reported to be in the ranges of 1.52- 8.24 mg GAE/g, 14.36-114.22 mg DE/g, 0.23-12.84 mg AAE/g, 1.05-17.66 mg TE/g, and 0.59-13.14 mg AAE/g, respectively, with a wide variation across adzuki beans. Except for DPPH• scavenging activity, the average values declined in the order gray > red > white adzuki beans, each demonstrating a significant variation (p < 0.05). White adzuki beans, which showed low metabolite content and antioxidant activity, were clearly separated from the gray and red genotypes using principal component and hierarchical cluster analyses. Moreover, TPC, TSC, and antioxidant activities were strongly correlated, regardless of seed color. Overall, the diversity of the TPC, TSC, and antioxidant activity in a broad population of adzuki bean genotypes was determined. Furthermore, this study found that seed color variation in adzuki beans had a significant effect on the metabolite content and antioxidant activity. Superior accessions with high levels of TPC, TSC, and antioxidant activity were also discovered and could be used for functional plant breeding and human consumption. The findings of this study may be useful for understanding the relationship between seed coat color and metabolite concentration in adzuki beans, paving the way for molecular-level analyses.