Occurrence of orally administered mulberry 1-deoxynojirimycin in rat plasma

1-deoxynojirimycin (DNJ), a potent glucosidase inhibitor, is a characteristic constituent of the mulberry leaf. Dietary mulberry DNJ may be beneficial for the suppression of abnormally high blood glucose levels, thereby preventing diabetes mellitus. Although there is considerable interest in the effects of mulberry DNJ, the intestinal absorption and pharmacokinetic profile of orally administered mulberry DNJ have never been characterized. In this study, we developed a method for determining the level of plasma DNJ by hydrophilic interaction chromatography coupled to a mass spectrometric detector (HILIC-MS) to investigate the absorption and metabolism of orally administered mulberry DNJ in rats. DNJ was separated from plasma extract on a TSK gel Amide-80 column, a representative column for HILIC. At postcolumn, DNJ was concurrently detected and identified by MS. The plasma DNJ concentration in fasted rats was below the detection limit [<1 microg (6 nmol)/mL]; however, the concentration reached a maximum [15 microg (92 nmol)/mL] 30 min after the administration of mulberry DNJ (110 mg/kg of body weight), and the DNJ concentration decreased rapidly thereafter. When the rats received different amounts of mulberry DNJ (1.1, 11, and 110 mg/kg of body weight), dose-dependent incorporation of DNJ into the plasma was confirmed. We did not detect any DNJ metabolites in the plasma. These findings indicate that orally administered mulberry DNJ is absorbed as an intact form from the alimentary tract and then is quickly excreted from the body. The developed HILIC-MS method could be applied in determining levels of DNJ in urine and tissues, and therefore, the method would be a powerful tool for studying the metabolic fate of mulberry DNJ as well as its bioavailability.     

Antihypertensive effects of Lactobacillus-fermented milk orally administered to spontaneously hypertensive rats

Products fermented with lactic acid bacteria may show antihypertensive effects via substances such as angiotensin I-converting enzyme inhibitor (ACEI) and γ-aminobutyric acid (GABA). It was previously found that milk fermented with Lactobacillus paracasei subsp. paracasei NTU 101 (101FM) or Lactobacillus plantarum NTU 102 (102FM) has ACEI and GABA activities. This study aimed to investigate the antihypertensive effects of 101FM and 102FM orally administered to spontaneously hypertensive rats (SHRs). Eight hours after a single oral administration or after 8 weeks of weekly (chronic) administration, 101FM and 102FM significantly decreased systolic and diastolic blood pressures in the SHRs. Microscopic examination of aortic tissue demonstrated that 101FM and 102FM reduced the disorganization of the media layer. These findings suggest that orally administered 101FM and 102FM have antihypertensive effects, possibly via ACEI and GABA activity, in SHRs. Therefore, 101FM and 102FM may be useful ingredients in physiologically functional foods to prevent hypertension.     

Automated fluorometric determination of vitamin C in foods.

Two automated fluorometric methods were compared with the official AOAC methods for determining vitamin C in fortified ready-to-eat cereals, fruits, vegetables, baby foods, flour products, pet foods, meats, frozen dinners, juices, and nutritional health bars. Each sample was analyzed in duplicate on 2 days and included a recovery study on all products. Egberg's semiautomated method (Method 1) and Roy's automated method (Method 2) were compared with the manual AOAC tritrimetric and fluorometric methods. The correlation factor for Methods 1 and 2 were 0.999 and 0.979, respectively, when compared with the AOAC methods. The recovery study showed average recoveries of 97.8% for Method 1, 99.3% for Method 2, and 100.6% for the AOAC methods. The results suggest that Method 1 is the method of choice for the majority of the products analyzed.     

Combination of lipids and emulsifiers enhances the absorption of orally administered quercetin in rats

The effects of lipids, emulsifiers, and ethanol on the absorption of orally administered quercetin in rats were investigated for its efficient intestinal absorption. Rats were administered 150 micromol/kg quercetin in water supplemented with lipids and/or emulsifiers, or ethanol, and blood was collected from the tail for 6 h after administration. Co-administration of lipids such as lecithin and soybean oil or emulsifiers including sucrose fatty acid ester, polyglycerol fatty acid ester, and sodium taurocholate had no statistically significant effects on quercetin absorption, although these constituents rather increased the accumulation of conjugated forms of quercetin and those of isorhamnetin in rat plasma. However, the combination of lipids and emulsifiers enhanced the absorption of quercetin significantly. Thirty and fifty percent (v/v) of the ethanol in the vehicle raised the efficiency of quercetin absorption in a concentration-dependent manner. Quercetin absorption-enhancing effects of these constituents seemed to be affected by quercetin's solubility in respective vehicles used for the administration. Ethanol is not helpful for the effective absorption of quercetin, as a high concentration is required. In conclusion, a combination of lipids and emulsifiers is necessary for enhancing quercetin absorption.     

Automated analysis of vitamin C in pharmaceutical products.

The determination of total vitamin C in the form of both l-ascorbic acid (AA) and dehydroascorbic acid (DHAA) present in pharmaceutical preparations has been automated. Total vitamin C (completely oxidized to DHAA) was determined by reaction with 2,4-dinitrophenylhydrazine while blanks utilized the same reagent after reducing all DHAA to AA. The automated method was applicable to a variety of multivitamin preparations including those containing iron and copper. The mean recovery of L-ascorbic acid added to 11 multivitamin preparations was 99.4% with a coefficient of variation of 2.5%. In the analysis of these products, results obtained by the automated method were essentially the same as those obtained by the original manual method. For preparations containing no copper salts, the results were also comparable to those obtainable by titration with 2,6-dichloroindophenol except in 1 product which contained some DHAA.     

Some effects of replacement of metaphosphoric acid/acetic acid solvent system with trichloroacetic acid in microfluorometric determination of vitamin C

Trichloroacetic acid (TCA) is suggested as a substitute for the metaphosphoric acid/acetic acid (HPO3-HOAc) solvent system in the AOAC microfluorometric determination of vitamin C. Comparative advantages of TCA are easier handling, greater stability, and the approximate 10-fold increase in sensitivity. For both solvent systems, the influence of acid concentration on fluorescence is described. TCA provides maximum fluorescence enhancement at pH 5.5-6.0.     

Identification and quantification of the conjugated metabolites derived from orally administered hesperidin in rat plasma

Hesperidin is a biologically effective flavonoid. Several studies have reported that dietary hesperidin was converted to conjugated metabolites, such as hesperetin-glucuronides and sulfoglucuronides, during absorption and metabolism. However, the chemical structures of the conjugated metabolites, especially the sites of glucuronidation and sulfoglucuronidation in plasma, were unconfirmed. Therefore, the concentrations of the metabolites conjugated at various sites in plasma could not be individually quantified. In the present study, we identified the chemical structures and concentrations of the major conjugated metabolites in rat plasma after oral administration of hesperidin. Two hesperetin-glucuronides were prepared and identified as hesperetin-7-O-beta-D-glucuronide and hesperetin-3'-O-beta-D-glucuronide. Using these authentic compounds, the concentrations of hesperetin-7-O-beta-D-glucuronide and hesperetin-3'-O-beta-D-glucuronide in rat plasma were individually determined by liquid chromatography-mass spectrometry. In rat plasma, hesperetin-glucuronides were primarily comprised of hesperetin-7-O-beta-D-glucuronide and hesperetin-3'-O-beta-D-glucuronide. The concentration of hesperetin-7-O-beta-D-glucuronide was slightly higher than that of hesperetin-3'-O-beta-D-glucuronide. Furthermore, not only hesperetin conjugates but also homoeriodictyol conjugates were observed in rat plasma. The present study is the first report elucidating the chemical structures and changes in individual concentrations in rat plasma of glucuronides derived from orally administered hesperidin.     

The fate of trans-caftaric acid administered into the rat stomach

trans-Caftaric acid is the most abundant nonflavonoid phenolic compound in grapes and wines. It occurs in chicory and is one of the bioactive components of Echinacea purpurea. In order to fill the gap of knowledge about its bioavailability in mammals, we investigated its absorption, tissue distribution, and metabolism in rats. Assuming that the stomach is a relevant site of absorption of dietary polyphenols, a solution of trans-caftaric acid was maintained in the ligated stomach of anaesthetized rats for 20 min. Intact trans-caftaric acid was detected in rat plasma at both 10 and 20 min (293 +/- 45 and 334 +/- 49 ng/mL, respectively), along with its O-methylated derivative trans-fertaric acid, whose concentration rose over time (from 92 +/- 12 to 185 +/- 24 ng/mL). At 20 min, both trans-caftaric acid and trans-fertaric acid were detected in the kidney (443 +/- 78 and 2506 +/- 514 ng/g, respectively) but not in the liver. Only trans-fertaric acid was found in the urine (33.3 +/- 12.8 microg/mL). In some rats, trans-caftaric acid was detected in the brain (180 +/- 20 ng/g).     

Effects of low aluminum activity in nutrient solutions on the organic acid concentrations in maize plants

The effects of low aluminum (Al) activity in nutrient solution on the concentrations of organic acids in two cultivars of maize (Zea mays L.), HS7777 Al‐sensitive and C525‐M Al‐tolerant, were studied. Aluminum stress increased total organic acid concentration in the roots and in the shoots for both cultivars. The relative increase of t‐aconitic, citric, formic, malic, and quinic acids was higher in the roots than in the shoots for both cultivars. The concentrations of c‐aconitic, isocitric, malonic, oxalic, and succinic organic acids were reduced by Al stress, principally for C525‐M. There were no consistent differences in organic acid concentrations between the cultivars to discriminate Al tolerance. The Al tolerance for C525‐M may be justified by lower Al concentrations in the root tips where cellular division takes place and/or by higher excretion of organic acids from roots to the rhizosphere for detoxification of Al by chelation.     

红枣汁中维生素C热降解的动力学研究(简报)

为了了解加热温度对红枣汁中维生素C含量变化的影响,降低红枣汁在加工过程中维生素C的损失,该文以红枣澄清汁为材料,采用可逆的一级反应模型研究了不同加热温度下还原型维生素C（AA）的降解规律并推导出氧化型维生素C（DHAA）含量变化的数学模型。在此基础上利用Arrhenius 方程计算得到AA和DHAA的降解反应活化能。结果表明,在303,313,323,333,343 K温度条件下,可逆的一级反应模型适用于表达红枣汁中AA的降解规律,非线性回归决定系数r2均大于0.98。DHAA的数学模型也能较好地预测DHAA在红枣汁中的含量变化规律。在不同的加热温度下,AA与DHAA均能发生降解反应,但DHAA的降解速率较AA低,DHAA 的降解主要发生在AA 的降解反应达到平衡之后。AA热降解反应活化能较低,表明红枣汁中的AA对热处理较敏感。该研究为优化红枣汁的加工工艺、提高红枣汁的品质提供理论依据。     

Rapid determination of polyphenols and vitamin C in plant-derived products

Polyphenols, widely spread in our diet by the consumption of plant food products, are commonly determined using Folin-Ciocalteu reagent that interacts with other different reducing nonphenolic substances and leads to an overestimation of polyphenol content. In this paper we report an optimized Folin-Ciocalteu method to specifically determine the contents of total polyphenols and vitamin C. After the optimal conditions for the colorimetric assay were set, solid-phase extraction (Oasis HLB (hydrophilic-lipophilic balance)) was carried out to eliminate the water-soluble reducing interferences including vitamin C. Colorimetric correction was thus performed by subtracting interfering substances contained in the water washing extract from the raw extract. Moreover, vitamin C present in the water washing extract can be destroyed by heating and thus colorimetrically deduced. This procedure was set up with synthetic solutions and validated on different extracts from fruit products.