In vitro and in vivo effects of sorghum condensed tannins encapsulated in kafirin microparticles on digestive amylases

• Main Author: Links, Malory R.
• Other Authors: Taylor, J.R.N. (John Reginald Nuttall)
• Language: en
• Published: 2015
• Subjects: UCTD
• Online Access: http://hdl.handle.net/2263/50313; Links, MR 2015, In vitro and in vivo effects of sorghum condensed tannins encapsulated in kafirin microparticles on digestive amylases, MSc Dissertation, University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/50313>

The International Diabetes Federation reported that by 2035 the expected increase in diabetes in sub-Saharan Africa will be 109%, the highest rise in the world. Furthermore, almost a quarter of the world‘s adult population have the metabolic syndrome. One therapeutic approach for type 2 diabetes (T2D) treatment is to inhibit digestive amylases and thereby decrease post-prandial hyperglycaemia. Polyphenols like sorghum condensed tannins (SCT) inhibit α-amylase and α-glucosidase enzymes. However, orally administered SCT may have poor inhibitory action against amylases, due to non-specific protein binding. Research is required to determine how to effectively deliver SCT to the small intestine to inhibit digestive amylases and decrease post-prandial hyperglycaemia. This study investigated the encapsulation of SCT in kafirin microparticles (KEMS) using aqueous ethanol and acetic acid coacervation methods. The inhibitory action of SCT on α- amylase and α-glucosidase were compared to acarbose (standard drug). The inhibition of SCT-KEMS after simulated gastrointestinal digestion was assessed. Electron microscopy was used to characterise microparticle morphology. A confirmatory in vivo test was performed using an oral starch tolerance test (OSTT) on healthy rats. SCT were about 20 000 times more effective at inhibiting α-glucosidase (IC50 = 0.4 μg/ml) than acarbose (IC50 = 8464.0 μg/ml), while acarbose (IC50 = 3.1 μg/ml) inhibited α-amylase better than SCT (IC50 = 554.5 μg/ml). The aqueous ethanol method of encapsulating SCT resulted in higher encapsulation efficiency (48%) than the acetic acid method (25%). Electron microscopy and quantitative data showed that SCT-KEMS were hardly digested by pepsin and trypsin-chymotrypsin during simulated digestion. SCT-KEMS retained their inhibitory activity against both amylases after simulated digestion, while SCT alone lost most of their inhibitory activity. In vivo data showed that the SCT-KEMS treatment decreased the maximum blood glucose level of rats by on average 11.8% and the area under the curve by 9%, compared to the water control. Acarbose decreased the blood glucose spike of the rats by on average 18.5% compared to the control. SCT-KEMS and acarbose did not elevate serum insulin levels and actually decreased insulin secretion by 60% and 48%, respectively, compared to the control. These findings indicate that KEMS are effective SCT encapsulating agents as they deliver the SCT to the small intestine. SCT-KEMS prevents hyperglycaemia by inhibiting digestive amylases and seems to substantially reduce insulin secretion when carbohydrate is consumed. Therefore, SCT-KEMS could be employed as a nutraceutical to inhibit digestive amylases and thereby attenuate post-prandial hyperglycaemia associated with the metabolic syndrome and T2D. === Dissertation (MSc)--University of Pretoria, 2015. === tm2015 === Food Science === MSc === Unrestricted