Sorghum condensed tannins encapsulated in kafirin microparticles as a nutraceutical for inhibition of amylases during digestion to attenuate hyperglycaemia

• Sorghum condensed tannins were stronger α-glucosidase inhibitors than acarbose.
• Tannins were encapsulated in kafirin microparticles via simple coacervation.
• Kafirin microparticles encapsulating tannins withstand simulated digestion.
• Microparticles encapsulating tannins inhibit amylases after simulated digestion.
• The microparticles have potential as a nutraceutical to attenuate hyperglycaemia.

Type 2 diabetes (T2D) is increasing rapidly in Africa. An appropriate therapeutic approach is to inhibit intestinal carbohydrate digesting enzymes using plant polyphenols. A crude preparation of sorghum condensed tannins (SCT) was highly effective (approx. 20,000 times) at inhibiting α-glucosidase compared to acarbose, while acarbose was a better α-amylase inhihitor (approx. 180 times). Kafirin microparticles (KEMS) were investigated as an oral delivery system for SCT. Using a simple aqueous alcohol coacervation method, the encapulation efficiency of SCT in the KEMS was approx. 48%. Quantitative data and electron microscopy revealed that KEMS encapsulating SCT were digested to only a limited extent during simulated gastrointestinal digestion with pepsin and trypsin–chymotrypsin. Hence, SCT encapsulated in KEMS retained their inhibitory activity against both amylases, throughout simulated gastrointestinal digestion, whereas unencapsulated SCT lost most of their inhibitory activity. Thus, KEMS encapsulating SCT have potential as a nutraceutical to attenuate hyperglycaemia and control T2D.