A comparison of the components and biological activities in raw and boiled red beans (Phaseolus radiatus L.)

Abstract

In the course of study for the development of functional food using red beans (azuki beans, Phaseolus radiatus L.), the ethanol extracts from raw-red bean (RRB) and boiled-red bean (BRB) were prepared, and the components and various biological activities of both were compared. It was observed that the extraction yield, and the total polyphenol content, of the BRB were 1.2 times higher than that of the RRB. However, the contents of total flavonoid, total sugar and reducing sugar in the BRB were 30, 27.9 and 30.8% respectively when compared with those of RRB. In relation to antioxidative activity, both RRB and BRB exhibited moderate DPPH anion, ABTS cation, and nitrite scavenging activities and reducing power, though in all cases RRB demonstrated stronger activities than BRB. The extracts of RRB and BRB did not reveal any antimicrobial activities. In a α-amylase inhibitory activity assay, RRB was higher than BRB, while BRB showed higher α-glucosidase inhibitory activity than RRB. A strong and particular activity was observed in an anti-thrombosis activity assay of RRB. The extract of RRB demonstrated strong inhibitions against prothrombin and blood coagulation factors, with moderate thrombin inhibition. However, the extract of BRB did not exhibit any significant anti-thrombosis activity. Our results indicate that RRB has different, but useful biological activities, and loss or elimination of the biologically active substances in RRB occurs during the production of BRB. Therefore, to develop more functional foods from red beans, a study of suitable boiling, heating and drying processes is essential, and the efficient re-use of boiled waste water from the boiling process is necessary. These results could be applied to the further development of functional red bean beverages and sweat red bean pastes. © 2014, The Korean Society for Microbiology and Biotechnology.