Acute assessment of an aspalathin enriched green rooibos (Aspalathus linearis) extract with hypoglycaemic potential

C.J.F Muller, E. Joubert, D. de Beer, M. Sanderson, C.J. Malherbe, S. J. Fey, J. Louw

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Rooibos, an endemic South African plant, known for its use as herbal tea, has potential as an antidiabetic
herbal product, following recent demonstration of the glucose lowering effect of its major flavonoid, the
dihydrochalcone C-glucoside aspalathin. The purpose of this study was to confirm antidiabetic activity
for rooibos extract high in aspalathin content. An extract (SB1) was selected after screening for high
aspalathin content and -glucosidase inhibition activity. On-line HPLC-biochemical detection confirmed
-glucosidase inhibitory activity for aspalathin. In vitro the extract induced a dose response increase in
glucose uptake (5×10−5 to 5 µM/ml) on C2C12 myotubules. Aspalathin was effective at 1, 10 and 100 µM, while rutin was effective at 100 µM. In the Chang cells only the extract was effective. In vivo the extract
sustained a glucose lowering effect comparable to metformin over a 6 h period after administration
(25 mg/kg body weight (BW)) to STZ-induced diabetic rats. In an oral glucose tolerance test the extract
(30 mg/kg BW) was more effective than vildagliptin (10 mg/kg BW), a dipeptidyl peptidase-4 inhibitor. An
aspalathin–rutin mixture (1:1; m/m) dosed at 1.4 mg/kg BW, but not the single compounds separately,
reduced blood glucose concentrations of STZ-induced diabetic rats over a 6 h monitoring period. The
improved hypoglycemic activity of the aspalathin–rutin mixture and the extract illustrated synergistic
interactions of polyphenols in complex mixtures.
Sider (fra-til)32-39
Antal sider8
StatusUdgivet - 2012

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