Anti-Diabetes Functionality of Kefir Culture-Mediated Fermented Soymilk Supplemented with Rhodiola Extracts

Abstract

Natural α-amylase and α-glucosidase inhibitors from food-grade plants offer an attractive strategy to manage of postprandial hyperglycemia for Type II diabetes. Inhibition of Angiotensin I-Converting Enzyme (ACE) is also considered useful as a therapeutic approach in the treatment of high blood pressure, one of the long-term complications of diabetes. In the current study, we evaluated the inhibitory activity of phenolic extracts produced during Kefir culture-mediated fermentation of soymilk supplemented with Rhodiola extracts against α-amylase, α-glucosidase and angiotensin converting enzyme (ACE). We also investigated phenolic-linked antioxidant activity and content of salidroside and tyrosol with fermentation time. α-Glucosidase inhibitory activity increased moderately with fermentation after 24 h and correlated to increased tyrosol and reduced salidroside contents. α-Amylase inhibitory activity decreased to zero with fermentation time, and the initial high activity prior to fermentation strongly correlated to high salidroside and low tyrosol contents. Angiotensin converting enzyme inhibitory activity seemed to change independent of tyrosol and salidroside contents with fermentation time. These results indicate that Kefir culture-mediated fermentation of soymilk supplemented with Rhodiola extracts resulted in mobilization of total phenolics, which could be effectively designed as complimentary therapies for postprandial hyperglycemia linked to Type II diabetes management. Due to the significantly reduced α-amylase inhibitory activity at the end of fermentation, this approach would have minimal side effects such as abdominal distention, flatulence, meteorism and possibly diarrhea, which are caused by the excessive inhibition of pancreatic α-amylase by current drug therapies.