alpha-Amylase inhibitory activity of some Malaysian plants used to treat diabetes; with particular reference to Phyllanthus amarus

Preparative separation of structural isomeric pentacyclic triterpene oleanolic acid and ursolic acid from natural products by pH-zone-refining countercurrent chromatography

In this work, pH-zone-refining countercurrent chromatography was investigated in the preparative separation of two bioactive components, oleanolic acid and ursolic acid, from three different natural products, Aralia chinensis, apple peels and Eriobotrya japonica Thunb. Oleanolic acid and ursolic acid are structurally isomeric pentacyclic triterpene acids that are widely distributed in many natural products. However, it was difficult to separate these components with high purity by conventional methods. A biphasic solvent system composed of n-hexane–dichloromethane–methanol–water (7 : 3 : 2 : 8, v/v) was selected, in which an optimized concentration of 10 mmol L⁻¹ trifluoroacetic acid was added in the upper phase as the retainer and 10 mmol L⁻¹ ammonia (with 25–28% NH₃) was added in the aqueous phase as the eluter. Consequently, 38.56 mg of oleanolic acid with 99.01% purity was separated from 100 mg of the crude extract of Aralia chinensis, while 65.6 mg of a mixture of ursolic acid (90.98%) and oleanolic acid (6.51%) and 46.6 mg of a mixture of ursolic acid (74.35%) and oleanolic acid (23.61%) were separated from 100 mg of the crude extract of apple peels and 100 mg of the crude extract of Eriobotrya japonica Thunb., respectively, by pH-zone-refining countercurrent chromatography using the above selected biphasic solvent system. The results showed that pH-zone-refining countercurrent chromatography is an efficient method for the preparative separation of pentacyclic triterpene acids from natural products.

pH-zone-refining countercurrent chromatography was investigated in preparative separation of oleanolic acid and ursolic acid from three different natural products, Aralia chinensis, apple peels and Eriobotrya japonica Thunb.

A Multi-Mode Bioactive Agent Isolated From Ficus microcarpa L. Fill. With Therapeutic Potential for Type 2 Diabetes Mellitus

Type 2 diabetes is a metabolic disorder, characterized by hyperglycemia and glucose intolerance. Natural products and its derived active compounds may be achievable alternatives for the treatment of type 2 diabetes. In present study we investigated the antidiabetic potential of Ficus microcarpa and isolated bioactive compounds i.e., Plectranthoic acid A (PA-A) and 3,4,5,7-Flavantetrol (FL). Anti-hyperglycemic potential was evaluated via α-glucosidase, α-amylase and dipeptidyl peptidase 4 (DPP-4) assays. 5'AMP-activated kinase (AMPK) activation potential was assessed by using primary hepatocytes. Distribution of PA-A in different parts of Ficus microcarpa was evaluated by using rapid high-performance liquid chromatography (HPLC). Ethyl acetate fraction (FME) exhibited significant inhibition of α-glucosidase, α-amylase, and DPP-4, therefore, was selected for isolation of bioactive compounds. Among isolated compounds PA-A was more potent and possessed pleotropic inhibitory activity with IC50 values of 39.5, 55.5, and 51.4 μM against α-glucosidase, α-amylase, and DPP-4, respectively. Our results showed that PA-A is also a potent activator of AMPK which is a central hub of metabolic regulation. Molecular docking studies confirmed the activity of PA-A against α-glucosidase, α-amylase, and DPP-4. Rapid HPLC method revealed that maximum concentration of PA-A is present in the stem (2.25 μg/mg dry weight) of Ficus microcarpa. Both in vitro and in silico studies proposed that Ficus microcarpa and its isolated compound PA-A could be an important natural source for alleviating the symptoms of type 2 diabetes mellitus and we suggest that PA-A should be explored further for its ultimate use for the treatment of type 2 diabetes.

Inhibitory Reactivity of Capsaicin with α-Amylase and α-Glucosidase Related to Antidiabetes using Molecular Docking and Quantum Calculation Methods

This work aims to investigate the inhibitory activity of capsaicin, which is one of capsaicinoid compounds, on these enzymes using a molecular docking and quantum calculation. Acarbose, a commercial diabetes drug, was also investigated for comparison. The docking results revealed that acarbose yields better inhibition efficiency with binding free energy (ΔGbinding) of about -8.2 to -11.9 kcal/mol, and inhibition constant (Ki) of about 0.0002 to 0.4 µM, whereas capsaicin provided the ΔGbinding of -5.8 to -6.1 kcal/mol and Ki of 23.7 to 45.9 µM. The total binding energy (ΔEbinding) between each inhibitor and amino acids in active site of enzyme obtained from quantum calculation with MP2/6-31G(d,p) level is in agreement with the ΔGbinding, i.e. the ΔEbinding of acarbose was larger negative than that of capsaicin. The amino acids interacting with inhibitor as hydrogen bond mainly contribute to the total binding energy. Nevertheless, it could be concluded that capsaicinoids have high potential to be developed as an alternative drug for diabetes disease.

Hypoglycemic and hypolipidemic effects of total saponins from Stauntonia chinensis in diabetic db/db mice

Stauntonia chinensis DC. has been utilised as a traditional herbal medicine for its anti‐hyperglycemic characteristic, which has been associated with triterpene saponins. The goal of the current evaluation was to examine hypoglycemic activity and affiliated mechanism of total saponins from S. chinensis. The chemical composition was analysed by HPLC‐ESI‐MS/MS. The fasting blood glucose, oral glucose tolerance test, insulin tolerance test, insulin and glycogen levels of type 2 diabetic db/db mice administered total saponins were quantified to determine the hypoglycemic effects. The serum lipid profiles were assessed to determine the hypolipidemic effects. Western blotting was used to quantify the protein levels of insulin receptor substrates (IRS)‐1/PI3K/AKT, AMPK/ACC and GLUT4. Twenty triterpene saponins were identified from the total saponins, which exhibited hypoglycemic activities and modulated hyperlipidemia that was associated with type 2 diabetes. The hypoglycemic effects were partly due to the activation of GLUT4, which is regulated by IRS‐1/PI3K/AKT. The activation of the AMPK/ACC signalling pathway may be responsible for the hypolipidemic activity. This study revealed that total saponins from S. chinensis have significant hypoglycemic and hypolipidemic activity in diabetic db/db mice, indicating that these may be utilised in the development of saponins based on S. chinensis for the treatment of type 2 diabetes.

Antihyperglycemic and Antihyperlipidemic Effects of Aqueous Extracts of Lannea edulis in Alloxan-Induced Diabetic Rats

Lannea edulis (Sond.) Engl. commonly known as wild grape is used traditionally for the treatment of diabetes. It is only found in Eastern and Southern Africa. Phytochemical screening, antihyperglycemic and antihyperlipidemic effects of aqueous extracts of L. edulis in alloxan induced diabetic rats were carried out. We report herein the findings of this research work. Lannea edulis crude aqueous extracts were obtained by hot infusion and evaporation method. Phytochemical screening was carried out and subsequently toxicity studies of the aqueous extracts were performed to establish the Lethal Dose 50 (LD50) in albino rats. Alloxan monohydrate was used to induce diabetes in the rats. Lannea edulis positive control group doses of 100, 300, and 500 mg/kg were administered to 3 groups for 14 days. The positive control group was administered 5 mg/kg of glibenclamide. The negative and normal control groups were administered distilled water. To determine fasting blood glucose, blood was drawn on days 0, 1, 3, 5, 7, and 14 while it was drawn on days 0 and 14 for the determination of lipids. Phytochemical screening revealed the presence of flavonoids, saponins, tannins, cardiac glycosides, alkaloids and steroids. L. edulis diabetic positive control groups showed significant (P < 0.05) dose dependent reductions in fasting blood glucose levels. When day 0 mean blood glucose levels were compared to day 3 mean blood glucose levels of their respective groups, the 300 mg/kg L. edulis group showed a 23.3% drop and the 500 mg/kg L. edulis group showed a 52.6% drop. The 100 mg/kg L. edulis diabetic positive control group showed a 25.1% drop by day 5, the day on which it showed statistical significance (P < 0.05) compared to the diabetic control. In addition, administration of aqueous extracts of L. edulis to diabetic rats for 14 days significantly decreased (P < 0.05) the levels of serum total cholesterol, triglycerides, Low Density Lipoprotein (LDL) and Very Low Density Lipoprotein (VLDL) whilst increasing the levels of High Density Lipoprotein (HDL), when compared to the diabetic control group. It was concluded that L. edulis showed significant and dose dependent antihyperglycemic and antihyperlipidemic effects thus confirming its traditional use.

Antidiabetic potential of Musa spp. inflorescence: a systematic review

Objectives

Extracts of parts Musa spp. have been used for the treatment of various diseases in traditional medicine. Studies have shown that these extracts have hypoglycaemic properties. The aim of this work was to gather evidence on the antidiabetic effects of Musa spp. inflorescence.

Methods

A systematic review was conducted with searches in three electronic databases, along with manual searches. Studies evaluating the antidiabetic properties of extracts of flower or bract of the genus Musa (in vitro or in vivo) were included.

Key findings

Overall, 16 studies were found. The reported assays were of hypoglycaemic effects, oral glucose tolerance, inhibitory activities in carbohydrate metabolism and digestive enzymes, enhanced glucose uptake activity and popular use of the extract in patients with diabetes type 2. In vitro studies showed that use of the extract was associated with antidiabetic effects (e.g. increased glucose uptake and inhibition of carbohydrate digestion enzymes). In induced diabetic models, Musa spp. extracts showed dose-dependent glycaemic level reductions compared with pharmacological drugs (P &lt; 0.05).

Summary

In general, promising results regarding antidiabetic activity were found for inflorescence of Musa spp., suggesting that this plant could represent a natural alternative therapy for treating diabetes mellitus type 2.

Antiviral Activities of Oleanolic Acid and Its Analogues

Viral diseases, such as human immune deficiency virus (HIV), influenza, hepatitis, and herpes, are the leading causes of human death in the world. The shortage of effective vaccines or therapeutics for the prevention and treatment of the numerous viral infections, and the great increase in the number of new drug-resistant viruses, indicate that there is a great need for the development of novel and potent antiviral drugs. Natural products are one of the most valuable sources for drug discovery. Most natural triterpenoids, such as oleanolic acid (OA), possess notable antiviral activity. Therefore, it is important to validate how plant isolates, such as OA and its analogues, can improve and produce potent drugs for the treatment of viral disease. This article reports a review of the analogues of oleanolic acid and their selected pathogenic antiviral activities, which include HIV, the influenza virus, hepatitis B and C viruses, and herpes viruses.

The role of pollutants in type 2 diabetes mellitus (T2DM) and their prospective impact on phytomedicinal treatment strategies

Type 2 diabetes mellitus (T2DM) is the most common form of diabetes and it is characterized by high blood sugar and abnormal sera lipid levels. Although the specific reasons for the development of these abnormalities are still not well understood, traditionally, genetic and lifestyle behavior have been reported as the leading causes of this disease. In the last three decades, the number of diabetic patients has drastically increased worldwide, with current statistics suggesting the number is to double in the next two decades. To combat this incurable ailment, orthodox medicines, to which economically disadvantaged patients have minimal access to, have been used. Thus, a considerable amalgamation of medicinal plants has recently been proven to possess therapeutic capabilities to manage T2DM, and this has prompted studies primarily focusing on the healing aspect of these plants, and ultimately, their commercialization. Hence, this review aims to highlight the potential threat of pollutants, i.e., polyfluoroalkyl compounds (PFCs), endocrine disrupting chemicals (EDCs) and heavy metals, to medicinal plants, and their prospective impact on the phytomedicinal therapy strategies for T2DM. It is further suggested that auxiliary research be undertaken to better comprehend the factors that influence the uptake of these compounds by these plants. This should include a comprehensive risk assessment of phytomedicinal products destined for the treatment of T2DM. Regulations that control the use of PFC-precursors in certain developing countries are also long overdue.

Antidiabetic phytoconstituents and their mode of action on metabolic pathways

Diabetes Mellitus, characterized by persistent hyperglycaemia, is a heterogeneous group of disorders of multiple aetiologies. It affects the human body at multiple organ levels thus making it difficult to follow a particular line of the treatment protocol and requires a multimodal approach. The increasing medical burden on patients with diabetes-related complications results in an enormous economic burden, which could severely impair global economic growth in the near future. This shows that today's healthcare system has conventionally been poorly equipped towards confronting the mounting impact of diabetes on a global scale and demands an urgent need for newer and better options. The overall challenge of this field of diabetes treatment is to identify the individualized factors that can lead to improved glycaemic control. Plants are traditionally used worldwide as remedies for diabetes healing. They synthesize a diverse array of biologically active compounds having antidiabetic properties. This review is an endeavour to document the present armamentarium of antidiabetic herbal drug discovery and developments, highlighting mechanism-based antidiabetic properties of over 300 different phytoconstituents of various chemical categories from about 100 different plants modulating different metabolic pathways such as glycolysis, Krebs cycle, gluconeogenesis, glycogen synthesis and degradation, cholesterol synthesis, carbohydrate metabolism as well as peroxisome proliferator activated receptor activation, dipeptidyl peptidase inhibition and free radical scavenging action. The aim is to provide a rich reservoir of pharmacologically established antidiabetic phytoconstituents with specific references to the novel, cost-effective interventions, which might be of relevance to other low-income and middle-income countries of the world.

Assessment and comparison of phytochemical constituents and biological activities of bitter bean (Parkia speciosa Hassk.) collected from different locations in Malaysia

Background

Parkia speciosa seeds are a common ingredient in Malay cuisine with traditional interest because of its medicinal importance and content of health-promoting phytochemicals. This study evaluated the phytochemical constituents and biological activities (antioxidant and antibacterial activities) of Parkia speciosa Hassk seeds collected from three different regions of Malaysia (Perak, Negeri Sembilan and Johor). Phytochemical constituents (total flavonoid and total phenolic) were measured using the spectrophotometric method, and individual flavonoids and phenolic acids were identified using ultra-high-performance liquid chromatography. Ferric reducing antioxidant potential (FRAP) assay and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay we used in order to evaluation of antioxidant activities. Disc diffusion method was employed for the evaluation of antibacterial activity of extracts against Gram-positive and Gram-negative bacterial strains.

Results

The primary screening of phytochemicals showed that P. speciosa seeds contain alkaloids, terpenoids, flavonoids, and phenolics. Samples collected from Perak contained the highest levels of the phytochemical constituents, with highest DPPH and FRAP activity followed by Negeri sembilan and Johor. From the identified compounds, quercetin and gallic acid were identified as the most abundant compounds. Seeds collected from the Perak location exhibited potent antibacterial activity, against both Gram-positive and Gram-negative bacteria strains. Staphylococcus aureus and Bacillus subtilis were recorded as the bacterial strains most sensitive to P. speciosa seed extracts. Correlation analysis showed that flavonoid compounds are responsible for the antioxidant activities of the P. speciosa seeds studied, while antibacterial activity showed a high correlation with the levels of gallic acid.

Conclusions

Parkia speciosa seed grown in Perak exhibit the highest concentrations of phytochemicals, as well as the highest biological activity. It may also be recommended for the food industry to use seeds from this area for their products, which are going to compete in the expanding functional food markets.

Antidiabetic activities of entagenic acid in type 2 diabetic db/db mice and L6 myotubes via AMPK/GLUT4 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Entada phaseoloides (L.) Merr., a traditional Chinese folk medicine, has been used in treating diabetes and other inflammatory disorders. Our previous study revealed that the triterpene saponins in E.Phaseoloides possessed an antidiabetic effect in type 2 diabetic rats by activating AMP-activated protein kinase (AMPK). Entagenic acid, the principal aglycon, isolated from the seed kernels of E. phaseoloides, has been proposed to possess a significant role in the antidiabetic effect, however, its actual effect and pertinent mechanisms are still unknown.

AIM OF THE STUDY

The aim of the present study was to investigate the antidiabetic effect of entagenic acid in a type 2 diabetic animal model (C57BIKsj db/db mice) and its role in the regulation of glucose uptake in L6 myotubes, and to explore the possible molecular mechanisms.

MATERIALS AND METHODS

In vivo, average weekly body weight, daily water, food intake and postprandial blood glucose levels, the intraperitoneal insulin tolerance test, glucose tolerance test, serum lipid profiles and pancreatic histopathological changes in db/db mice treated with entagenic acid orally at different doses (5, 10 and 20mg/kg) were assessed and compared with wild-type littermates or vehicle- and metformin-treated db/db mice. In vitro, effects of entagenic acid on the glucose consumption and the phosphorylation of protein kinase B (AKT) and AMPK in L6 myotubes were evaluated.

RESULTS

In vivo, entagenic acid significantly lowered postprandial blood glucose levels but not the body weight, normalized the serum lipid imbalance, improved the impaired glucose tolerance, insulin resistance, as well as the pathological changes in pancreatic islets. In vitro, entagenic acid dose-dependently promoted glucose utilization and enhanced the translocation and expression of glucose transporter 4 (GLUT4), and phosphorylation of AMPK but not AKT.

CONCLUSIONS

The present study demonstrated that entagenic acid can markedly maintain the glucose homeostasis, improve insulin resistance and ameliorate dyslipidemia. Its antihyperglycemic effect could be caused by promoting AMPK mediated cellular signaling and GLUT4 translocation in muscles.

Deconvoluting the dual hypoglycemic effect of wedelolactone isolated fromWedelia calendulacea: investigationviaexperimental validation and molecular docking

Wedelia calendulacea has a long history of use in the Indian Ayurvedic System of Medicine for the treatment, prevention, and cure of a diverse range of human diseases such as diabetes obesity, and other metabolic diseases. A wide range of chemical constituents, such as triterpenoid saponin, kauren diterpene, and coumestans, has been isolated from the plant. Conversely, no published literature is available in relation to the isolation of wedelolactone (WEL) for its anti-diabetic effect. The aim of the present study was to isolate the bioactive phyto-constituent from Wedelia calendulacea and to scrutinize the antidiabetic effect with its possible mechanism of action. The structure of the isolated compound was elucidated by different spectroscopy techniques. Proteins, such as dipeptidyl peptidase-4 (DPPIV), glucose transporter 1 (GLUT1), and peroxisome proliferator-activated receptors-γ (PPARγ), were also subjected to in silico docking. Later, this isolated compound was scrutinized against α-glucosidase and α-amylase enzyme activity along with an oral glucose tolerance test (OGTT) for estimation of glucose utilization. Streptozotocin (STZ) was used for the induction of type II diabetes mellitus (DM) in Wistar rats. The rats were divided into different groups and received the WEL (5, 10, and 20 mg kg⁻¹, b.w.) and glibenclamide (2.5 mg kg⁻¹, b.w.) for 28 days. The blood glucose level (BGL), plasma insulin, and body weight were determined at regular time intervals. The serum lipid profile hypolipidemic effect for the different antioxidant markers and hepatic tissue markers were scrutinized along with an inflammatory mediator to deduce the possible mechanism. With the help of spectroscopy techniques, the isolated compound was identified as wedelolactone. In the docking study, WEL showed docking scores of −6.17, −9.43, and −7.66 against DPP4, GLUTI, and PRARY, respectively. WEL showed the inhibition of α-glucosidase (80.65%) and α-amylase (93.83%) and suggested an effect on postprandial hyperglycemia. In the OGTT, WEL significantly (P < 0.001) downregulated the BGL, a marker for better utilization of drugs. In the diabetes model, WEL reduced the BGL and enhanced the plasma insulin and body weight. It also significantly (P < 0.001) modulated the lipid profile; this suggested an anti-hyperlipidemia effect. WEL significantly (P < 0.001) distorted the hepatic tissue, acting as an antioxidant marker in a dose-dependent manner. WEL significantly (P < 0.001) downregulated the C-reactive protein (CRP), tumor necrosis factor alpha (TNF-α), and interleukin 6 (IL-6) level. On the basis of the available results, we can conclude that WEL can be an alternative drug for the treatment of type II DM either by inhibiting the production of inflammatory mediator or by the downregulation of oxidative stress.

Wedelia calendulacea has a long history of use in the Indian Ayurvedic System of Medicine for the treatment, prevention, and cure of a diverse range of human diseases such as diabetes obesity, and other metabolic diseases.

Antioxidant and Inhibitory Effects of Saponin Extracts from Dianthus basuticus Burtt Davy on Key Enzymes Implicated in Type 2 Diabetes In vitro

Context:

Dianthus basuticus is a plant of South African origin with various acclaimed pharmaceutical potentials.

Aims:

This study explored the antioxidant and antidiabetic activities of saponin extract from D. basuticus in vitro.

Materials and Methods:

Antioxidant activity of saponin was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (*NO)-free radical scavenging activity while antidiabetic potentials were measured by the α-amylase and α-glucosidase inhibitory activities of the saponin extract.

Results:

The results showed that the saponin extract, compared with quercetin, displayed better DPPH (IC₅₀ = 6.95 mg/ml) and NO (IC₅₀ = 3.31 mg/ml) radical scavenging capabilities. Similarly, the saponin extracts elicited stronger α-glucosidase (IC₅₀ = 3.80 mg/ml) and moderate α-amylase (IC₅₀ = 4.18 mg/ml) inhibitory activities as compared to acarbose. Saponin exhibited a competitive mode of inhibition on α-amylase with same maximum velocity (Vmax) of 0.0093 mM/min for saponin compared with control 0.0095 mM/min and different the Michaelis constant (Km) values of 2.6 × 10^-6 mM and 2.1 × 10^-5 mM, respectively, while for α-glucosidase, the inhibition was uncompetitive, Vmax of 0.027 mM/min compared with control 0.039 mM/min and Km values of 1.02 × 10^-6 mM and 1.38 × 10^-6 mM, respectively. The gas chromatography-mass spectrometric analysis revealed the presence of bioactive like β- and α-amyrin, 3-O-methyl-D-glucose, methyl commate, and olean-12-en-3-beta-ol.

Conclusion:

Overall, the data suggested that the saponin extract from D. basuticus has potentials as natural antioxidants and antidiabetics.

SUMMARY

Saponin extract from Dianthus basuticus displayed promising antidiabetic and antioxidant activity

Saponin competitively and uncompetitively inhibited a-amylase and a-glucosidase, respectively

The stronger inhibition of α-glucosidase and moderate inhibition of α-amylase by saponin extract from D. basuticus is promising good antidiabetes compared with existing drugs with associated side effects.

Abbreviations used: DPPH: 2,2-diphenyl-1-picrylhydrazyl, Km: The Michaelis constant, Vmax: Maximum velocity, ROS: Reactive oxygen species, NIDDM: Non-insulin-dependent diabetes mellitus, UFS: University of the Free State, GC-MS: Gas chromatography-mass spectrometric, MS: Mass spectrometry, NIST: National Institute of Standards and Technology, DNS: 3,5-dinitrosalicylic acid, NO: Nitric oxide, RNS: Reactive nitrogen species, PNPG: p-Nitrophenyl-α-D-glucopyranoside.

Starch Hydrolysis, Polyphenol Contents, and In Vitro Alpha Amylase Inhibitory Properties of Some Nigerian Foods As Affected by Cooking

The effect of cooking on starch hydrolysis, polyphenol contents, and in vitro α-amylase inhibitory properties of mushrooms (two varieties Russula virescens and Auricularia auricula-judae), sweet potato (Ipomea batatas), and potato (Solanum tuberosum) was investigated. The total, resistant, and digestible starch contents of the raw and cooked food samples (FS) ranged from 6.4 to 64.9; 0 to 10.1; and 6.4 to 62.7 g/100 g, respectively, while their percentages of starch digestibility (DS values expressed as percentages of total starch hydrolyzed) ranged from 45.99 to 100. Raw and boiled unpeeled potato, raw and boiled peeled potato, raw A. auricula-judae, and sweet potato showed mild to high α-amylase inhibition (over a range of concentration of 10-50 mg/mL), which was lower than that of acarbose (that had 69% inhibition of α-amylase over a range of concentration of 2-10 mg/mL), unlike raw R. virescens, boiled A. auricula-judae, and boiled sweet potatoes that activated α-amylase and boiled R. virescens that gave 0% inhibition. The FS contained flavonoids and phenols in addition. The significant negative correlation (r = -0.55; P = 0.05) between the α-amylase inhibitory properties of the raw and cooked FS versus their SD indicates that the α-amylase inhibitors in these FS also influenced the digestibility of their starches. In addition, the significant positive correlation between the α-amylase inhibitory properties of the raw and cooked FS versus their resistant starch (RS) (r = 0.59; P = 0.01) contents indicates that the RS constituents of these FS contributed to their α-amylase inhibitory properties. The study showed the usefulness of boiled unpeeled potato, boiled potato peeled, and raw sweet potato as functional foods for people with type 2 diabetes.

Bioassay-guided fractionation and identification of α-amylase inhibitors from Syzygium cumini leaves

CONTEXT

Pancreatic α-amylase and α-glucosidase inhibitors serve as important strategies in the management of blood glucose. Even though Syzygium cumini (L.) Skeels (Myrtaceae) (SC) is used extensively to treat diabetes; scientific evidence on antidiabetic effects of SC leaves is scarce.

OBJECTIVE

SC leaf extract was investigated for α-amylase inhibitory effect and continued with isolation and identification of α-amylase inhibitors.

MATERIALS AND METHODS

Bioassay-guided fractionation was conducted using in vitro α-amylase inhibitory assay (with 20-1000 μg/mL test material) to isolate the inhibitory compounds from ethyl acetate extract of SC leaves. Structures of the isolated inhibitory compounds were elucidated using 1H NMR and 13C NMR spectroscopic analysis and direct TLC and HPLC comparison with authentic samples. Study period was from October 2013 to October 2015.

RESULTS

An active fraction obtained with chromatographic separation of the extract inhibited porcine pancreatic α-amylase with an IC50 of 39.9 μg/mL. Furthermore, it showed a strong inhibition on α-glucosidase with an IC50 of 28.2 μg/mL. The active fraction was determined to be a 3:1 mixture of ursolic acid and oleanolic acid. Pure ursolic acid and oleanolic acid showed IC50 values of 6.7 and 57.4 μg/mL, respectively, against α-amylase and 3.1 and 44.1 μg/mL respectively, against α-glucosidase.

DISCUSSION AND CONCLUSIONS

The present study revealed strong α-amylase and α-glucosidase inhibitory effects of ursolic acid and oleanolic acid isolated from SC leaves for the first time validating the use of SC leaves in antidiabetic therapy.

Enhanced Glucose Uptake in Human Liver Cells and Inhibition of Carbohydrate Hydrolyzing Enzymes by Nordic Berry Extracts

A Western lifestyle with low physical activity and a diet rich in sugar, fat and processed food contribute to higher incidences of diabetes and obesity. Enhanced glucose uptake in human liver cells was observed after treatment with phenolic extracts from different Nordic berries. All berry extracts showed higher inhibition against α-amylase and α-glucosidase than the anti-diabetic agent acarbose. Total phenolic content and phenolic profiles in addition to antioxidant activities, were also investigated. The berries were extracted with 80% methanol on an accelerated solvent extraction system (ASE) and then purified by C-18 solid phase extraction (SPE). Among the ASE methanol extracts, black chokeberry, crowberry and elderberry extracts showed high stimulation of glucose uptake in HepG2 cells and also considerable inhibitory effect towards carbohydrate hydrolyzing enzymes. SPE extracts with higher concentrations of phenolics, resulted in increased glucose uptake and enhanced inhibition of α-amylase and α-glucosidase compared to the ASE extracts. Crowberry and cloudberry were the most potent 15-lipoxygenase inhibitors, while bog whortleberry and lingonberry were the most active xanthine oxidase inhibitors. These results increase the value of these berries as a component of a healthy Nordic diet and have a potential benefit against diabetes.

Defatting of acetone leaf extract of Acacia karroo (Hayne) enhances its hypoglycaemic potential

BACKGROUND

Conventional drugs used to treat diabetes are too expensive, toxic and rarely available to rural communities. This study was aimed at investigating the phytochemical differences and hypoglycaemic effects (α-amylase enzyme inhibition, glucose uptake, GLUT4 translocation and phosphorylation of MAPKs) of non-defatted and defatted acetone leaf extract of Acacia karroo.

METHODS

Qualitative phytochemical analyses of extracts were determined using standard chemical tests and total phenolic contents using the Folin-Ciocalteu reagent method. Presence of antioxidant constituents was determined using DPPH scavenging and ferric reducing power assays. Alpha amylase enzyme inhibitory potential was determined chromogenically and cytotoxicity of the extracts on C2C12 muscle and 3T3-L1 cells using the MTT assay. Glucose uptake by the cells was determined colorimetrically and the most active extract was evaluated for its ability to translocate GLUT4 and MAPKs phosphorylation potential using immunofluorescence microscopy and dot blot analysis, respectively.

RESULTS

Phenols, flavonoids, tannins, saponins and cardiac glycosides were detected in both extracts. Defatting of the plant material resulted in low amounts of phenols (0.432 ± 0.014 TAE/mg), DPPH scavenging activity (EC₅₀ 0.40 ± 0.012 mg/ml), low toxicity and high ferric reducing power (EC₅₀ 1.13 ± 0.017 mg/ml), α-amylase enzyme inhibition (IC₅₀ 30.2 ± 3.037 μg/ml) and glucose uptake by both cells. The defatted extract showed an increase in GLUT4 translocation (at 25 μg/ml) with decrease in Akt expression while in combination with insulin showed a decrease in GLUT4 translocation. A finding, that is implicative that the effect of the extract on GLUT4 translocation in C2C12 cells was not Akt dependent. The defatted extract in the absence and presence of insulin show varying phosphorylation levels of CREB, p38, GSK-3 and ERK2 which are important in cell survival and metabolism.

CONCLUSION

This study represents the first report on the hypoglycemic potential of A. karroo and presence of compounds that can be exploited in the search for therapeutics with antidiabetic effect.

Phytochemical Compositions and In vitro Assessments of Antioxidant and Antidiabetic Potentials of Fractions from Ehretia cymosa Thonn

BACKGROUND

Ehretia cymosa Thonn. is a popular medicinal plant used in different parts of West Africa for the treatment of various ailments including diabetes mellitus.

OBJECTIVE

The current study investigates bioactive constituents and in vitro antioxidant and antidiabetic potentials of fractions from extract of E. cymosa.

MATERIALS AND METHODS

Phytochemical investigation and antioxidant assays were carried out using standard procedures. Antidiabetic potential was assessed by evaluating the inhibitory effects of the fractions on the activities of α-amylase and α-glucosidase, while bioactive constituent's identification was carried out using gas chromatography-mass spectrometric (GC-MS) analysis.

RESULTS

The phytochemistry tests of the fractions revealed the presence of tannins, phenols, flavonoids, steroids, terpene, alkaloid, and cardiac glycosides. Methanol fraction shows higher phenolic (27.44 mg gallic acid/g) and flavonoid (235.31 mg quercetin/g) contents, while ethyl acetate fraction revealed higher proanthocyanidins (28.31 mg catechin/g). Methanol fraction displayed higher (P < 0.05) 1,1-diphenyl-2-picryl-hydrazyl (0.47 mg/mL), 2,2-azino-bis (3-ethylbenzothiazoline)-6-sulfonic acid (0.49 mg/mL), and hydroxyl radical (0.55 mg/mL) scavenging activities, while ethyl acetate exhibited strong metal chelating (0.61 mg/mL) and superoxide anion (1.68 mg/mL) scavenging activity. Methanol and ethyl acetate fractions displayed higher inhibition (P < 0.05) against α-glucosidase (0.60 mg/mL) and α-amylase (2.11 mg/mL), respectively. Methanol fraction also inhibited α-amylase and α-glucosidase in competitive and noncompetitive modes, respectively. The GC-MS chromatogram of the methanol fraction revealed 24 compounds, which include phytol (1.78%), stearic acid (1.02%), and 2-hexadecyloxirane (34.18%), which are known antidiabetic and antioxidant agents.

CONCLUSION

The results indicate E. cymosa leaves as source of active phytochemicals with therapeutic potentials in the management of diabetes.

SUMMARY

E. cymosa fractions possess antioxidant and antidiabetic activities. Hence, it is a source of active phytochemicals with therapeutic potentials in the management of diabetesThe high flavonoid, phenolic, and proanthocyanidin contents of fractions from E. cymosa also contribute to its antioxidant and antidiabetic propertiesMethanol fraction of E. cymosa displayed better antidiabetic activities compared to acarbose as revealed by their half maximal inhibitory concentration valuesMethanol fraction of E. cymosa extract contains phytol, hexadecyl oxirane, and stearic acid, which are reported to possess antidiabetic and antioxidant potentials. Abbreviations used: ABTS: 2,2- Azino-bis (3-ethylbenzothiazoline)-6-sulfonic acid, DPPH: 1,1-diphenyl-2-picryl-hydrazyl, PMS: Phenazine methosulfate, NBT: Nitroblue tetrazolium, NADH: Nicotinamide adenine dinucleotide, TCA: Trichloroacetic acid, TBA: Thiobarbituric acid, DNS: Dinitrosalicylic acid.

Pentacyclic triterpenes as α-glucosidase and α-amylase inhibitors: Structure-activity relationships and the synergism with acarbose

In this paper, the inhibition of α-amylase and α-glucosidase by nine pentacyclic triterpenes was determined. For α-amylase inhibitory activity, the IC₅₀ values of ursolic acid, corosolic acid, and oleanolic acid were 22.6±2.4μM, 31.2±3.4μM, and 94.1±6.7μM, respectively. For α-glucosidase inhibition, the IC₅₀ values of ursolic acid, corosolic acid, betulinic acid, and oleanolic acid were 12.1±1.0μM, 17.2±0.9μM, 14.9±1.9μM, and 35.6±2.6μM, respectively. The combination of corosolic acid and oleanolic acid with acarbose showed synergistic inhibition against α-amylase. The combination of the tested triterpenes with acarbose mainly exhibited additive inhibition against α-glucosidase. Kinetic studies revealed that corosolic acid and oleanolic acid showed non-competitive inhibition and acarbose showed mixed-type inhibition against α-amylase. The results provide valuable implications for the triterpenes (ursolic acid, corosolic acid, and oleanolic acid) alone or in combination with acarbose as a therapeutic agent for the treatment of diabetes mellitus.

Ursolic acid derivatives for pharmaceutical use: a patent review (2012-2016)

INTRODUCTION

Ursolic acid (UA), belongs to a group of pentacyclic triterpenoids and is known to possess some very interesting biological properties. Protocols have been developed in order to synthesize bioactive UA analogs which have resulted in numerous ursolic acid analogs being synthesized during the period 2012-2016. Ursolic acid and its analogues can be employed to treat various cancers, inflammatory diseases, diabetes, Parkinson's disease, Alzheimer's disease, hepatitis B, hepatitis C and AIDS to mention but a few. Areas covered: This review covers patents on therapeutic activities of ursolic acid (UA) and its synthetic derivatives published during the four year period 2012-2016. A discussion about structure-activity relationships (SAR) of these analogs is also included. Expert opinion: Ursolic acid and its synthetic derivatives demonstrated excellent anticancer, antidiabetic, antiarrhythmic, anti-hyperlipidemic, antimicrobial, anti-hypercholesterolemic, and anti-cardiovascular properties. Additionally, various ursolic acid analogues have been synthesized through modification at positions C2-OH, C3-OH and C17-CO2H. It is noteworthy that the C-17 amide and amino analogs of UA possessed better anticancer activity compared to the parent compound (UA). Most importantly, UA has the potential to conjugate with other anticancer drugs or be transformed into its halo derivatives since this will greatly facilitate scientists to get lead compounds in cancer drug discovery.

Effect of Ursolic Acid on Metabolic Syndrome, Insulin Sensitivity, and Inflammation

To evaluate the effect of ursolic acid on metabolic syndrome, insulin sensitivity, and inflammation, a randomized, double-blind, placebo-controlled clinical trial was carried out in 24 patients (30-60 years) with a diagnosis of metabolic syndrome without treatment. They were randomly assigned to two groups of 12 patients, each to receive orally 150 mg of ursolic acid or homologated placebo once a day for 12 weeks. Before and after the intervention, the components of metabolic syndrome, insulin sensitivity (Matsuda index), and inflammation profile (interleukin-6 and C-reactive protein) were evaluated. After ursolic acid administration, the remission of metabolic syndrome occurred in 50% of patients (P = .005) with significant differences in body weight (75.7 ± 11.5 vs. 71 ± 11 kg, P = .002), body mass index (BMI) (29.9 + 3.6 vs. 24.9 ± 1.2 kg/m2, P = .049), waist circumference (93 ± 8.9 vs. 83 + 8.6 cm, P = .008), fasting glucose (6.0 ± 0.5 vs. 4.7 ± 0.4 mmol/L, P = .002), and insulin sensitivity (3.1 ± 1.1 vs. 4.2 ± 1.2, P = .003). Ursolic acid administration leads to transient remission of metabolic syndrome, reducing body weight, BMI, waist circumference and fasting glucose, as well as increasing insulin sensitivity.

Antidiabetic and antioxidant functionality associated with phenolic constituents from fruit parts of indigenous black jamun (Syzygium cumini L.) landraces

ABSTRACT

Fruit phenolics are important dietary antioxidant and antidiabetic constituents. The fruit parts (pulp, seed, seed coat, kernel) of underutilized indigenous six black jamun landraces (Syzygium cumini L.), found in Gir forest region of India and differed in their fruit size, shape and weight, are evaluated and correlated with antidiabetic, DPPH radical scavenging and phenolic constituents. The α-amylase inhibitors propose an efficient antidiabetic strategy and the levels of postprandial hyperglycemia were lowered by restraining starch breakdown. The sequential solvent systems with ascending polarity-petroleum ether, ethyl acetate, methanol and water were performed for soxhlet extraction by hot percolation method and extractive yield was found maximum with methanolic fruit part extracts of six landraces. The methanolic extracts of fruit parts also evidenced higher antidiabetic activity and hence utilized for further characterization. Among the six landraces, pulp and kernel of BJLR-6 (very small, oblong fruits) evidenced maximum 53.8 and 98.2% inhibition of α-amylase activity, respectively. The seed attained inhibitory activity mostly contributed by the kernel fraction. The inhibition of DPPH radical scavenging activity was positively correlated with phenol constituents. An HPLC-PDA technique was used to quantify the seven individual phenolics. The seed and kernel of BJLR-6 exhibited higher individual phenolics-gallic, catechin, ellagic, ferulic acids and quercetin, whereas pulp evidenced higher with gallic acid and catechin as α-amylase inhibitors. The IC₅₀ value indicates concentration of fruit extracts exhibiting ≥50% inhibition on porcine pancreatic α-amylase (PPA) activity. The kernel fraction of BJLR6 evidenced lowest (8.3 µg ml^-1) IC₅₀ value followed by seed (12.9 µg ml^-1), seed coat (50.8 µg ml^-1) and pulp (270 µg ml^-1). The seed and kernel of BJLR-6 inhibited PPA at much lower concentrations than standard acarbose (24.7 µg ml^-1) considering good candidates for antidiabetic herbal formulations.

GRAPHICAL ABSTRACT

Oleanolic acid and ursolic acid as potential inhibitors of human salivary α-amylase: insights from in vitro assays and in silico simulations

It is known that inhibiting α-amylase, an important enzyme in digestion of starch and glycogen, is a useful strategy for treating disorders in carbohydrate uptake. Two natural components distributed in many fruits and plants, oleanolic acid and ursolic acid, are endowed with important pharmacological activities and wide therapeutic possibilities. Until now, only a tiny fraction of their applications have been identified and exploited. Our in vitro inhibition studies demonstrated that oleanolic acid and ursolic acid non-competitively inhibit the activity and function of human salivary α-amylase. The molecular simulations revealed that oleanolic acid and ursolic acid interact with amino acid residues within the binding pocket of human salivary α-amylase, among which the side chain of Arg195 and Asp 197 was supposed to be important in imparting the inhibitory activity of triterpenoids. The present work will provide meaningful information for future development of functional drugs for the treatment of disorders in carbohydrate metabolism. Graphical abstract This work is valuable for providing a deeper insight into the interaction mechanism of oleanolic acid and ursolic acid with α-amylase.

In vitro and in silico interaction of porcine α-amylase with Vicia faba crude seed extract and evaluation of antidiabetic activity

Diabetes mellitus is a group of metabolic disorder of glucose metabolism. The proper management of blood glucose level is an indicator in the treatment of this complex pathology. The aim of the present study was to evaluate the inhibitory potential of Vicia faba crude seed extracts on the activities of α-amylase. Phytochemical screening, FTIR and HPLC analysis confirmed the presence of a phenolic compound with percentage yield of 9.87% in the acetone extract. Acetone extract of seed had highest inhibitory potential against porcine α-amylase (IC50 value of 2.94 mg/mL). Kinetic analysis revealed that the acetone and methanol extract displayed mixed mode of inhibition toward α-amylase. In-silico analysis was agreement with in-vitro studies in which phenolic compounds (catechin, epicatechin, gallic acid, and proanthocyanidin) showed more negative free energy against standard drug (acarbose) and bound with catalytic residues of α-amylase. These results might be due to the synergistic action of constituents present in seed extract or acting separately.

In vitro biological assessment of Homalium zeylanicum and isolation of lucidenic acid A triterpenoid

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Current investigation supports antioxidant, anti-diabetic activities of H. zeylanicum.

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Current investigation also supports anti-inflammatory activity of H. zeylanicum.

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The research successfully isolated and analysed structure of lucidenic acid A.

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Lucidenic acid A reported first time in the bark of H. zeylanicum.

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Lucidenic acid A produces a significant anti-inflammatory activity.

Homalium zeylanicum (Gardner) Benth. (Flacourtiaceae) is a medicinal plant useful in controlling rheumatism, inflammation and diabetes. The objective of this work evaluates in vitro antioxidant, antidiabetic, and antiinflammatory properties of hydroalcohol extract of bark of H. zeylanicum (HAHZ). It also describes isolation and structure determination of lucidenic acid A, which is the first report in this plant. In order to explain the role of antioxidant principles, DPPH, nitric oxide, hydroxyl, superoxide and metal chelating assays were performed. Antidiabetic and anti-inflammatory activities were investigated by quantifying α-amylase, α-glucosidase and protein denaturation inhibitory activities of HAHZ. Biochemical estimations were performed. The chemical structure of the triterpenoid was elucidated using ¹H, ¹³C NMR and high resolution-MS. IC₅₀ of DPPH, nitric oxide, hydroxyl, superoxide and metal chelating activities were of 36.23 ± 0.27, 40.11 ± 0.32, 35.23 ± 0.57, 43.34 ± 0.22 and 11.54 ± 0.08 μg/mL, respectively. IC₅₀ of α-amylase and α-glucosidase activities were 29.12 ± 0.54, and 18.55 ± 0.15 μg/mL. Total phenolic and total flavonoid contents were recorded at 233.65 mg/g GAE and 172.7 mg/g QE. Regarding kinetic behaviour, HAHZ showed competitive inhibition on α-glucosidase and mixed competitive inhibition on α-amylase. Lucidenic acid A was confirmed by spectroscopic studies. Anti-inflammatory activity of lucidenic acid A was determined by using protein denaturation assay with IC₅₀ 13 μg/mL but HAHZ showed 30.34 ± 0.13 μg/mL. Phenols and flavonoids could be attributed to inhibition of intestinal carbohydrases for anti-diabetic activities whereas triterpenoids could be responsible for anti-inflammatory activity of H. zeylanicum.

Fatty Acid Profiling and In Vitro Antihyperglycemic Effect of Leucas cephalotes (Roth) Spreng via Carbohydrate Hydrolyzing Enzyme Inhibition

Background:

Leucas cephalotes has been used by many tribes to treat variety of diseases and known to have many essential secondary metabolites. To the best of our knowledge, it is the first comparative analysis of total fatty acid (FA) composition and α-amylase inhibition activity of L. cephalotes.

Objective:

The present study is carried out to explore the antihyperglycemic activity and FA contents of all parts of L. cephalotes.

Material and Method:

Fruits, leaves, stems, and roots part of L. cephalotes have been extracted in ethanol. Simultaneously, all plant parts have been extracted in hexane with Soxhlet extraction. Ethanolic extracts have been evaluated for antihyperglycemic activity and hexane extract have been analyzed for FA identification.

Result:

The present study indicated that ethanolic extract of fruit and leaves have shown significant α-amylase inhibitory activity with IC₅₀ value of 92.86 ± 0.89 and 98.09 ± 0.69 μg/mL, respectively. FA composition of all the parts of L. cephalotes was analyzed by GC/MS. Nineteen FAs have been identified in all parts of L. cephalotes in which palmitic acid, oleic acid, linolenic acid, and linoleic acid were major FAs.

Conclusion:

The study indicates that L. cephalotes has significant potential to inhibit α-amylase enzyme and it is a rich source of essential FAs.

SUMMARY

L. cephalotes has significant antidiabetic activity and will be beneficial for diabetic patients to reduce the starch breakdown and helps in reduction of postprandial hyperglycemia. It can be used in the formulation of diabetic drugs.

L. cephalotes is rich source of essential FAs and may be used as a nutraceutical.

Ethanol extract of fruits and leaves of L. cephalotes are showed the maximum α-amylase inhibition when compared with standard drug acarbose.

Abbreviations used: DM: Diabetes Mellitus, FA: Fatty Acid, FFAs: Free Fatty Acids, FAME: Fatty Acid Methyl Ester, IC50: Inhibitor Concentration, GC-MS: Gas Chromatography- Mass Spectrophotometer

In vitro anti-diabetic activity of flavonoids and pheophytins from Allophylus cominia Sw . on PTP1B, DPPIV, alpha-glucosidase and alpha-amylase enzymes

BACKGROUND

Ethno-botanical information from diabetic patients in Cuba led to the identification of Allophylus cominia as a possible source of new drugs for the treatment of type 2 diabetes mellitus (T2-DM).

EXPERIMENTAL

Chemical characterization of the extracts from A. cominia was carried out using chromatographic and spectroscopic methods. The extracts were tested for their activity on PTP1B, DPPIV, α-glucosidase enzymes and α-amylase.

RESULTS

The flavonoid rich fractions from A. cominia inhibited DPPIV enzyme (75.3±2.33%) at 30µg/ml and produced a concentration-dependent inhibition against DPPIV with a Ki value of 2.6µg/ml. At 30µg/ml, flavonoids and pheophytins extracts significantly inhibited PTP1B enzyme (100±2.6% and 68±1% respectively). The flavonoids, pheophytin A and pheophytin B fractions showed significant concentration-dependent inhibition against PTP1B with Ki values of 3µg/ml, 0.64µg/ml and 0.88µg/ml respectively. At 30µg/ml, the flavonoid fraction significantly inhibited α-glucosidase enzyme (86±0.3%) in a concentration-dependent pattern with a Ki value of 2µg/ml. None of the fractions showed significant effects on α-amylase. Fatty acids, tannins, pheophytins A and B, and a mixture of flavonoids were detected in the methanolic extract from A. cominia. The identified flavonoids were mearnsitrin, quercitrin, quercetin-3-alloside, and naringenin-7-glucoside.

CONCLUSION

The pharmacological effects of the extracts from A. cominia earlier observed in experimental diabetic models was confirmed in this study. Thus a new drug or formulation for the treatment of T2-DM could be developed from A. cominia.

Evaluation of cytogenotoxicity, antioxidant and hypoglycemiant activities of isolate compounds from Mansoa hirsuta D.C. (Bignoniaceae)

Mansoa hirsuta (Bignoniaceae) is a native plant from caatinga in Brazilian semiarid. This plant has been locally used as antimicrobial and hypoglycemiant agents, but their action mechanisms and toxicity remain largely unknown. Therefore, we evaluated the composition and antioxidant, cytoprotective and hypoglycemiant effects of raw extract, fractions and compounds from leaves of M. hirsuta. The cytogenotoxic effects of ursolic and oleanolic acids, the main phytotherapic components of this plant, were assessed. The raw extract and fractions presented steroids, saponins, flavonols, flavanonols, flavanones, xanthones, phenols, tannins, anthocyanins, anthocyanidins and flavonoids. The ethyl acetate fraction inhibited efficiently the cascade of lipid peroxidation while the hydroalcoholic fraction was richer in total phenols and more efficient in capturing 2,2-diphenyl-1-picrylhydrazyl (·DPPH) and 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS·+) radicals. The isolated fraction of M. hirsuta also inhibited the α-amylase activity. Cytotoxic effects were absent in both raw extract and fractions while ursolic+oleanolic acids were efficient in protecting cells after exposure to hydrogen peroxide. Moreover, this mixture of acid shad no significant interference on the mitotic index and frequency of nuclear and/or chromosomal abnormalities in Allium cepa test. Therefore, M. hirsuta represents a potential source of phytochemicals against inflammatory and oxidative pathologies, including diabetes.