Suppression of blood lipid concentrations by volatile Maillard reaction products

Progress on the Synthesis Pathways and Pharmacological Effects of Naturally Occurring Pyrazines

As one of the most essential types of heterocyclic compounds, pyrazines have a characteristic smell and taste and have a wide range of commercial applications, especially in the food industry. With the development of the food industry, the demand for pyrazines has increased. Therefore, understanding the properties, functions, and synthetic pathways of pyrazines is one of the fundamental methods to produce, control, and apply pyrazines in food or medical systems. In this review, we provide an overview of the synthesis pathways and physiological or pharmacological functions of naturally occurring pyrazines. In particular, we focus on the biosynthesis and pharmacological effects of 2,3,5,6-Tetramethylpyrazine (TTMP), 2,5-Dimethylpyrazine (2,5-DMP), and 2,3,5-trimethylpyrazine (TMP). Furthermore, areas where further research on pyrazines is needed are discussed in this work.

Alkylpyrazines from Coffee are Extensively Metabolized to Pyrazine Carboxylic Acids in the Human Body

SCOPE

Coffee is a complex mixture of over 1000 compounds, including diverse heteroaromatic compounds such as alkylpyrazines. Little is known about the intake, metabolism, and bodily distribution of these compounds. Therefore, a human intervention study is conducted to investigate the excretion of alkylpyrazine metabolites in urine after the ingestion of brewed coffee containing alkylpyrazines.

METHODS AND RESULTS

After consuming a diet without heat-processed food, ten volunteers consumed 500 mL of freshly brewed coffee prepared from coffee pads, providing intakes of 2-methylpyrazine (2-MeP), 2,5-dimethylpyrazine (2,5-DMeP), and 2,6-dimethylpyrazine (2,6-DMeP) amounting to 17.2, 4.4, and 4.9 µmol, respectively. These alkylpyrazines are metabolized into the corresponding pyrazine carboxylic acids, namely pyrazine-2-carboxylic acid (PA), 5-hydroxypyrazine-2-carboxylic acid (5-OHPA), 5-methylpyrazine-2-carboxylic acid (5-MePA), and 6-methylpyrazine-2-carboxylic acid (6-MePA). In total, 64% of the ingested 2-MeP is excreted as PA, as well as 26% as 5-OHPA, while 91% and 97% of the ingested 2,5-DMeP and 2,6-DMeP are recovered as 5-MePA and 6-MePA, respectively, in urine samples collected after coffee consumption.

CONCLUSION

This study provides evidence that alkylpyrazines are rapidly metabolized into the corresponding carboxylic acids and excreted via urine by humans, which is consistent with earlier rodent studies.

Efficient Discovery of Quality Control Markers for Gastrodia elata Tuber by Fingerprint-Efficacy Relationship Modelling

INTRODUCTION

Gastrodia elata tuber (GET) has been widely used in China as a famous herbal medicine. However, the quality control markers (QCMs) for GET still need further investigation.

OBJECTIVE

To develop a rational strategy based on fingerprint-efficacy relationship modelling to discover the efficacy-related QCMs, using GET as a case study.

METHODOLOGY

The high-performance liquid chromatography (HPLC) fingerprints of 13 batches of GET extracts were established and 10 common peaks were structurally characterised by HPLC coupled with quadrupole time-of-flight mass spectrometry (QTOF-MS). The neuroprotective effects of GET samples were evaluated using the in vitro model of β-amyloid peptide (Aβ_25-35 )-induced PC12 cell death. The fingerprint-efficacy relationship of chemical fingerprints and neuroprotective effects was linked by orthogonal projection to latent structure-discriminant analysis (OPLS-DA) model.

RESULTS

The chemical combination of 5-hydroxymethyl-2-furaldehyde (5-HMF), parishin B (PB) and parishin C (PC) was discovered and confirmed as QCMs of GET by the OPLS-DA method. The selected QCMs allowed to evaluate the relative quality of GET samples.

CONCLUSION

This study has demonstrated that the rational strategy based on fingerprint-efficacy relationship modelling might be generally applicable for the quality control of herbal medicines. Copyright © 2017 John Wiley & Sons, Ltd.

5-HMF Attenuates Liver Fibrosis in CCl4-Plus-Alcohol-Induced Mice by Suppression of Oxidative Stress

The aim of this study was to investigate the effects of 5-hydroxymethyl-2-furfural (5-HMF) on liver fibrosis induced by carbon tetrachloride (CCl₄) and alcohol. Male ICR mice were treated with CCl₄ dissolved in olive oil (10% v/v, 2.5 μg/L) intraperitoneally (i.p.), and given at a dose of 2.5×10^-5 mg/kg B.W. twice a week for 7 wk. Concurrently, mice received drinking water with or without alcohol. The mice in treatment groups and positive control group were gavaged with 5-HMF (7.5, 15, and 30 mg/kg B.W.) or Huganpian (350 mg/kg B.W.) daily starting in the fourth week and lasting for 4 wk. The blood samples were analyzed for biochemical markers of hepatic injury and tissue samples were subjected for estimation of liver antioxidants and histopathological studies. The concentrations of HA (hyaluronic acid), LN (laminin), CIV (collagen type IV), and MDA (malondialdehyde), as well as the serum levels of ALT (alanine aminotransferase) and AST (aspartate aminotransferase) were markedly reduced by 5-HMF. On the other hand, enzymatic antioxidants SOD (superoxide dismutase), CAT (catalase) and GSH-Px (glutathione peroxidase) were markedly elevated in liver tissue treated with 5-HMF. Histopathological examination revealed that 5-HMF treatment noticeably prevented hepatocyte apoptosis, fatty degeneration and inflammatory cell infiltration on liver fibrosis induced by CCl₄ and alcohol. Hoechst 33258 staining also revealed hepatocyte apoptosis. 5-HMF could exert protective effects against liver injury and reduce liver fibrosis induced by CCl₄ and alcohol in mice.

Isolation, structural elucidation, and biological evaluation of a 5-hydroxymethyl-2-furfural derivative, asfural, from enzyme-treated asparagus extract

A novel 5-hydroxymethyl-2-furfural (HMF; 1) derivative, which is named asfural (compound 2), was isolated from enzyme-treated asparagus extract (ETAS) along with HMF (1) as a heat shock protein 70 (HSP70) inducible compound. The structure of compound 2 was elucidated on the basis of its spectroscopic data from HREIMS and NMR, whereas the absolute configuration was determined using chiral HPLC analysis, compared to two synthesized compounds, (S)- and (R)-asfural. As a result, compound 2 derived from ETAS was assigned as (S)-(2-formylfuran-5-yl)methyl 5-oxopyrrolidine-2-carboxylate. When compound 2, synthesized (S)- and (R)-asfural, and HMF (1) were evaluated in terms of HSP70 mRNA expression-enhancing activity in HL-60 cells, compound 2 and (S)-asfural significantly increased the expression level in a concentration-dependent manner. HMF (1) also showed significant activity at 0.25 mg/mL.

Effect of 5-hydroxymethylfurfural derived from processed Cornus officinalis on the prevention of high glucose-induced oxidative stress in human umbilical vein endothelial cells and its mechanism

The aim of this study was to investigate the protective effect of 5-HMF on human umbilical vein endothelial cells (HUVECs) injured by high glucose in vitro, and the mechanism underlying this process. Our results demonstrated that high glucose-induced oxidative stress in HUVECs was mainly mediated through activation of reactive oxygen species (ROS), Jun N-kinase 2/3 (JNK2/3) and plasma interleukin-8 (IL-8), and inactivation of phosphorylated protein kinase B (P-Akt). Treatment of HUVECs with media containing high glucose (4.5%) in the presence of 5-HMF (100, 200 and 400 μM) resulted in significant inhibition of high glucose-induced oxidative stress and expression of JNK1 and JNK2/3. Furthermore, 5-HMF rapidly inhibited high glucose-induced activation of IL-8, a downstream activator of P-Akt. Diabetes mellitus can cause a wide variety of vascular complications and high glucose can induce vascular endothelial cell apoptosis. Free radicals are formed disproportionately in diabetes by glucose oxidation. The finding of this study highlights the pharmacological application of 5-HMF for preventing cardiovascular and diabetes mellitus diseases, and provides the theoretical basis for further development of a Cornus officinalis agent for diabetes-associated vascular diseases.

Effects of short-term streptozotocin-induced diabetes and vitamin C on platelet non-enzymatic glycation

Diabetes mellitus is one of the most prevalent metabolic syndromes worldwide. Glycation, a chemical modification of proteins with reducing sugars, indicates a possible explanation for the association between hyperglycemia and the wide variety of tissue pathologies. Non-enzymatic glycation (NEG) of platelet proteins is one of the key mechanisms in the pathogenesis of diabetic complications and may be significant in diabetic atherothrombosis. The aim of this study was to investigate the effects of streptozotocin (STZ)-induced short-term experimental diabetes on the glycation of platelets and to find out if vitamin C affected this glycation. A total of 40 male Wistar albino rats, 200-250 g, were randomly divided into 4 groups (2 diabetic and 2 control groups). The diabetic groups were made diabetic by intraperitoneal injection of STZ (65 mg/kg, citrate buffer pH 4.5). By daily intraperitoneal injection, 80 mg/kg vitamin C (Roche, Turkey) was administered until the end of the experiment. Blood glucose levels of the diabetic groups were significantly higher than those at day 0 and also higher than those of the non-diabetic control groups. The changes in total protein, NEG and vitamin C levels were not statistically significant. Although the differences among the groups were not statistically significant, vitamin C administration increased NEG levels in the diabetic group. The results of this study demonstrate that 8 days of STZ-induced short-term diabetes did not cause a significant increase in NEG of platelets. However, the effect of vitamin C on platelet NEG needs to be further investigated.

Protective effect of 5-hydroxymethylfurfural derived from processed Fructus Corni on human hepatocyte LO2 injured by hydrogen peroxide and its mechanism

AIM OF THE STUDY

The aim of the present study was to evaluate the putative protective effect of 5-hydroxymethylfurfural (5-HMF) derived from processed Fructus Corni on human hepatocyte cell line (LO2) injured by hydrogen peroxide in vitro and the mechanism of its protection.

MATERIALS AND METHODS

The percentage of cell viability was evaluated by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay. The hepatocyte cell apoptosis and cell cycle were detected by flow cytometric analysis. The content of nitric oxide and caspase-3 activity were quantified spectrophotometrically by enzyme-linked immunoassay.

RESULT

The study showed that incubation with 5-HMF caused significant increase in the viability of LO2 cell, decrease of cell apoptosis and recovery of cell cycle in LO2 cell injured by hydrogen peroxide, which was accompanied with the decreased nitric oxide level and caspase-3 activity.

CONCLUSIONS

Our data suggest that 5-HMF protects LO2 cell against damage induced by hydrogen peroxide through inhibiting effect of cell apoptosis caused by promoting S phase to G2/M phase and the decreased caspase-3 activity and nitric oxide level. 5-HMF is one of the active principles in processed Fructus Corni.

Protective effects of coffee-derived compounds on lipopolysaccharide/D-galactosamine induced acute liver injury in rats

OBJECTIVES

The protective effects of coffee-derived compounds on lipopolysaccharide/D-galactosamine (LPS/D-GalN) induced acute liver injury in rats were investigated.

METHODS

Wistar rats were orally administered saline (control) or one of the test compounds (caffeine, chlorogenic acid, trigonelline, nicotinic acid or eight pyrazinoic acids) at a dose of 100 mg/kg, respectively. This was followed by intraperitoneal injection with LPS (100 mug/kg)/D-GalN (250 mg/kg) 1 h after administration of the test compounds. Blood samples were collected up to 12 h after LPS/D-GalN injection, followed by determination of plasma aspartate aminotransferase, alanine aminotransferase, tumour necrosis factor alpha (TNF-alpha) and interleukin 10 (IL-10) levels.

KEY FINDINGS

Plasma aspartate aminotransferase and alanine aminotransferase levels were significantly increased after LPS/D-GalN-treatment, but were suppressed by pretreatment with caffeine (n = 5), nicotinic acid, non-substituted pyrazinoic acid or 5-methylpyrazinoic acid (n = 6, respectively) 12 h after LPS/D-GalN-treatment (P < 0.01, respectively). Moreover, the animals pretreated with these test compounds showed significantly higher survival rates (83-100%) compared with the control (23%). Only pretreatment with caffeine significantly suppressed the LPS/D-GalN induced elevation of plasma TNF-alpha levels 1 and 2 h after LPS/D-GalN-treatment (P < 0.01, respectively). Pretreatment with caffeine, nicotinic acid or non-substituted pyrazinoic acid activated the LPS/D-GalN induced elevation of plasma IL-10 levels at 1 and 2 h, although there were no statistically significant differences in IL-10 levels between control and nicotinic acid or non-substituted pyrazinoic acid treated rats.

CONCLUSIONS

The results suggest that caffeine, nicotinic acid, non-substituted pyrazinoic acid and 5-methylpyrazinoic acid can protect against LPS/D-GalN induced acute liver injury, which may be mediated by the reduction of TNF-alpha production and/or increasing IL-10 production.