This study was conducted to analyze the antioxidant and antidiabetic activities of acorns according to the types of Quercus serrata Thunb (QST) and Q. acutissima Carruther (QAC). The total polyphenol contents of the extracts from QST and QAC were 220.59 and 320.96 mg GAE/g, respectively. The content of total polyphenol of QAC was higher than that of QAC (p<0.001). DPPH (2,2 Diphenyl 1 picrylhydrazyl) radical scavenging activity, reducing power and superoxide dismutase (SOD)-like activity were increased in a concentration-dependent manner by both acorn extracts, and QAC showed high activity in all antioxidant experiments (p<0.05). The inhibitory activities of α-glucosidase and α-amylase were also increased in a concentration-dependent manner, and QAC showed higher inhibitory activity than QST (p<0.05). Our study indicates that QST and QAC are functional food materials with high antioxidant and antidiabetic activities. In addition, QAC has a higher physiological activity than QST.

This study aimed to evaluate the efficacy of the antioxidative and antidiabetic activities of the flowers, leaves, and roots of the Jerusalem artichoke (Helianthus tuberosus L.). The total polyphenol and flavonoid contents of the leaves were higher than those of the flowers and roots. However, the DPPH radical-scavenging and hydroxyl radical-scavenging activities of the flowers were higher than those of the leaves and roots. The nitrite-scavenging ability under acidic conditions was high in Jerusalem artichoke flower extracts. The α-glucosidase inhibitory activity and α-amylase inhibitory activity of a methanol extract of Jerusalem artichoke roots were about 60% (5 mg/mL concentration). Based on these experiments, it can be concluded that the flowers leaves, and roots of the Jerusalem artichoke can be used as natural preservatives. Therefore, they can be developed as functional foods, to take advantage of their antioxidant activity and abundant polyphenols. This study suggests that the whole Jerusalem artichoke, including roots, leaves, and flowers, is useful as a functional, nutritious food product.

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.

This study investigated the antioxidant and antidiabetic activities of Stachys sieboldii Miq. extracts by solvents (water, ethanol, butanol, chloroform, and hexane). The contents of total polyphenols (7.18-37.25 mg/g) and flavonoids (0.21-5.21 mg/g) in extracts from Stachys sieboldii Miq. showed a significant difference dependent on the extraction solvents, butanol > ethanol > water > chloroform > hexane. Antioxidant activities by DPPH and ABTS radical scavenging were increased in a dose-dependent manner. These activity trends associated with the extraction solvent were different at each concentration, but resembled phenolic compound contents trend, generally. FRAP value increased in a dose-dependent manner, but there was a difference in radical scavenging activities when comparing between extraction solvents by butanol > ethanol > hexane > chloroform > water on all concentrations. The trend of α-amylase inhibition of extracts from 1,000 μg/mL to 2,000 μg/mL was not affected as enzyme activity is promoted and not inhibited. The inhibition of α-glucosidase was increased in a dose-dependent manner without water extracts, the activity on hexane extracts was higher than others per the extraction solvent. α-Glucosidase inhibition of hexane extracts showed 57.76% at 250 μg/mL, which is 2.8 times higher than the second highest chloroform extract (20.65%). From these results, we presume that the active ingredients of Stachys sieboldii Miq. is different according to the extraction solvent and also the activity is different by these major functional groups.