Jijun Yang

Antioxidant Capacity of Different Fractions of Vegetables and Correlation with the Contents of Ascorbic Acid, Phenolics, and Flavonoids

The antioxidant capacity of different fractions of 17 vegetables were analyzed using ferric reducing antioxidant power assay (FRAP assay) after water and acetone extractions. The contents of ascorbic acid, phenolics, and flavonoids were determined and their correlations with FRAP value were investigated. The results showed that the peel or leaf fractions of vegetables were stronger than the pulp or stem fractions in antioxidant capacity based on total FRAP value. Lotus root peel was the highest and cucumber pulp the lowest in total FRAP value among the vegetable fractions analyzed. All water extracts were higher in FRAP value than the acetone extracts. The FRAP value was significantly correlated with the contents of ascorbic acid, phenolics, or flavonoids in water extracts, in which the phenolics contributed most based on multivariate regression analysis. We conclude that different vegetable fractions were remarkably different in antioxidant capacity. The phenolics are responsible mostly for the antioxidant capacity of vegetables in vitro.

Changes of metabolic profiles in urine after oral administration of quercetin in rats.

Quercetin has been studied extensively. However, its actions in vivo are not well understood. We investigated the overall metabolic changes in urine after oral quercetin administration in rats and try to provide useful information on the actions of quercetin in vivo. Rats were orally administered a single dose of quercetin aglycon (40 mg/kg body weight). Urine samples were collected and subjected to (1)H nuclear magnetic resonance (NMR)-based metabolomic analysis and high performance liquid chromatography-mass spectrometry (HPLC-MS). Significant changes of metabolic profiles were observed in urine after quercetin administration. Relative increase in the concentrations of choline, creatinine, dimethylglycine, hippurate, taurine, trimethylamine N-oxide and reduction in acetate, alanine, lactate were observed. The concentrations of citrate, 2-oxoglutarate and succinate increased in the 0-24h period after treatment and decreased thereafter. Some peaks assignable to quercetin metabolites were found in the aromatic regions of (1)H NMR spectra. HPLC-MS analysis identified quercetin, methyl quercetin, quercetin sulfate, quercetin monoglucuronide, and methyl quercetin monoglucuronide in urine after administration of quercetin. Our current findings indicate that quercetin behaves not only as an antioxidant, but also a modulator for some metabolic processes in vivo. The active forms of quercetin present in the biofluids must be investigated further.

Brazilian green propolis improves immune function in aged mice

Aging weakened innate and adaptive immunity both quantitatively and qualitatively. Some components in propolis could stimulate immune function in young animals or cultured immune cells in vitro. Few studies had been carried out in the aged. The present study was to evaluate the effects of Brazilian green propolis supplementation on the immunological parameters in aged mice. Eighty Kunming mice, aged 15–18 months, were randomly assigned to the control and three experimental groups supplemented with different doses (83.3, 157.4 and 352.9 mg/kg.bw respectively) of Brazilian green propolis. The experiment lasted for 4 weeks. Contents of total polyphenol, flavonoid, cinnamic acid and artepillin-C in Brazilian green propolis were analyzed. Splenic NK cytotoxic, T lymphocyte proliferation and antibody generation cells, as well as the phagocytosis of peritoneal macrophages, ear swelling, and serum contents of IgG, IgM, hemolysin and cytokines were measured. After 4 weeks of treatment, the phagocytosis of peritoneal macrophages was enhanced in 157.4 mg/kg and 352.9 mg/kg groups. Ear swelling increased in all propolis treatmented groups. Antibodies specific to sheep erythrocytes were higher in the groups receiving 157.4 and 352.9 mg/kg.bw than that of control group. IgG level dramatically increased in the groups receiving 83.3 and 157.4 mg/kg.bw in comparison to the control group. These results indicate that administration of Brazilian green propolis have a positive effect on innate and adaptive immunity in aged mice.

Cholesterol metabolism is modulated by quercetin in rats.

Quercetin has attracted much attention recently because of its antioxidant capacity and potential in the prevention of chronic degenerative diseases. However, its actions and the mechanisms involved are not completely understood. In this study, male Wistar rats were fed a diet containing 0.5% quercetin for 14 days. Serum samples were collected at the end of the experiment, and the overall serum metabolic profile was investigated by (1)H nuclear magnetic resonance (NMR)-based metabolomic analysis. Remarkable changes in the serum metabolic profile were manifested with the relative increase in the levels of lactate and low-density lipoprotein/very low-density lipoprotein (LDL/VLDL) and reduction in glucose, high-density lipoprotein (HDL), and some amino acids after quercetin exposure. Biochemical measurements confirmed that the serum low-density lipoprotein cholesterol (LDL-C) level was increased significantly after quercetin treatment. Our current findings indicate that quercetin can induce a remarkable change in cholesterol metabolism. Further studies are needed to investigate the molecular mechanisms and the possible links to the health effects or toxic actions of quercetin.

Necessity of Carnitine Supplementation in Semistarved Rats Fed a High-Fat Diet

We investigated the effects of carnitine supplementation on lipid metabolism in semistarved rats. The semistarved rats were fed a high-fat diet and half the normal energy intake for 2 wk. Carnitine was supplied daily at a dose of 250 mg/kg of body weight. The results showed that the concentration of plasma free carnitine increased significantly in semistarved and carnitine-supplemented rats compared with normal and semistarved rats. The activities of muscle carnitine palmitoyltransferase I and preheparin plasma lipoprotein lipase also were significantly increased in semistarved and carnitine-supplemented rats. The plasma triacylglycerol secretion rate was restored to normal by carnitine supplementation in semistarved rats. Urinary excretion of ketone bodies was reduced significantly after carnitine supplementation. We concluded that supplementation of carnitine can significantly increase the concentration of plasma free carnitine and improve lipid metabolism in semistarved rats fed a high-fat diet.

Quercetin alters energy metabolism in swimming mice

Quercetin has been demonstrated to be effective in increasing physical endurance in mice and humans. However, the mechanisms involved are not fully understood. In this study, male Kunming mice were fed a diet containing 0.1% quercetin for 14 days before swimming for 60 min. The overall serum metabolic profile was investigated by a ¹H nuclear magnetic resonance-based metabolomic approach. Serum glucose, lactate, nonesterified fatty acids (NEFA), and nonprotein nitrogen (NPN), as well as hepatic and muscular glycogen were measured biochemically. The results of metabolomic analysis showed that swimming induced a significant change in serum metabolic profile. Relative increases in the levels of lactate, alanine, low-density lipoprotein-very low-density lipoprotein, and unsaturated fatty acids, and decreases in choline, phosphocholine, and glucose were observed after swimming. With quercetin supplementation, these changes were attenuated. The results of biochemical assays were consistent with the data obtained from metabolomic analysis, in that serum NEFA was increased while lactate and NPN decreased after exposed to quercetin in swimming mice. Similar change in NEFA was also found in liver and gastrocnemius muscle tissues. Our current findings suggest that quercetin alters energy metabolism in swimming mice and increased lipolysis may contribute to the actions of quercetin on physical endurance.

Dietary quercetin supplementation increases serum antioxidant capacity and alters hepatic gene expression profile in rats.

The aim of this study was to determine the effect of quercetin on hepatic gene expression profile in rats. Twenty male Wistar rats were divided into the control group and the quercetin-treated group, in which a diet containing 0.5% quercetin was provided. After two weeks of feeding, serum and liver samples were collected. Biomarkers of oxidative stress, including serum ferric reducing antioxidant power (FRAP) values and levels of ascorbic acid, vitamin E (VE), glutathione (GSH) and malondialdehyde (MDA) were measured. The hepatic gene expression profile was examined using a microarray technique. The results showed that serum FRAP value, levels of ascorbic acid and VE were increased significantly, whereas serum levels of GSH and MDA were not changed significantly after quercetin supplementation. The microarray analysis revealed that some hepatic genes involved in phase 2 reaction, metabolism of cholesterol and homocysteine, and energy production were expressed differentially in response to quercetin administration. These findings provide a molecular basis for the elucidation of the actions played by quercetin in vivo.

Quercetin reduces serum homocysteine level in rats fed a methionine-enriched diet

OBJECTIVE The aim of this study was to determine the effects of quercetin on homocysteine (Hcy) metabolism and hepatic antioxidant status in high methionine (Met)-fed rats. METHODS Rats were fed for 6 wk the following diets: control, 1.0% Met, 1.0% Met and 0.1% quercetin, 1.0% Met and 0.5% quercetin, 1.0% Met and 2.5% quercetin-supplemented diets. Serum Hcy, Met, cysteine, serine, taurine, glutathione (GSH), quercetin and its metabolites, and activities of alanine transaminase (ALT) and aspartate transaminase (AST) were assayed. Hepatic malondialdehyde, GSH and carbonyls, and activity of superoxide dismutase and ferric-reducing antioxidant power also were measured. RESULTS Serum Hcy was increased significantly after Met treatment and decreased after quercetin supplementation. Meanwhile, serum taurine was increased and serine decreased. However, the content of GSH in serum and liver was decreased in the quercetin-supplemented groups and activities of serum ALT and AST were enhanced in the 1.0% Met and 2.5% quercetin-supplemented groups. CONCLUSIONS Quercetin is effective in decreasing serum Hcy level in high Met-fed rats and one of possible mechanisms is associated with increased transsulfuration of Hcy. Quercetin can acts as a prooxidant at high intake levels.

Metabolomic study on vitamins B1, B2, and PP supplementation to improve serum metabolic profiles in mice under acute hypoxia based on 1H NMR analysis.

OBJECTIVE To explore metabolic changes after acute hypoxia and modulating effect of vitamins B₁, B₂, and PP supplementation in mice exposed to acute hypoxia. METHODS Fifty male Kunming mice were randomly divided into 5 groups: normal, acute hypoxia, acute hypoxia with 2, 4 and 8 time-vitamins B₁, B₂, and PP supplementation. All mice were fed with corresponding diets for two weeks and then were exposed to a simulated altitude of 6,000 meters for 8 h, except for the normal group. Nuclear magnetic resonance analysis was used to identify the changes of serum metabolic profiles. RESULTS There were significant changes in some serum metabolites under induced acute hypoxia, essentially relative increase in the concentrations of lactate, sugar and lipids and decrease in ethanol. The serum levels of choline, succinate, taurine, alanine, and glutamine also increased and phosphocholine decreased in the acute hypoxia group. After vitamins B₁, B₂, and PP supplementation, all these metabolic changes gradually recovered. CONCLUSIONS Significant changes in serum metabolic profile were observed by metabolomics in mice exposed to acute hypoxia, and vitamins B₁, B₂, and PP supplementation proved to be beneficial to improving some metabolic pathways. It is suggested that the dietary intakes of vitamins B₁, B₂, and PP should be increased under hypoxia condition.