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Special Issue "Plant Polyphenols as Potential Therapeutic Agents for Diabetes and Obesity"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Natural Products".

Deadline for manuscript submissions: closed (31 May 2017)

Special Issue Editors

Guest Editor
Prof. Solomon Habtemariam

Pharmacognosy Research Laboratories & Herbal Analysis Services, University of Greenwich, Central Avenue, Charham-Maritime, Kent ME4 4TB, UK
Website | E-Mail
Interests: pharmacognosy; herbal medicine standardization; drug discovery; pharmacology; phytochemistry
Guest Editor
Prof. Giovanni Lentini

Department of Pharmacy-Drug Sciences, University of Studies of Bari Aldo Moro, Via E. Orabona n. 4, Bari 70126, Italy
Website | E-Mail
Interests: medicinal chemistry; drug discovery; chirality; pharmacology; phytochemistry

Special Issue Information

Dear Colleagues,

Plant polyphenols are a diverse group of secondary metabolites predominantly synthesised through the shikimic acid and acetate/polyketide pathways. The common perception of polyphenols’ pharmacological effect is that they are mediated through a nonspecific interaction with proteins/enzymes and general antioxidant mechanisms. Numerous specific biological effects at sub-micromolar concentration are however common for many polyphenols. One of the distinct advantages of polyphenols is in their therapeutic potential for complex diseases like diabetes and obesity, where a one drug → one target → one disease approach offers limited efficacy. Through their multifunctional actions, plant polyphenols could ameliorate the various components of such diseases and offer a better outcome through the one drug → multitarget → one/multidisease principle. They could also work in a synergistic manner, with their crude mixtures often showing a higher activity than the isolated pure compounds (multidrug → multitarget → one/multidisease approach). Since both diabetes and obesity cases are now growing in the world with epidemic proportions, our desperate search for safer drugs from natural sources must continue. In this regard, polyphenols are best placed and this Special Issue is designed to scrutinise recent developments in the chemistry, pharmacology, and medical implications of polyphenols as potential therapeutics for diabetes and/or obesity. We are thus inviting colleagues to join us by making their valuable contributions to Molecules.

Prof. Solomon Habtemariam
Prof. Giovanni Lentini
Guest Editors

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Keywords

  • plant polyphenols
  • diabetes
  • obesity
  • mechanism of action
  • drug discovery

Published Papers (8 papers)

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Research

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Open AccessArticle Development of a UPLC-MS/MS Method for Simultaneous Determination of Six Flavonoids in Rat Plasma after Administration of Maydis stigma Extract and Its Application to a Comparative Pharmacokinetic Study in Normal and Diabetic Rats
Molecules 2017, 22(8), 1267; doi:10.3390/molecules22081267
Received: 23 June 2017 / Revised: 12 July 2017 / Accepted: 27 July 2017 / Published: 29 July 2017
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Abstract
Maydis stigma is an important medicine herb used in many parts of the world for treatment of diabetes mellitus, which main bioactive ingredients are flavonoids. This paper describes for the first time a study on the comparative pharmacokinetics of six active flavonoid ingredients
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Maydis stigma is an important medicine herb used in many parts of the world for treatment of diabetes mellitus, which main bioactive ingredients are flavonoids. This paper describes for the first time a study on the comparative pharmacokinetics of six active flavonoid ingredients of Maydis stigma in normal and diabetic rats orally administrated with the decoction. Therefore, an efficient and sensitive ultra high performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous determination of six anti-diabetic ingredients (cynaroside, quercetin, luteolin, isorhamnetin, rutin and formononetin) of Maydis stigma in rat plasma has been developed and validated in plasma samples, which showed good linearity over a wide concentration range (r2 > 0.99), and gave a lower limit of quantification of 1.0 ng·mL−1 for the analytes. The intra- and interday assay variability was less than 15% for all analytes. The mean extraction recoveries and matrix effect of analytes and IS from rats plasma were all more than 85.0%. The stability results showed the measured concentration for six analytes at three QC levels deviated within 15.0%. The results indicated that significant differences in the pharmacokinetic parameters of the analytes were observed between the two groups of animals, whereby the absorptions of these analytes in the diabetic group were all significantly higher than those in the normal group, which provides an experimental basis for the role of Maydis stigma in anti-diabetic treatment. Full article
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Open AccessArticle Resveratrol Improves Glycemic Control in Type 2 Diabetic Obese Mice by Regulating Glucose Transporter Expression in Skeletal Muscle and Liver
Molecules 2017, 22(7), 1180; doi:10.3390/molecules22071180
Received: 16 June 2017 / Revised: 5 July 2017 / Accepted: 6 July 2017 / Published: 14 July 2017
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Abstract
Insulin resistance participates in the glycaemic control disruption in type 2 diabetes mellitus (T2DM), by reducing muscle glucose influx and increasing liver glucose efflux. GLUT4 (Slc2a4 gene) and GLUT2 (Slc2a2 gene) proteins play a fundamental role in the muscle and liver
[...] Read more.
Insulin resistance participates in the glycaemic control disruption in type 2 diabetes mellitus (T2DM), by reducing muscle glucose influx and increasing liver glucose efflux. GLUT4 (Slc2a4 gene) and GLUT2 (Slc2a2 gene) proteins play a fundamental role in the muscle and liver glucose fluxes, respectively. Resveratrol is a polyphenol suggested to have an insulin sensitizer effect; however, this effect, and related mechanisms, have not been clearly demonstrated in T2DM. We hypothesized that resveratrol can improve glycaemic control by restoring GLUT4 and GLUT2 expression in muscle and liver. Mice were rendered obese T2DM in adult life by neonatal injection of monosodium glutamate. Then, T2DM mice were treated with resveratrol for 60 days or not. Glycaemic homeostasis, GLUT4, GLUT2, and SIRT1 (sirtuin 1) proteins (Western blotting); Slc2a4, Slc2a2, and Pck1 (key gluconeogenic enzyme codifier) mRNAs (RT-qPCR); and hepatic glucose efflux were analysed. T2DM mice revealed: high plasma concentration of glucose, fructosamine, and insulin; insulin resistance (insulin tolerance test); decreased Slc2a4/GLUT4 content in gastrocnemius and increased Slc2a2/GLUT2 content in liver; and increased Pck1 mRNA and gluconeogenic activity (pyruvate tolerance test) in liver. All alterations were restored by resveratrol treatment. Additionally, in both muscle and liver, resveratrol increased SIRT1 nuclear content, which must participate in gene expression regulations. In sum, the results indisputably reveals that resveratrol improves glycaemic control in T2DM, and that involves an increase in muscle Slc2a4/GLUT4 and a decrease in liver Slc2a2/GLUT2 expression. This study contributes to our understanding how resveratrol might be prescribed for T2DM according to the principles of evidence-based medicine. Full article
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Open AccessArticle Evaluation of the Antidiabetic Activity and Chemical Composition of Geranium collinum Root Extracts—Computational and Experimental Investigations
Molecules 2017, 22(6), 983; doi:10.3390/molecules22060983
Received: 2 May 2017 / Revised: 3 June 2017 / Accepted: 9 June 2017 / Published: 13 June 2017
Cited by 1 | PDF Full-text (1231 KB) | HTML Full-text | XML Full-text
Abstract
The root of Geranium collinum Steph is known in Tajik traditional medicine for its hepatoprotective, antioxidant, and anti-inflammatory therapeutic effects. The present study was conducted to evaluate of potential antidiabetic, antioxidant activities, total polyphenolic and flavonoid content from the different extracts (aqueous, aqueous-ethanolic)
[...] Read more.
The root of Geranium collinum Steph is known in Tajik traditional medicine for its hepatoprotective, antioxidant, and anti-inflammatory therapeutic effects. The present study was conducted to evaluate of potential antidiabetic, antioxidant activities, total polyphenolic and flavonoid content from the different extracts (aqueous, aqueous-ethanolic) and individual compounds isolated of the root parts of G. collinum. The 50% aqueous-ethanolic extract possesses potent antidiabetic activity, with IC50 values of 0.10 μg/mL and 0.09 μg/mL for the enzymes protein-tyrosine phosphatase (1B PTP-1B) and α-glucosidase, respectively. Phytochemical investigations of the 50% aqueous-ethanolic extract of G. collinum, led to the isolation of ten pure compounds identified as 3,3′,4,4′-tetra-O-methylellagic acid (1), 3,3′-di-O-methylellagic acid (2), quercetin (3), caffeic acid (4), (+)-catechin (5), (–)-epicatechin (6), (–)-epigallocatechin (7), gallic acid (8), β-sitosterol-3-O-β-d-glucopyranoside (9), and corilagin (10). Their structures were determined based on 1D and 2D NMR and mass spectrometric analyses. Three isolated compounds exhibited strong inhibitory activity against PTP-1B, with IC50 values below 0.9 μg/mL, more effective than the positive control (1.46 μg/mL). Molecular docking analysis suggests polyphenolic compounds such as corilagin, catechin and caffeic acid inhibit PTP-1B and β-sitosterol-3-O-β-d-gluco-pyranoside inhibits α-glucosidase. The experimental results suggest that the biological activity of G. collinum is related to its polyphenol contents. The results are also in agreement with computational investigations. Furthermore, the potent antidiabetic activity of the 50% aqueous-ethanolic extract from G. collinum shows promise for its future application in medicine. To the best of our knowledge, we hereby report, for the first time, the antidiabetic activity of G. collinum. Full article
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Open AccessArticle Baccharis trimera (Less.) DC Exhibits an Anti-Adipogenic Effect by Inhibiting the Expression of Proteins Involved in Adipocyte Differentiation
Molecules 2017, 22(6), 972; doi:10.3390/molecules22060972
Received: 17 March 2017 / Revised: 20 May 2017 / Accepted: 7 June 2017 / Published: 12 June 2017
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Abstract
Baccharis trimera (Less.) DC (gorse) is a plant popularly used for the treatment of obesity. In this study, we prepared three B. trimera extracts aqueous extract (AE), decoction (AE-D), and methanol extract (ME) and investigated their antioxidant effects in six different tests and
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Baccharis trimera (Less.) DC (gorse) is a plant popularly used for the treatment of obesity. In this study, we prepared three B. trimera extracts aqueous extract (AE), decoction (AE-D), and methanol extract (ME) and investigated their antioxidant effects in six different tests and their anti-adipogenic effect in 3T3-L1 cells. The extracts showed a dose-dependent antioxidant activity in all tests. AE was the most potent antioxidant in copper and ferric ion chelation assays, whereas AE-D was the most potent in superoxide and hydroxyl radical scavenging assays, reducing power assay, and total antioxidant capacity analysis. Only ME showed a cytotoxic effect against 3T3-L1 cells. Lipid accumulation decreased in 3T3-L1 adipocytes in the presence of AE and AE-D extracts (0.5 to 1.0 mg/mL). In addition, the extracts dramatically attenuated the levels of adipogenic transcriptional factors, including CCAAT enhancer-binding protein α (C/EBPα), CCAAT enhancer-binding protein β (C/EBPβ), and gamma receptors by peroxisome proliferators (PPARγ), during adipogenesis. AE-D (1.0 mg/mL) caused an approximately 90% reduction in the levels of these molecules. We propose that B. trimera has an anti-adipogenic effect and could be used in the development of functional foods. Full article
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Open AccessArticle Effects of Flavonoids and Triterpene Analogues from Leaves of Eleutherococcus sieboldianus (Makino) Koidz. ‘Himeukogi’ in 3T3-L1 Preadipocytes
Molecules 2017, 22(4), 671; doi:10.3390/molecules22040671
Received: 16 February 2017 / Revised: 16 April 2017 / Accepted: 19 April 2017 / Published: 22 April 2017
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Abstract
Eleutherococcus sieboldianus (Makino) Koidz. is a local product from the area in and around Yonezawa City in Yamagata Prefecture, Japan. It has been used as a medicinal plant for a long time. We isolated and identified four types of flavonoid glycosides [astragalin (
[...] Read more.
Eleutherococcus sieboldianus (Makino) Koidz. is a local product from the area in and around Yonezawa City in Yamagata Prefecture, Japan. It has been used as a medicinal plant for a long time. We isolated and identified four types of flavonoid glycosides [astragalin (1), isoquercetin (2), rhamnocitrin 3-O-glucoside (3), and nicotiflorin (4)], a triterpene [methyl hederagenin (5)], and three types of triterpene glycosides [δ-hederin (6), echinocystic acid 3-O-arabinoside (7), and cauloside B (8)] from the methanol extract of E. sieboldianus, which regulates lipid accumulation in 3T3-L1 preadipocytes. Among the compounds isolated, 2 and 8 up- and down-regulated lipid accumulation and insulin induced adipocyte differentiation in 3T3-L1 preadipocytes. Compound 2 induced up-regulation of lipid accumulation and decreased adipocyte size, while 8 down-regulated lipid accumulations without decreasing cell size. Additionally, 2 increased adipogenic proteins [peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer-binding protein alpha (C/EBPα), and fatty-acid-binding protein 4 (FABP4)]. In contrast, 8 decreased the levels of all adipogenic proteins and glucose transporter type 4 (GLUT4), but increased adiponectin. Full article
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Review

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Open AccessReview Bioactive Compounds from Mexican Varieties of the Common Bean (Phaseolus vulgaris): Implications for Health
Molecules 2017, 22(8), 1360; doi:10.3390/molecules22081360
Received: 22 June 2017 / Revised: 9 August 2017 / Accepted: 12 August 2017 / Published: 17 August 2017
Cited by 1 | PDF Full-text (1511 KB) | HTML Full-text | XML Full-text
Abstract
As Mexico is located within Mesoamerica, it is considered the site where the bean plant originated and where it was domesticated. Beans have been an integral part of the Mexican diet for thousands of years. Within the country, there are a number of
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As Mexico is located within Mesoamerica, it is considered the site where the bean plant originated and where it was domesticated. Beans have been an integral part of the Mexican diet for thousands of years. Within the country, there are a number of genotypes possessing highly diverse physical and chemical properties. This review describes the major bioactive compounds contained on the Mexican varieties of the common bean. A brief analysis is carried out regarding the benefits they have on health. The effect of seed coat color on the nutraceutical compounds content is distinguished, where black bean stands out because it is high content of anthocyanins, polyphenols and flavonoids such as quercetin. This confers black bean with an elevated antioxidant capacity. The most prominent genotypes within this group are the “Negro San Luis”, “Negro 8025” and “Negro Jamapa” varieties. Conversely, the analyzed evidence shows that more studies are needed in order to expand our knowledge on the nutraceutical quality of the Mexican bean genotypes, either grown or wild-type, as well as their impact on health in order to be used in genetic improvement programs or as a strategy to encourage their consumption. The latter is based on the high potential it has for health preservation and disease prevention. Full article
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Open AccessReview The Antidiabetic Mechanisms of Polyphenols Related to Increased Glucagon-Like Peptide-1 (GLP1) and Insulin Signaling
Molecules 2017, 22(6), 903; doi:10.3390/molecules22060903
Received: 4 May 2017 / Revised: 24 May 2017 / Accepted: 26 May 2017 / Published: 30 May 2017
Cited by 4 | PDF Full-text (1227 KB) | HTML Full-text | XML Full-text
Abstract
Type-2 diabetes mellitus (T2DM) is an endocrine disease related to impaired/absent insulin signaling. Dietary habits can either promote or mitigate the onset and severity of T2DM. Diets rich in fruits and vegetables have been correlated with a decreased incidence of T2DM, apparently due
[...] Read more.
Type-2 diabetes mellitus (T2DM) is an endocrine disease related to impaired/absent insulin signaling. Dietary habits can either promote or mitigate the onset and severity of T2DM. Diets rich in fruits and vegetables have been correlated with a decreased incidence of T2DM, apparently due to their high polyphenol content. Polyphenols are compounds of plant origin with several documented bioactivities related to health promotion. The present review describes the antidiabetic effects of polyphenols, specifically related to the secretion and effects of insulin and glucagon-like peptide 1 (GLP1), an enteric hormone that stimulates postprandial insulin secretion. The evidence suggests that polyphenols from various sources stimulate L-cells to secrete GLP1, increase its half-life by inhibiting dipeptidyl peptidase-4 (DPP4), stimulate β-cells to secrete insulin and stimulate the peripheral response to insulin, increasing the overall effects of the GLP1-insulin axis. The glucose-lowering potential of polyphenols has been evidenced in various acute and chronic models of healthy and diabetic organisms. Some polyphenols appear to exert their effects similarly to pharmaceutical antidiabetics; thus, rigorous clinical trials are needed to fully validate this claim. The broad diversity of polyphenols has not allowed for entirely describing their mechanisms of action, but the evidence advocates for their regular consumption. Full article
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Open AccessReview Antidiabetic Effects of Tea
Molecules 2017, 22(5), 849; doi:10.3390/molecules22050849
Received: 18 April 2017 / Revised: 13 May 2017 / Accepted: 18 May 2017 / Published: 20 May 2017
Cited by 2 | PDF Full-text (254 KB) | HTML Full-text | XML Full-text
Abstract
Diabetes mellitus (DM) is a chronic endocrine disease resulted from insulin secretory defect or insulin resistance and it is a leading cause of death around the world. The care of DM patients consumes a huge budget due to the high frequency of consultations
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Diabetes mellitus (DM) is a chronic endocrine disease resulted from insulin secretory defect or insulin resistance and it is a leading cause of death around the world. The care of DM patients consumes a huge budget due to the high frequency of consultations and long hospitalizations, making DM a serious threat to both human health and global economies. Tea contains abundant polyphenols and caffeine which showed antidiabetic activity, so the development of antidiabetic medications from tea and its extracts is increasingly receiving attention. However, the results claiming an association between tea consumption and reduced DM risk are inconsistent. The advances in the epidemiologic evidence and the underlying antidiabetic mechanisms of tea are reviewed in this paper. The inconsistent results and the possible causes behind them are also discussed. Full article
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