Antihyperglycemic effect of protocatechuic acid on streptozotocin-diabetic rats

Pharmacodynamic material basis and pharmacological mechanisms of Cortex Mori against diabetes mellitus

ETHNOPHARMACOLOGICAL RELEVANCE

The application of Cortex Mori (CM) in the treatment of diabetes mellitus (DM) has been extensively documented in traditional medicine. In recent years, the chemical composition of CM has been gradually unraveled, and its therapeutic mechanism in treating DM, diabetic nephropathy, diabetic cardiomyopathy, and other related conditions has been highlighted in successive reports. However, there is no systematic study on the treatment of DM based on the chemical composition of CM.

AIM OF THE STUDY

This study was conducted to systematically explore the hypoglycemic activity mechanism of CM based on its chemical composition.

METHODS

The material basis of Cortex Mori extract (CME) was investigated through qualitative analyses based on liquid chromatography-mass spectrometry (LC-MS). The possible acting mechanism was simulated using network pharmacology and validated in streptozotocin (STZ) + high fat diet (HFD)-induced diabetic rats and glucosamine-induced IR-HepG2 model with the assistance of molecular docking techniques.

RESULTS

A total of 39 compounds were identified in CME by the LC-MS-based qualitative analysis. In diabetic rats, it was demonstrated that CME significantly ameliorated insulin resistance, blood lipid levels, and liver injury. The network pharmacology analysis predicted five major targets, including AKT1, PI3K, FoxO1, Gsk-3β, and PPARγ. Additionally, three key compounds (resveratrol, protocatechuic acid, and kaempferol) were selected based on their predicted contributions. The experimental results revealed that CME, resveratrol, protocatechuic acid, and kaempferol could promote the expression of AKT1, PI3K, and PPARγ, while inhibiting the expression of FoxO1 and Gsk-3β. The molecular docking results indicated a strong binding affinity between resveratrol/kaempferol and their respective targets.

CONCLUSIONS

CME contains a substantial amount of prenylated flavonoids, which may be the focal point of research on the efficacy of CM in the treatment of DM. Besides, CME is effective in controlling blood glucose and insulin resistance, improving lipid levels, and mitigating liver injury in patients with DM. Relevant mechanisms may be associated with the activation of the PI3K/Akt pathway, the inhibition of the expression of FoxO1 and Gsk-3β, and the enhancement of PPARγ activity. This study represents the first report on the role of CME in the treatment of DM through regulating PPARγ, FoxO1, and Gsk-3β.

Antidiabetic Properties of the Root Extracts of Dandelion (Taraxacum officinale) and Burdock (Arctium lappa)

Several preclinical studies suggest the potential of edible plants in controlling blood sugar levels and stabilizing diet. The goals of the study were to examine, analyze, and describe whether there are chemical compounds in dandelion and burdock roots that could have antidiabetic properties. The 70% ethyl alcohol and lyophilizate extracts (AE and LE, respectively), were used, and analyses were carried out on their total polysaccharide (TP), total phenolic content (TPC), tannin, and inulin. The antioxidant activity of extracts was determined using the DPPH (2,2-diphenyl-1-picrylhydrazyl) assay, and hypoglycemic properties were based on α-amylase activity. Liquid chromatography-mass spectrometry was used for the tentative identification of the chemical components. Qualitative techniques confirmed the presence of inulin in both roots. Analysis of TPC, tannin content, DPPH assay, and α-amylase activity revealed higher values for burdock compared to dandelion. However, dandelion exhibited higher TP content. Burdock contained a small amount of tannin, whereas the tannin content in dandelion was insignificant. All LE consistently exhibited higher values in all analyses and assays for all roots compared to AE. Despite burdock root showing overall better results, it is uncertain whether these plants can be recommended as antidiabetic agents without in vivo studies.

Can Polyherbal Medicine be used for the Treatment of Diabetes? - A Review of Historical Classics, Research Evidence and Current Prevention Programs

Diabetes mellitus (DM), a chronic medical condition, has attained a global pandemic status over the last few decades affecting millions of people. Despite a variety of synthetic drugs available in the market, the use of herbal medicines for managing diabetes is gaining importance because of being comparatively safer. This article reviews the result of a substantial literature search on polyherbal formulations (PHFs) developed and evaluated with potential for DM. The accumulated data in the literature allowed us to enlist 76PHFs consisting of different parts of 147 plant species belonging to 58 botanical families. The documented plant species are laden with bioactive components with anti-diabetic properties and thus draw attention. The most favoured ingredient for PHFs was leaves of Gymnema sylvestre and seeds of Trigonella foenum-graecum used in 27 and 22 formulations, respectively. Apart from herbs, shilajit (exudates from high mountain rocks) formed an important component of 9 PHFs, whereas calcined Mytilus margaritiferus and goat pancreas were used in Dolabi, the most commonly used tablet form of PHF in Indian markets. The healing properties of PHFs against diabetes have been examined in both pre-clinical studies and clinical trials. However, the mechanism(s) of action of PHFs are still unclear and considered the pitfalls inherent in understanding the benefits of PHFs. From the information available based on experimental systems, it could be concluded that plant-derived medicines will have a considerable role to play in the control of diabetes provided the challenges related to their bioavailability, bioefficacy, optimal dose, lack of characterization, ambiguous mechanism of action, and clinical efficiency are addressed.

Food Polyphenols and Type II Diabetes Mellitus: Pharmacology and Mechanisms

Type II diabetes mellitus and its related complications are growing public health problems. Many natural products present in our diet, including polyphenols, can be used in treating and managing type II diabetes mellitus and different diseases, owing to their numerous biological properties. Anthocyanins, flavonols, stilbenes, curcuminoids, hesperidin, hesperetin, naringenin, and phenolic acids are common polyphenols found in blueberries, chokeberries, sea-buckthorn, mulberries, turmeric, citrus fruits, and cereals. These compounds exhibit antidiabetic effects through different pathways. Accordingly, this review presents an overview of the most recent developments in using food polyphenols for managing and treating type II diabetes mellitus, along with various mechanisms. In addition, the present work summarizes the literature about the anti-diabetic effect of food polyphenols and evaluates their potential as complementary or alternative medicines to treat type II diabetes mellitus. Results obtained from this survey show that anthocyanins, flavonols, stilbenes, curcuminoids, and phenolic acids can manage diabetes mellitus by protecting pancreatic β-cells against glucose toxicity, promoting β-cell proliferation, reducing β-cell apoptosis, and inhibiting α-glucosidases or α-amylase. In addition, these phenolic compounds exhibit antioxidant anti-inflammatory activities, modulate carbohydrate and lipid metabolism, optimize oxidative stress, reduce insulin resistance, and stimulate the pancreas to secrete insulin. They also activate insulin signaling and inhibit digestive enzymes, regulate intestinal microbiota, improve adipose tissue metabolism, inhibit glucose absorption, and inhibit the formation of advanced glycation end products. However, insufficient data are available on the effective mechanisms necessary to manage diabetes.

Protocatechuic Acid Ameliorates High Fat Diet-Induced Obesity and Insulin Resistance in Mice

SCOPE

Insulin resistance is a common feature of obesity and type 2 diabetes and partly results from an imbalance between food intake and energy expenditure. Therefore, efficient and safe insulin resistance treatment therapies are warranted. This work is aim to access the impact of protocatechuic acid (PCA), a catechol-type O-diphenol phenolic acid, in high fat diet (HFD)-induced glucose, and lipid dysregulation.

METHODS AND RESULTS

Five-week-old male C57BL/6 mice are fed with HFD for 4 weeks and then are randomly divided into two cohorts: one cohort feed with HFD is free access to sterile water for 4 weeks, another cohort is free access to PCA-containing water (2.7 mM) for 4 weeks with HFD. In this study, using a hyperinsulinemic-euglycemic mouse clamp, it is showed that PCA-treated mice display improved systemic insulin resistance via enhanced fatty acid mobilization and utilization, thereby reducing ectopic lipid accumulation and promoting hepatic and peripheral insulin action.

CONCLUSIONS

This study provides insights on the potent pharmacological effects of PCA from food sources on improving high fat diet (HFD)-induced whole-body insulin resistance and type 2 diabetes.

Anthocyanins as Promising Molecules Affecting Energy Homeostasis, Inflammation, and Gut Microbiota in Type 2 Diabetes with Special Reference to Impact of Acylation

Anthocyanins, the red-orange to blue-violet colorants present in fruits, vegetables, and tubers, have antidiabetic properties expressed via modulating energy metabolism, inflammation, and gut microbiota. Acylation of the glycosyl moieties of anthocyanins alters the physicochemical properties of anthocyanins and improves their stability. Thus, acylated anthocyanins with probiotic-like property and lower bioavailability are likely to have different biological effects from nonacylated anthocyanins on diabetes. This work highlights recent findings on the antidiabetic effects of acylated anthocyanins from the perspectives of energy metabolism, inflammation, and gut microbiota compared to the nonacylated anthocyanins and particularly emphasizes the cellular and molecular mechanisms associated with the beneficial effects of these bioactive molecules, providing a new perspective to explore the different biological effects induced by structurally different anthocyanins. Acylated anthocyanins may have greater modulating effects on energy metabolism, inflammation, and gut microbiota in type 2 diabetes compared to nonacylated anthocyanins.

Ultrasound-alkaline combined extraction improves the release of bound polyphenols from pitahaya (Hylocereus undatus 'Foo-Lon') peel: Composition, antioxidant activities and enzyme inhibitory activity

In this study, ultrasound-assisted alkaline hydrolysis was used to extract polyphenols from pitahaya peel. The effects of sonication time, ultrasonic density, NaOH concentration and the liquid-material ratio on the total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity of the extracts were studied. The composition and content difference of the extracts were analyzed and the inhibitory effect of α-amylase and α-glucosidase was measured. The results of single-factor analysis showed that when the sonication time was 45 min, the ultrasonic density was 32 W/L, the NaOH solution concentration was 6 M and the liquid-material ratio was 30 mL/g, the release of phenolic compounds was the largest and the antioxidant activity was the strongest. An UPLC-QTOF-MS/MS method was used to analyze the components and contents of the extracts. We found that there was a great difference in the component content of the free polyphenol extract and the bound polyphenol extract. From the results, we concluded that there was a strong correlation between the type and content of phenolic compounds and antioxidant activities, indicating that phenolic compounds were the main compounds of these biological activities. Moreover, the bound polyphenol extracts showed a significant inhibitory effect on α-amylase and α-glucosidase was stronger than that of the free polyphenol extracts. In addition, scanning electron microscopy showed that ultrasound-assisted extraction is crucial to the destruction of the cell wall and the release of bound polyphenols. Therefore, the pitahaya peel has the potential for therapeutic, nutritional, and functional food applications, and ultrasound-assisted alkaline hydrolysis is an effective means to release phenolic compounds.

Clinical Potential of Himalayan Herb Bergenia ligulata: An Evidence-Based Study

Herbal products have been used in traditional systems of medicine and by ethnic healers for ages to treat various diseases. Currently, it is estimated that about 80% of people worldwide use herbal traditional medicines against various ailments, partly due to easy accessibility and low cost, and the lower side effects they pose. Bergenia ligulata, a herb ranging from the Himalayas to the foothills, including the north-eastern states of India, has traditionally been used as a remedy against various diseases, most prominently kidney stones. The medicinal properties of B. ligulata have been attributed to bergenin, its most potent bioactive component. Apart from bergenin, the other compounds available in B. ligulata are arbutin, gallic acid, protocatechuic acid, chlorogenic acid, syringic acid, catechin, ferulic acid, afzelechin, paashaanolactone, caryophyllene, 1,8-cineole, β-eudesmol, stigmasterol, β-sitosterol, parasorbic acid, 3-methyl-2-buten-1-ol, phytol, terpinen-4-ol, tannic acid, isovalaric acid, avicularin, quercetin, reynoutrin, and sitoinoside I. This review summarizes various medicinal properties of the herb, along with providing deep insight into its bioactive molecules and their potential roles in the amelioration of human ailments. Additionally, the possible mechanism(s) of action of the herb's anti-urolithiatic, antioxidative, antipyretic, anti-diabetic, anti-inflammatory and hepatoprotective properties are discussed. This comprehensive documentation will help researchers to better understand the medicinal uses of the herb. Further studies on B. ligulata can lead to the discovery of new drug(s) and therapeutics for various ailments.

Phytochemical Study of Eryngium cymosum F. Delaroche and the Inhibitory Capacity of Its Main Compounds on Two Glucose-Producing Pathway Enzymes

One undescribed acylated flavonol glucoside and five known compounds were isolated from the aerial parts of Eryngium cymosum F. Delaroche, a plant that is used in traditional Mexican medicine to treat type 2 diabetes. The chemical structures of the isolated compounds were elucidated using a variety of spectroscopic techniques, including 1D and 2D nuclear magnetic resonance (NMR) and mass spectrometry (MS). Chlorogenic acid (1), rosmarinic acid (2), caffeic acid (3), protocatechuic acid (4), kaempferol-3-O-(2,6-di-O-trans-ρ-coumaryl)-β-d-glucopyranoside (5), and the new acylated flavonol glucoside quercetin-3-O-(2,6-di-O-trans-ρ-coumaryl)-β-d-glucopyranoside (6) were isolated. This is the first report on the natural occurrence of quercetin-3-O-(2,6-di-O-trans-ρ-coumaryl)-β-D-glucopyranoside (6). In addition, according to the HPLC profile obtained for the water extract (WE), chlorogenic acid (1) and rosmarinic acid (2) were identified as the main compounds, while kaempferol-3-O-(2,6-di-O-trans-ρ-coumaryl)-β-d-glucopyranoside (5) were the main compound in the butanolic extract. We demonstrate the important role of compound 5 over the inhibition of G6Pase and FBPase. The isolated compounds may play an important role in the hypoglycemic effect of the extract and may act in a synergic way, but more experiments are needed to corroborate these findings.

The Use of Bioactive Compounds in Hyperglycemia- and Amyloid Fibrils-Induced Toxicity in Type 2 Diabetes and Alzheimer’s Disease

It has become increasingly apparent that defective insulin signaling may increase the risk for developing Alzheimer’s disease (AD), influence neurodegeneration through promotion of amyloid formation or by increasing inflammatory responses to intraneuronal β-amyloid. Recent work has demonstrated that hyperglycemia is linked to cognitive decline, with elevated levels of glucose causing oxidative stress in vulnerable tissues such as the brain. The ability of β-amyloid peptide to form β-sheet-rich aggregates and induce apoptosis has made amyloid fibrils a leading target for the development of novel pharmacotherapies used in managing and treatment of neuropathological conditions such as AD-related cognitive decline. Additionally, deposits of β-sheets folded amylin, a glucose homeostasis regulator, are also present in diabetic patients. Thus, therapeutic compounds capable of reducing intracellular protein aggregation in models of neurodegenerative disorders may prove useful in ameliorating type 2 diabetes mellitus symptoms. Furthermore, both diabetes and neurodegenerative conditions, such as AD, are characterized by chronic inflammatory responses accompanied by the presence of dysregulated inflammatory biomarkers. This review presents current evidence describing the role of various small bioactive molecules known to ameliorate amyloidosis and subsequent effects in prevention and development of diabetes and AD. It also highlights the potential efficacy of peptide–drug conjugates capable of targeting intracellular targets.

Antioxidant Effects of Protocatechuic Acid and Protocatechuic Aldehyde: Old Wine in a New Bottle

Phenolic compounds are naturally present as secondary metabolites in plant-based sources such as fruits, vegetables, and spices. They have received considerable attention for their antioxidant, anti-inflammatory, and anti-carcinogenic properties for protection against many chronic disorders such as neurodegenerative diseases, diabetes, cardiovascular diseases, and cancer. They are categorized into various groups based on their chemical structure and include phenolic acids, flavonoids, curcumins, tannins, and quinolones. Their structural variations contribute to their specific beneficial effects on human health. The antioxidant property of phenolic compounds protects against oxidative stress by up-regulation of endogenous antioxidants, scavenging free radicals, and anti-apoptotic activity. Protocatechuic acid (PCA; 3,4-dihydroxy benzoic acid) and protocatechuic aldehyde (PAL; 3,4-dihydroxybenzaldehyde) are naturally occurring polyphenols found in vegetables, fruits, and herbs. PCA and PAL are the primary metabolites of anthocyanins and proanthocyanidins, which have been shown to possess pharmacological actions including antioxidant activity in vitro and in vivo. This review aims to explore the therapeutic potential of PCA and PAL by comprehensively summarizing their pharmacological properties reported to date, with an emphasis on their mechanisms of action and biological properties.

Alpinia officinarum water extract inhibits the atopic dermatitis-like responses in NC/Nga mice by regulation of inflammatory chemokine production

Alpinia officinarum (AO) has been traditionally used in Asia as an herbal medicine to treat inflammatory and internal diseases. However, the therapeutic effect of AO on atopic dermatitis (AD) is unclear. Therefore, we examined whether Alpinia officinarum water extract (AOWex) affects AD in vivo and in vitro. Oral administration of AOWex to NC/Nga mice with Dermatophagoies farina extract (DfE)-induced AD-like symptoms significantly reduced the severity of clinical dermatitis, epidermal thickness, and mast cell infiltration into the skin and ear tissue. Decreased total serum IgE, macrophage-derived chemokine (MDC), and regulated on activation, normal T-cell expressed and secreted (RANTES) levels were observed in DfE-induced NC/Nga mice in the AOWex-treated group. These effects were confirmed in vitro using HaCaT cells. Treatment with AOWex inhibited the expression of proinflammatory chemokines such as MDC, RANTES, IP-10 and I-TAC in interferon-γ and tumor necrosis factor-α-stimulated HaCaT cells. The anti-inflammatory effects of AOWex were due to its inhibitory action on MAPK phosphorylation (ERK and JNK), NF-κB, and STAT1. Furthermore, galangin, protocatechuic acid, and epicatechin from AOWex were identified as candidate anti-AD compounds. These results suggest that AOWex exerts therapeutic effects against AD by alleviating AD-like skin lesions, suppressing inflammatory mediators, and inhibiting major signaling molecules.

In-vitro Investigation of Polyphenol-Rich Date (Phoenix dactylifera L.) Seed Extract Bioactivity

Date seeds are a by-product of the date fruit processing industry with minimal human use; however, they are a rich source of polyphenols with a range of potential biological properties. The current study investigates the cytotoxicity of date seed polyphenols against cancer cell lines, its ability to combat hyperglycemia, its antioxidant potential and its anti-adipogenic effect. The present work aimed to establish the usefulness of date seeds in the food industry as a functional ingredient. The anti-tumour activity of DSE was tested in a panel of cell lines such as MCF-7, MDA-MB-231, Hep-G2, Caco-2, and PC-3 by measuring cell viability and cleaved PARP. Lipid accumulation and effect on the differentiation of 3T3-L1 cells (adipocytes) were tested with date seed extract treatments. The influence of date seed polyphenols on glucose uptake was studied in 3T3-L1 cells and C2C12 cells (muscle cells). The antioxidant activity of the polyphenols from date seed products such as date seed extract (DSE), date seed powder (DSP), and date seeds fortified bread (DSB) was tested following in-vitro digestion to study their stability in the gastrointestinal milieu. DSE treatment resulted in significantly reduced viability in MCF-7 and Hep-G2 cells with 48-h treatments. Glucose uptake increased in the adipocytes with DSE treatments; moreover, it inhibited adipocyte differentiation and lipid accumulation. DSE decreased the expression levels of PPAR-γ, C/EBPα, adiponectin and upregulated GLUT-4, and phospho-AMPK. This study also found that date seed samples retained antioxidant activity in the digestive milieu and concludes that the date seed polyphenols remain active in the digestive milieu and exhibit potential anti-hyperglycemic and anti-adipogenic activity.

Gundelia tournefortii: Fractionation, Chemical Composition and GLUT4 Translocation Enhancement in Muscle Cell Line

Type 2 diabetes (T2D) is a chronic metabolic disease, which could affect the daily life of patients and increase their risk of developing other diseases. Synthetic anti-diabetic drugs usually show severe side effects. In the last few decades, plant-derived drugs have been intensively studied, particularly because of a rapid development of the instruments used in analytical chemistry. We tested the efficacy of Gundelia tournefortii L. (GT) in increasing the translocation of glucose transporter-4 (GLUT4) to the myocyte plasma membrane (PM), as a main strategy to manage T2D. In this study, GT methanol extract was sub-fractionated into 10 samples using flash chromatography. The toxicity of the fractions on L6 muscle cells, stably expressing GLUTmyc, was evaluated using the MTT assay. The efficacy with which GLUT4 was attached to the L6 PM was evaluated at non-toxic concentrations. Fraction 6 was the most effective, as it stimulated GLUT4 translocation in the absence and presence of insulin, 3.5 and 5.2 times (at 250 μg/mL), respectively. Fraction 1 and 3 showed no significant effects on GLUT4 translocation, while other fractions increased GLUT4 translocation up to 2.0 times. Gas chromatography-mass spectrometry of silylated fractions revealed 98 distinct compounds. Among those compounds, 25 were considered anti-diabetic and glucose disposal agents. These findings suggest that GT methanol sub-fractions exert an anti-diabetic effect by modulating GLUT4 translocation in L6 muscle cells, and indicate the potential of GT extracts as novel therapeutic agents for T2D.

Water-soluble palm fruit extract: composition, biological properties, and molecular mechanisms for health and non-health applications

The oil palm (Elaeis guineensis) fruit is a source of vegetable oil and various phytonutrients. Phytochemical compounds present in palm oil include tocotrienols, carotenoids, phytosterols, squalene, coenzyme Q₁₀, and phospholipids. Being a fruit, the oil palm is also a rich source of water-soluble phytonutrients, including phenolic compounds. Extraction of phytonutrients from the oil palm vegetation liquor of palm oil milling results in a phenolic acid-rich fraction termed Water-Soluble Palm Fruit Extract (WSPFE). Pre-clinical in vitro, ex vivo, and in vivo studies carried out using various biological models have shown that WSPFE has beneficial bioactive properties, while clinical studies in healthy volunteers showed that it is safe for human consumption and confers antioxidant and anti-inflammatory effects. The composition, biological properties, and relevant molecular mechanisms of WSPFE discovered thus far are discussed in the present review, with a view to offer future research perspectives on WSPFE for health and non-health applications.

Ethnopharmacological perspectives of glucokinase activators in the treatment of diabetes mellitus

Traditional medicinal plants have wide-reaching utilisation in the treatment of diabetes especially in developing countries where medical resources are meagre. Traditionally used anti-diabetic plants act by numerous mechanisms, however, only a few of them act through activation of the glucokinase enzyme. Glucokinase is a key regulatory enzyme in glucose metabolism thereby controls glucose homeostasis and insulin secretion. The present review significantly analyses the knowledge about various plant-based glucokinase activators including numerous phytochemicals which modulate the activity and gene expression of glucokinase and would provide data support and perspective regarding future research in the discovery and development of different plant-derived glucokinase activators.

Characterisation and in vivo evaluation of Araucaria angustifolia pinhão seed coat nanosuspension as a functional food source

Araucaria angustifolia seeds from South America are culturally important; however, the seed coat is generally discarded and it has yet to find a beneficial commercial impact. Herein, we propose a new formulation for the use of the seed coat for the production of a food source. A nanosuspension was developed under two conditions, bleached and unbleached treatment. Initial characterisation of the seed coat, as well as the nanosuspension, was conducted, in which nanofibrils with antioxidant activity and high values of phenol and sterol classes with health-promoting ability were detected by GC-MS; however, after bleaching, the compounds were removed. The nanosuspension induced a decrease in cholesterol, triglycerides, glucose levels and weight gain when added to the daily rat diet. No significant differences were determined when bleach treatment was used, suggesting that dietary fibre plays a more significant role. Histology analysis and biochemical markers reported no toxicity from the rat ingestion of the nanoformulation.

Protocatechuic acid improves hepatic insulin resistance and restores vascular oxidative status in type-2 diabetic rats

This work explored influences of protocatechuic acid (PCA) on type 2 diabetes (T2D)-associated hepatic insulin resistance and other metabolic, hepatic and vascular irregularities using the rat model of high fat diet (HFD)+high fructose+low dose streptozotocin (STZ). Twenty-four male Wister rats were used. Twelve rats were ad libitum supplied with HFD and high fructose drinking water (25 % w/v) for 60 days. On day 30, they received a single injection of STZ (35 mg/kg, i.p). On day 32, they were divided into two subgroups (n = 6/each): T2D + PCA, received PCA (100 mg/kg/day, orally) and T2D, received PCA vehicle till the end of experiment. Rats provided with regular diet and fructose-free drinking water, with or without PCA treatment, served as PCA and control groups (n = 6/each), respectively. PCA treatment significantly reduced the elevated levels of fasting glycemia and insulin, AUCOGTT, AUCITT, and HOMA-IR index, while it boosted HOMA-β and insulinogenic index values in T2D rats. PCA ameliorated serum lipid levels and hepatic function parameters and mitigated hepatosteatosis in T2D rats. Mechanistically, PCA mitigated hepatic lipid peroxidation and restored reduced glutathione (GSH) and superoxide dismutase (SOD) to near-normal levels. Moreover, PCA enhanced hepatic protein levels of P-AKTser473 and hepatic mRNA expression of insulin receptor substrate 1 (IRS1), phosphatidylinositol 3 kinase (PI3K)-p85 and AKT2. Furthermore, PCA ameliorated aortic oxidative stress in T2D rats, possibly via reducing serum levels of advanced glycation end products (AGEs) and diminishing vascular expression of RAGE and NOX4 mRNA. Collectively, PCA may improve hepatic insulin resistance and vascular oxidative status by modulating IRS1/PI3K/AKT2 and AGE-RAGE-NOX4 pathways, respectively.

Bioactive component analysis and investigation of antidiabetic effect of Jerusalem thorn (Paliurus spina-christi) fruits in diabetic rats induced by streptozotocin

ETHNOPHARMACOLOGICAL RELEVANCE

The extracts of Jerusalem thorn fruits (JT-FE) have been commonly used for the treatment of diabetes mellitus in Turkey.

AIM OF THE STUDY

In this study, it is aimed to investigate the effects of the JT-FE, prepared by decoction, on blood glucose, insulin and glycated haemoglobin levels of diabetic rats induced with streptozotocin (STZ). Hypoglycemic activity of the extracts was examined in streptozotocin-induced diabetic rats.

MATERIALS AND METHODS

For this purpose, pre-prandial blood sugar, insulin and glycated hemoglobin levels were measured. To investigate active substances that were responsible for the antidiabetic activity, phytochemical analysis was carried out with optimized and validated LC-MS/MS method using 53 phytochemicals in JT-FE. In addition, ICP-OES analysis was performed to determine the mineral content.

RESULTS

The findings of the study demonstrate that when insulin and JT-FE applied groups were compared with the diabetic control group, their blood sugar and glycated hemoglobin levels were seen to statistically decrease (p < 0,001). Morewer, When JT-FE treated groups were compared with insulin-treated groups, a statistically decrease (p < 0,05) in their levels was observed. On the other hand, it was also found that the increase in extract concentration didn't contribute significantly to antidiabetic activity. As a result of the phytochemical analysis, total of 31 different phenolic compounds were defined in JT-FE. The major components of JT-FE (as analyte/g extract) were; rutin (98753.4 ± 24.39 μg), catechin (58695.3 ± 12.971 μg), hesperidin (47445.2 ± 15.894 μg), quinic acid (38279.5 ± 14.239 μg) and malic acid (17536.8 ± 2.279 μg). In the mineral analysis we made; Sodium, calcium, magnesium and phosphorus elements were found at macro level, Zn and Cr³⁺ minerals were found at trace level.

CONCLUSION

Our findings show that JT-FE, prepared by decoction, is rich in phenolic and mineral content and strong in antihyperglycemic activity. That's why Jerusalem thorn fruits can be a useful antidiabetic phytotherapy agent.

Metabolomic profiling to reveal the therapeutic potency of Posidonia oceanica nanoparticles in diabetic rats

Posidonia oceanica is a sea grass belonging to the family Posidoniaceae, which stands out as a substantial reservoir of bioactive compounds. In this study, the secondary metabolites of the P. oceanica rhizome were annotated using UPLC-HRESI-MS/MS, revealing 86 compounds including simple phenolic acids, flavonoids, and their sulphated conjugates. Moreover, the P. oceanica butanol extract exhibited substantial antioxidant and antidiabetic effects in vitro. Thus, a reliable, robust drug delivery system was developed through the encapsulation of P. oceanica extract in gelatin nanoparticles to protect active constituents, control their release and enhance their therapeutic activity. To confirm these achievements, untargeted GC-MS metabolomics analysis together with biochemical evaluation was employed to investigate the in vivo anti-diabetic potential of the P. oceanica nano-extract. The results of this study demonstrated that the P. oceanica gelatin nanoparticle formulation reduced the serum fasting blood glucose level significantly (p < 0.05) in addition to improving the insulin level, together with the elevation of glucose transporter 4 levels. Besides, multivariate/univariate analyses of the GC-MS metabolomic dataset revealed several dysregulated metabolites in diabetic rats, which were restored to normalized levels after treatment with the P. oceanica gelatin nanoparticle formulation. These metabolites mainly originate from the metabolism of amino acids, fatty acids and carbohydrates, indicating that this type of delivery was more effective than the plain extract in regulating these altered metabolic processes. Overall, this study provides novel insight for the potential of P. oceanica butanol extract encapsulated in gelatin nanoparticles as a promising and effective antidiabetic therapy.

The potential of P. oceanica butanol extract encapsulated in gelatin nanoparticles as a promising and effective antidiabetic therapy has been investigated via metabolomics.

Dolichandrone serrulata flower extract ameliorates male reproductive damages in type 2 diabetic rats

Dolichandrone serrulata flower (DSF) has been believed to reduce blood glucose in hyperglycaemic persons with sub-fertility but its effect on improvement of male reproductive impairment has never been elucidated scientifically. This study attempted to investigate the hypoglycaemic effects of DSF on male reproductive damages in type 2 diabetes mellitus (T2DM) rats. Adult Sprague Dawley rats were divided into four groups (control, T2DM, DSF200 + T2DM and DSF600 + T2DM; n = 10/each). Control rats received low-fat diet for 14 days before saline injection while streptozocin (50 mg/kg BW) induced T2DM groups received high-fat diet and were orally administered with DSF (200 and 600 mg/kg BW) for 28 days. At the end, fasted blood glucose (FBG), malondialdehyde (MDA), testosterone, sperm quality, histology and protein expressions were examined. The result showed that DSF decreased high FBG and testicular MDA and increased testosterone levels of T2DM-treated rats. Low-sperm quality and histological malfunction were ameliorated in DSF-treated group. There was significant decrease in the expression of androgen receptor, heat-shock 70 and steroidogenic acute regulatory proteins of T2DM-treated rats. Our study demonstrated changes of six bands (116, 51, 45, 39, 35 and 29 kDas) of tyrosine-phosphorylated proteins. In conclusion, DSF could reduce the FBGand ameliorate the reproductive damages in male T2DM rats.

The Potential Mechanisms of the Neuroprotective Actions of Oil Palm Phenolics: Implications for Neurodegenerative Diseases

Neurodegenerative diseases (ND) can be characterized by degradation and subsequent loss of neurons. ND has been identified as the leading cause of disability-adjusted life years (DALYs) worldwide and is associated with various risk factors such as ageing, certain genetic polymorphisms, inflammation, immune and metabolic conditions that may induce elevated reactive oxygen species (ROS) release and subsequent oxidative stress. Presently, no specific cure or prevention is available for ND patients; the symptoms can be only alleviated via drug treatment or surgery. The existing pharmacological treatments are only available for partial treatment of the symptoms. A natural product known as oil palm phenolics (OPP), which is high in antioxidant, could become a potential supplementary antioxidant for neurodegenerative health. OPP is a water-soluble extract from palm fruit that demonstrated medicinal properties including anti-tumor, anti-diabetic and neuroprotective effects. In this review, OPP was proposed for its neuroprotective effects via several mechanisms including antioxidant and anti-inflammatory properties. Besides, OPP has been found to modulate the genes involved in neurotrophic activity. The evidence and proposed mechanism of OPP on the neuroprotective health may provide a comprehensive natural medicine approach to alleviate the symptoms of neurodegenerative diseases.

In vivo and in vitro antidiabetic potential of Taraxacum officinale root extracts

Taraxacum officinale F.H. Wigg (Asteraceae) root is traditionally used to treat diabetes, dyspepsia, heartburn, anorexia and hepatitis. In this work, petroleum ether, chloroform, methanol and aqueous extracts of T. officinale root were evaluated for their antidiabetic activity in normoglycemic and alloxan-induced diabetic mice at two concentrations (200 and 400 mg/kg) using antidiabetic and subcutaneous glucose tolerance tests. Herein, in vitro glucose uptake assay was performed using HepG2 and 2-NDBG, while LC-MS/MS was employed for the phytochemical study of the main active constituents in the active extract. In the experiments, T. officinale root aqueous extract (400 mg/kg) showed a significant decrement in blood glucose level (62.33%, p ≤0.05), while other extracts (p >0.05) showed insignificant activity – in alloxan-induced diabetic mice with no apparent effect on the normoglycemic model. The extracts also showed an insignificant reduction in glucose levels (p >0.05) in the subcutaneous glucose tolerance test. However, a significant glucose uptake enhancement (149.6724%, p ≤0.05) was exhibited by the aqueous extract. Phytochemical study of the aqueous extract showed higher total phenolic than total flavonoid content, in which chlorogenic acid, protocatechuic acid, and luteolin-7-glucoside were identified.

Diabetic complications and oxidative stress: The role of phenolic-rich extracts of saw palmetto and date palm seeds

Recently, we reported that the date palm seed (DP) and saw palmetto seed (SP) extracts possessed a great amount of phenolic contents with potent antioxidant, antimicrobial, and anti-inflammatory activities. Therefore, this study aimed to assess the role of DP and SP phenolic-rich extracts in modulating diabetic complications and oxidative stress in the STZ- diabetic rat. DP and SP extracts significantly inhibited both microbial and pancreatic α-amylases. The STZ-induced diabetic rat groups treated with DP and SP extracts exhibited reversed hyperglycemia (40% and 54%, p < .001-.01) and body weight (70%, p < .001) alteration close to normal. Moreover, DP and SP extracts modulated serious damages in the structures of the pancreas, kidney, and liver of diabetic rats. DP and SP extracts improved the decline of the activities of antioxidant enzymes: Catalase, glutathione-S-transferase, glutathione reductase, and glutathione peroxidase in liver, kidney, and pancreas of the diabetic rats. PRACTICAL APPLICATIONS: Generally, date seed is a rich source of dietary fibers, polyphenols, and antioxidants and used in foods and pharmaceuticals. Our study reported that date palm seed (DP) and saw palmetto seed (SP) phenolic-rich extracts attenuated diabetes and its complications, probably tissue regeneration and normalizing the oxidative stress in the STZ-induced diabetic rat.

Characterization of the Corynebacterium glutamicum dehydroshikimate dehydratase QsuB and its potential for microbial production of protocatechuic acid

The dehydroshikimate dehydratase (DSD) from Corynebacterium glutamicum encoded by the qsuB gene is related to the previously described QuiC1 protein (39.9% identity) from Pseudomonas putida. Both QuiC1 and QsuB are two-domain bacterial DSDs. The N-terminal domain provides dehydratase activity, while the C-terminal domain has sequence identity with 4-hydroxyphenylpyruvate dioxygenase. Here, the QsuB protein and its N-terminal domain (N-QsuB) were expressed in the T7 system, purified and characterized. QsuB was present mainly in octameric form (60%), while N-QsuB had a predominantly monomeric structure (80%) in aqueous buffer. Both proteins possessed DSD activity with one of the following cofactors (listed in the order of decreasing activity): Co2+, Mg2+, Mn2+. The Km and kcat values for the QsuB enzyme (Km ~ 1 mM, kcat ~ 61 s-1) were two and three times higher than those for N-QsuB. 3,4-DHBA inhibited QsuB (Ki ~ 0.38 mM, Ki' ~ 0.96 mM) and N-QsuB (Ki ~ 0.69 mM) enzymes via mixed and noncompetitive inhibition mechanism, respectively. E. coli MG1655ΔaroEPlac‒qsuB strain produced three times more 3,4-DHBA from glucose in test tube fermentation than the MG1655ΔaroEPlac‒n-qsuB strain. The C-terminal domain activity towards 3,4-DHBA was not established in vitro. This domain was proposed to promote protein oligomerization for maintaining structural stability of the enzyme. The dimer formation of QsuB protein was more predictable (ΔG = ‒15.8 kcal/mol) than the dimerization of its truncated version N-QsuB (ΔG = ‒0.4 kcal/mol).

Twelve-Week Protocatechuic Acid Administration Improves Insulin-Induced and Insulin-Like Growth Factor-1-Induced Vasorelaxation and Antioxidant Activities in Aging Spontaneously Hypertensive Rats

Protocatechuic acid (PCA), a strong antioxidant, has been reported for its cardiovascular-protective effects. This study aimed to investigate the effects of PCA administration on vascular endothelial function, mediated by insulin and insulin-like growth factor-1 (IGF-1), and antioxidant activities in aging hypertension. Thirty-six-week-old male aging spontaneously hypertensive rats were randomly divided into vehicle control (SHR) and PCA (SHR+PCA) groups, while age-matched Wistar–Kyoto rats (WKY) served as the normotensive vehicle control group. The oral PCA (200 mg/kg/day) was administered daily for a total of 12 weeks. When the rats reached the age of 48 weeks, the rat aortas were isolated for the evaluation of vascular reactivity and Western blotting. Also, nitric oxide (NO) production and antioxidant activities were examined among the three groups. The results showed that, when compared with the SHR group, the insulin-induced and IGF-1-induced vasorelaxation were significantly improved in the SHR+PCA group. There was no significant difference in the endothelium-denuded vessels among the three groups. After the pre-incubation of phosphatidylinositol 3-kinase (PI3K) or NO synthase (NOS) inhibitors, the vasorelaxation was abolished and comparable among the three groups. The protein levels of insulin receptors, IGF-1 receptors, phospho-protein kinase B (p-Akt)/Akt, and phospho-endothelial NOS (p-eNOS)/eNOS in aortic tissues were significantly enhanced in the SHR+PCA group when compared with the SHR group. Moreover, significant improvements of nitrate/nitrite concentration and antioxidant activities, including superoxide dismutase, catalase, and total antioxidants, were also found in the SHR+PCA group. In conclusion, the 12 weeks of PCA administration remarkably improved the endothelium-dependent vasorelaxation induced by insulin and IGF-1 in aging hypertension through enhancing the PI3K–NOS–NO pathway. Furthermore, the enhanced antioxidant activities partly contributed to the improved vasorelaxation.

The Pharmacological Potential of Oil Palm Phenolics (OPP) Individual Components

The oil palm tree (Elaeis guineensis) from the family Arecaceae is a high oil-producing agricultural crop. A significant amount of vegetation liquor is discarded during the palm oil milling process amounting to 90 million tons per year around the world. This water-soluble extract is rich in phenolic compounds known as Oil Palm Phenolics (OPP). Several phenolic acids including the three isomers of caffeoylshikimic acid (CFA), p-hydroxybenzoic acid (PHBA), protocatechuic acid (PCA) and hydroxytyrosol are among the primary active ingredients in the OPP. Previous investigations have reported several positive pharmacological potentials by OPP such as neuroprotective and atheroprotective effects, anti-tumor and reduction in Aβ deposition in Alzheimer's disease model. In the current review, the pharmacological potential for CFA, PHBA, PCA and hydroxytyrosol is carefully reviewed and evaluated.

Timbe (Acaciella angustissima) Pods Extracts Reduce the Levels of Glucose, Insulin and Improved Physiological Parameters, Hypolipidemic Effect, Oxidative Stress and Renal Damage in Streptozotocin-Induced Diabetic Rats

In Mexico one in 14 deaths are caused by diabetes mellitus (DM) or by the macro and microvascular disorders derived from it. A continuous hyperglycemic state is characteristic of DM, resulting from a sustained state of insulin resistance and/or a dysfunction of β-pancreatic cells. Acaciella angustissima is a little studied species showing a significant antioxidant activity that can be used as treatment of this disease or preventive against the complications. The objective of this study was to explore the effect of oral administration of A. angustissima methanol extract on physiological parameters of streptozotocin-induced diabetic rats. The results indicated a significant reduction in blood glucose levels, an increase in serum insulin concentration, a decrease in lipid levels and an improvement in the parameters of kidney damage by applying a concentration of 100 mg/Kg B.W. However, glucose uptake activity was not observed in the adipocyte assay. Moreover, the extract of A. angustissima displayed potential for the complementary treatment of diabetes and its complications likely due to the presence of bioactive compounds such as protocatechuic acid. This study demonstrated that methanol extract of Acacciella angustissima has an antidiabetic effect by reducing the levels of glucose, insulin and improved physiological parameters, hypolipidemic effect, oxidative stress and renal damage in diabetic rats.

Natural products for the treatment of type 2 diabetes mellitus: Pharmacology and mechanisms

Epidemiological studies have implied that diabetes mellitus (DM) will become an epidemic accompany with metabolic and endocrine disorders worldwide. Most of DM patients are affected by type 2 diabetes mellitus (T2DM) with insulin resistance and insulin secretion defect. Generally, the strategies to treat T2DM are diet control, moderate exercise, hypoglycemic and lipid-lowing agents. Despite the therapeutic benefits for the treatment of T2DM, most of the drugs can produce some undesirable side effects. Considering the pathogenesis of T2DM, natural products (NPs) have become the important resources of bioactive agents for anti-T2DM drug discovery. Recently, more and more natural components have been elucidated to possess anti-T2DM properties, and many efforts have been carried out to elucidate the possible mechanisms. The aim of this paper was to overview the activities and underlying mechanisms of NPs against T2DM. Developments of anti-T2DM agents will be greatly promoted with the increasing comprehensions of NPs for their multiple regulating effects on various targets and signal pathways.

Antihypertensive and antioxidant effects of protocatechuic acid in deoxycorticosterone acetate-salt hypertensive rats

Protocatechuic acid (PCA) is a natural antioxidant with beneficial cardiovascular properties. In this study, the effect of supplementation with PCA was investigated in deoxycorticosterone acetate (DOCA)-salt hypertension. Male Wistar rats received DOCA (25 mg/kg, s.c.) twice weekly and 1% NaCl in drinking water and simultaneously treated with PCA (50, 100 and 200 mg/kg, p.o.) for 4 weeks. Systolic blood pressure (SBP) was detected using tail-cuff method. Electrolytes including Na⁺, K⁺ and chloride, catalase activity, glutathione, total antioxidant capacity, malondialdehyde (MDA) and hydroperoxides concentration were measured in serum samples. Body and organs weight, water intake and, kidney and heart histopathology were also evaluated. Administration of PCA reversed the changes caused by DOCA-salt approximately at all doses. At the lowest dose, PCA significantly decreased SBP (132.5 ± 4.0 vs 152.3 ± 4.5 mmHg, P < .05), serum sodium (138.5  ± 1.52 vs 141 ± 1.50, P < .05) and chloride level (101.6 ± 1.47 vs 110 ± 1.39, P < .01) and raised serum potassium level (3.8 ± 0.09 vs 3.1 ± 0.17, P < .05) compared with DOCA-salt hypertensive rats. PCA increased serum catalase activity, total antioxidant capacity and glutathione concentration and reduced MDA and hydroperoxides levels. PCA also improved organ weight changes, reduced water intake and moderately prevented histopathological changes of kidney and heart upon DOCA-salt administration. The present study indicates the antihypertensive and antioxidant effects of PCA against DOCA-salt hypertension.

Sansevieria roxburghiana Schult. & Schult. F. (Family: Asparagaceae) Attenuates Type 2 Diabetes and Its Associated Cardiomyopathy

BACKGROUND

Sansevieria roxburghiana Schult. & Schult. F. (Family: Asparagaceae) rhizome has been claimed to possess antidiabetic activity in the ethno-medicinal literature in India. Therefore, present experiments were carried out to explore the protective role of edible (aqueous) extract of S. roxburghiana rhizome (SR) against experimentally induced type 2 diabetes mellitus (T2DM) and its associated cardiomyopathy in Wistar rats.

METHODS

SR was chemically characterized by GC-MS analysis. Antidiabetic activity of SR (50 and 100 mg/kg, orally) was measured in high fat diets (ad libitum) + low-single dose of streptozotocin (35 mg/kg, intraperitoneal) induced type 2 diabetic (T2D) rat. Fasting blood glucose level was measured at specific intermissions. Serum biochemical and inflammatory markers were estimated after sacrificing the animals. Besides, myocardial redox status, expressions of signal proteins (NF-κB and PKCs), histological and ultrastructural studies of heart were performed in the controls and SR treated T2D rats.

RESULTS

Phytochemical screening of the crude extract revealed the presence of phenolic compounds, sugar alcohols, sterols, amino acids, saturated fatty acids within SR. T2D rats exhibited significantly (p < 0.01) higher fasting blood glucose level with respect to control. Alteration in serum lipid profile (p < 0.01) and increased levels of lactate dehydrogenase (p < 0.01) and creatine kinase (p < 0.01) in the sera revealed the occurrence of hyperlipidemia and cell destruction in T2D rats. T2DM caused significant (p < 0.05-0.01) alteration in the biochemical markers in the sera. T2DM altered the redox status (p < 0.05-0.01), decreased (p < 0.01) the intracellular NAD and ATP concentrations in the myocardial tissues of experimental rats. While investigating the molecular mechanism, activation PKC isoforms was observed in the selected tissues. T2D rats also exhibited an up-regulation in nuclear NF-κB (p65) in the cardiac tissues. So, oral administration of SR (50 and 500 mg/kg) could reduce hyperglycemia, hyperlipidemia, membrane disintegration, oxidative stress, vascular inflammation and prevented the activation of oxidative stress induced signaling cascades leading to cell death. Histological and ultra-structural studies of cardiac tissues supported the protective characteristics of SR.

CONCLUSIONS

From the present findings it can be concluded that, SR could offer protection against T2DM and its associated cardio-toxicity via multiple mechanisms viz. hypoglycemic, antioxidant and anti-inflammatory actions.

Protocatechuic Acid: Inhibition of Fibril Formation, Destabilization of Preformed Fibrils of Amyloid-β and α-Synuclein, and Neuroprotection

Protocatechuic acid (PCA) is the major metabolite of the anthocyanin known as cyanidin 3-glucoside. It is found in plasma and tissues, such as the brain, heart, liver, and kidneys, following consumption of a rich source of this flavonoid. The abnormal pathological assembly of amyloid-β (Aβ) and α-synuclein (αS) is an underlying mechanism involved in the formation of amyloid plaques and Lewy bodies in the brain, which are responsible for neuropathology symptoms in Alzheimer's (AD) and Parkinson's diseases (PD), respectively. This research was performed to evaluate the protective effects of PCA, by establishing its potential role in inhibiting aggregation and fibril destabilization of Aβ and αS proteins. It has been found that PCA inhibits the aggregation of Aβ and αS and destabilizes their preformed fibrils. These results were confirmed by TEM images, electrophoresis, and immunoblotting experiments. Furthermore, PCA prevents the death of PC12 cells triggered by Aβ- and αS-induced toxicity.

The Chemistry of Gut Microbial Metabolism of Polyphenols

Gut microbiota contribute to the metabolism of dietary polyphenols and affect the bioavailability of both the parent polyphenols and their metabolites. Although there is a large number of reports of specific polyphenol metabolites, relatively little is known regarding the chemistry and enzymology of the metabolic pathways utilized by specific microbial species and taxa, which is the focus of this review. Major classes of dietary polyphenols include monomeric and oligomeric catechins (proanthocyanidins), flavonols, flavanones, ellagitannins, and isoflavones. Gut microbial metabolism of representatives of these polyphenol classes can be classified as A- and C-ring cleavage (retro Claisen reactions), C-ring cleavage mediated by dioxygenases, dehydroxylations (decarboxylation or reduction reactions followed by release of H₂O molecules), and hydrogenations of alkene moieties in polyphenols, such as resveratrol, curcumin, and isoflavones (mediated by NADPH-dependent reductases). The qualitative and quantitative metabolic output of the gut microbiota depends to a large extent on the metabolic capacity of individual taxa, which emphasizes the need for assessment of functional analysis in conjunction with determinations of gut microbiota compositions.

Allium hookeri root protects oxidative stress-induced inflammatory responses and β-cell damage in pancreas of streptozotocin-induced diabetic rats

Background

Water extract from the root of Allium hookeri (AH) shows anti-inflammatory, antioxidant, and free radical scavenging effects. In this study, the ameliorating effects of AH on oxidative stress-induced inflammatory response and β-cell damage in the pancreas of streptozotocin (STZ)-induced type 1 diabetic rats were investigated.

Methods

AH (100 mg/kg body weight/day) was orally administered every day for 2 weeks to STZ-induced diabetic rats. After the final administration of AH, biochemical parameters including glucose, insulin, reactive oxygen species levels, and protein expressions related to antioxidant defense system in the pancreas of STZ-induced diabetic rats.

Results

The diabetic rats showed loss of body weight and increased pancreatic weight, while the oral administration of AH attenuated body and pancreatic weight changes. Moreover, the administration of AH caused a slightly decrease in the serum glucose level and a significant increase in the serum and pancreatic insulin levels in the diabetic rats. AH also significantly reduced the enhanced levels of reactive oxygen species, oxidative stress biomarker, in the serum and pancreas. The diabetic rats exhibited a down-regulation of the protein expression related to antioxidant defense system in the pancreas, but AH administration significantly up-regulated the expression of the heme oxygenase-1 (HO-1). Furthermore, AH treatment was reduced the overexpression of nuclear factor-kappa B (NF-кB)p65 and NF-кBp65-induced inflammatory cytokines such as tumor necrosis factor-α and interleukin-6. In addition, AH treatment was less pancreatic β-cell damaged compared with those of the diabetic rats.

Conclusion

These results provide important evidence that AH has a HO-1 activity on the oxidative stress conditions showing pancreato-protective effects against the development of inflammation in the diabetic rats. This study provides scientific evidence that AH protects the inflammatory responses by modulated NF-кBp65 signaling pathway through activation of HO-1 in the pancreas of STZ-induced diabetic rats.

Antidiabetic Effects of Simple Phenolic Acids: A Comprehensive Review

Diabetes mellitus (DM) has become a major public health threat across the globe. Current antidiabetic therapies are based on synthetic drugs that very often have side effects. It has been widely acknowledged that diet plays an important role in the management of diabetes. Phenolic acids are widely found in daily foods such as fruits, vegetables, cereals, legumes, and wine and they provide biological, medicinal, and health properties. Simple phenolic acids have been shown to increase glucose uptake and glycogen synthesis, improve glucose and lipid profiles of certain diseases (obesity, cardiovascular diseases, DM, and its complication). The current review is an attempt to list out the antidiabetic effects of simple phenolic acids from medicinal plants and botanical foods.

Therapeutic and Prophylactic Potential of Morama (Tylosema esculentum): A Review

Tylosema esculentum (morama) is a highly valued traditional food and source of medicine for the San and other indigenous populations that inhabit the arid to semi-arid parts of Southern Africa. Morama beans are a rich source of phenolic acids, flavonoids, certain fatty acids, non-essential amino acids, certain phytosterols, tannins and minerals. The plant's tuber contains griffonilide, behenic acid and starch. Concoctions of extracts from morama bean, tuber and other local plants are frequently used to treat diarrhoea and digestive disorders by the San and other indigenous populations. Information on composition and bioactivity of phytochemical components of T. esculentum suggests that the polyphenol-rich extracts of the bean testae and cotyledons have great potential as sources of chemicals that inhibit infectious microorganisms (viral, bacterial and fungal, including drug-resistant strains), offer protection against certain non-communicable diseases and promote wound healing and gut health. The potential antinutritional properties of a few morama components are also highlighted. More research is necessary to reveal the full prophylactic and therapeutic potential of the plant against diseases of the current century. Research on domestication and conservation of the plant offers new hope for sustainable utilisation of the plant.

Protocatechuic acid protects brain mitochondrial function in streptozotocin-induced diabetic rats

Brain mitochondrial dysfunction has been demonstrated in diabetic animals with neurodegeneration. Protocatechuic acid (PCA), a major metabolite of anthocyanin, has been shown to exert glycemic control and oxidative stress reduction in the heart. However, its effects on oxidative stress and mitochondrial function in the brain under diabetic condition have never been investigated. We found that PCA exerted glycemic control, attenuates brain mitochondrial dysfunction, and contributes to the prevention of brain oxidative stress in diabetic rats.

Pharmacological properties of protocatechuic Acid and its potential roles as complementary medicine

This paper reviews the reported pharmacological properties of protocatechuic acid (PCA, 3,4-dihydroxy benzoic acid), a type of phenolic acid found in many food plants such as olives and white grapes. PCA is a major metabolite of anthocyanin. The pharmacological actions of PCA have been shown to include strong in vitro and in vivo antioxidant activity. In in vivo experiments using rats and mice, PCA has been shown to exert anti-inflammatory as well as antihyperglycemic and antiapoptotic activities. Furthermore, PCA has been shown to inhibit chemical carcinogenesis and exert proapoptotic and antiproliferative effects in different cancerous tissues. Moreover, in vitro studies have shown PCA to have antimicrobial activities and also to exert synergistic interaction with some antibiotics against resistant pathogens. This review aims to comprehensively summarize the pharmacological properties of PCA reported to date with an emphasis on its biological properties and mechanisms of action which could be therapeutically useful in a clinical setting.

Protocatechuic acid exerts a cardioprotective effect in type 1 diabetic rats

Oxidative stress has been shown to play an important role in the pathogenesis of diabetes-induced cardiac dysfunction. Protocatechuic acid (PCA) is a phenolic compound, a main metabolite of anthocyanin, which has been reported to display various pharmacological properties. We proposed the hypothesis that PCA exerts cardioprotection in type 1 diabetic (T1DM) rats. T1DM was induced in male Sprague-Dawley rats by a single i.p. injection of 50 mg/kg streptozotocin (STZ) and groups of these animals received the following treatments for 12 weeks: i) oral administration of vehicle, ii) oral administration of PCA at a dose of 50  mg/kg per day, iii) oral administration of PCA at a dose of 100 mg/kg per day, iv) s.c. injection of insulin at a dose of 4 U/kg per day, and v) a combination of PCA, 100 mg/kg per day and insulin, 4 U/kg per day. Metabolic parameters, results from echocardiography, and heart rate variability were monitored every 4 weeks, and the HbA1c, cardiac malondialdehyde (MDA), cardiac mitochondrial function, and cardiac BAX/BCL2 expression were evaluated at the end of treatment. PCA, insulin, and combined drug treatments significantly improved metabolic parameters and cardiac function as shown by increased percentage fractional shortening and percentage left ventricular ejection fraction and decreased low-frequency:high-frequency ratio in T1DM rats. Moreover, all treatments significantly decreased plasma HbA1c and cardiac MDA levels, improved cardiac mitochondrial function, and increased BCL2 expression. Our results demonstrated for the first time, to our knowledge, the efficacy of PCA in improving cardiac function and cardiac autonomic balance, preventing cardiac mitochondrial dysfunction, and increasing anti-apoptotic protein in STZ-induced T1DM rats. Thus, PCA possesses a potential cardioprotective effect and could restore cardiac function when combined with insulin treatment. These findings indicated that supplementation with PCA might be helpful for the prevention and alleviation of cardiovascular complications in T1DM.

Hydroxybenzoic acid isomers and the cardiovascular system

Today we are beginning to understand how phytochemicals can influence metabolism, cellular signaling and gene expression. The hydroxybenzoic acids are related to salicylic acid and salicin, the first compounds isolated that have a pharmacological activity. In this review we examine how a number of hydroxyphenolics have the potential to ameliorate cardiovascular problems related to aging such as hypertension, atherosclerosis and dyslipidemia. The compounds focused upon include 2,3-dihydroxybenzoic acid (Pyrocatechuic acid), 2,5-dihydroxybenzoic acid (Gentisic acid), 3,4-dihydroxybenzoic acid (Protocatechuic acid), 3,5-dihydroxybenzoic acid (α-Resorcylic acid) and 3-monohydroxybenzoic acid. The latter two compounds activate the hydroxycarboxylic acid receptors with a consequence there is a reduction in adipocyte lipolysis with potential improvements of blood lipid profiles. Several of the other compounds can activate the Nrf2 signaling pathway that increases the expression of antioxidant enzymes, thereby decreasing oxidative stress and associated problems such as endothelial dysfunction that leads to hypertension as well as decreasing generalized inflammation that can lead to problems such as atherosclerosis. It has been known for many years that increased consumption of fruits and vegetables promotes health. We are beginning to understand how specific phytochemicals are responsible for such therapeutic effects. Hippocrates’ dictum of ‘Let food be your medicine and medicine your food’ can now be experimentally tested and the results of such experiments will enhance the ability of nutritionists to devise specific health-promoting diets.

Protocatechuic acid improves cognitive deficits and attenuates amyloid deposits, inflammatory response in aged AβPP/PS1 double transgenic mice

Protocatechuic acid (PCA), a phenolic compound of Radix Salviae Miltiorrhizae (RSM), has been found to have a protective effect on improving cognitive deficits in STZ-induced AD rats. The present study aimed to evaluate the potential protection activity of PCA on improving cognitive deficits and attenuating Aβ deposition and inflammatory responses in aged AβPP/PS1 double transgenic AD-model mice. The results of Morris water maze test showed that PCA (100mg/kg) significantly prolonged the mean latency time and the path length of AβPP/PS1 mice. PCA could significantly reduce the number of Aβ positive expressions in the hippocampus and cerebral cortex of AβPP/PS1 mice by immunocytochemical assay with Congo red staining and decrease remarkably APP expression level by Western blot analysis (P<0.01). The results from ELISA and Western blot analysis showed that the levels of inflammatory cytokines including TNF-α, IL-1β, IL-6 and IL-8 decreased remarkably by the treatment with PCA (P<0.01). Further, there was a substantial increase of brain derived neurotrophic factor (BDNF) in the hippocampus and cerebral cortex of AβPP/PS1 mice treated with PCA (P<0.01). The present study provided confirmatory evidence that PCA significantly decreased Aβ deposits, APP and inflammatory response, whereas increased learning and memory ability, as well as enhanced BDNF level. Our findings indicated that PCA is an effective neuroprotective agent for AD therapy. It might be associated with the attenuation on Aβ deposits and inflammation responses involved in the process.

An in vitro assessment of the effect of Athrixia phylicoides DC. aqueous extract on glucose metabolism

Athrixia phylicoides DC. is an aromatic shrub indigenous to the eastern parts of Southern Africa. Indigenous communities brew "bush tea" from dried twigs and leaves of A. phylicoides, which is consumed as a beverage and used for its medicinal properties. Plant polyphenols have been shown to be beneficial to Type 2 diabetes mellitus (T2D) and obesity. Aqueous extracts of the plant have been shown to be rich in polyphenols, in particular phenolic acids, which may enhance glucose uptake and metabolism. The aim of this study was to determine the phenolic composition of a hot water A. phylicoides extract and assess its in vitro effect on cellular glucose utilisation. The most abundant phenolic compounds in the extract were 6-hydroxyluteolin-7-O-glucoside, chlorogenic acid, protocatechuic acid, a di-caffeoylquinic acid and a methoxy-flavonol derivative. The extract increased glucose uptake in C2C12, Chang and 3T3-L1 cells, respectively. Intracellular glucose was utilised by both oxidation (C2C12 myocytes and Chang cells; p < 0.01 and p < 0.05, respectively) and by increased glycogen storage (Chang cells; p < 0.05). No cytotoxicity was observed in Chang cells at the concentrations tested. The effects of the extract were not dose-dependent. A. phylicoides aqueous extract stimulated in vitro glucose uptake and metabolism, suggesting that consumption of this phenolic-rich extract could potentially ameliorate metabolic disorders related to obesity and T2D.