In this study, we conducted an oral glucose tolerance test (OGTT) so as to compare antidiabetic activities of general potatoes, purple-flesh potatoes, and potato pigments in rats at various concentration levels. After allowing the rats to abstain from food for 12 hours, 10%/20% general potato, purple-flesh potato, and potato extract was orally administered to rats at 100 and 500 mg/kg concentrations. The blood glucose level was measured after an hour. Then, immediately, 1.5 g/kg of sucrose was administered through the abdominal cavity and the blood glucose measured after 30, 60, 120, and 180 minutes. 20% purple-flesh potato group and 10% general potato group, both 100 and 500 mg/kg, showed a significant concentration-dependent decrease in blood glucose levels after 30 minutes. The 100 mg/kg potato pigment group also showed a statistically significant decrease after 30 minutes. In conclusion, administration of 10% general potato, 20% purple-flesh potato, and potato pigment can reduce blood glucose level in an OGTT using rats.

Takju lees extract is expected to be a promising material for functional food. This study was conducted in order to assess the glycemic index (GI) of Takju lees extract and its effects in an oral glucose tolerance test (OGTT). The GI for Takju lees extract was evaluated with 10 healthy young adults (Male 5, Female 5). OGTT was conducted in 20 male db/db mice, fed on a diet containing 2% Takju lees extract for 4 weeks. Those animals were subjected to OGTT after one oral administration of Takju lees extract at 2 g/kg BW. The GI of the Takju lees extract was measured at 97.97. The effects of the Takju lees extract on the oral glucose tolerance test in db/db mice evidenced no differences as compared to the control group. In conclusion, Takju lees extract is a high GI material, and it has no effect on blood glucose levels in a type II diabetic animal model. Further studies will be required to confirm its anti-diabetic effects.

Guava (Psidium guajava) contain a great deal of polyphenol compound and work on the treatment of Diabetes mellitus effectively. In this study, the bioactivities of aqueous extract (GLEx) of guava leaf were investigated. Total phenolic contents of GLEx was 266.9 mg tan/g. The effects of GLEx on digestive enzymes, α-amylase, maltase and sucrase were investigated. IC50 values of GLEx against α-amylase, maltase and sucrase were 0.65 mg/ml, 2.0 mg/ml and 3.5 mg/ml respectively. The effect of GLEx on oral glucose tolerance test (OGTT) was performed in normal ICR mouse, control (dstilled water) and GLEx (aqueous extract of Guava leaf) were co-administered orally with glucose, showed reducing effect on the blood glucose level. The guava is likely to useful for prevention or improvement of hyperglycemia by lowering the blood glucose level and inhibiting glycoside hydrolase activity.