Nutr Res Pract.  2010 Dec;4(6):486-491.

Hypoglycemic effects of Welsh onion in an animal model of diabetes mellitus

• Kang MJ
• Kim JH
• Choi HN
• Kim MJ
• Han JH
• Lee JH
• Kim JI

Abstract

Tight control of blood glucose is the most important strategy for the treatment of diabetes mellitus. Here, we investigated the beneficial effects of Welsh onion on fasting and postprandial hyperglycemia. Inhibitory activities of hot water extracts from the green stalk and white bulb, which are the edible portions of the Welsh onion, and the fibrous root extract against yeast alpha-glucosidase were measured in vitro. To study the effects of Welsh onion on postprandial hyperglycemia, a starch solution (1 g/kg) with and without Welsh onion fibrous root extract (500 mg/kg) or acarbose (50 mg/kg) was administered to streptozotocin-induced diabetic rats after an overnight fast. Postprandial plasma glucose levels were measured and incremental areas under the response curve were calculated. To study the hypoglycemic effects of chronic feeding of Welsh onion, five-week-old db/db mice were fed an AIN-93G diet or a diet containing either Welsh onion fibrous root extract at 0.5% or acarbose at 0.05% for 7 weeks after 1 week of adaptation. Fasting plasma glucose and blood glycated hemoglobin were measured. Compared to the extract from the edible portions of Welsh onion, the fibrous root extract showed stronger inhibition against yeast alpha-glucosidase, with an IC50 of 239 microg/mL. Oral administration of Welsh onion fibrous root extract (500 mg/kg) and acarbose (50 mg/kg) significantly decreased incremental plasma glucose levels 30-120 min after oral ingestion of starch as well as the area under the postprandial glucose response curve, compared to the control group (P < 0.01). The plasma glucose and blood glycated hemoglobin levels of the Welsh onion group were significantly lower than those of the control group (P < 0.01), and were not significantly different from those fed acarbose. Thus, we conclude that the fibrous root of Welsh onion is effective in controlling hyperglycemia in animal models of diabetes mellitus.

Keyword

Welsh onion; alpha-glucosidase inhibition; diabetes; glucose; glycated hemoglobin

MeSH Terms

Acarbose
Administration, Oral
alpha-Glucosidases
Animals
Blood Glucose
Diabetes Mellitus
Diet
Eating
Fasting
Glucose
Hemoglobins
Humans
Hyperglycemia
Hypoglycemic Agents
Inhibitory Concentration 50
Mice
Models, Animal
Onions
Plasma
Rats
Starch
Water
Yeasts
Acarbose
Blood Glucose
Glucose
Hemoglobins
Hypoglycemic Agents
Starch
Water
alpha-Glucosidases

Figure

• 

  Fig. 1 Inhibitory activities of Welsh onion against yeast α-glucosidase. The inhibitory activities of the hot water extracts of the edible portions (green stalk and white bulb) and fibrous root of Welsh onion as well as acarbose were measured at concentrations of 25, 50, 100, 250, and 500 µg/mL. ●, edible part (green stalk and white bulb) of Welsh onion; ○, fibrous root of Welsh onion; ■, acarbose. Values represent means ± SD of triplicate measurements.

• 

  Fig. 2 Increase in blood glucose after administration of Welsh onion extract in STZ-induced diabetic rats. Control group (●): Starch (1 g/kg) was administered orally to streptozotocin-induced diabetic rats after an overnight fast. Welsh onion group (○): Starch (1 g/kg) plus water extract of fibrous root of Welsh onion (500 mg/kg) was administered orally to rats after an overnight fast. Acarbose group (■): Starch (1 g/kg) plus acarbose (50 mg/kg) was administered orally to rats after an overnight fast. Values represent means ± SD (n = 6). Means that do not share a common letter are significantly different at P < 0.01 (**).

• 

  Fig. 3 Hypoglycemic effects of Welsh onion extract in db/db mice. A. Fasting plasma glucose; B. Blood glycated hemoglobin (HbA1C). Values represent means ± SD (n = 7). Means that do not share a common letter are significantly different at P < 0.01.

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