Potential insulin secretagogue effects of isovitexin and swertisin isolated from Wilbrandia ebracteata roots in non-diabetic rats

Anti-obesity and anti-diabetic bioactive peptides: A comprehensive review of their sources, properties, and techno-functional challenges

The scourge of obesity arising from obesogens and poor dieting still ravages our planet as half of the global population may be overweight and obese by 2035. This metabolic disorder is intertwined with type 2 diabetes (T2D), both of which warrant alternative therapeutic options other than clinically approved drugs like orlistat with their tendency of abuse and side effects. In this review, we comprehensively describe the global obesity problem and its connection to T2D. Obesity, overconsumption of fats, the mechanism of fat digestion, obesogenic gut microbiota, inhibition of fat digestion, and natural anti-obesity compounds are discussed. Similar discussions are made for diabetes with regard to glucose regulation, the diabetic gut microbiota, and insulinotropic compounds. The sources and production of anti-obesity bioactive peptides (AOBPs) and anti-diabetic bioactive peptides (ADBPs) are also described while explaining their structure-function relationships, gastrointestinal behaviors, and action mechanisms. Finally, the techno-functional applications of AOBPs and ADBPs are highlighted.

Identification of phytocompounds as potent inhibitors of sodium/glucose cotransporter-2 leading to diabetes treatment

Type-II diabetes, a major metabolic disorder has threatened the very existence of a healthy life since long ago. Commercially available antidiabetic drugs are known for several adverse effects. The present study attempted to identify potential phytocompounds as inhibitors of sodium/glucose cotransporter-2 (SGLT2), a major protein that helps in glucose re-absorption from renal tubules. A total of 28 phytocompounds were collected based on the literature survey. 3D co-ordinates of phytocompounds were collected from PubChem database. Molecular docking was carried out with SGLT2 protein and the best 3 docking complexes were subjected to molecular dynamics simulation for 100 ns. Free energy changes were also analyzed using MM/PBSA analysis. Phytocompounds were also analyzed for their drug-likeness and ADMET properties. Docking study observed a strong binding affinity of phytocompounds (> -7.0 kcal/mol). More than 10 phytocompounds showed better binding affinity compared to reference drugs. Further analysis of three best docking complexes when analyzed by MD simulation showed better stability and compactness of the complexes compared to reference drug, empagliflozin. MM/PBSA analysis also revealed that van der Waals force and electrostatic energy are the major binding energy involved in the complex formation. Like docking energy, free energy analysis also observed stronger binding energies (ΔGGAS) in SGLT2-phytocompound complexes compared to empagliflozin complex. All the phytocompounds showed drug-likeness and considerable ADMET properties. The study, therefore, suggests that Trifolirhizin-6'-monoacetate, Aspalathin, and Quercetin-3-glucoside could be a possible inhibitor of SGLT2 protein. However, further studies need to be carried out to reveal the exact mode of activity.Communicated by Ramaswamy H. Sarma.

Enhanced Two-Step Extraction from Biomass of Two Cymbopogon Species Cultivated in Santander, Colombia

The insertion of circular economy principles into the essential oil (EO) production chain aims to reduce waste generation and make integral use of harvested plant material. Higher profits from integral use with reduced waste generation contribute to the eventual use of the EO value chain as an alternative to illicit crops in Colombia (mostly coca). In this study, Java-type citronella (Cymbopogon winterianus) and palmarosa (C. martinii) plant materials were used in two consecutive processes to obtain EOs and extracts. The residual biomass after EO distillation was subjected to ultrasound-assisted hydroethanolic extraction to afford extracts that contained bioactive compounds. Citronella and palmarosa were distilled with typical EO yields (1.0 ± 0.1% for citronella; 0.41 ± 0.06% for palmarosa; n = 5) either through hydrodistillation assisted by microwave radiation or through steam distillation, and their composition (determined via GC/FID/MS analysis) and physicochemical parameters fell within their ISO standard specifications. The concentration of citronellal, the major compound of citronella oil, was 500 ± 152 mg/g. Geraniol, the main component of palmarosa oil, was found at 900 ± 55 mg/g. The citronella and palmarosa hydroalcoholic extracts (4-11% yield) were analyzed with UHPLC-ESI-Orbitrap-MS, which permitted the identification of 30 compounds, mainly C-glycosylated flavones and hydroxycinnamic acids. Both extracts had similar antioxidant activity values, evaluated using the ABTS+● and ORAC assays (110 ± 44 µmol Trolox®/g extract and 1300 ± 141 µmol Trolox®/g extract, respectively).

Acute Effects of Kawakawa (Piper excelsum) Intake on Postprandial Glycemic and Insulinaemic Response in a Healthy Population

Background: Piper excelsum (kawakawa) is an endemic shrub of Aotearoa, New Zealand, of cultural and medicinal importance to Māori. Its fruits and leaves are often consumed. These tissues contain several compounds that have been shown to be biologically active and which may underpin its putative health-promoting effects. The current study investigates whether kawakawa tea can modulate postprandial glucose metabolism. Methods: We report a pilot three-arm randomized crossover study to assess the bioavailability of kawakawa tea (BOKA-T) in six male participants with each arm having an acute intervention of kawakawa tea (4 g/250 mL water; 1 g/250 mL water; water) and a follow-up two-arm randomized crossover study to assess the impact of acute kawakawa tea ingestion on postprandial glucose metabolism in healthy human volunteers (TOAST) (4 g/250 mL water; and water; n = 30 (15 male and 15 female)). Participants consumed 250 mL of kawakawa tea or water control within each study prior to consuming a high-glycemic breakfast. Pre- and postprandial plasma glucose and insulin concentrations were measured, and the Matsuda index was calculated to measure insulin sensitivity. Results: In the BOKA-T study, lower plasma glucose (p < 0.01) and insulin (p < 0.01) concentrations at 60 min were observed after consumption of a high-dose kawakawa tea in comparison to low-dose or water. In the TOAST study, only plasma insulin (p = 0.01) was lower at 60 min in the high-dose kawakawa group compared to the control group. Both studies showed a trend towards higher insulin sensitivity in the high-dose kawakawa group compared to water only. Conclusions: Consuming kawakawa tea may modulate postprandial glucose metabolism. Further investigations with a longer-term intervention study are warranted.

A Citrullus colocynthis fruit extract acutely enhances insulin-induced GLUT4 translocation and glucose uptake in adipocytes by increasing PKB phosphorylation

ETHNOPHARMACOLOGICAL RELEVANCE

Citrullus colocynthis (L.) Schrad is a common fruit in traditional medicine and used as remedy against various diseases, especially diabetes. Up to now, its anti-diabetic effects have been fully attributed to its enhancement of pancreatic insulin secretion. Whether C. colocynthis also ameliorates insulin action in peripheral tissues has not been investigated.

AIM OF THE STUDY

In the present study, using 3T3-L1 adipocytes as cell model, we have investigated whether colocynth fruit extracts affect insulin action.

MATERIALS AND METHODS

Various extracts were prepared from the C. colocynthis fruit and screened using a cell-based 96 well plate GLUT4 translocation assay. Promising extracts were further studied for their effects on glucose uptake and cell viability. The effect on insulin signal transduction was determined by Western blot and the molecular composition was established by LC-MS.

RESULTS

The ethyl acetate fractions of aqueous non-defatted extracts of seed and pulp, designated Sna1 and Pna1, acutely enhanced insulin-induced GLUT4 translocation. In accordance, both extracts increased insulin-stimulated cellular glucose uptake. Pna1, which displayed greater effects on GLUT4 and glucose uptake than Sna1, was further investigated and was demonstrated to increase GLUT4 translocation without changing the half-maximum dose (ED50) of insulin, nor changing GLUT4 translocation kinetics. At the molecular level, Pna1 was found to enhance insulin-induced PKB phosphorylation without changing phosphorylation of the insulin receptor. Pna1 appeared not to be toxic to cells and, like insulin, restored cell viability during serum starvation. By investigating the molecular composition of Pna1, nine compounds were identified that made up 87% of the mass of the extract, one of which is likely to be responsible for the insulin-enhancing effects of Pna1.

CONCLUSIONS

The C. colocynthis fruit possesses insulin-enhancing activity. This activity may explain in part its anti-diabetic effects in traditional medicine. It also identifies the C. colocynthis as a source of a potential novel insulin enhancer that may prove to be useful to reduce hyperglycemia in type 2 diabetes.

Multitargeted Effects of Vitexin and Isovitexin on Diabetes Mellitus and Its Complications

BACKGROUND

Till date, there is no known antidote to cure diabetes mellitus despite the discovery and development of diverse pharmacotherapeutic agents many years ago. Technological advancement in natural product chemistry has led to the isolation of analogs of vitexin and isovitexin found in diverse bioresources. These compounds have been extensively studied to explore their pharmacological relevance in diabetes mellitus. Aim of the Study. The present review was to compile results from in vitro and in vivo studies performed with vitexin and isovitexin derivatives relating to diabetes mellitus and its complications. A systematic online literature query was executed to collect all relevant articles published up to March 2020.

RESULTS

In this piece, we have collected data and presented it in a one-stop document to support the multitargeted mechanistic actions of vitexin and isovitexin in controlling diabetes mellitus and its complications.

CONCLUSION

Data collected hint that vitexin and isovitexin work by targeting diverse pathophysiological and metabolic pathways and molecular drug points involved in the clinical manifestations of diabetes mellitus. This is expected to provide a deeper understanding of its actions and also serve as a catapult for clinical trials and application research.

Anti-hepatitis B virus activity of swertisin isolated from Iris tectorum Maxim

ETHNOPHARMACOLOGICAL RELEVANCE

Iris tectorum Maxim (I. tectorum, Yuan Wei in Chinese) is a common and traditional Chinese medicinal herb that be used to treat liver-related diseases. However, the anti-HBV activity of I. tectorum and its isolates has not been systemically studied.

AIM OF THE STUDY

To screen the active part of I. tectorum and systemically evaluate their anti-HBV activity.

MATERIALS AND METHODS

In this study, a series of compounds from I. tectorum were evaluated for their ability to inhibit HBV replication. Swertisin showed a significant inhibitory function on HBV replication. Then, the suppression effect of different concentrations of swertisin in HBsAg, HBeAg and HBV DNA level in HepG2.2.15 cells and HBV-infected HepG2-NTCP cells were comprehensive evaluated, respectively. Moreover, the anti-HBV effects of swertisin were confirmed in HBV transgenic mice model.

RESULTS

Among these compounds, swertisin strongly inhibited the HBsAg, HBeAg and HBV DNA level in a dose-dependent manner in HepG2.2.15 cells and HBV-infected HepG2-NTCP cells. Furthermore, swertisin showed a significant inhibition role on HBV replication in HBV transgenic mice model, the inhibition effect of which was enhanced when combined with ETV.

CONCLUSIONS

We have identified that swertisin can inhibit HBeAg and HBsAg production, as well as HBV DNA in vitro and in vivo. This study show that we may found a novel compound isolated from traditional Chinese medicines with potent anti-HBV function.

Phenolic Composition, Mineral Content, and Beneficial Bioactivities of Leaf Extracts from Black Currant (Ribes nigrum L.), Raspberry (Rubus idaeus), and Aronia (Aronia melanocarpa)

Currently, the incidence of lifestyle diseases is increasing due to inappropriate nutrition and environmental pollution. To prevent these diseases, various groups of bioactive compounds are needed with a broad spectrum of action and without adverse side effects. Polyphenolic compounds are the most widely studied group of this type of compounds. They occur widely in plants, but their content depends on many factors, including the type of plant, climatic conditions, and the date of harvest. The spectrum of bioactivity of phenolic compounds is determined by their chemical structure, concentration, and interaction with other compounds. Traditional recipes have been studied to search for active plant ingredients. Leaves of shrubs and fruit trees were used in folk medicine as a panacea for many diseases and have been forgotten with time, but their benefits are now being rediscovered. In recent years, much new information about biological activity of phenolic compounds from berry bushes (black currant, raspberry, and aronia) was published. This was reviewed and discussed in this article. The mineral content of their leaves was also summarized because minerals constitute a significant component of plant infusions. It has been shown that high antioxidant and biological activity of leaf extracts results from the presence of active phenolic compounds, which occur in definitely higher amounts than in fruits. Therefore, the leaves of berry bushes seem to be a promising source of substances that can be used as replacements for synthetic agents in the treatment and prevention of lifestyle diseases.

HPLC-ESI- MS/MS analysis of beet (Beta vulgaris) leaves and its beneficial properties in type 1 diabetic rats

The phenolic profile of the leaves of Beta vulgaris subspecies vulgaris variety rubra was investigated by high-performance liquid chromatography (HPLC) coupled to electrospray ionization high resolution mass spectrometric (ESI-HRMS-MS) detection. Mass spectrometry-based molecular networking was employed to dereplicate the known compounds. Twelve known compounds, seven of which are previously undescribed as constituents in the B. vulgaris leaves were dereplicated and assigned with various levels of identification confidence. The ameliorative effects of the aqueous methanolic extract of the leaves were assessed against alloxan induced diabetic rats. It was found that the extract significantly decreased (p < 0.001) serum glucose, lipid profile, ALT, AST, TNF-α, IL-1β, IL-6, and hepatic MDA levels; and significantly increased (p < 0.001) hepatic TAO and GSH; and down-regulated the expression of hepatic NF-κB versus the untreated diabetic groups, in a dose-dependent manner. In molecular docking, all identified compounds exhibited good glide score against the PPAR-ɣ target, confirming the in vivo observed activities. In conclusion, B. vulgaris has immunomodulatory / antioxidant effects that could be helpful in slowing the progression of diabetic complications.

Astragalin augments basal calcium influx and insulin secretion in rat pancreatic islets

Astragalin is a flavonol glycoside with several biological activities, including antidiabetic properties. The objective of this study was to investigate the effects of astragalin on glycaemia and insulin secretion, in vivo, and on calcium influx and insulin secretion in isolated rat pancreatic islets, ex vivo. Astragalin (1 and 10 mg / kg) was administered by oral gavage to fasted Wistar rats and serum glucose and plasma insulin were measured. Isolated pancreatic islets were used to measure basal insulin secretion and calcium influx. Astragalin (10 mg/ kg) decreased glycaemia and increased insulin secretion significantly at 15-180 min, respectively, in the glucose tolerance test. In isolated pancreatic cells, astragalin (100 μM) stimulated calcium influx through a mechanism involving ATP-dependent potassium channels, L-type voltage-dependent calcium channels, the sarcoendoplasmic reticulum calcium transport ATPase (SERCA), PKC and PKA. These findings highlight the dietary coadjuvant, astragalin, as a potential insulin secretagogue that may contribute to glucose homeostasis.

Antihyperglycemic, antihyperlipidemic and antioxidant effects of standard ethanol extract of Bombax ceiba leaves in high-fat-diet- and streptozotocin-induced Type 2 diabetic rats

The present study aimed at exploring the therapeutic potential of standard extract of Bombax ceiba L. leaves (BCE) in type 2 diabetic mellitus (T2DM). Oral administration of BCE at doses of 70, 140, and 280 mg·kg^-1, to the normal rats and the high-fat-diet- and streptozotocin-induced T2DM rats were carried out. Effects of BCE on blood glucose, body weight, and a range of serum biochemical parameters were tested, and histopathological observation of pancreatic tissues was also performed. HPLC-ESI-Q/TOF-MS/MS analysis indicated that the chemical composition of BCE mainly contained mangiferin, isoorientin, vitexin, isomangiferin, isovitexin, quercetin hexoside, 2'-trans-O-cumaroyl mangiferin, and nigricanside. BCE caused a significant decrease in the concentrations of fasting blood glucose, glycosylated hemoglobin, total cholesterol, triglyceride, low density lipoprotein-cholesterol, serum insulin, and malondialdehyde, and increases in oral glucose tolerance, high density lipoprotein-cholesterol, and superoxide dismutase in the T2DM model rats. Moreover, considerable pancreatic β-cells protection effect and stimulation of insulin secretion from the remaining pancreatic β-cells could be observed after BCE treatment. The results indicated that BCE exhibited an excellent hypoglycemic activity, and alleviated dyslipidemia which is associated with T2DM. Antioxidant activity and protecting pancreatic β-cells are the possible mechanisms involved in anti-diabetic activity of BCE.

Gentiana kurroo Royle attenuates the metabolic aberrations in diabetic rats; Swertiamarin, swertisin and lupeol being the possible bioactive principles

Background Gentiana kuroo Royle is a medicinally important plant of north-western Himalayas used for various ailments. In the present study, the plant extracts were investigated for the antidiabetic effects in streptozotocin-induced diabetic rats. Methods The impact of the extracts on serum glucose levels of diabetic rats was compared with reference drug - glibenclamide-treated diabetic rats. Streptozotocin injection was used to induce diabetes in fasted rats. Various biochemical, physiological and histopathological parameters in diabetic rats were observed for assessing the antidiabetic activity. Results The serum glucose concentrations in diabetic rats were significantly lowered by the extracts (methanolic and hydroethanolic at the doses of 250 and 500 mg/kg body weight). Several related biochemical parameters like creatinine, low-density lipoproteins, triglycerides, cholesterol, alkaline phosphatase, serum glutamate oxaloacetate transaminase and serum glutamate pyruvate transaminase were likewise decreased by the concentrates. The extracts also showed reduction in feed and water consumption of diabetic rats when compared with the diabetic control. The extracts were found to demonstrate regenerative/protective effect on β-cells of pancreas in diabetic rats. The methanolic and hydroethanolic extracts also exhibited hypoglycaemic effect in normal glucose-fed rats (oral glucose tolerance tests). LC-MS characterization of this extract showed the presence of these compounds - Swertiamarin, swertisin, lupeol, etc. Conclusions The current study demonstrated the counter diabetic capability of G. kuroo Royle being powerful in hyperglycaemia and can viably ensure against other metabolic deviations created by diabetes in rats. The possible bioactive principles responsible for the antidiabetic activity of G. kurroo Royle are Swertiamarin, swertisin and lupeol.

Echinodorus grandiflorus: Ethnobotanical, phytochemical and pharmacological overview of a medicinal plant used in Brazil

Echinodorus grandiflorus (Cham. & Schltdl.) Micheli is a native Brazilian species used in traditional practices for the treatment of several conditions such as inflammatory diseases, arthritis and hypertension. Through a systematic review of the accumulated knowledge about the species E. grandiflorus, the botanical, phytochemistry, ethnobotanical and pharmacological properties of this medicinal plant demonstrates its potential to naturally provide anti-inflammatory and anti-oxidant with a special emphasis on anti-hypertensive and cardioprotective effects. The body of literature reports that the chemical composition of crude E. grandiflorus extracts are notably composed of diterpenoids and flavonoids metabolites. Pharmacological studies have shown that oral treatments using the hydroalcoholic extracts of leaves from this plant has a significant anti-inflammatory, anti-hypertensive, diuretic and cardioprotective effects in rats with no toxicity. The holistic activities of complex extracts are corroborated by the individuals mechanisms of action, as well as, synergistic benefits attributed to the isolated chemical major constituents in this species. In light of the serious health concerns ascribed, it is important to investigate medicinal plant species with histories of traditional use for circulatory problems to meet the growing demands by scientifically validating their use and safety.

Swertisin ameliorates pre-pulse inhibition deficits and cognitive impairment induced by MK-801 in mice

Swertisin, a plant-derived C-glucosylflavone, is known to have antidiabetic, anti-inflammatory and antioxidant effects. In the present study, we investigated in mice the effects of swertisin on glutamatergic dysfunction induced by dizocilpine (MK-801), a non-competitive N-methyl-D-aspartate receptor antagonist. In the Acoustic Startle Response test, their MK-801-induced (given 0.2 mg/kg i.p.) pre-pulse inhibition deficit was significantly attenuated by the administration of swertisin (30 mg/kg p.o.). In the Novel Object Recognition Test, the recognition memory impairments that were induced by MK-801 (0.2 mg/kg, given i.p.) were also reversed by administration of swertisin (30 mg/kg p.o.). In addition, swertisin normalized the MK-801-induced elevation of phosphorylation levels of Akt and GSK-3β signaling molecules in the prefrontal cortex. These results indicated that swertisin may be useful in managing the symptoms of schizophrenia, including sensorimotor gating disruption and cognitive impairment, and that these behavioral outcomes may be related to Akt-GSK-3β signaling in the prefrontal cortex.

Pharmacokinetic Study of Swertisin by HPLC-MS/MS After Intravenous Administration in Rats

A sensitive and reliable high-performance liquid chromatography with tandem mass spectrometry was developed and validated for the quantification of swertisin in rat plasma. The samples were prepared with methanol by protein precipitation. Swertisin was separated by using an Agilent Poroshell 120 EC-C₁₈ column (4.6 mm × 50 mm, 2.7 μm) with the mobile phase consisted of acetonitrile and water containing 0.1% formic acid running at a flow rate of 0.3 mL/min for 5 min. The analytes were detected with the multiple reaction monitoring in the negative electrospray ionization source for quantitative response of swertisin [M-H]^- (445.1→281.7) and puerarin (internal standard) [M-H]^- (415.1→295.0). Precision (relative standard deviation, RSD%) of the inter-day and the intra-day was <9.89% and 11.34% while accuracy (relative error, RE%) ranged from -6.01% to 4.92% and -3.97% to 4.39%, respectively. Interestingly, the expression of the γ-aminobutyric acid (GABA) receptor subunits (GABA_Aα₁, GABA_Aα₅ and GABA_Aβ₁) mRNAs was enhanced in the rat hippocampal neurons treated with swertisin as analyzed by real-time polymerase chain reaction. Moreover, the method was successfully applied to determine the pharmacokinetic of swertisin in rats after tail vein injection with 4.0 mg/kg of the compound. Our results provide useful pharmacokinetic information for swertisin in vivo and suggest that the sedative function of this compound may be through inducing the expression of the GABA_A receptor subunits.

The Occurrence, Fate and Biological Activities of C-glycosyl Flavonoids in the Human Diet

The human diet contains a wide variety of plant-derived flavonoids, many of which are glycosylated via an O- or less commonly a C-glycosidic linkage. The distribution, quantity, and biological effects of C-glycosyl flavonoids in the human diet have received little attention in the literature in comparison to their O-linked counterparts, however, despite being present in many common foodstuffs. The structural nature, nomenclature, and distribution of C-glycosyl flavonoids in the human diet are, therefore, reviewed. Forty-three dietary flavonoids are revealed to be C-glycosylated, arising from the dihydrochalcone, flavone, and flavan-3-ol backbones, and distributed among edible fruits, cereals, leaves, and stems. C-linked sugar groups are shown to include arabinose, galactose, glucose, rutinose, and xylose, often being present more than once on a single flavonoid backbone and occasionally in tandem with O-linked glucose or rutinose groups. The pharmacokinetic fate of these compounds is discussed with particular reference to their apparent lack of interaction with hydrolytic mechanisms known to influence the fate of O-glycosylated dietary flavonoids, explaining the unusual but potentially important appearance of intact C-glycosylated flavonoid metabolites in human urine following oral administration. Finally, the potential biological significance of these compounds is reviewed, describing mechanisms of antidiabetic, antiinflammatory, anxiolytic, antispasmodic, and hepatoprotective effects.

Cucumis melo ssp. Agrestis var. Agrestis Ameliorates High Fat Diet Induced Dyslipidemia in Syrian Golden Hamsters and Inhibits Adipogenesis in 3T3-L1 Adipocytes

Background:

Cucumis melo ssp. agrestis var. agrestis (CMA) is a wild variety of C. melo. This study aimed to explore anti-dyslipidemic and anti-adipogenic potential of CMA.

Materials and Methods:

For initial anti-dyslipidemic and antihyperglycemic potential of CMA fruit extract (CMFE), male Syrian golden hamsters were fed a chow or high-fat diet with or without CMFE (100 mg/kg). Further, we did fractionation of this CMFE into two fractions namely; CMA water fraction (CMWF) and CMA hexane fraction (CMHF). Phytochemical screening was done with liquid chromatography-mass spectrometry LC- (MS)/MS and direct analysis in real time-MS to detect active compounds in the fractions. Further, high-fat diet fed dyslipidemic hamsters were treated with CMWF and CMHF at 50 mg/kg for 7 days.

Results:

Oral administration of CMFE and both fractions (CMWF and CMHF) reduced the total cholesterol, triglycerides, low‐density lipoprotein cholesterol, and very low‐density lipoprotein-cholesterol levels in high fat diet-fed dyslipidemic hamsters. CMHF also modulated expression of genes involved in lipogenesis, lipid metabolism, and reverse cholesterol transport. Standard biochemical diagnostic tests suggested that neither of fractions causes any toxicity to hamster liver or kidneys. CMFE and CMHF also decreased oil-red-O accumulation in 3T3-L1 adipocytes.

Conclusion:

Based on these results, it is concluded that CMA possesses anti-dyslipidemic and anti-hyperglycemic activity along with the anti-adipogenic activity.

SUMMARY

The oral administration of Cucumis melo agrestis fruit extract (CMFE) and its fractions (CMWF and CMHF) improved serum lipid profile in HFD fed dyslipidemic hamsters.

CMFE, CMWF and CMHF significantly attenuated body weight gain and eWAT hypertrophy.

The CMHF decreased lipogenesis in both liver and adipose tissue.

CMFE and CMHF also inhibited adipogenesis in 3T3-L1 adipocytes.

Abbreviation used: CMA: Cucumis melo ssp. agrestis var. agrestis, CMFE: CMA fruit extract, CMWF: CMA water fraction, CMHF: CMA hexane fraction, FAS: Fatty acid synthase, SREBP1c: Sterol regulatory element binding protein 1c, ACC: Acetyl CoA carboxylase, LXR α: Liver X receptor α.

Identification and functional analysis of 2-hydroxyflavanone C-glucosyltransferase in soybean (Glycine max)

C-Glucosyltransferase is an enzyme that mediates carbon-carbon bond formation to generate C-glucoside metabolites. Although it has been identified in several plant species, the catalytic amino acid residues required for C-glucosylation activity remain obscure. Here, we identified a 2-hydroxyflavanone C-glucosyltransferase (UGT708D1) in soybean. We found that three residues, His20, Asp85, and Arg292, of UGT708D1 were located at the predicted active site and evolutionarily conserved. The substitution of Asp85 or Arg292 with alanine destroyed C-glucosyltransferase activity, whereas the substitution of His20 with alanine abolished C-glucosyltransferase activity but enabled O-glucosyltransferase activity. The catalytic mechanism is discussed on the basis of the findings.

WITHDRAWN: The paradox of natural flavonoid C-glycosides and health benefits: When more occurrence is less research

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Interval multivariate curve resolution in the dereplication of HPLC-DAD data from Jatropha gossypifolia

INTRODUCTION

Jatropha gossypifolia has been used quite extensively by traditional medicine for the treatment of several diseases in South America and Africa. This medicinal plant has therapeutic potential as a phytomedicine and therefore the establishment of innovative analytical methods to characterise their active components is crucial to the future development of a quality product.

OBJECTIVE

To enhance the chromatographic resolution of HPLC-UV-diode-array detector (DAD) experiments applying chemometric tools.

METHODS

Crude leave extracts from J. gossypifolia were analysed by HPLC-DAD. A chromatographic band deconvolution method was designed and applied using interval multivariate curve resolution by alternating least squares (MCR-ALS).

RESULTS

The MCR-ALS method allowed the deconvolution from up to 117% more bands, compared with the original HPLC-DAD experiments, even in regions where the UV spectra showed high similarity. The method assisted in the dereplication of three C-glycosylflavones isomers: vitexin/isovitexin, orientin/homorientin and schaftoside/isoschaftoside.

CONCLUSION

The MCR-ALS method is shown to be a powerful tool to solve problems of chromatographic band overlapping from complex mixtures such as natural crude samples.

The role of calcium in intracellular pathways of rutin in rat pancreatic islets: potential insulin secretagogue effect

Rutin is a flavonol glycoside with multiple biological activities and it has been demonstrated that rutin modulates glucose homeostasis. In pancreatic β-cell, an increase in intracellular calcium concentration triggers exocytosis and thus insulin secretion. The aim of the study reported herein was to investigate the effect of rutin associated intracellular pathways on Ca(2+) uptake in isolated rat pancreatic islets. We focused on the acute effects of rutin on in vivo insulin secretion and the in vitro cellular signaling of pancreatic islets related to this effect. The results show that rutin significantly increased glucose-induced insulin secretion in an in vivo treatment. Moreover, it was demonstrated that rutin stimulated Ca(2+) uptake after 10 min of incubation compared with the respective control group. The involvement of L-type voltage-dependent Ca(2+) channels (L-VDCCs) was evidenced using nifedipine, while the use of glibenclamide and diazoxide demonstrated that the ATP-sensitive potassium (KATP) channels are not involved in the rutin action in pancreatic islets. In conclusion, rutin diminish glycemia, potentiate insulin secretion in vivo and significantly stimulates Ca(2+) uptake in rat pancreatic islets. A novel cellular mechanism of action of rutin in Ca(2+) uptake on pancreatic β-cells was elucidated. Rutin modulates Ca(2+) uptake in pancreatic islets by opening L-VDCCs, alter intracellular Ca(2+), PLC and PKC signaling pathways, characterizing KATP channel-independent pathways. These findings highlight rutin, a dietary adjuvant, as a potential insulin secretagogue contributing to glucose homeostasis.

Rutin potentiates calcium uptake via voltage-dependent calcium channel associated with stimulation of glucose uptake in skeletal muscle

Rutin is a flavonoid with several pharmacological properties and it has been demonstrated that rutin can modulate glucose homeostasis. In skeletal muscle, an increase in intracellular calcium concentration may induce glucose transporter-4 (GLUT-4) translocation with consequent glucose uptake. The aim of this study was to investigate the effect of rutin and intracellular pathways on calcium uptake as well as the involvement of calcium in glucose uptake in skeletal muscle. The results show that rutin significantly stimulated calcium uptake through voltage-dependent calcium channels as well as mitogen-activated kinase (MEK) and protein kinase A (PKA) signaling pathways. Also, rutin stimulated glucose uptake in the soleus muscle and this effect was mediated by extracellular calcium and calcium-calmodulin-dependent protein kinase II (CaMKII) activation. In conclusion, rutin significantly stimulates calcium uptake in rat soleus muscles. Furthermore, the increase in intracellular calcium concentration is involved in DNA activation by rutin. Also, rutin-induced glucose uptake via CaMKII may result in GLUT-4 translocation to the plasma membrane, characterizing an insulin-independent pathway. These findings indicate that rutin is a potential drug candidate for diabetes therapy.

Vitexin and isovitexin from the Leaves of Ficus deltoidea with in-vivo α-glucosidase inhibition

ETHNOPHARMACOLOGICAL RELEVANCE

The leaves of Ficus deltoidea are used as a traditional medicine by diabetes patients in Malaysia.

AIM OF THE STUDY

The objective of the study is to identify and evaluate bioactive constituents with in vivo α-glucosidase inhibition.

MATERIALS AND METHODS

The partitioned extracts, subfractions and pure bioactive constituents were subjected to α-glucosidase inhibition assay. The identified bioactive constituents were administered orally to sucrose loaded normoglycemic mice and induced diabetic rats. The postprandial blood glucose levels were monitored at 30 min interval. Acute toxicity was evaluated in both normoglycemic mice and induced diabetic rats.

RESULTS

Bioactivity guided fractionation led to the isolation of both vitexin (1) and isovitexin (2). Oral administration of 1mg/kg of either vitexin (1) or isovitexin (2) significantly (p<0.05) reduced the postprandial blood glucose level in sucrose loaded normoglycemic mice at 30 min. The percentage of postprandial blood glucose reduction was highest in sucrose loaded induced diabetic rats administered orally with 200mg/kg of vitexin (1) or 100mg/kg of isovitexin (2). Both vitexin (1) and isovitexin (2) did not exert any signs of toxicity at the highest dose of 2g/kg administered orally to normoglycemic mice and induced diabetic rats.

CONCLUSION

Both the C-glycosyl bioflavonoids, namely, vitexin (1) and isovitexin (2) exhibited in vivo α-glucosidase inhibition.

Influence of the traditional Brazilian drink Ilex paraguariensis tea on glucose homeostasis

In this study we examined the acute in vivo effect and short- and long-term in vitro effects of samples from native and commercial Ilex paraguariensis on glucose homeostasis. Also, the potential effect of I. paraguariensis on serum insulin secretion was investigated. The chemical identification and quantification of methyl xanthines and polyphenols in CH₂Cl₂, EtOAc and n-BuOH fractions of native I. paraguariensis as well as infusions of green and roasted I. paraguariensis from a commercial source was verified by high-performance liquid chromatography. The results for the serum glucose-lowering indicated that both fractions and both infusions were able to improve significantly the oral glucose tolerance curve. Additionally, both the EtOAc and n-BuOH fractions induced-insulin secretion, but EtOAc induced an early (at 15 min) and late (at 60 min) biphasic peak of insulin secretion similar to glipizide stimulatory effect. Both fractions increased liver glycogen content compared with fasted normal rats. Also, EtOAc and n-BuOH fractions inhibited in vitro disaccharidases activities after an acute treatment. The maximum inhibitory effect of the EtOAc and n-BuOH fractions on maltase activity (at 5 min) was around 35%. The evident reduction of protein glycation by glucose or fructose with EtOAc and n-BuOH fractions increased from 7 to 28 days of in vitro incubation. Inhibition of bovine serum albumin glycation by glucose and fructose, by around 50% and 90%, respectively, was observed. Additionally, the green and roasted mate infusions reduced the formation of AGEs in a characteristic long-term effect. In conclusion, this study shows that I. paraguariensis has an anti-hyperglycemic potential role able to improve the diabetic status and is probably a source of multiple hypoglycemic compounds.

Short and long-term effects of Baccharis articulata on glucose homeostasis

In this study, the in vivo effect of the crude extract and n-butanol and aqueous residual fractions of Baccharis articulata (Lam.) Pers. on serum glucose levels, insulin secretion and liver and muscle glycogen content, as well as in vitro action on serum intestinal disaccharidase activity and albumin glycation were investigated. Oral administration of the extract and fractions reduced glycemia in hyperglycemic rats. Additionally, the n-butanol fraction, which has high flavonoids content, stimulated insulin secretion, exhibiting an insulinogenic index similar to that of glipizide. Also, the n-butanol fraction treatment significantly increased glycogen content in both liver and muscle tissue. In vitro incubation with the crude extract and n-butanol and aqueous residual fractions inhibited maltase activity and the formation of advanced glycation end-products (AGEs). Thus, the results demonstrated that B. articulata exhibits a significant antihyperglycemic and insulin-secretagogue role. These effects on the regulation of glucose homeostasis observed for B. articulata indicate potential anti-diabetic properties.

Effects of flavonoids on α-glucosidase activity: potential targets for glucose homeostasis

OBJECTIVE

Flavonoids are naturally occurring compounds widely distributed in plants, which have hypoglycemic potential and have been described as glucosidase inhibitors. This study evaluated the effect of flavonoids on intestinal glucosidase activity after in vivo and in vitro treatment.

METHODS

For the in vivo studies animals received quercetin by gavage and for the in vitro assays a segment of the small intestine was used. To obtain the oral glucose tolerance curve fasted normal rats were loaded with glucose plus flavonoids. The glycemia was measured by the glucose oxidase method.

RESULTS

Quercetin reduced the effect of sucrase and maltase in the in vivo and in vitro treatments. It was observed in the in vitro studies that the maximum inhibitory effect of kaempferitrin was around 23% for maltase activity. Also, for the sucrose substrate the specific enzyme activity was significantly decreased. Aglycone, flavonoids, and kaempferol decreased significantly the maltase activity at all concentrations assayed. Finally, rutin reduced maltase-specific activity at all concentrations studied. According to the oral glucose tolerance curve, rutin reduced the serum glucose levels at 15, 30, and 60 min when administered by oral gavage 30 min before glucose overload in rats.

CONCLUSION

Based on these results, we can conclude that disaccharidases are targets of flavonoids in the regulation of glucose absorption and consequently glucose homeostasis.

Aleurites moluccana (L.) Willd. Leaves: Mechanical Antinociceptive Properties of a Standardized Dried Extract and Its Chemical Markers

Seeking to develop a new analgesic phytomedicine, a spray-dried extract (SDE) of Aleurites moluccana (L.) Willd. leaves was developed in scale up (5 kg). The SDE was standardized at 3% w/w in relation to the flavonoid 2′′-O-rhamnosylswertisin. The SDE batches were evaluated in relation to their physical, physiochemical, and pharmacological characteristics. The results demonstrated the reproducibility of the scale up SDE process which, when dosed orally, reduced carrageenan-induced mechanical hypernociception, with an ID₅₀% of 443 mg/kg. Similar results were obtained with animals injected with complete Freund's adjuvant (CFA), in which SDE caused inhibition of 48 ± 4%. SDE was effective in preventing prostaglandin E2 (PGE2)-induced mechanical hypernociception (inhibition of 26 ± 10% and 33 ± 3%, at 250 and 500 mg/kg, respectively). Swertisin and 2′′-O-rhamnosylswertisin isolated from the own extract were effective in inhibiting the hypernociceptive response induced by carrageenan (70 ± 2% and 50 ± 5%, resp.). Furthermore, 2′′-O-rhamnosylswertisin was capable of significantly inhibiting the mechanical sensitization induced by CFA or PGE2, with inhibitions of 25 ± 3% and 94 ± 6%, respectively. These results suggest that the effects of SDE are related, at least in part, to the presence of these flavonoids.