Dietary polyphenols as antidiabetic agents: Advances and opportunities

Investigating Polyphenol Nanoformulations for Therapeutic Targets against Diabetes Mellitus

Diabetes mellitus (DM) is a fatal metabolic disorder, and its prevalence has escalated in recent decades to a greater extent. Since the incidence and severity of the disease are constantly increasing, plenty of therapeutic approaches are being considered as a promising solution. Many dietary polyphenols have been reported to be effective against diabetes along with its accompanying vascular consequences by targeting multiple therapeutic targets. Additionally, the biocompatibility of these polyphenols raises questions about their use as pharmacological mediators. Nevertheless, the pharmacokinetic and biopharmaceutical properties of these polyphenols limit their clinical benefit as therapeutics. Pharmaceutical industries have attempted to improve compliance and therapeutic effects. However, nanotechnological approaches to overcome the pharmacokinetic and biopharmaceutical barriers associated with polyphenols as antidiabetic medications have been shown to be effective to improve clinical compliance and efficacy. Therefore, this review highlighted a comprehensive and up-to-date assessment of polyphenol nanoformulations in the treatment of diabetes and vascular consequences.

Anti-diabetic Potential of Indigenous Medicinal Plants of Cholistan Desert, Pakistan: A Review

Cholistan Desert is a sandy desert located in southern Punjab, Pakistan. The area is rich in more than 64 medicinal plants among 138 plant species. It is noteworthy that this remote desert lacks modern health care facilities and its inhabitants are dependent on locally-available plant species for the treatment of acute and chronic illnesses. Medicinal plants, traditionally have been ideal sources of remedies for the management of many non-communicable diseases; most modern prescriptions drugs have their origins from plants. Diabetes is increasing at an alarming rate in the past few decades. Whereas medicinal plants are used globally, the specific properties of only a few have been identifies scientifically. Similarly, little scientific evidence exists that confirms the efficacy of the medicinal plants of this region for diabetes management. Ethnobotanical studies show that locally-available medicinal plants do have anti-diabetic potential. We reviewed the medicinal properties of 36 of these plants. Several ingredients derived from these plants have chemical constituents that demonstrate anti-diabetic activity, thereby validating their importance for the management of diabetes.

Dietary Ferulic Acid Ameliorates Metabolism Syndrome-Associated Hyperuricemia in Rats via Regulating Uric Acid Synthesis, Glycolipid Metabolism, and Hepatic Injury

Ferulic acid is a well-known phenolic acid compound and possesses multiple health-promoting and pharmacological effects. Metabolic syndrome (MetS) and hyperuricemia (HUA) have become health problems worldwide and are closely connected. The aim of this study was to explore the influence of ferulic acid on MetS-related HUA and its underlying mechanisms. Rats were administered high-fructose and high-fat diet (HFFD) with or without ferulic acid (0.05 and 0.1%) for 20 weeks. Intake of HFFD resulted in obesity, hyperglycemia, insulin resistance, and dyslipidemia, which were alleviated by ferulic acid consumption. Treatment of rats with ferulic acid diminished the levels of lipids and inflammatory cytokines and enhanced the activities of antioxidant enzymes in the liver caused by HFFD. Additionally, administration of ferulic acid blocked a HFFD-induced elevation in activities and mRNA expression of enzymes involving in uric acid (UA) synthesis. Molecular docking analysis denoted that ferulic acid bound to the active center of these enzymes, indicative of the potential interaction with each other. These two aspects might partially be responsible for the decrement in serum UA content after ferulic acid ingestion. In conclusion, ferulic acid supplementation ameliorated lipid and glucose metabolic abnormalities, hepatic damage, and UA formation in MetS rats. There was a dose correlation between lipid deposition and UA synthesis-related indicators. These findings implied that ferulic acid could be applied as a promising dietary remedy for the management of MetS-associated HUA.

In Vitro and In Vivo Digestive Fate and Antioxidant Activities of Polyphenols from Hulless Barley: Impact of Various Thermal Processing Methods and β-Glucan

The unfavorable bioaccessibility of polyphenols in cereal-based food limits their physiological functions as most polyphenols bind spontaneously to the cell-wall polysaccharides. Effects of β-glucan and various thermal processing methods including flaking and roasting, stir-frying, steam-flash explosion, and popping expansion on the bioaccessibility and antioxidant properties of polyphenols from hulless barley in vitro and in vivo were investigated in this study. The bioaccessibility and antioxidant capacity (via DPPH, ·OH, and ·O₂^- free radical scavenging, TAC, and FRAP assays) of polyphenol extracts from hulless barley treated by steam-flash explosion and popping expansion increased significantly before and after in vitro digestion compared to those from raw and other processed hulless barley. Further, the total polyphenol content of hulless barley elevated dramatically following hydrolyzing with β-glucanase, which was positively correlated with the antioxidant activity. Additionally, the hulless barley treated with steam-flash explosion exhibited potent antidiabetic effects and antioxidant capacity (via TAC, SOD, GSH-Px, CAT, and MDA assays) in type 2 diabetic rats. The absorption of individual phenolic compounds in the alimentary canal of rats was impacted obviously by thermal processing. This study provides new insights into enhancing the bioaccessibility of the polyphenols and suggests that β-glucans interact with polyphenols and proteins in the hulless barley matrix.

The anti-inflammatory effects of apigenin and genistein on the rat intestinal epithelial (IEC-6) cells with TNF-α stimulation in response to heat treatment

The aims of the present study were to investigate the anti-inflammatory function of two flavonoids apigenin and genistein in rat intestinal epithelial (IEC-6) cells stimulated by tumor necrosis factor-alpha (TNF-α) and to clarify whether the heat treatment of the flavonoids might affect flavonoid activity. The flavonoids at lower dosage (e.g. 5 μmol/L) had no toxic effect but growth promotion on the cells. Meanwhile, the flavonoid pretreatment of the cells before TNF-α stimulation could maintain cellular morphology, decrease the production of prostaglandin E₂ and two pro-inflammatory cytokines interleukin-1β (IL-1β) and IL-6, but increase the production of two anti-inflammatory cytokines IL-10 and transforming growth factor-β. Additionally, the flavonoids could block off the nuclear translocation of nuclear factor-kappaB (NF-κB) p65, and suppress the expression of phosphorylated IκBα and p65 induced by TNF-α. Meanwhile, the NF-κB inhibitor BAY 11-7082 shared a similar function with the flavonoids to mediate the production of IL-6/IL-10. Furthermore, in silico analysis also declared that the flavonoids could interact with the IκBα-NF-κB complex at the binding pockets to yield the binding energies ranging from -31.7 to -34.0 kJ/mol. However, the heated flavonoids were consistently less effective than the unheated counterparts to perform these anti-inflammatory effects. It is thus proposed that both apigenin and genistein have anti-inflammatory potential to the TNF-α-stimulated IEC-6 cells by inactivating the NF-κB pathway, while heat treatment of the flavonoids caused a negative impact on these assessed anti-inflammatory effects.

Antilipidemic and Hepatoprotective Effects of Ethanol Extract of Justicia spicigera in Streptozotocin Diabetic Rats

Oxidative stress is a factor that contributes to the development of complications in diabetes; however, its effects can be counteracted using exogenous antioxidants that are found in some plants, which is why people turn to traditional medicines in the search for therapeutic treatment. Justicia spicigera has been demonstrated to have the capacity to reduce glycemic levels; however, its effects on non-insulin-dependent organs such as the liver have not been reported. During 30 days of administration of Justicia spicigera ethanol extract, the blood glucose and weight of rats were measured every 5 days. Once the treatment was concluded, the rats were sacrificed. Corporal weight, blood glucose, cholesterol, very-low-density lipoprotein (VLDL), triglycerides, total lipids, and liver profile were reduced in the diabetic condition and normalized with the application of ethanol extract from J. spicigera (EJS). Additionally, there was a significant increase in catalase and superoxide dismutase activity in the control diabetic rats, a decrease in their activity with the extract administration, and no effect on normoglycemic rats. In conclusion, EJS is considered to be capable of reducing oxidative stress by maintaining diminished lipid and liver function profiles in male Wistar rats with streptozotocin-induced diabetes.

Effects of blueberry and cranberry on type 2 diabetes parameters in individuals with or without diabetes: A systematic review and meta-analysis of randomized clinical trials

AIMS

Blueberry and cranberry are rich in polyphenols that are associated with diabetes reduction. This study aimed: 1) to systematically review the literature on the effects of blueberry and cranberry consumption and type 2 diabetes parameters in individuals with or without type 2 diabetes and 2) to quantify these effects by carrying out a meta-analysis.

DATA SYNTHESIS

A systematic review and meta-analysis were performed using articles present in seven databases (PubMed, LILACS, Scielo, Scopus, Web of Science, Cochrane, and Embase), including publications until May 2021. We included randomized clinical trials that compared blueberry or cranberry effects on type 2 diabetes parameters, such as fasting blood glucose, insulin resistance, and glycated hemoglobin. Quality of the studies was performed using the Cochrane scale, while the Egger test assessed the publication bias and meta-regression the estimated effect sizes with potential moderator variables. From the 2034 studies identified, 39 were read in full and 22 were included in meta-analysis. In individuals with diabetes, the consumption of blueberry or cranberry significantly reduced fasting blood glucose [MD: -17.72 mg/dl; 95% CI: -29.62, -5.82; p = 0.03; I2 = 57%] and glycated hemoglobin [MD: -0.32%; 95% CI: -0.57, -0.07; p = 0.15; I2 = 39%], whereas for insulin resistance the effects were null. Results were not significant for the general population, except in the sensitivity analysis for fasting blood glucose.

CONCLUSIONS

The consumption of blueberry and cranberry significantly reduced fasting blood glucose and glycated hemoglobin levels in individuals with diabetes, with high credibility of the evidence.

Association between non-tea flavonoid intake and risk of type 2 diabetes: the Australian diabetes, obesity and lifestyle study

Studies examining the association between flavonoid intake and measures of insulin resistance and β-cell dysfunction, as markers of type 2 diabetes (T2DM) across the adult lifespan, may provide insights into how flavonoids influence T2DM risk. This study examined the cross-sectional associations between flavonoid intakes, from dietary sources other than tea, and biomarkers of glucose tolerance and insulin sensitivity in adults aged 25 years and older participating in the Australian diabetes, obesity and lifestyle (AusDiab) study. Additionally, longitudinal associations between non-tea flavonoid intakes and incident T2DM over 12 years were explored. Eligible participants (n = 7675) had no previous history of T2DM and had completed a food-frequency questionnaire at baseline (1999-2000) from which flavonoid intakes were calculated using United States Department of Agriculture Databases. Restricted cubic splines in regression models were used to examine cross-sectional associations between intakes of total non-tea flavonoids and selected flavonoid subclasses and measures of glucose tolerance and insulin sensitivity including glycated haemoglobin (HbA1c), homeostasis model assessment of β-cell function (HOMA2-% β) and insulin sensitivity (HOMA2-% S), 2-hour post load plasma glucose (PLG), fasting plasma glucose (FPG) and fasting insulin levels. Associations between flavonoid intakes and T2DM risk were estimated using Cox proportional hazards models. Cross-sectionally, significant beneficial associations were observed for intakes of total flavonoids and the flavan-3-ol-monomer, proanthocyanidin, flavonol and anthocyanidin subclasses with measures of glucose tolerance and insulin sensitivity (P < 0.05 for all), except fasting plasma glucose. During follow-up, 344 incident T2DM cases were recorded. Participants with the highest total flavonoid intake had a 21% lower risk of T2DM over 12 years, although this was not statistically significant in multivariable adjusted models [HR (95% CI): 0.79 (0.57, 1.09)]. This study provides some evidence that consuming flavonoid-rich foods may be protective against T2DM through mechanisms related to glucose tolerance and insulin sensitivity.

Upregulation of GLUT4 and PI3K, and downregulation of GSK3 mediate the anti-hyperglycemic effects of proanthocyanidins

Diabetes mellitus is the most common chronic metabolic disorder worldwide. The present study was designed to investigate the potential role of cinnamon bark extract oligomeric proanthocyanidins (OPCs) in controlling streptozotocin (STZ)-induced hyperglycemia and to clarify the underlying molecular mechanisms underlying its effects. For this purpose, 60 male rats were equally divided into six groups as follows: The normal control group; OPC control group (non-diabetic rats treated with OPC at 300 mg/kg orally for 21 days); the untreated diabetic control group; the wortmannin control group [diabetic rats treated with wortmannin at 1 mg/kg, intraperitoneal (i.p.) on the final day of the experiment]; the OPC diabetic group (diabetic rats treated with OPC at 300 mg/kg orally for 21 days); and the OPC diabetic + wortmannin co-treated group (diabetic rats treated with OPC at 300 mg/kg/day for 21 consecutive days and then 24 h after the final OPC dose treated with a single wortmannin injection at 1 mg/kg, i.p.). The results indicated that OPC ameliorated the diabetic state, as evidenced by a significant decrease in serum glucose levels, and a significant increase in the levels of insulin, amylin, insulin receptor phosphorylation, glycogen and glucose transporter-4 translocation; it also improved the lipid profile in STZ-diabetic rats. On the whole, the findings of the present study provide biochemical evidence that OPC treatment is effective as an anti-diabetic and anti-hyperlipidemic agent by enhancing glucose uptake through the activation of insulin receptor kinase activity and the PI3K/Akt pathway.

Licania rigida leaf extract: Protective effect on oxidative stress, associated with cytotoxic, mutagenic and preclinical aspects

Brazilian plant biodiversity is a rich alternative source of bioactive compounds since plant-derived extracts and/or their secondary metabolites exhibit potential properties to treat several diseases. In this context, Licania rigida Benth (Chrysobalanaceae Family), a large evergreen tree distributed in Brazilian semi-arid regions, deserves attention for its widespread use in popular medicine, although its biological properties are still poorly studied. The aim of this study was to examine (1) acute and sub-chronic oral toxicity at 2000 mg/kg dose; (2) in vitro cytotoxicity at 0.1; 1; 10; 100 or 1000 µg/ml; (3) in vivo mutagenicity at 5, 10 or 20 mg/ml, and (4) potential antioxidant protective effect of L. rigida aqueous leaf extract of (AELr). No marked apparent toxic and genotoxic effects were observed using in vitro and in vivo assays after in vitro treatment of Chinese hamster ovary cell line (CHO-K1) with AELr or in vivo exposure of Wistar rats and Drosophila melanogaster to different extract concentrations. Concerning the antioxidant effect, the extract exhibited a protective effect by decreasing lipid peroxidation as determined by malondialdehyde levels. No significant changes were observed for glutathione (GSH) levels and activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx). Data demonstrate the beneficial potential of AELr to be employed for therapeutic purposes. However, further studies are required to validate the pharmacological application of this plant extract to develop as a phytotherapeutic formulation.

UHPLC-ESI-QTOF-MS2 analysis of Acacia pennata extract and its effects on glycemic indices, lipid profile, pancreatic and hepatorenal alterations in nicotinamide/streptozotocin-induced diabetic rats

Diabetes mellitus (DM) is a chronic disorder associated with severe metabolic derangement and comorbidities. The constant increase in the global population of diabetic patients coupled with some prevailing side effects associated with synthetic antidiabetic drugs has necessitated the urgent need for the search for alternative antidiabetic regimens. This study investigated the antidiabetic, antioxidant, and pancreatic protective effects of the Acacia pennata extract (APE) against nicotinamide/streptozotocin induced DM in rats. The antidiabetic activity of APE was evaluated and investigated at doses of 100 and 400 mg/kg body weight, while metformin (150 mg/kg bw) was used as a standard drug. APE markedly decreased blood glucose level, homeostatic model assessment for insulin resistance, serum total cholesterol, triglycerides, low‐density lipoprotein, blood urea nitrogen, creatinine, alanine transaminase, aspartate transaminase, and alanine phosphatase levels. Additionally, treatment with APE increased the body weight, serum insulin concentration, and high‐density lipoprotein. Moreover, activities of pancreatic superoxide dismutase, catalase, and glutathione peroxidase were increased, while the altered pancreatic architecture in the histopathological examination was notably restored in the treated rats. Ultra‐high performance liquid chromatography combined with electrospray ionization quadrupole time‐of‐flight mass spectrometry (UHPLC‐ESI‐QTOF‐MS) analysis of APE showcases the prevailing presence of polyphenolic compounds. Conclusively, this study showed the beneficial effects of the Acacia pennata in controlling metabolic derangement, pancreatic and hepatorenal dysfunction in diabetic rats.

The mechanism of molecular cross-linking against nonenzymatic degradation in the body wall of ready-to-eat sea cucumber

Ready-to-eat sea cucumbers (RSC) treated by high pressure steam were easily degraded during storage. Celery (Apium graveolens, AG) and chlorogenic acid (CA) were screened for enhancing the stability of RSC. After RSC cross-linked by AG or CA, the hardness was significantly increased by 108% or 254% at 30 d, and the relaxation time decrease by 31.90 or 39.89 ms, and the proportion of T₂₃ reduced by 0.40% or 1.15%. The crosslinked RSC exhibited smaller pore size with finer collagen fibrils. CA treatment caused the secondary structure changes in RSC. In addition, it also inhibited the break of peptide bonds in RSC collagen, observing the decrease of free hydroxyproline level from 46.63 to 34.53 μg/g, and the reduction of free ammonia nitrogen from 20.96 to 15.30 μmol/g. Therefore, AG and CA will have an important application in RSC processing industry.

General Health Benefits and Pharmacological Activities of Triticum aestivum L

Common wheat (Triticum aestivum), one of the world's most consumed cereal grains, is known for its uses in baking and cooking in addition to its medicinal uses. As this plant's medical benefits are enormous and scattered, this narrative review was aimed at describing the pharmacological activities, phytochemistry, and the nutritional values of Triticum aestivum. It is a good source of dietary fiber, resistant starch, phenolic acids, alkylresorcinols, lignans, and diverse antioxidant compounds such as carotenoids, tocopherols and tocotrienols. These constituents provide Triticum aestivum with a wide range of pharmacological properties, including anticancer, antimicrobial, antidiabetic, hypolipemic, antioxidant, laxative, and moisturizing effects. This review summarized the established benefits of wheat in human health, the mode of action, and different clinical, in vitro and in vivo studies for different varieties and cultivars. This review also gives an insight for future research into the better use of this plant as a functional food. More clinical trials, in vivo and in vitro studies are warranted to broaden the knowledge about the effect of Triticum aestivum on nutrition-related diseases prevention, and physical and mental well-being sustenance.

Special Thai Oolong Tea: Chemical Profile and In Vitro Antidiabetic Activities

Special Thai oolong tea is oolong tea (Camellia sinensis (L.) Kuntze) steamed with selected Thai botanical drugs. Oolong tea steamed with ginger (Zingiber officinale), lemongrass (Cymbopogon citratus), and celery (Anathallis graveolens L.) is called eternity tea (EN), whereas peaceful rest (PR) tea is made of oolong tea leaves steamed with Indian gooseberry (Phyllanthus emblica), Turkey berry (Solanum torvum), and wild betel leaf bush leaves (Piper sarmentosum). Oolong tea is known for its numerous biological activities including antidiabetic properties. However, the effect of the additional botanical drugs on the biological activities of special oolong teas has not yet been explored. From the results, the PR extract exhibited the best activity in the in vitro assays relevant to antidiabetic properties such as chemical antioxidant, anti-inflammation, anti-adipogenesis, enzyme inhibition, and glucose uptake and consumption. The UHPLC-QTOF-MS/MS profiles of PR and EN extracts indicated chemical profiles different from oolong tea. For instance, gingerdiol and gingerol were detected in EN, whereas piperettine I was detected in PR. Therefore, it was inferred that among the three tea extracts, the additional compounds in PR contributed to good activities compared to oolong and EN. It is also important to highlight that the PR extract inhibited glucose uptake and consumption by adipocytes and skeletal muscles at concentrations of 500 and 100 μg/ml, respectively, as well as metformin activity (p < 0.05). Findings from this study support the antidiabetic potential of PR tea.

Arabinoxylan ameliorates type 2 diabetes by regulating the gut microbiota and metabolites

Type 2 diabetes (T2D) is a metabolic disease characterized by hyperglycemia. Intake of dietary fiber is inversely associated with risks of T2D. Here, metabolomics and 16S rRNA gene sequencing were employed to investigate the effects of arabinoxylan on gut microbiota and their metabolites in type 2 diabetic rats. T2D increased the abundance of opportunistic pathogens (such as Desulfovibrio and Klebsiella) and the levels of 12α-hydroxylated bile acids and acylcarnitines (C3) in diabetic rats, which eventually contribute to insulin resistance and hyperglycemia. Supplementation with arabinoxylan promoted the growth of fiber-degrading bacteria to increase short-chain fatty acids (SCFAs), as well as decreased the abundance of opportunistic pathogens. Arabinoxylan treatment also decreased the concentrations of 12α-hydroxylated bile acids, and increased the levels of equol, indolepropionate, and eicosadienoic acid. This study indicated that the beneficial effects of arabinoxylan on T2D may be partially attributed to the modification of gut microbiota and related metabolites.

Insights into the leaves of Ceriscoides campanulata: Natural proanthocyanidins alleviate diabetes, inflammation, and esophageal squamous cell cancer via in vitro and in silico models

Fourteen flavones (1-14) including twelve polymethoxylated flavones, two A-type proanthocyanidins (oligomeric flavonoids) (15, 16), one benzoyl glucoside (17), one triterpenoid (18), and one phenylpropanoid (19) were isolated from the leaves of the South Asian medicinal plant Ceriscoides campanulata (Roxb.) Tirveng (Rubiaceae). The structures of the compounds were identified based on their spectroscopic and spectrometric data and in comparison with literature data. Isolated compounds were tested in vitro against inflammatory enzymes (COX-2, iNOS), pro-inflammatory cytokines (IL-1β, IL-6, TNF-α), esophageal squamous carcinoma cell line (TE13), and carbohydrate digestion enzymes (α-amylase, α-glucosidase). Proanthocyanidins 15 and 16 significantly attenuated the LPS-induced inflammatory response of COX-2, iNOS, IL-1β, IL-6, TNF-α in RAW 264.7 cells. Proanthocyanidins also satisfactorily inhibited the regrowth (64%), migration (51%), and formation of tumor-sphere (48%) in ESCC cell line TE13 at 50% toxic concentration. Compounds 15 and 16 showed the most potent effect against mammalian α-amylase (IC₅₀ 8.4 ± 0.3 μM and 3.5 ± 0.02 μM, respectively) compared to reference standard acarbose (IC₅₀ 5.9 ± 0.1 μM). As yeast α-glucosidase inhibitors, compounds 15 and 16 also displayed significant activities (IC₅₀ 6.2 ± 0.3 and 4.7 ± 0.1 μM, respectively), while compounds 1-6 displayed weaker α-glucosidase inhibitory activities, ranging from 49 to 142 μM, compared to acarbose (IC₅₀ 665 ± 42 μM). In an anticholinesterase assay, compounds 1, 2, 6 (IC₅₀ 51 ± 2, 53 ± 7, 64 ± 5 μM, respectively), and 4 (IC₅₀ 44 ± 1 μM) showed moderate inhibitory activities against acetylcholinesterase and butyrylcholinesterase, respectively. Furthermore, molecular docking and molecular dynamic simulation analyses of compounds 15 and 16 were performed against human pancreatic α-amylase and human lysosomal acid α-glucosidase to elucidate the interactions of these compounds in the respective enzymes' active sites.

Dietary proanthocyanidins on gastrointestinal health and the interactions with gut microbiota

Many epidemiological and experimental studies have consistently reported the beneficial effects of dietary proanthocyanidins (PAC) on improving gastrointestinal physiological functions. This review aims to present a comprehensive perspective by focusing on structural properties, interactions and gastrointestinal protection of PAC. In brief, the main findings of this review are summarized as follows: (1) Structural features are critical factors in determining the bioavailability and subsequent pharmacology of PAC; (2) PAC and/or their bacterial metabolites can play a direct role in the gastrointestinal tract through their antioxidant, antibacterial, anti-inflammatory, and anti-proliferative properties; (3) PAC can reduce the digestion, absorption, and bioavailability of carbohydrates, proteins, and lipids by interacting with them or their according enzymes and transporters in the gastrointestinal tract; (4). PAC showed a prebiotic-like effect by interacting with the microflora in the intestinal tract, and the enhancement of PAC on a variety of probiotics, such as Bifidobacterium spp. and Lactobacillus spp. could be associated with potential benefits to human health. In conclusion, the potential effects of PAC in prevention and alleviation of gastrointestinal diseases are remarkable but clinical evidence is urgently needed.

In Vivo and In Silico Assessment of Diabetes Ameliorating Potentiality and Safety Profile of Gynura procumbens Leaves

BACKGROUND

Diabetes mellitus is one of the most notable health dilemmas. Analyzing plants for new antidiabetic remedies has become an impressive territory for life science researchers. Gynura procumbens has long been used to treat diabetes. Thus, we strived to ascertain the hypoglycemic potentiality of extract of leaves of G. procumbens by in vivo and in silico approaches.

METHODS

Fresh leaves of G. procumbens were collected and shade-dried to prepare ethanolic extracts to evaluate pharmacological parameters. Diabetes was induced in rats via injecting alloxan through the intraperitoneal route at a dose of 150 mg/kg body weight. Humalyzer 3000 was used to perform a biochemical assay of collected samples from rats. Anti-hyperglycemic activity study along with overdose toxicity test was performed. The pharmacological activity of this plant was also evaluated through a molecular docking study. This in silico study investigated the binding affinity of natural ligands from G. procumbens against glycoside hydrolase enzymes.

RESULTS

We detected a peak plasma concentration of G. procumbens at 3 hours 45 minutes that is roughly similar to the peak plasma concentration of metformin. Again, in OGTT and anti-hyperglycemic tests, it has been ascertained that both plant extract and metformin can exert significant (P < 0.05) and highly significant (P < 0.01) hypoglycemic activity in a dose-dependent manner. Metformin exhibited better therapeutic efficacy than that of plant extract, but it possessed null statistical significance. Also, our safety profile expressed that, similar to metformin, the plant extract can restore the disturbed pathological state in a dose-oriented approach with a wide safety margin. In silico study also validated the potentialities of natural constituents of G. procumbens. Conclusion. This study suggested that G. procumbens can be considered as potential antidiabetic plant. Robust and meticulous investigation regarding plant chemistry and pharmacology in the future may bring about a new dimension that will aid in discovering antidiabetic drugs from this plant in the diabetes management system.

Antidiabetic potential of polysaccharides from Brasenia schreberi regulating insulin signaling pathway and gut microbiota in type 2 diabetic mice

This study aimed to investigate the hypoglycemic activities and gut microbial regulation effects of polysaccharides from Brasenia schreberi (BS) in diabetic mice induced by high-fat diet and streptozotocin. Our data indicated that BS polysaccharides not only improved the symptoms of hyperglycemia and relieved metabolic endotoxemia-related inflammation but also optimized the gut microbiota composition of diabetic mice with significantly decreased Firmicutes/Bacteroidetes ratios. More importantly, altered gut microbiota components may affect liver glycogen and muscle glycogen by increasing the mRNA expression of phosphatidylinositol-3-kinase (PI3K) and protein kinase B (Akt) in the liver of mice through modulated the abundance of beneficial bacteria (Lactobacillus). Altogether, our findings, for the first time, demonstrate that BS polysaccharides may be used as a beneficial probiotic agent that reverses gut microbiota dysbiosis and the hypoglycemic mechanisms of BS polysaccharides may be related to enhancing the abundance of Lactobacillus to activate PI3K/Akt-mediated signaling pathways in T2DM mice.

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Brasenia schreberi polysaccharides ameliorated hyperglycemia and dyslipidemia in mice.

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The polysaccharides regulated glucose metabolism through activating PI3K-Akt pathway.

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The polysaccharides modulated gut microbiota profile of diabetic mice.

Oxidative Stress and DNA Lesion Reduction of a Polyphenolic Enriched Extract of Thymus marschallianus Willd. in Endothelial Vascular Cells Exposed to Hyperglycemia

The present study aimed to compare two polyphenolic-enriched extracts obtained from the Thymus marschallianus Willd. (Lamiaceae) species, harvested from culture (TMCE in doses of 0.66 μg GAE/mL and 0.066 μg GAE/mL) and from spontaneous flora (TMSE in doses of 0.94 μg GAE/mL and 0.094 μg GAE/mL) by assessing their biological effects on human umbilical vein endothelial cells (HUVECs) exposed to normoglycemic (137 mmol/L glucose) and hyperglycemic conditions (200 mmol/L glucose). Extracts were obtained by solid phase extraction (SPE) and analyzed by chromatographical (HPLC-DAD) and spectrophotometrical methods. Their effects on hyperglycemia were evaluated by the quantification of oxidative stress and NF-ĸB, pNF-ĸB, HIF-1α, and γ-H₂AX expressions. The HPLC-DAD analysis highlighted significant amounts of rosmarinic acid (ranging between 0.18 and 1.81 mg/g dry extract), luteolin (ranging between 2.04 and 17.71 mg/g dry extract), kaempferol (ranging between 1.85 and 7.39 mg/g dry extract), and apigenin (ranging between 4.97 and 65.67 mg/g dry extract). Exposure to hyperglycemia induced oxidative stress and the activation of NF-ĸ increased the expression of HIF-1α and produced DNA lesions. The polyphenolic-enriched extracts proved a significant reduction of oxidative stress and γ-H₂AX formation and improved the expression of HIF-1α, suggesting their protective role on endothelial cells in hyperglycemia. The tested extracts reduced the total NF-ĸB expression and diminished its activation in hyperglycemic conditions. The obtained results bring evidence for the use of the polyphenolic-enriched extracts of T. marschallianus as adjuvants in hyperglycemia.

Omnifarious fruit polyphenols: an omnipotent strategy to prevent and intervene diabetes and related complication?

Diabetes mellitus is a metabolic syndrome which cannot be cured. Recently, considerable interest has been focused on food ingredients to prevent and intervene in complications of diabetes. Polyphenolic compounds are one of the bioactive phytochemical constituents with various biological activities, which have drawn increasing interest in human health. Fruits are part of the polyphenol sources in daily food consumption. Fruit-derived polyphenols possess the anti-diabetic activity that has already been proved either from in vitro studies or in vivo studies. The mechanisms of fruit polyphenols in treating diabetes and related complications are under discussion. This is a comprehensive review on polyphenols from the edible parts of fruits, including those from citrus, berries, apples, cherries, mangoes, mangosteens, pomegranates, and other fruits regarding their potential benefits in preventing and treating diabetes mellitus. The signal pathways of characteristic polyphenols derived from fruits in reducing high blood glucose and intervening hyperglycemia-induced diabetic complications were summarized.

A review on the medicinal potential, toxicology, and phytochemistry of litchi fruit peel and seed

The perception that many fruit wastes, particularly the peel, contain more phytochemicals than the edible portions has been largely supported by scientific evidence, making them potential sources of bioactive and therapeutic phytochemicals. The peel and seed of Litchi (Litchi chinensis Sonn.) contain bioactive principles and have been shown to exhibit antioxidative, antidiabetic, cancer preventive, anti-obesogenic, and anti-inflammatory properties. This review presents a critical analysis of previous and current perspectives on the medicinal, toxicological, and phytochemical profiles of litchi fruit peel and seed, thus providing an evidence-based platform to explore their medicinal potential. A literature search was done on "PubMed," "Google Scholar," and "ScienceDirect." Peer-reviewed published data on the medicinal profiles of litchi fruit peel and seed were identified and critically analyzed. The fruit peel and seed improved glycemic control and insulin signaling and downregulated lipogenic and cholesterogenic processes. Their neuroprotective, hepatoprotective, and renal protective potentials were influenced by antioxidative and anti-inflammatory actions. The anticancer effect was mediated by upregulated proapoptotic, proinflammatory, antiproliferative, and anti-metastatic processes in cancer cells. Simple flavonols, sesquiterpenes, phenolic acids, jasmonates, and proathocyanidins are the possible bioactive principles influencing the medicinal effects. Appropriate toxicity studies are, however, still lacking. Litchi fruit wastes may be further studied as useful sources of therapeutic agents that may have medicinal relevance in oxidative, metabolic, vascular, and carcinogenic ailments. PRACTICAL APPLICATIONS: Underutilized fruit wastes contribute to environmental pollution. Interestingly, these wastes contain phytochemicals that could be of medicinal relevance if their medicinal potentials are maximized. Litchi fruit is a widely consumed fruit with commercial value. Its peel and seeds contribute to fruit wastes. The review exposes the medicinal potential and bioactive principles and/or nutrients of the fruit's peel and seed while elucidating the underlying therapeutic mechanisms or modes of actions through which litchi peel and seed potentiate medicinal effects. Thus, the review provides an evidence-based platform to explore the medicinal potential of underutilized wastes from litchi fruit. Additionally, the fruit peel and seed could be low-cost residues that could afford ecofriendly opportunity if their medicinal potentials are properly maximized.

Preliminary in vitro study of anti-oxidant activity and anti-diabetic potential of plant extracts from 4 herbal substances not traditionally used for treatment of diabetes mellitus

The focus of the presented study is the in vitro anti-oxidant activity and anti-diabetic potential of water extracts from the following four herbal substances, not traditionally used for treatment of diabetes mellitus – leaves of Sambucus ebulus L. and Prunus mahaleb L., and flowering stems of Cichorium intybus L. and Satureja kitaibelii Wierzb. ex Heuff. The water extracts are obtained through ultrasonication. The extract of S. kitaibelii stands out due to its highest values in all studied indicators – total phenolic content, scavenging potential (DPPH, ABTS) and α-glucosidase inhibitory activity which was six times higher than acarbose. The extract of C. intybus also showed significant α-glucosidase inhibitory activity compared to acarbose. The flowering stems of both species are promising sources of biologically active substances for blood sugar control in diabetes mellitus.

Plants Secondary Metabolites as Blood Glucose-Lowering Molecules

Recently, significant advances in modern medicine and therapeutic agents have been achieved. However, the search for effective antidiabetic drugs is continuous and challenging. Over the past decades, there has been an increasing body of literature related to the effects of secondary metabolites from botanical sources on diabetes. Plants-derived metabolites including alkaloids, phenols, anthocyanins, flavonoids, stilbenoids, saponins, tannins, polysaccharides, coumarins, and terpenes can target cellular and molecular mechanisms involved in carbohydrate metabolism. In addition, they can grant protection to pancreatic beta cells from damage, repairing abnormal insulin signaling, minimizing oxidative stress and inflammation, activating AMP-activated protein kinase (AMPK), and inhibiting carbohydrate digestion and absorption. Studies have highlighted many bioactive naturally occurring plants' secondary metabolites as candidates against diabetes. This review summarizes the current knowledge compiled from the latest studies published during the past decade on the mechanism-based action of plants-derived secondary metabolites that can target various metabolic pathways in humans against diabetes. It is worth mentioning that the compiled data in this review will provide a guide for researchers in the field, to develop candidates into environment-friendly effective, yet safe antidiabetics.

Using polyphenols as a relevant therapy to diabetes and its complications, a review

Diabetes is currently a worldwide health concern. Hyperglycemia, hypertension, obesity, and oxidative stress are the major risk factors that inevitably lead to all the complications from diabetes. These complications severely impact the quality of life of patients, and they can be managed, reduced, or even reverted by several polyphenols, plant extracts and foods rich in these compounds. The goal of this review is to approach diabetes not as a single condition but rather an interconnected combination of risk factors and complications. This work shows that polyphenols have multi target action and effects and they have been systematically proven to be relevant in the reduction of each risk factor and improvement of associated complication.

Comprehensive metabolomic, lipidomic and pathological profiles of baobab (Adansonia digitata) fruit pulp extracts in diabetic rats

Baobab fruit pulp Adansonia digitata (AD) has received attention due to its numerous nutritional and medicinal values. In the current study, tentative identification was performed due to limited information available on its phytochemical composition. Phytochemicals from AD fruit pulp were obtained using successive organic solvent fractionation. The LC-MSMS analysis led to identification of 91 metabolites from methanol, butanol and ethyl acetate extracts. Moreover, 20 compounds were identified in the petroleum ether extract based on high resolution ion masses. In vitro antidiabetic and antioxidant properties of selected extracts were investigated using enzyme activity and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method, respectively. Biological screening of the antidiabetic effects of target extracts was performed against streptozotocin-induced diabetes in experimental animals, following daily oral treatment for 3 successive weeks. Serum glucose, insulin, adiponectin, superoxide dismutase (SOD), lipid peroxide, cholesterol and HDL levels were measured. Finally, histopathological and immunohistochemical examinations of pancreas were carried out. Results revealed that animal groups treated daily with butanol (BuOH) and petroleum ether extracts of AD (oil) exhibited a significant improvement in carbohydrate and lipid metabolism as well as antioxidant effect. Both extracts revealed superior effects with respect to the total (TT) and ethyl acetate (EtOAc) extracts. Histopathological and immunohistochemical findings supported these results, showing marked protection of the pancreas. Thus, baobab oil and butanolic extract of the fruit pulp protected animals against STZ-induced diabetic changes, in addition to attenuation of lipid peroxidation, hypercholesterolemia and oxidation.

Nano-based drug delivery systems used as vehicles to enhance polyphenols therapeutic effect for diabetes mellitus treatment

Diabetes mellitus is one of the biggest health emergencies of the 21^st century worldwide, characterized by deficiency in insulin secretion and/or action, leading to hyperglycemia. Despite the currently available antidiabetic therapeutic options, 4.2 million people died in 2019 due to diabetes. Thus, new effective interventions are required. Polyphenols are plant secondary metabolites and have been recognized for their vast number of biological activities, including potential antidiabetic effects. However, the poor bioavailability and high metabolization of polyphenols restrict their biological effects in vivo. Nanotechnology is a promising area of research to improve the therapeutic effect of several compounds. Therefore, this review provides an overview of the literature about the utility of nano-based drug delivery systems as vehicles of polyphenols in diabetes treatment. It was possible to conclude that, in general, nano-based drug delivery systems can potentiate the beneficial antidiabetic properties of polyphenols, when compared with the free compounds, opening a new field of research in diabetology.

Number of galloyl moiety and intramolecular bonds in galloyl-based polyphenols affect their interaction with alpha-glucosidase

The inhibition of α-glucosidase by nine galloyl-based polyphenols with free and unfree galloyl moieties (GMs) was studied. The results show that the inhibitory activity increased with the free GM number increasing. For the compounds with unfree GMs, ellagic acid and hexahydroxydiphenoyl group contributed to the enzyme inhibition. Free GMs could bind not only with the active site of α-glucosidase (competitive inhibition character), but also with the non-active sites (uncompetitive one); however, the former binding interaction was stronger than the latter one. All polyphenols that had inhibitory effects quenched α-glucosidase fluorescence in a static mode through forming a polyphenol-enzyme complex. The number of amino acid residues involved in polyphenol-enzyme binding interactions (hydrogen bonding and π-conjugations) increased with the inhibitory activity increasing. Additionally, two polyphenols with 5 free GMs showing certain hypoglycemic effects in maltose-loading test suggests that GM may be an advisable functional factor for alleviation of type II diabetes symptoms.

Chemical Profile of Launaea nudicaulis Ethanolic Extract and Its Antidiabetic Effect in Streptozotocin-Induced Rats

Launaea nudicaulis is used in folk medicine worldwide to treat several diseases. The present study aimed to assess the antidiabetic activity of L. nudicaulis ethanolic extract and its effect on diabetic complications in streptozotocin-induced hyperglycemic rats. The extract was orally administrated at 250 and 500 mg/kg/day for 5-weeks and compared to glibenclamide as a reference drug at a dose of 5 mg/kg/day. Administration of the extract exhibited a potential hypoglycemic effect manifested by a significant depletion of serum blood glucose concurrent with a significant elevation in serum insulin secretion. After 5-weeks, extract at 250 and 500 mg/kg/day decreased blood glucose levels by about 53.8 and 68.1%, respectively, compared to the initial values (p ≤ 0.05). The extract at the two dosages prevented weight loss of rats from the 2nd week till the end of the experiment, compared to diabetic control rats. The extract further exhibited marked improvement in diabetic complications including liver, kidney and testis performance, oxidative stress, and relative weight of vital organs, with respect to diabetic control. Histopathological examinations confirmed the previous biochemical analysis, where the extract showed a protective effect on the pancreas, liver, kidney, and testis that degenerated in diabetic control rats. To characterize extract composition, UPLC-ESI-qTOF-MS identified 85 chromatographic peaks belonging to flavonoids, phenolics, acyl glycerols, nitrogenous compounds, and fatty acids, with four novel phenolics reported. The potential anti-diabetic effect warrants its inclusion in further studies and or isolation of the main bioactive agent(s).

A comprehensive review on the antidiabetic activity of flavonoids targeting PTP1B and DPP-4: a structure-activity relationship analysis

Type 2 diabetes (T2D) is an expanding global health problem, resulting from defects in insulin secretion and/or insulin resistance. In the past few years, both protein tyrosine phosphatase 1B (PTP1B) and dipeptidyl peptidase-4 (DPP-4), as well as their role in T2D, have attracted the attention of the scientific community. PTP1B plays an important role in insulin resistance and is currently one of the most promising targets for the treatment of T2D, since no available PTP1B inhibitors were still approved. DPP-4 inhibitors are among the most recent agents used in the treatment of T2D (although its use has been associated with possible cardiovascular adverse events). The antidiabetic properties of flavonoids are well-recognized, and include inhibitory effects on the above enzymes, although hitherto not therapeutically explored. In the present study, a comprehensive review of the literature of both synthetic and natural isolated flavonoids as inhibitors of PTP1B and DPP-4 activities is made, including their type of inhibition and experimental conditions, and structure-activity relationship, covering a total of 351 compounds. We intend to provide the most favorable chemical features of flavonoids for the inhibition of PTP1B and DPP-4, gathering information for the future development of compounds with improved potential as T2D therapeutic agents.

Flavonoid-rich wheatgrass (Triticum aestivum L.) diet attenuates diabetes by modulating antioxidant genes in streptozotocin-induced diabetic rats

Wheatgrass, young germinated shoots of Triticum aestivum L., is proclaimed as antidiabetic nutraceutical by traditional medicines across the world. In this study, the effects of the wheatgrass diet in ameliorating oxidative stress (OS) induced during diabetes were investigated. Total phenolic and flavonoid contents (TPC and TFC) and in vitro antioxidant activity of wheatgrass extract were estimated at different days (5, 7, 9, 11, 13, and 15) after germination. Correlating the TPC and TFC with in vitro antioxidant activity, 9th DAG wheatgrass was found to possess maximum antioxidant potential. UHPLC-MS/MS analysis also revealed the presence of nine flavonoids. For in vivo studies, diabetes was induced by streptozotocin in Wistar rats fed with a high-fat diet. Concomitant administration of 9th-day wheatgrass diet (200 and 400 mg/kg) for 60 days exhibited significant improvements in hyperglycemia, body weight, lipid profile, biochemical indices (AST, ALT, GSH, GPx), and restoration of tissue architectures equivalent to normal rats. Further, qRT-PCR-based expression profiling revealed a significant modulation of major antioxidant marker genes and insulin gene which substantiated that the wheatgrass diet is effective in reducing OS during diabetes. Therefore, flavonoid-rich 9th-day wheatgrass could be used as a functional food to control diabetes. PRACTICAL APPLICATIONS: The present research supported that wheatgrass protects against oxidative stress and therefore could be utilized to ameliorate diabetes. The findings may contribute to the development and formulation of wheatgrass-based functional food or dietary supplement for diabetes by nutraceutical industries.

Polyphenols as Prebiotics in the Management of High-Fat Diet-Induced Obesity: A Systematic Review of Animal Studies

Obesity is a disease growing at an alarming rate and numerous preclinical studies have proven the role of polyphenols in managing this disease. This systematic review explores the prebiotic effect of polyphenols in the management of obesity among animals fed on a high-fat diet. A literature search was carried out in PubMed, Scopus, CINAHL, Web of Science, and Embase databases following the PRISMA guidelines. Forty-four studies reported a significant reduction in obesity-related parameters. Most notably, 83% of the studies showed a decrease in either body weight/visceral adiposity/plasma triacylglyceride. Furthermore, 42 studies reported a significant improvement in gut microbiota (GM), significantly affecting the genera Akkermansia, Bacteroides, Blautia, Roseburia, Bifidobacteria, Lactobacillus, Alistipes, and Desulfovibrio. Polyphenols’ anti-obesity, anti-hyperglycaemic, and anti-inflammatory properties were associated with their ability to modulate GM. This review supports the notion of polyphenols as effective prebiotics in ameliorating HFD-induced metabolic derangements in animal models.

Polyphenol-rich Indian ginger cultivars ameliorate GLUT4 activity in C2C12 cells, inhibit diabetes-related enzymes and LPS-induced inflammation: An in vitro study

Diabetes is a chronic metabolic disorder that results in distorted insulin signaling and microvascular complications. Current antidiabetic drugs possess harmful long term side effects, necessitating the need for alternate or compliment therapy with lesser issues. Medicinal plants such as ginger have been reported to possess several beneficial activities including antidiabetic activity. The antidiabetic efficacy of microwave-assisted polyphenolic extracts of Indian ginger cultivars from Odisha (MPO) and Tamil Nadu (MPT) is reported here. MPT and MPO showed insulin stimulated glucose uptake of 1.74 ± 0.25 and 1.47 ± 0.15 fold at 6.25 µg/ml of concentrations in C2C12 cells respectively when compared to control. MPT possessed α-amylase, α-glucosidase inhibitory and anti-glycation properties. It also showed DPPH radical scavenging activity (7.69 ± 0.001%), inhibited LPS-induced nitric oxide production (1.06 ± 0.004 fold) than the latter and increased the GLUT4 protein expression by 1.4 fold. Major active compounds such as shogaol and gingerol derivatives, curcumene, zingiberone were identified through GC-ESI/MS analysis and D-pinitol (cyclitol) was identified through HPLC analysis in this variety. This is the first paper to report the presence of an antidiabetic compound, D-pinitol, in the ginger variety. Polyphenol rich, biologically potent ginger extracts can be a good food and nutraceutical supplement to address diabetes and related complications. PRACTICAL APPLICATIONS: Ginger is a native spice of South Asian Countries including India. Ginger extracts possess several medicinal properties such as anti-inflammatory, antidiabetic and antioxidant activities. It is used to treat nausea, vomiting and commonly used as a food flavouring agent and dietary food supplement. Our study shows the antidiabetic, anti-glycation and antioxidant efficacy of polyphenol rich Indian ginger cultivars grown in different geographical regions. Variations in the biological activities between the MPT and MPO ginger variety was observed. Different environmental conditions and their corresponding metabolite accumulation can be correlated with the better activity shown by MPT variety. It showed an increased GLUT4 expression even at a lower dose of 6.25 µg/ml. Ginger cultivar, especially MPT variety can be used as an adjuvant therapy for treating diabetes. Therefore, our study indicates that polyphenols rich ginger cultivar has major application in functional food product development.

Pterostilbene influences glycemia and lipidemia and enhances antioxidant status in the liver of rats that consumed sucrose solution

AIMS

The present study investigated the potential effects of pterostilbene (PT) on glycemic and lipid profiles, fat storage, cardiovascular indices, and hepatic parameters of rats fed with sucrose solution.

MAIN METHODS

24 male Wistar rats received either drinking water or a 40% sucrose solution over a period of 140 days. After this period, animals were randomly allocated into four groups (n = 6): Control (C), C + Pterostilbene (PT), Sucrose (S), and S + PT. Pterostilbene (40 mg/kg) was given orally for 45 consecutive days.

KEY FINDINGS

Pterostilbene did not influence morphometric and nutritional parameters. The insulin sensitivity index TyG was elevated in the C + PT group (p < 0.01) and reduced in S + PT group (p < 0.05). Basal glucose levels were lower in the S + PT group (p < 0.05), and the glycemic response was improved with PT treatment in glucose provocative tests. Conversely, rats from the C + PT group showed impaired glucose disposal during those tests. Lipid profile was partially improved by PT treatment. Hepatic oxidative stress in the S group was improved after PT treatment. In the C group, PT reduced SOD activity, glutathione levels, and increased catalase activity. Collagen content was reduced by PT treatment.

SIGNIFICANCE

PT effects depends on the type of diet the animals were submitted. In rats fed with sucrose-solution, PT confirmed its positive effects, improving glucose and lipid profile, and acting as a potent antioxidant. The effects of PT on rats that consumed a normal diet were very discrete or even undesirable. We suggest caution with indiscriminate consume of natural compounds by healthy subjects.