Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Biology

Supervisor

Marsolais, Frédéric

2nd Supervisor

Cumming, Robert C.

Abstract

The common bean (Phaseolus vulgaris L.) plays an important role in human nutrition, especially among low-income people in developing countries, primarily due to the high protein content of this legume, ranging from 19% to 27%. Previous studies have indicated that cooked bean bio-active peptides also exhibit anti-diabetic, antioxidant, and antimicrobial properties. It is hypothesized that small peptides (600-1000 Da) derived from different common bean strains are primarily responsible for eliciting bio-active effects. This project evaluated protein isolated extracts from 4 different strains of common bean for antioxidant capacity, anti-diabetic effects, and antimicrobial activity. Surprisingly, the bio-active compounds identified in this research revealed that the anti-diabetic effects of common bean extracts originate from lipids, not peptides. The findings that some bio-active properties of common bean extracts are of lipid origin are novel and previously unrecognized. Future in vitro and in vivo experiments are required to further identify and characterize the bio-active molecules from common bean strains that promote human health benefits.

Summary for Lay Audience

The common bean (Phaseolus vulgaris L.) plays an important role in human nutrition, especially among low-income people in developing countries, primarily due to the high protein content of this legume, ranging from 19% to 27%. Peptides are the intermediate products of protein digestion that occur in the human gastrointestinal system, and have unique physiological activities and beneficial properties to humans, which the original intact proteins do not have. This study focused on common bean small peptides, generated by a process that mimics cooking followed by digestion in the stomach. In particular, the antioxidant, anti-diabetic, and antimicrobial properties of extracts enriched with small bean peptides were assessed. We compared 4 different strains of common bean, which are genetically related but different in storage protein content, extracted proteins, and simulated the human gastrointestinal digestion process to generate small peptides. Peptides isolated from each bean strain were analyzed using multiple antioxidants, anti-diabetic, and antimicrobial tests. This study also looked further into specifically identifying the bio-active compounds in cooked common bean that exhibited anti-diabetic properties.

Surprisingly, the bioactive compounds identified in this research revealed that the anti-diabetic effects derived from common bean extracts appear to originate from lipids, not peptides. The findings that some bio-active properties of common bean extracts are of lipid origin are novel and previously unrecognized. Results of the study also showed that bioactive compounds exhibiting antimicrobial properties were probably also not peptides. These newly identified compounds may provide new antibacterial resources against bacterial drug resistance. However, more information is required to identify the nature of the bioactive molecules precisely. Studies of antioxidant capacity suggest that the bioactive molecules were probably a mixture of small peptides. Future in vitro and in vivo experiments are required to further identify and characterize the bio-active molecules from common bean strains that promote human health benefits.

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