Evaluation of Phenolic Phytochemical Enriched Commercial Plant Extracts on the In Vitro Inhibition of α-Glucosidase.

Green tea (GT), cranberry (CR), and tart cherry extracts were evaluated for their ability to inhibit yeast α-glucosidase, relevant to glucose uptake. The total phenolic content (TPC), antioxidant activity, and in vitro inhibitory activity of yeast α-glucosidase were examined for the extracts in the present study. GT had higher TPC and antioxidant activity, but CR demonstrated a greater α-glucosidase inhibitory activity, on phenolic basis. CR was fractionated using LH-20 column chromatography into two fractions: 30% methanol (CME) and 70% acetone (CAE). TPC, antioxidant activity, and yeast α-glucosidase inhibitory activity were determined for the fractions. CAE had a greater TPC and antioxidant activity than CME, but the two fractions had a synergistic effect when inhibiting yeast α-glucosidase. Our findings suggest that CR has the greatest potential to possibly manage post-prandial blood glucose levels via the inhibition of α-glucosidase, and that the effect is through synergistic activity of the extract's phenolic compounds.

Effect of Black Tea and Black Tea Pomace Polyphenols on α-Glucosidase and α-Amylase Inhibition, Relevant to Type 2 Diabetes Prevention.

This study evaluates the potential mechanism of action and bioactivity of black tea and black tea pomace for type 2 diabetes prevention via inhibition of carbohydrate hydrolyzing enzymes. Black tea leaves were extracted in hot water and black tea pomace was extracted in 70% acetone. The phenolic content of the water extract (WBT) and pomace acetone extracts (AOBT) were 5.77 and 8.9 mg/mL, respectively, both based on the same concentration of solid tea in the extract. The water extract was subjected to C18 extraction and the resulting hydrophobic fraction (HBBT) was further subjected to LH-20 extraction to recover a low molecular weight phenolic enriched fraction (LMW) and a high molecular weight enriched fraction (HMW). The phenolic content of the LMW and HMW fraction were 1.42 and 2.66 mg/mL, respectively. Among water extracts the HMW fraction was most bioactive against α-glucosidase (IC50 = 8.97 µg/mL) followed by HBBT fraction (IC50 = 14.83 µg/mL). However, the HBBT fraction was the most bioactive fraction against α-amylase (IC50 = 0.049 mg/mL). The black tea pomace (AOBT) had significant α-glucosidase inhibitory activity (IC50 = 14.72 µg/mL) but lower α-amylase inhibitory activity (IC50 = 0.21 mg/mL). The phenolic profiles for LMW and HMW fractions were evaluated using HPLC and the differences between the two profiles were identified. Further research is underway to identify and evaluate the phenolic compounds that are present in the HMW fraction. Our findings suggest that black tea and black tea pomace has potential for carbohydrate hydrolyzing enzyme inhibition and this activity depends on high molecular weight phenolic compounds.

In vivo proton magnetic resonance spectroscopy reveals region specific metabolic responses to SIV infection in the macaque brain.

BACKGROUND: In vivo proton magnetic resonance spectroscopy (1H-MRS) studies of HIV-infected humans have demonstrated significant metabolic abnormalities that vary by brain region, but the causes are poorly understood. Metabolic changes in the frontal cortex, basal ganglia and white matter in 18 SIV-infected macaques were investigated using MRS during the first month of infection. RESULTS: Changes in the N-acetylaspartate (NAA), choline (Cho), myo-inositol (MI), creatine (Cr) and glutamine/glutamate (Glx) resonances were quantified both in absolute terms and relative to the creatine resonance. Most abnormalities were observed at the time of peak viremia, 2 weeks post infection (wpi). At that time point, significant decreases in NAA and NAA/Cr, reflecting neuronal injury, were observed only in the frontal cortex. Cr was significantly elevated only in the white matter. Changes in Cho and Cho/Cr were similar across the brain regions, increasing at 2 wpi, and falling below baseline levels at 4 wpi. MI and MI/Cr levels were increased across all brain regions. CONCLUSION: These data best support the hypothesis that different brain regions have variable intrinsic vulnerabilities to neuronal injury caused by the AIDS virus.

Regional metabolite T2 in the healthy rhesus macaque brain at 7T.

Although the rhesus macaque brain is an excellent model system for the study of neurological diseases and their responses to treatment, its small size requires much higher spatial resolution, motivating use of ultra-high-field (B(0)) imagers. Their weaker radio-frequency fields, however, dictate longer pulses; hence longer TE localization sequences. Due to the shorter transverse relaxation time (T(2)) at higher B(0)s, these longer TEs subject metabolites to T(2)-weighting, that decrease their quantification accuracy. To address this we measured the T(2)s of N-acetylaspartate (NAA), choline (Cho), and creatine (Cr) in several gray matter (GM) and white matter (WM) regions of four healthy rhesus macaques at 7T using three-dimensional (3D) proton MR spectroscopic imaging at (0.4 cm)(3) = 64 mul spatial resolution. The results show that macaque T(2)s are in good agreement with those reported in humans at 7T: 169 +/- 2.3 ms for NAA (mean +/- SEM), 114 +/- 1.9 ms for Cr, and 128 +/- 2.4 ms for Cho, with no significant differences between GM and WM. The T(2) histograms from 320 voxels in each animal for NAA, Cr, and Cho were similar in position and shape, indicating that they are potentially characteristic of "healthy" in this species.

Proton MR spectroscopic imaging of rhesus macaque brain in vivo at 7T.

Due to the overall similarity of their brains' structure and physiology to its human counterpart, nonhuman primates provide excellent model systems for the pathogenesis of neurological diseases and their response to treatments. Its much smaller size, 80 versus 1250 cm(3), however, requires proportionally higher spatial resolution to study, nondestructively, as many analogous regions as efficiently as possible in anesthetized animals. The confluence of these requirements underscores the need for the highest sensitivity, spatial coverage, resolution, and exam speed. Accordingly, we demonstrate the feasibility of 3D multi-voxel, proton ((1)H) MRSI at (0.375 cm)(3)=0.05 cm(3) isotropic spatial resolution over 21 cm(3) (approximately 25%) of the anesthetized rhesus macaques brain at 7T in 25 min. These voxels are x10(2)-10(1) times smaller than the 8-1 cm(3) common to (1)H-MRS in humans, retaining similar proportions between the macaque and human brain. The spectra showed a signal-to-noise-ratio (SNR) approximately 9-10 for the major metabolites and the interanimal SNR spatial distribution reproducibility was in the +/-10% range for the standard error of their means (SEMs). Their metabolites' linewidths, 9+/-2 Hz, yield excellent spectral resolution as well. These results indicate that 3D (1)H-MRSI can be integrated into comprehensive MR studies in primates at such high fields.

New insights into the neuroimmunity of SIV infection by magnetic resonance spectroscopy.

(1)H magnetic resonance spectroscopy (MRS) was employed to noninvasively monitor neuronal injury in eight rhesus macaques infected with simian immunodeficiency virus (SIV), whose immune system was compromised by CD8 T lymphocyte depletion and treated with highly active antiretroviral therapy (HAART). SIV infection and CD8 depletion resulted in a rapid decline in cerebral N-acetylaspartate (NAA) levels, a sensitive marker of neuronal health. Within 3 months of SIV infection and CD8 depletion, four animals developed AIDS and severe SIV encephalitis. The other four macaques underwent daily doses of HAART beginning 4 weeks after infection/CD8 depletion. HAART involved drugs that do not penetrate the central nervous system (CNS) including 9-[2(R)-(phosphonomethoxy)propyl]adenine and a racemic mixture of D: -L: -enantiomers of 2',3'-dideoxy-5-fluoro-3'thiacytidine. HAART resulted in reversal of NAA/Cr decline after 4 weeks of therapy, and no virus or encephalitis was found in brain samples analyzed. These results indicate that the CNS injury in AIDS is entirely dependent on events involving the peripheral immune system mediated by trafficking of SIV-infected monocytes into the brain. The rapid decline in NAA/Cr with SIV infection/CD8 depletion and its rapid recovery with HAART suggest that: (1) infected monocyte turnover in the CNS is rapid, occurring in days to weeks; (2) there are endogenous mechanisms that reverse neuronal injury; and (3) a threshold level of infected monocytes/macrophages in the CNS is required to overcome the neuronal recovery processes. These observations explain the clinical success of antiretroviral therapy in reducing the incidence of HIV-associated dementia and minor cognitive/motor disorder and suggest novel targets for drug development.

Comparisons of brain metabolites observed by HRMAS 1H NMR of intact tissue and solution 1H NMR of tissue extracts in SIV-infected macaques.

The objective of this study was to compare ex vivo proton high-resolution magic angle spinning magnetic resonance spectra of intact tissue with those spectra obtained by solution (1)H NMR of brain extracts of the same sample. Sixteen brain tissue samples from simian immunodeficiency virus-infected rhesus macaques from both frontal cortex and putamen were evaluated by comparing brain metabolite quantities of N-acetylaspartate (NAA), choline-containing compounds (Cho), myo-inositol (MI), creatine (Cr), lactate (Lac), glutamate (Glu) and acetate (Ace). The ratios of the individual NMR peak areas of all metabolites relative to the creatine peak area were calculated. Linear regression analysis revealed significant correlations between measurements using the two methods. The strength of the correlations varied depending on the metabolite studied. We found highly significant correlations for NAA/Cr (r2 = 0.77; p < 0.0001), NAA + Ace/Cr (r2 = 0.73; p < 0.0001) and MI/Cr (r2 = 0.75; p < 0.0001). We observed somewhat less strong correlations for Glu/Cr (r2 = 0.54; p < 0.002) and Lac/Cr (r2 = 0.54; p < 0.002). There was a substantially weaker correlation for Cho/Cr (r2 = 0.32; p = 0.02). When plotting the metabolite ratios obtained by 1H HRMAS NMR of the intact tissue sample on the ordinate vs 1H NMR of the tissue extract on the abscissa, most metabolites exhibited a slope close to unity, and a positive intercept probably due to macromolecular contributions to the MAS spectra. The slope for Cho/Cr was substantially less than unity. Generally, samples from the frontal cortex showed a better correlation between intact and extracted tissue samples than putamen. This is most prominent in the cases of NAA/Cr and Cho/Cr. We conclude that both methods provide substantially the same information for most major brain metabolites, with the exception of the Cho resonance.

Solid-state NMR studies of the adsorption and photooxidation of ethanol on mixed TiO2--SnO2 photocatalysts.

In situ solid-state NMR methodologies have been used to investigate the photocatalytic oxidation of ethanol (CH3CH2OH) over a series of SnO2-based photocatalysts. The adsorption of ethanol on commercially available SnO2 powder was studied using both cross-polarization 13C NMR and REDOR experiments, and showed the formation of two surface ethanol species, hydrogen-bonded ethanol at surface hydroxyl groups and ethanol chemisorbed to the SnO2 surface (Sn--OCH2CH3). 13C NMR of the adsorbed ethanol was used to characterize the surface of monolayer SnO2--TiO2 coupled photocatalysts supported on porous Vycor glass. In situ solid-state NMR studies showed that the photooxidation of ethanol over the monolayer photocatalysts was slower than that over a supported TiO2 monolayer photocatalyst due to the build-up of reaction intermediates such as acetic acid on the catalyst surface. 119Sn NMR experiments characterized the tin species on the porous Vycor glass support.