To clarify the suppression of postprandial blood glucose rise via a a-glucosidase (AGH) inhibitory action by natural compounds, propolis was examined in this study. A single oral administration of propolis extract (50% methanol fraction on XAD-2 column chromatography) in Sprague-Dawley rats demonstrated a potent antihyperglycemic effect with the significant AUC 0-120 min reduction of 38% at a dose of 20 mg/kg compared to that of controls. Among the active compounds isolated from the fraction, 3,4,5-tri-caffeoylquinic acid was found to be a prominent candidate that exerts the effect and shows a strong maltase-specific inhibition with an IC 50 value of 24 m mM. In addition, the noncompetitive inhibition power apparently increased with the number of caffeoyl groups bound to quinic acid.

Dietary factors such as taste and nutrients are known to affect satiety and energy balance. We hypothesized that food texture might contribute to the regulation of energy metabolism through the process of mastication in the oral cavity as well. The effects of long-term feeding of different-textured pellets on body weight gain, adiposity, and thermogenesis were assessed. From weaning at 4 wks, rats were divided into 2 groups fed on either standard (controls) or soft pellets (soft-fed) that required less chewing with the same nutritional composition. At 26 wks, the soft-fed rats showed greater adiposity than did the controls. Daily food intake did not differ between the 2 groups. The increase in body temperature following feeding was significantly lower in the soft-fed rats. These results suggested that food texture affected energy metabolism by changing post-prandial thermogenesis. The long-term deficiency of thermogenesis associated with soft foods resulted in a greater tendency toward obesity.

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Both the ventromedial hypothalamus (VMH) and the mesencephalic trigeminal sensory nucleus (Me5) are densely innervated by histaminergic neurons. The depletion of neuronal histamine (HA) from the Me5 by the bilateral microinfusion of 448 nmol/rat alpha-fluoromethylhistidine (FMH), a specific suicide inhibitor of histidine decarboxylase, reduced the eating speed and prolonged meal duration, while leaving the meal size unaffected. HA depletion from the VMH increased the size of the meal and prolonged its duration, but not the eating speed. When the HA turnover rate was measured at 15 min after the scheduled feeding following fasting for less than 24 hr, the rate increased in the region including the Me5, but not in the hypothalamus. The turnover rate reached higher levels at 60 min in both regions. Gastric intubation of an isocaloric liquid diet or an equivolume of water with the liquid diet abolished the increase in HA turnover both in the Me5 region and the hypothalamus. The present findings indicate that brain HA thus modulates satiation through both the VMH and masticatory function as well as due to the action of the Me5. The HA function activated by mastication began earlier in the Me5 and later in the hypothalamus due to a signal originating from the oral proprioceptors and initiated by chewing.

Four Nigerian medicinal plants used for the treatment of various ailments in traditional ethnomedicine were evaluated for their anti-diabetic potential. The plants Irvingia gabonensis (O'Rorke) Bail, Eucalyptus torreliana F.v. Muell, Securidata longependuculata Fers and Murraya paniculata (L.) Jack were used in the study. Only the aqueous extract of I. gabonensis exhibited a potent maltase-inhibitory activity with an IC/* of *.+* mg/mL, as well as a sucrase-inhibitory activity (IC/* of *.++ mg/mL), whereas a-amylase inhibitory activity was quite poor (IC/* of *./-mg/mL). A significant lowering of the blood glycemic response to maltose ingestion in 2-week old Sprague-Dawley rats was observed at a dose of-** mg/kg, in response to significant reduction in postprandial insulin response level.

The content of synephrine, an adrenergic phenethylamine, was determined by high performance liquid chromatography (HPLC) in Shiikuwasha (Citrus depressa, Hayata) plant material (flesh and peel) during fruit development, as well as in 45 species and cultivars of Citrus genus. HPLC conditions were as follows: column, Develosil ODS-5; mobile phase, acetonitrile-H 2 O (2:98)-10 mM phosphoric acid and flow rate, 0.8 mL/min. In the extraction of synephrine from the sample citrus peel, a large quantity of synephrine was detected in water (100%) while no synephrine was found in the methanol extract (more than 60% concentration of methanol). Synephrine content in the peels during Shiikuwasha fruit development was gradually decreased to half the amount in January compared with that in August. Synephrine was detected in 30 of the 45 species and cultivars of Citrus genus, and was mainly found in the samples of Aurantium and Acrumen sections according to Tanaka's classification.

To evaluate the duration of antihyperglycemic effects of 6-O-caffeoylsophorose (CS), a newly identified natural α-glucosidase inhibitor from fermented purple-sweet potato, a single oral administration of CS was given to maltose-loaded Sprague-Dawley rats. Administration of CS (200 mg/kg) 30 min or 60 min before maltose administration produced an elevation of blood glucose level by administration of 2 g/kg of maltose in rats that was significantly lower than for no administration (control). In contrast, simultaneous or pro-administration of CS with maltose eliminated the antihyperglycemic effect. CS significantly reduced rat intestinal α-glucosidase activity in all of the small intestinal mucosal regions with a maximal reduction ratio of ca. 40% up to 60 min after CS administration. Thereafter, the intestinal α-glucosidase activity tended to return to basal level. These findings suggest that the antihyperglycemic effect of CS is restricted to pre-administration within 60 min.Keywords: α-glucosidase, caffeoylsophorose, antihyperglycemic effect, diabetes *To whom correspondence should be addressed. Email: tfujise@nakamura-u.ac.jp IntroductionAnthocyanins, one of the families of polyphenol compounds found in fruits and plants, are valued for their beneficial health effects. Pharmacologically, anthocyanins are reputed to be antimutagenic (Yoshimoto et al., 2001) and to have antioxidative effects (Oki et al., 2002). Crude anthocyanin extract of Ipomoea batatas cv Ayamurasaki has also been demonstrated to have considerable antihyperglycemic effect in Sprague Dawley (SD) rats (Matsui et al., 2002). In our previous reports, (Matsui et al., 2001a;Matsui et al., 2001b;Matsui et al., 2002) the main compounds showing antihyperglycemic effects in the extract were found to be acylated anthocyanins, both of which possess α-glucosidase (AGH, EC 3.3.1.20) inhibitory activity: YGM-3 (Cyanidin; 3-O-(2-O-(6-O-E-feruloyl-β-D-glucopyranosyl)-6-O-Ecaffeoyl-β-D-glucopyranoside)-5-O-β-D-gluconopyranoside) and YGM-6 (Peonidin; 3-O-(2-O-(6-O-E-feruloyl-β-D-glucopyranosyl) -6-O-E-caffeoyl-β-D-glucopyranoside)-5-O-β-D-gluconopyranoside).Further study regarding the structure-AGH inhibition relationship revealed that the acylated moieties (e.g., 6-O-E-caffeoyl-β-D-glucopyranoside) were responsible for eliciting AGH inhibition (Matsui et al., 2001b; Terahara et al., 2003). 6-O-Caffeoylsophorose (CS), which is a constituent of YGM-3 and YGM-6, was successfully produced by fermentation of purple-fleshed sweet potato and was identified for the first time as a natural compound and proven to be a potent AGH inhibitor Terahara et al., 2003).Recently, AGH inhibitors have attracted much attention as being effective drugs for noninsulin-dependent diabetes mellitus (NIDDM), as they can suppress or delay excessive postprandial elevation of blood glucose level (BGL) without promoting insulin secretion. In addition, the effective use of long-term therapeutic drug acarbose treatment in the prevention of NIDDM was reported (Chiasson et al., 2002). Clinical ...

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