Kunihisa Iwai

Antioxidant activity and inhibitory effect of Gamazumi (Viburnum dilatatum THUNB.) on oxidative damage induced by water immersion restraint stress in rats

The antioxidant activity and antiulcer effects of Gamazumi (Viburnum dilatatum THUNB.) fruit squeezing solution (GSS) were investigated. GSS including no antioxidant additive showed strong antioxidant activity by the XYZ-dish method and the electron spin resonance (ESR) method. GSS showed to have no negative effect on growth of rats for 2 weeks of feeding with free access to GSS. After feeding, the GSS group showed a significant inhibitory effect on gastric ulcer formation by water immersion restraint stress for 6 hours compared with the Water group. Plasma, liver and stomach concentrations of lipid peroxide in the GSS group were reduced rather than the water group. Furthermore, the activities of plasma lactic dehydrogenase, amylase and creatine phosphokinase are ordinarily increased by stress; however these activities in the GSS group decreased to the level in the Control group having no stress. The physiological effects of GSS were similar to, or higher than, those of 0.1% (-)-epigallocatechin gallate (EGCg) solution. These effects of EGCg and GSS were similar to the order of antioxidant activity against hydroxyl radical found by both the XYZ-dish and the ESR methods. It was concluded that after ingestion of GSS, during the period of strong antioxidant activity in the body, it could prevent stress-induced oxidative damage.The antioxidant activity and antiulcer effects of Gamazumi (Viburnum dilatatum THUNB.) fruit squeezing solution (GSS) were investigated. GSS including no antioxidant additive showed strong antioxidant activity by the XYZ-dish method and the electron spin resonance (ESR) method. GSS showed to have no negative effect on growth of rats for 2 weeks of feeding with free access to GSS. After feeding, the GSS group showed a significant inhibitory effect on gastric ulcer formation by water immersion restraint stress for 6 hours compared with the Water group. Plasma, liver and stomach concentrations of lipid peroxide in the GSS group were reduced rather than the water group. Furthermore, the activities of plasma lactic dehydrogenase, amylase and creatine phosphokinase are ordinarily increased by stress; however these activities in the GSS group decreased to the level in the Control group having no stress. The physiological effects of GSS were similar to, or higher than, those of 0.1% (-)-epigallocatechin gallate (EGCg) solution. These effects of EGCg and GSS were similar to the order of antioxidant activity against hydroxyl radical found by both the XYZ-dish and the ESR methods. It was concluded that after ingestion of GSS, during the period of strong antioxidant activity in the body, it could prevent stress-induced oxidative damage.

Chronic ingestion of apple pectin can enhance the absorption of quercetin.

The effect of apple pectin (AP) on quercetin and rutin bioavailability was investigated. Rats received a basal (control) or AP-containing diet for 6 weeks followed by orally administered quercetin or rutin. With quercetin administration, the maximum concentration and area under the curve of concentration-time from 0 to 24 h for the sum of quercetin metabolites in the plasma were significantly higher in AP-fed rats than in the control group. However, AP did not significantly affect rutin bioavailability. The crypt depth of the jejunum and ileum and the villus thickness of the ileum of AP-fed rats were significantly greater than those of control rats. These results demonstrate that chronic AP ingestion enhances intestinal absorption of quercetin. This increase in quercetin absorption might be attributed to alteration of the absorptive capacity of the small intestine through AP-induced improvement of its morphological and physiological properties.

Simultaneous ingestion of high-methoxy pectin from apple can enhance absorption of quercetin in human subjects

Chronic ingestion of apple pectin has been shown to increase the absorption of quercetin in rats. The present study was designed to elucidate whether the simultaneous ingestion of quercetin with apple pectin could enhance the absorption of quercetin in humans, and the effects of dose dependency and degree of pectin methylation on quercetin absorption were also investigated. Healthy volunteers (n 19) received 200 ml of 0.5 mg/ml of quercetin drinks with or without 10 mg/ml of pectin each in a randomised cross-over design study with over 1-week intervals; urine samples from all the subjects were collected within 24 h after ingestion of the test drinks, and urinary deconjugated quercetin and its metabolites were determined using HPLC. The sum of urinary quercetin and its metabolites excreted was increased by 2.5-fold by the simultaneous ingestion of pectin. The metabolism of methylated quercetin (isorhamnetin and tamarixetin) was not affected by pectin ingestion. In six volunteers, who received quercetin drinks containing 0, 3 and 10 mg/ml of pectin, the sum of urinary quercetin and its metabolites excreted also increased in a pectin dose-dependent manner. Furthermore, the simultaneous ingestion of quercetin with low-methoxy and high-methoxy pectin, respectively, increased the sum of urinary excretion of quercetin and its metabolites by 1.69-fold and significantly by 2.13-fold compared with the ingestion of quercetin without pectin. These results elucidated that apple pectin immediately enhanced quercetin absorption in human subjects, and that its enhancing effect was dependent on the dose and degree of pectin methylation. The results also suggested that the viscosity of pectin may play a role in the enhancement of quercetin absorption.