Mahinur Bakri

beneficial effects of inhibition of soluble epoxide hydrolase on glucose homeostasis and islet damage in a streptozotocin-induced diabetic mouse model

Soluble epoxide hydrolase (sEH) is an enzyme involved in the metabolism of endogenous inflammatory and anti-apoptotic mediators. In the present study, we determined the effects of the inhibition of sEH on glucose homeostasis and islet damage in mice treated with streptozotocin (STZ), a model of chemical-induced diabetes. STZ increased daily water intake and decreased visceral (spleen and pancreas) weight in mice; sEH inhibition in STZ mice decreased water intake, but did not affect visceral weight. Hyperglycemia induced by STZ treatment in mice was attenuated by inhibiting sEH. The beneficial effects of sEH inhibition were accompanied, after 2 and 4 weeks of initial administration, by improving glucose tolerance. In contrast, sEH inhibition did not affect insulin tolerance. Using LC/MS analysis, neither STZ nor STZ plus sEH inhibition affected pancreatic and plasma ratios of epoxyeicosatrienoic acids (EETs) to dihydroxyeicosatrienoic acids (DHETs), an index of EETs levels. Western blot analysis showed that mouse cytochrome P450 (CYP) 2C enzymes are the major epoxygenases in islets. On day 5 after initial STZ treatment, STZ induced islet cell apoptosis, while sEH inhibition in STZ mice significantly reduced islet cell apoptosis. These studies provide pharmacological evidence that inhibiting sEH activity provides significant protection against islet β-cell damage and improves glucose homeostasis in STZ-induced diabetes.

A LC/QTOF-MS/MS Application to Investigate Chemical Compositions in a Fraction with Protein Tyrosine Phosphatase 1B Inhibitory Activity from Rosa Rugosa Flowers

INTRODUCTION Rosa rugosa flowers used as herbal medicine possess many activities. A fraction extracted by ethyl acetate exhibited strong inhibitive activity against protein tyrosine phosphatase 1B (PTP1B) in vitro. OBJECTIVE Establish an efficient method of LC coupled to quadrupole time-of-flight (QTOF) with tandem MS/MS to investigate the compositions in the active fraction. METHODS Chemical compositions were separated and investigated by LC/QTOF-MS/MS in negative electrospray ionisation (ESI) mode at different collision energy (CE) values. The maximal structural information was obtained for the identification of components. RESULTS A total of 75 compounds including tannins, their related compounds and flavonoids were identified or partially characterised according to accurate mass and the characteristic fragments at low and high CE. Meanwhile, the fragmentation pathways of gallotannins and ellagitannins (hexahydroxydiphenoyl group and lactonised valoneoyl group) were studied and proposed and were used to trace tannins in crude extracts. CONCLUSION The results suggest that this fraction is a source of PTP1B inhibitory activity with a potential for treating diabetes.

Vasorelaxant and hypotensive effects of a hydroalcoholic extract from the fruits of Nitraria sibirica Pall. (Nitrariaceae).

ETHNOPHARMACOLOGICAL RELEVANCE Fruits of Nitraria sibirica Pall. are traditionally used in Uighur medicine to treat hypertension. This study aimed to support that folk use by defining their vasoactive and hypotensive properties. MATERIALS AND METHODS The vasorelaxant activity and the underlying mechanisms of a hydroalcoholic extract from the fruits of Nitraria sibirica Pall. (NSHE) were evaluated on thoracic aortic rings isolated from Wistar rats. In addition, the acute hypotensive effect of NSHE was assessed in anesthetized spontaneously hypertensive rats (SHR) and in their normotensive control Wistar Kyoto (WKY) rats. RESULTS NSHE (0.1-10 g/l) was clearly more effective to induce vasodilation of phenylephrine- (PE, 1 μM) than high KCl- (60mM) pre-contracted aortic rings with respective E(max) values of 82.9±2.2% and 34.8±3.6%. The removal of endothelium almost abolished the relaxant effect of the extract. In addition, pre-treatment with N(w)-nitro-L-arginine-methyl ester (L-NAME, 100 μM), atropine (1 μM) or charybdotoxin (30 nM) plus apamin (30 nM), respective blockers of nitric oxide (NO) synthase, muscarinic receptors and endothelium-derived hyperpolarizing factor (EDHF), significantly reduced the observed effect of NSHE. By contrast, the cyclooxygenase (COX) inhibitor indomethacin (10 μM) or the K(+) channels blockers glibenclamide (10 μM), iberiotoxin (30 nM) and 4-amino-pyridine (4-AP, 1 mM) failed to modify the vasodilation. Finally, the acute intravenous injection of NSHE (1, 5, 10, 20 mg/kg) induced an immediate and transient hypotensive effect in anesthetized SHR and in WKY rats. CONCLUSIONS This experimental animal study suggests that hydroalcoholic extract from the fruits of Nitraria sibirica Pall. induces vasorelaxation through an endothelium-dependent pathway involving NO synthase (NOS) activation, EDHF production and muscarinic receptor stimulation. Additionally, our results determine that this vasorelaxant effect is translated by a significant hypotensive effect.

Separation and purification of two new and two known alkaloids from leaves of Nitraria sibirica by pH-zone-refining counter-current chromatography.

The total alkaloids from Nitraria sibirica leaves have been confirmed to exhibit significant protective effects against inflammatory renal injury, hypertension and albuminuria in angiotensin II-salt hypertension. In the present study, a separation method of pH-zone-refining counter-current chromatography was established for separation of the alkaloids from N. sibirica. The separation was performed with a solvent system of MtBE-n-BuOH-H2O (2:2:5, v/v) at a flow rate of 2.0mL/min. And 15mM triethylamine (TEA) was added to the upper organic phase, while 10mM hydrochloric acid was added to the lower aqueous phase. As a result, a new alkaloid, schobemine (5.6mg), and a known alkaloid, nitraramine (5.0mg), together with fractions A and B were obtained from the total alkaloids of N. sibirica. The fractions A and B were further purified by means of pH-zone-refining counter-current chromatography with solvent systems of n-hexane-n-BuOH-H2O (1.5:3.5:5, v/v) and (2:3:5, v/v), respectively. TEA (10mM) was added to the upper phase, and 10mM of HCl was added to the lower phase in above two solvent systems, respectively. As a result, a known alkaloid, schoberidine (5.0mg), and a new alkaloid, schoberimine (3.0mg) were obtained from fractions A and B, respectively. The purities of the compounds were measured by HPLC-ELSD, and their structures were identified by ESI-MS, 1D and 2D NMR.

SEPARATION OF (S)-DEHYDROVOMIFOLIOL FROM LEAVES OF NITRARIA SIBIRICA PALL. BY HIGH-SPEED COUNTER-CURRENT CHROMATOGRAPHY

An effective high-speed countercurrent chromatography (HSCCC) method was established for separation and purification of (S)-dehydrovomifoliol from the leaves of Nitraria sibirica Pall. (NS). HSCCC was performed with a two-phase solvent systems composed of n-hexane-ethyl acetate-methanol-water (1:5:1:5, v/v) at a flow rate of 2 mL/min. From 1 g crude sample of NS, 23 mg (S)-dehydrovomifoliol was obtained at purity of 95%. The chemical structure was confirmed by MS, 1H NMR, and 13C NMR. (S)-dehydrovomifoliol was isolated from Nitraria genus for the first time.An effective high-speed countercurrent chromatography (HSCCC) method was established for separation and purification of (S)-dehydrovomifoliol from the leaves of Nitraria sibirica Pall. (NS). HSCCC was performed with a two-phase solvent systems composed of n-hexane-ethyl acetate-methanol-water (1:5:1:5, v/v) at a flow rate of 2mL/min. From 1g crude sample of NS, 23mg (S)-dehydrovomifoliol was obtained at purity of 95%. The chemical structure was confirmed by MS, 1H NMR, and 13C NMR. (S)-dehydrovomifoliol was isolated from Nitraria genus for the first time.

Alkaloids of Nitraria sibirica Pall, decrease hypertension and albuminuria in angiotensin II-salt hypertension

In traditional Chinese medicine, Nitraria sibirica Pall. (Nitrariaceae) is used to treat hypertension. This study determined the effects of the total alkaloids of the leaves of Nitraria sibirica (NSTA) on blood pressure and albuminuria in mice treated with angiotensin II and a high-salt diet (ANG/HS). Adult mice were divided into three groups: control; infused with angiotensin II and fed a diet containing 4% NaCl (ANG/HS; and ANG/HS plus injection of NSTA (1 mg·kg(-1)·d(-1), i.p.). After treatment of these regimens, daily water and food intake, kidney weight, blood pressure, urinary albumin excretion, renal concentrations of inflammatory markers, including soluble intercellular adhesion molecule-1 (sICAM-1) and monocyte chemoattractant protein-1 (MCP-1), and the expression of renal fibrosis markers were determined. Compared to the control group, the ANG/HS group had higher blood pressure and urinary albumin excretion. Treatment with NSTA in ANG/HS mice for three weeks significantly reduced blood pressure and urinary albumin excretion. ANG/HS treatment caused elevated levels of sICAM-1 and MCP-1, as well as increased fibrosis markers. Concurrent treatment with ANG/HS and NSTA attenuated the levels and expression of renal inflammatory and fibrosis markers. Treatment with NSTA effectively reduces hypertension-induced albuminuria through the reduction of renal inflammatory and fibrosis markers.

Determination of total polyphenols in tea by a flow injection-fiber optic spectrophotometric system

ABSTRACT A flow injection-fiber optic spectrophotometric system was established for the online determination of total polyphenol content in tea samples. The method was based on the chromogenic reaction between the phenolic compounds (gallic acid) and ferrous tartrate which was used as the colorimetric reagent and the absorption was determined at the maximum absorption wavelength of 540 nm at 20°C and pH 7.5. The calibration curve from standard solutions of gallic acid was linear in the range from 0.010 to 0.100 mg/mL with a correlation coefficient of 0.9970. The relative standard deviation of polyphenol measurements for eight tea samples was between 0.55 and 3.18%. It can be concluded that the proposed method has allowed simple, fast, and accurate determination of total polyphenol content in tea products.

In Situ Liquid-Phase-Adsorption Measurement System Based on Fiber-Optic Sensing with the Aid of Membranes

At present, liquid phase adsorption (LPA) is still being quantitatively characterized in the way of manual sampling and off-line determination because of the complexity of the system comparing to gas adsorption. This paper describes a novel method for in situ, real-time measurement of LPA in general based on fiber-optic sensing (FOS) with the aid of membranes for the first time. A self-made measurement vessel was assembled from an adsorption bag, thermostatic devices with a stirrer, and a fiber-optic dipping probe. Also, macroporous adsorption resins (MARs) and rutin were chosen as model adsorbent and adsorbate to establish the FOS system. Here, in situ light absorption measurement was achieved by eliminating interference of adsorbent particles via encapsulating them with a membrane into the adsorption bag. In situ LPA measurement of rutin solution on MARs was obtained by detecting light absorption at 353 nm using dipping probe, in the broad concentration range from 0.3 to 60 mg/L with excellent linearity (R2 = 0.9996). In situ measurements of adsorption and desorption kinetics on five kinds of MARs with different polarities were systematically carried out, showing that the adsorption process obeyed the pseudo-second-model. As well as, the system was proved to be highly accurate and reproducible. More importantly, this method enabled to study the initial stage of the adsorption process, starting from the time of the first second, which is the most important part in the adsorption kinetics, and this is impossible for traditional sampling methods. The successful application of FOS to in situ measurement of LPA not only contributes to fast, automatic, and real-time monitoring of LPA process but also enriches the research connotation of adsorption.

Biological activity and LC-MS profiling of ethyl acetate extracts from Nitraria sibirica (Pall.) fruits

Abstract Nitraria sibirica is a traditional Uighur medicine. This study was undertaken to investigate the bioactivity of N. sibirica fruit extract and to evaluate their chemical compositions. The ethyl acetate extract from N. sibirica fruits exhibited the potential antioxidant activity (SC50 = 30.17 ± 0.06 μg/mL) and protein tyrosine phosphatase 1B inhibitory activity (IC50 = 7.15 ± 0.03 μg/mL) in vitro. In order to investigate the active constituents in this extract, a LC-QTOF-MS/MS method was developed and established. A total of 28 compounds including seven cinnamic acids, nine benzoic acids and 12 flavonoids were identified or partially characterised according to the accurate mass and the characteristic fragment ions at low and high collision energy. Most of them were reported for the first time in this plant. Phytochemical profiles of the active extract will help the development and utilisation of N. sibirica in food and medicine.

In-situ measurement of the adsorption thermodynamics of rutin on macroporous adsorption resins by fiber-optic sensing

Abstract This paper describes instrumentation of a spectrophotometric system and its application for in-situ, real-time measurement of adsorption thermodynamics in aqueous solution by use of laboratory-constructed fiber-optic measurements. A measurement vessel was assembled from an adsorption bag, stirring and thermostatic devices, and a fiber-optic dipping probe. A macroporous adsorption resin and rutin were selected as the model adsorbent and adsorbate. In-situ liquid phase adsorption measurement of the system was achieved through monitoring of the absorption by dipping the probe in a broad range of concentrations. In-situ measurement of the AB-8 resin adsorption at temperatures from 303 K to 323 K was systematically carried out, showing that temperature was an influencing factor for the adsorption capacity and initial adsorption rate. The adsorption thermodynamic parameters for AB-8 indicated that the results well fitted the Freundlich model. In addition, a favorable, exothermic, spontaneous, physical process of rutin was demonstrated on AB-8. The obtained results showed that this method was successful at keeping the adsorption temperature constant. The application of fiber-optic sensing to the in-situ measurement of liquid phase adsorption enables automated and real-time monitoring of adsorption thermodynamics.