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Superhongmi is a new rice variety, which was developed for the enrichment of bioactive compounds through cross-breeding three varieties of rice breeds in Korea. The high-performance liquid chromatography coupled with a photodiode array detector quadrupole and tandem time-of-flight mass spectrometry (HPLC/PDA/QTOF-MS) analysis has revealed that superhongmi bran extract contained four taxifolin derivatives as well as cyanidin 3-glucoside. The high-performance countercurrent chromatography (CCC) and reversed-phase HPLC led to the isolation of aforementioned five compounds, and spectroscopic analysis identified cyanidin 3-glucoside (1), along with (2R,3R)-taxifolin 3-O-β-d-glucopyranoside (2), (2R,3R)-4'-O-methyltaxifolin 3-O-β-d-glucopyranoside (a novel compound) (3), (2R,3R)-taxifolin (4), and (2R,3R)-4'-O-methyltaxifolin (5). Compound 2 had the highest rat small intestinal sucrase inhibitory activity (0.54 mM) relevant for potentially managing postprandial hyperglycemia, followed by compound 1 (0.97 mM) and compound 4 (1.74 mM, IC50). The anti-hyperglycemic effect of compound 4 (taxifolin), a main peak in HPLC analysis was investigated using a Sprague-Dawley (SD) rat model. Compared to a control, taxifolin treatment (p < 0.001) reduced significantly after sucrose loading the observed postprandial blood glucose and the maximum blood glucose (Cmax) by 15% (203.60 ± 15.86 to 172.30 ± 12.74). These results indicate that taxifolin derivatives that inhibit the activity of carbohydrate-hydrolyzing enzymes resulting in reduced dietary carbohydrate absorption can potentially be used as a strategy to manage diabetes.

Type 2 diabetes mellitus (T2DM) is a metabolic disorder characterized by postprandial hyperglycemia, which is an early defect of T2DM and thus a primary target for anti-diabetic drugs. A therapeutic approach is to inhibit intestinal α-glucosidase, the key enzyme for dietary carbohydrate digestion, resulting in delayed rate of glucose absorption. Although tea extracts have been reported to have anti-diabetic effects, the potential bioactivity of tea pomace, the main bio waste of tea beverage processing, is largely unknown. We evaluated the anti-diabetic effects of three selected tea water extracts (TWE) and tea pomace extracts (TPE) by determining the relative potency of extracts on rat intestinal α-glucosidase activity in vitro as well as hypoglycemic effects in vivo. Green, oolong, and black tea bags were extracted in hot water and the remaining tea pomace were dried and further extracted in 70% ethanol. The extracts were determined for intestinal rat α-glucosidases activity, radical scavenging activity, and total phenolic content. The postprandial glucose-lowering effects of TWE and TPE of green and black tea were assessed in male Sprague-Dawley (SD) rats and compared to acarbose, a known pharmacological α-glucosidase inhibitor. The IC50 values of all three tea extracts against mammalian α-glucosidase were lower or similar in TPE groups than those of TWE groups. TWE and TPE of green tea exhibited the highest inhibitory effects against α-glucosidase activity with the IC50 of 2.04 ± 0.31 and 1.95 ± 0.37 mg/mL respectively. Among the specific enzymes tested, the IC50 values for TWE (0.16 ± 0.01 mg/mL) and TPE (0.13 ± 0.01 mg/mL) of green tea against sucrase activity were the lowest compared to those on maltase and glucoamylase activities. In the animal study, the blood glucose level at 30 min after oral intake (0.5 g/kg body wt) of TPE and TWE of both green and black tea was significantly reduced compared to the control in sucrose-loaded SD rats. The TPE of all three teas had significantly higher phenolic content than those of the TWE groups, which correlated strongly with the DPPH radical scavenging activity. This is the first report of tea pomace extract significantly inhibits intestinal α-glucosidase, resulting in delayed glucose absorption and thereby suppressed postprandial hyperglycemia. Our data suggest that tea pomace-derived bioactives may have great potential for further development as nutraceutical products and the reuse of otherwise biowaste as valuable bioresources for the industry.

The effect of chitosan oligosaccharide (GO2KA1) administration on postprandial blood glucose levels of subjects with normal blood glucose levels was evaluated following bread consumption. Postprandial blood glucose levels were determined for 2 h after bread ingestion with or without 500 mg of GO2KA1. GO2KA1 significantly lowered the mean, maximum, and minimum levels of postprandial blood glucose at 30 min after the meal. Postprandial blood glucose levels were decreased by about 25% (from 155.11±13.06 to 138.50±13.59, p

After a mixed carbohydrate diet, inhibition of α-amylase and α-glucosidase involved in the digestion and absorption of carbohydrates can significantly decrease the postprandial increase of blood glucose level. In the course of screening these useful enzyme inhibitors, we selected five kinds of bean, using an in-vitro enzyme inhibition assay method. To evaluate the effect of germination process on the functionality of the bean, we investigated the inhibitory activities of the water extracts of non-germinated bean and germinated bean against α-amylase and α-glucosidase, relevant to postprandial hyperglycemia. We also investigated the oxygen radical absorbance capacity(ORAC), total phenolics content, and post-prandial blood glucose lowering effect in rats(Sprague-Dawley rat model). Most germinated beans showed significantly higher α-glucosidase inhibitory activity, compared with non-germinated beans. Among germinated beans, Glycine max had the highest α-glucosidase inhibitory activity(53.3%). The water extract of germinated Phaseolus vulgaris L. had the highest α-amylase inhibitory activity(95.1%), followed by Glycine max(58.7%), and Glycine max L. Merr(54.1%). Furthermore, the five germinated beans also showed high antioxidant activities in ORAC assay. Results suggested that the germination process may improve and enhance the anti-hyperglycemia potential and antioxidant activity of the bean.Key words: germination, bean, α-glucosidase, α-amylase, ORAC

The inhibitory activities of a water extract of Sanghwang mushroom(Phellinus linteusau)(SWE) against α-glucosidases were evaluated in this study. Inhibiting these enzymes involved in the absorption of disaccharides significantly decreases the postprandial increase in blood glucose level after a mixed carbohydrate diet. Oxygen radical absorbance capacity and 1,1-diphenyl-2-picryl hydrazyl scavenging activities of the SWE were evaluated to investigate the antioxidant activity of the SWE associated with complications of long-term diabetes. Furthermore, the postprandial blood glucose lowering effect of SWE was compared to a known type 2 diabetes drug(Acarbose ® ) in a Sprague-Dawley rat model. SWE significantly reduced the blood glucose increase after sucrose loading. These results suggest that SWE, which has high α-glucosidase inhibitory activity and high antioxidant activities, has the potential to contribute to a useful dietary strategy for controlling postprandial hyperglycemia.Key words: α-glucosidase, maltase, sucrase, glucoamylase, antihyperglycemic activity, antioxidant

During the heat processing of raw ginseng to produce red ginseng, amino acid derivatives such as arginyl-fructose (AF) and arginyl-fructosyl-glucose (AFG) are formed at high levels, through amadori rearrangement, the early step of Maillard reaction, from arginine and glucose or maltose, respectively. However, very limited information is available about the effect of the structural difference between AF and AFG on various biological activities. This is the first report of the mode of action and effect of AF and AFG on the type 2 diabetes management related inhibition of postprandial hyperglycemia in vitro and in animal model. In our previous study, standards AF and AFG were chemically synthesized and in this study their inhibitory activities against rat intestinal α-glucosidases and porcine pancreatic α-amylase were investigated in vitro. The IC(50) value of the in vitro inhibitory activity of AF and AFG on rat intestinal sucrase was high and in similar levels (6.40 and 6.20 mM, respectively). Additionally, a mild pancreatic α-amylase inhibitory activity was observed, with IC(50) values 36.30 and 37.60 mM for AF and AFG, respectively. The effect of AF and AFG on the postprandial blood glucose increase after meal was investigated in Sprague Dawley rats fed on starch or sucrose meals. Both amadori compounds significantly reduced the postprandial blood glucose levels after starch or sucrose loading. These results indicate that AF and AFG, Maillard reaction products, may have antidiabetic effect by suppressing carbohydrate absorption in the gastrointestinal level, and thereby reducing the postprandial increase of blood glucose.

The entrocytes of the small intestine can only absorb monosaccharides such as glucose and fructose from our diet. The intestinal absorption of dietary carbohydrates such as maltose and sucrose is carried out by a group of α-glucosidases. Inhibition of these enzymes can significantly decrease the postprandial increase of blood glucose level after a mixed carbohydrate diet. Therefore, the inhibitory activity of Omija (Schizandra chinensis) extract against rat intestinal α-glucosidase and porcine pancreatic α-amylase were investigated in vitro and in vivo. The in vitro inhibitory activities of water extract of Omija pulp/skin (OPE) on α-glucosidase and α-amylase were potent when compared to Omija seeds extract (OSE). The postprandial blood glucose lowering effect of Omija extracts was compared to a known type 2 diabetes drug (Acarbose), a strong α-glucosidase inhibitor in the Sprague-Dawley (SD) rat model. In rats fed on sucrose, OPE significantly reduced the blood glucose increase after sucrose loading. Furthermore, the oxygen radical absorbance capacity (ORAC) of OSE and OPE was evaluated. OPE had higher peroxyl radical absorbing activity than OSE. These results suggest that Omija, which has high ORAC value with α-glucosidase inhibitory activity and blood glucose lowering effect, could be physiologically useful for treatment of diabetes, although clinical trials are needed.

The effects of chitosan-oligosaccharide (GO2KA1) on postprandial blood glucose levels in adults with normal blood glucose levels were investigated. Postprandial blood glucose levels were measured at 30, 60, 90, and 120 min after sucrose administration with and without 500 mg of GO2KA1. GO2KA1 administration reduced the area under the blood glucose-time curve (AUC) and the blood glucose peak (Cmax) values while the time of peak plasma concentration of blood glucose (Tmax) value was significantly (p

Brassica juncea var. integrifolia, known as mustard leaf, is used as a medicinal plant in Asia, however, knowledge for their health benefits is limited. Here, we evaluate the total phenolic contents, phenolic profile, and antioxidant activity of green and red mustard leaves (EG and ER, respectively). Additionally, the inhibitory activity of EG and ER against rat intestinal α‐glucosidase and porcine‐pancreatic α‐amylase were investigated. The total phenolic contents of EG and ER were 1,228.48 ± 36.81 and 850.75 ± 28.88mg/100 g, respectively. The total phenolic contents correlated to the observed antioxidant activities. ER had significant α‐glucosidase but low α‐amylase inhibitory activity. Using an Sprague‐Dawley‐Rat model, ER appeared to have better glucose‐lowering effect when compared to EG, after a sucrose‐loading test. This is the first report evaluating mustard leaves for potential glucose‐lowering effects. Our observations suggest that ER has better potential for this bioactivity and this observation possibly correlates with the sinigrin contents observed in both extracts. PRACTICAL APPLICATIONS: Mustard seeds are widely used for the production of food products and have been evaluated for their health benefits. Currently, mustard leaves are considered a low‐value by‐product of the mustard plant and are significantly underutilized. To support the sustainable utilization of mustard plant, it is important to initiate the utilization of mustard leaves. Value addition in mustard leaves through research efforts that define possible health benefits of this resource will significantly assist toward the possible utilization of this low‐value, underutilized raw material to produce high‐value, health beneficial, food ingredients.

Amino acid derivatives such as arginyl-fructosyl-galactose (AFL) are formed through Amadori rearrangement, the early step of Maillard reaction from arginine and lactose in daily foods. However, very limited information is available about the effect of AFL on various biological activities. This is the first report of the mode of action and effect of AFL on the type 2 diabetes management related inhibition of postprandial hyperglycemia in vitro and in animal model. The inhibitory activities against a-glucosidase and porcine pancreatic a-amylase were investigated in vitro and in vivo animal model. In in vitro study, AFL had a significant inhibition against rat intestinal a-glucosidase but showed mild inhibitory activity on porcine pancreatic alpha-amylase. In rat fed on starch or sucrose meals, AFL significantly reduced the postprandial blood glucose increment after starch or sucrose loading in a dose dependent manner. These results indicate that AFL has an anti-diabetic effect by suppressing carbohydrate ab...

We have previously reported that Amadori compounds exert anti-diabetic effects by lowering sucrose-induced hyperglycemia in normal Sprague-Dawley rats. In the present study we extended our recent findings to evaluate whether α-glucosidase inhibitor arginyl-fructose (AF) lowers blood glucose level in diabetic db/db mice, a genetic model for type 2 diabetes. The db/db mice were randomly assigned to high-carbohydrate diets (66.1% corn starch) with and without AF (4% in the diet) for 6 weeks. Changes in body weight, blood glucose level, and food intake were measured daily for 42 days. Dietary supplementation of AF resulted in a significant decrease of blood glucose level (p < 0.001) and body weight (p < 0.001). The level of HbA1c, a better indicator of plasma glucose concentration over prolonged periods of time, was also significantly decreased for 6-week period (p < 0.001). Dietary treatment of acarbose® (0.04% in diet), a positive control, also significantly alleviated the level of blood glucose, HbA1c, and body weight. These results indicate that AF Maillard reaction product improves postprandial hyperglycemia by suppressing glucose absorption as well as decreasing HbA1c level.

The aim of present study is to assess whether if basal insulin, glargine, could improve insulin secretory function of β-cells compared with glimepiride when metformin alone was failed. This was an open-label and multi-center study for 52 weeks in Korean patients with uncontrolled type 2 diabetes by metformin monotherapy. Subjects were randomized to glargine or glimepiride groups (n = 38 vs. 36, respectively). The primary endpoint was to compare changes in c-peptide via glucagon test after 48 weeks. Glycemic efficacy and safety endpoints (glycated hemoglobin (HbA1c), HOMA-B, fasting plasma glucose (FPG), lipid profiles, and hypoglycemic events) were also checked. The mean disease duration of all subjects was 88.2 months. Changes in C-peptide was no significant different between groups (P = 0.73), even though insulin secretion was not worsened in both groups at the endpoint. Glargine was not superior to glimepiride in other β-cell function indexes such as HOMA-B (P = 0.28). HbA1c and FPG reduced significantly in each groups but not different between two groups. Although, severe hypoglycemia did not occur, symptomatic hypoglycemia was more frequent in glimepiride group (P = 0.01). Insulin glargine was as effective as glimepiride in controlling hyperglycemia and maintaining β-cell function in Korean patients with type 2 diabetes during 48 weeks study period, after failure of metformin monotherapy. Hypoglycemic profile was favorable in the insulin glargine group and less weight gain was observed in the glimepiride group. Our results suggest that glargine and glimepiride can be considered after failure of metformin monotherapy.

This research investigated the effect of enzymatically digested low molecular weight (MW) chitosan oligosaccharide on type 2 diabetes prevention. Three different chitosan oligosaccharide samples with varying MW were evaluated in vitro for inhibition of rat small intestinal α-glucosidase and porcine pancreatic α-amylase (GO2KA1; 10,000 Da). The in vitro results showed that all tested samples had similar rat α-glucosidase inhibitory and porcine α-amylase inhibitory activity. Based on these observations, we decided to further investigate the effect of all three samples at a dose of 0.1 g/kg, on reducing postprandial blood glucose levels in Sprague-Dawley (SD) rat model after sucrose loading test. In the animal trial, all tested samples had postprandial blood glucose reduction effect, when compared to control, however GO2KA1 supplementation had the strongest effect. The glucose peak (Cmax) for GO2KA1 and control was 152 mg/dL and 193 mg/dL, respectively. The area under the blood glucose-time curve (AUC) for GO2KA1 and control was 262 h mg/dL and 305 h mg/dL, respectively. Furthermore, the time of peak plasma concentration of blood glucose (Tmax) for GO2KA1 was significantly delayed (0.9 h) compared to control (0.5 h). These results suggest that GO2KA1 could have a beneficial effect for blood glucose management relevant to diabetes prevention in normal and pre-diabetic individuals. The suggested mechanism of action is via inhibition of the carbohydrate hydrolysis enzyme α-glucosidase and since GO2KA1 (MW < 1000 Da) had higher in vivo effect, we hypothesize that it is more readily absorbed and might exert further biological effect once it is absorbed in the blood stream, relevant to blood glucose management.

Background Type 2 diabetes is a serious problem for developed and developing countries. Prevention of prediabetes progression to type 2 diabetes with the use of natural products appears to be a cost-effective solution. Zingiber mioga has been used as a traditional food in Asia. Recent research has reported the potential health benefits of Zingiber mioga, but the blood glucose reducing effect has not been yet evaluated. Methods In this study Zingiber mioga extracts (water and ethanol) were investigated for their anti-hyperglycemic and antioxidant potential using both in vitro and animal models. The in vitro study evaluated the total phenolic content, the oxygen radical absorbance capacity (ORAC) and the inhibitory effect against carbohydrate hydrolyzing enzymes (porcine pancreatic α-amylase and rat intestinal sucrase and maltase) of both Zingiber mioga extracts. Also, the extracts were evaluated for their in vivo post-prandial blood glucose reducing effect using SD rat and db/db mice models. Results Our findings suggest that the ethanol extract of Zingiber mioga (ZME) exhibited the higher sucrase and maltase inhibitory activity (IC50, 3.50 and 3.13 mg/mL) and moderate α-amylase inhibitory activity (IC50, >10 mg/mL). Additionally, ZME exhibited potent peroxyl radical scavenging linked antioxidant activity (0.53/TE 1 μM). The in vivo study using SD rat and db/db mice models also showed that ZME reduces postprandial increases of blood glucose level after an oral administration of sucrose by possibly acting as an intestinal α-glucosidase inhibitor (ZME 0.1 g/kg 55.61 ± 13.24 mg/dL) Conclusion The results indicate that Zingiber mioga extracts exhibited significant in vitro α-glucosidase inhibition and antioxidant activity. Additionally, the tested extracts demonstrated in vivo anti-hyperglycemic effects using SD rat and db/db mice models. Our findings provide a strong rationale for the further evaluation of Zingiber mioga for the potential to contribute as a useful dietary strategy to manage postprandial hyperglycemia.