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Extraction of Raw and Cooked Pinto Beans Using Response Surface Methodology to Recover Total Flavonoids and Condensed Tannins to Inhibit Alpha Amylase and Alpha Glucosidase Alone or Combined with Acarbose

Mohammed Saeed Aldawsari, University of Nebraska - Lincoln


Pinto beans are rich dietary source of phenols, such as total flavonoids (TF) and total condensed tannins (TCT). Phenols have been linked to multiple health benefits, such as antidiabetic due, in part, to their ability to inhibit the hydrolysis of the key digestive, enzymes α-amylase and α-glucosidase thereby retarding glucose absorption. However, a lack of information exists on the phenols present in pinto beans and their inhibition capability of such enzymes. Therefore, the objective of this project was to determine the ability of phenols present in pinto beans extracts in remediating risk factors for diabetes, specifically inhibiting α-amylase and α -glucosidase. However, it was also expected that cooking impact the inhibitory nature of the extract. As such, both raw and steamed beans were used for this study. To understand the impact of extraction method on recovering phenol rich extracts, which are chemically diverse or and thus will likely differ in their biological response, and ultimately the phenolic composition of the product as a whole, a more comprehensive extraction approach must be applied to fulfill the objective of this research. Thus, a response surface methodology design was used that consisted of a faced central composite design with three coded independent variables, (solvent:water ration, solid:solvent ratio and mixing time), which resulted in 17 extracts with three center points (Chapter 1). From this study, the highest predicted value of TF was obtained from the steamed beans with 2.65 mg/g TF mg/g beans (68:32 acetone:water, 5.0% solid:solvent, 180 minute mix time), whereas the raw beans predicted value was 1.71 mg TF mg/g beans (56:44 ethanol:water, 5.0% solid:solvent, 128 minute mix time). For total condensed tannins (TCT), the highest predicted values for the raw and cooked beans were 7.013 mg TCT / g beans (75:25 acetone:water, 5% solid:solvent, 60 minute mix time), and 4.99 mg TCT / g beans (75:25 acetone:water, 8.75% solid:solvent, 130 minute mix time), respectively. Still, the information was needed on the ability of these phenolic extracts to inhibit α-amylase and α -glucosidase. Therefore, each extract obtained from the surface response design cited previously was monitored for their ability to inhibit α-amylase and α-glucosidase, which was 78% for α-amylase and 31% for α-glucosidase exerted by two different extracts of steamed beans. These potent extracts were then examined individually at different concentrations and then in combination with the typical drug (acarbose) prescribed to inhibit the cited enzymes, in an effort to understand the interactions and to possibly lower the drug dosage (Chapter 3). Thus, the selected extractions (Extract 1 and 14) with acarbose were able to inhibit the hydrolysis enzymes, but their inhibitory effects were dependent on the dosage of each extract and acarbose. Analysis of the extractions via HPLC showed the presence of gallic acid, ferulic acid, chlorogenic acid, and kaempferol in each extract. Overall, this work indicates that pinto beans extracts exhibited the potential to overcome the postprandial glucose and hyperlipidemia individually or in combination with drug.

Subject Area

Food Science|Nutrition

Recommended Citation

Aldawsari, Mohammed Saeed, "Extraction of Raw and Cooked Pinto Beans Using Response Surface Methodology to Recover Total Flavonoids and Condensed Tannins to Inhibit Alpha Amylase and Alpha Glucosidase Alone or Combined with Acarbose" (2018). ETD collection for University of Nebraska-Lincoln. AAI10793021.