Onion (Allium cepa L.) is widely consumed as food or medicinal plant due to its well-defined health benefits. The
antioxidant and
antihyperlipidemic effects of onion and its extracts have been reported well. However, very limited information on anti-hyperglycemic effect is available in processed onion extracts. In our previous study, we reported that Amadori rearrangement compounds (
ARCs) produced by heat-processing in Korean ginseng can reduce
carbohydrate absorption by inhibiting intestinal
carbohydrate hydrolyzing
enzymes in both in vitro and in vivo animal models. To prove the enhancement of anti-hyperglycemic effect and
ARCs content by heat-processing in onion extract, a correlation between the anti-hyperglycemic activity and the total content of
ARCs of heat-processed onion extract (ONI) was investigated. ONI has a high content of
ARCs and had high rat small intestinal
sucrase inhibitory activity (0.34 ± 0.03 mg/mL, IC50) relevant for the potential management of
postprandial hyperglycemia. The effect of ONI on the postprandial
blood glucose increase was investigated in Sprague Dawley (SD) rats fed on
sucrose or
starch meals. The maximum
blood glucose levels (Cmax) of heat-processed onion extract were significantly decreased by about 8.7% (from 188.60 ± 5.37 to 172.27 ± 3.96, p < 0.001) and 14.2% (from 204.04 ± 8.73 to 175.13 ± 14.09, p < 0.01) in
sucrose and
starch loading tests, respectively. These results indicate that
ARCs in onion extract produced by heat-processing have anti-diabetic effect by suppressing
carbohydrate absorption via inhibition of intestinal
sucrase, thereby reducing the postprandial increase of
blood glucose. Therefore, enhancement of
ARCs in onion by heat-processing might be a good strategy for the development of the new product on the management of
hyperglycemia.