Enzymes inhibitors from natural sources with antidiabetic activity: A review

Antidiabetic and antimicrobial flavonoids from the twigs and roots of Erythrina subumbrans (Hassk.) Merr

The phytochemical investigation of the twig and root extracts of Erythrina subumbrans (Hassk.) Merr. (Fabaceae) resulted in the isolation and identification of a new pterocarpan, erythrinocarpan (1), along with 27 known compounds (2-28). All isolated compounds were evaluated for their antidiabetic, antimicrobial, and anti-inflammatory properties. Compounds 3, 8, 9, and 22 had α-glucosidase inhibitory activity with IC50 values of 13.4 ± 0.05, 24.5 ± 0.13, 29.0 ± 0.05, and 12.8 ± 0.14 μM, respectively, while compound 2 inhibited α-amylase activity with an IC50 value of 67.6 ± 1.12 μM. Compounds 22 and 24 inhibited glycation activity with the IC50 values of 36.9 ± 0.62 and 40.5 ± 0.37 μM, respectively. From cell-based assays, compound 27 showed the highest ability to induce glucose consumption (IC50 29.1 ± 0.86 μM) and glucose uptake (2.8-fold), and to inhibit nitric oxide (NO) production (IC50 52.5 ± 0.56 μM) without cell toxicity. Furthermore, compound 9 showed antimicrobial activities against Gram-positive bacteria and fungi with MIC values ranging from 2-4 μg/mL.

Indole-3-acetamides: As Potential Antihyperglycemic and Antioxidant Agents; Synthesis, In Vitro α-Amylase Inhibitory Activity, Structure-Activity Relationship, and In Silico Studies

Indole-3-acetamides (1-24) were synthesized via coupling of indole-3-acetic acid with various substituted anilines in the presence of coupling reagent 1,1-carbonyldiimidazole. The structures of synthetic molecules were elucidated through different spectroscopic techniques including electron ionization-mass spectroscopy (EI-MS), 1H-, 13C NMR, and high-resolution EI-MS (HREI-MS). These compounds were screened for their antihyperglycemic and antioxidant potentials. All compounds displayed good to moderate inhibition against α-amylase enzyme with IC50 values ranging between 1.09 ± 0.11 and 2.84 ± 0.1 μM compared to the standard acarbose (IC50 = 0.92 ± 0.4 μM). Compound 15 (IC50 = 1.09 ± 0.11 μM) was the most active compound of the series and exhibited good inhibition against α-amylase; in addition, this compound also exhibited good antioxidant potential with IC50 values of 0.35 ± 0.1 and 0.81 ± 0.25 μM in 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays, respectively. The binding interactions of synthetic molecules with the enzyme's active site were confirmed via in silico studies. The current study had identified a number of lead molecules as potential antihyperglycemic and antioxidant agents.

Modeling and simulation in medical sciences: an overview of specific applications based on research experience in EMRI (Endocrinology and Metabolism Research Institute of Tehran University of Medical Sciences)

The concomitant use of various types of models (in silico, in vitro, and in vivo) has been exemplified here within the context of biomedical researches performed in the Endocrinology and Metabolism Research Institute (EMRI) of Tehran University of Medical Sciences. Two main research aeras have been discussed: the search for new small molecules as therapeutics for diabetes and related metabolic conditions, and diseases related to protein aggregation. Due to their multidisciplinary nature, the majority of these studies have needed the collaboration of different specialties. In both cases, a brief overview of the subject is provided through literature examples, and sequential use of these methods is described.

Forty-One Plant Extracts Screened for Dual Antidiabetic and Antioxidant Functions: Evaluating the Types of Correlation between -Amylase Inhibition and Free Radical Scavenging

Dysregulation of glucose homeostasis followed by chronic hyperglycemia is a hallmark of diabetes mellitus (DM), a disease spreading as a worldwide pandemic for which there is no satisfactory dietary treatment or cure. The development of glucose-controlling drugs that can prevent complications of DM, such as hyperglycemia and oxidative stress, which contribute to the impairment of the key physiological processes in the body, is of grave importance. In pursuit of this goal, this study screened 41 plant extracts for their antidiabetic and antioxidant activities by employing assays to test for α-amylase inhibition and free radical scavenging activity (FRSA) and by measuring glucose uptake in L6-GLUT4myc cells. While extracts of Rhus coriaria, Punica granatum, Olea europaea, Pelargonium spp., Stevia rebaudiana, and Petroselinum crispum demonstrated significant α-amylase inhibition, the extracts of Rhus coriaria and Pelargonium spp. also demonstrated increased FRSA, and the extract of Rhus coriaria stimulated glucose uptake. These natural extracts, which are believed to have fewer side effects because they are prepared from edible plants, interfere with the process in the small intestine that breaks down dietary carbohydrates into monosaccharide and disaccharide derivatives, and thereby suppress increases in diet-induced blood glucose; hence, they may have clinical value for type 2 diabetes management. The Pelargonium spp. and Rhus coriaria extracts demonstrated the highest antidiabetic and antioxidant activities. Both plants may offer valuable medical benefits, especially because they can be taken as dietary supplements by patients with diabetes and can serve as sources of new, natural-based antidiabetic drug candidates. The enhancement of cellular glucose uptake stimulated by Rhus coriaria extract could lead to the development of clinical applications that regulate blood glucose levels from within the circulatory system. Isolating bioactive substances from these plant extracts and testing them in diabetic mice will significantly advance the development of natural drugs that have both antidiabetic and free radical-scavenging properties, likely with lesser side effects.

Tangerines Cultivated on Madeira Island-A High Throughput Natural Source of Bioactive Compounds

Tangerines (Citrus reticulata) are popular fruits worldwide, being rich in many bioactive metabolites. The setubalense variety cultivated on Madeira Island has an intense aroma easily distinguishable from other tangerines, being traditionally used to enrich several foods and beverages. Nonetheless, setubalense volatile composition has never been characterized, and we aimed to unveil the bioactive potential of peels and juices of setubalense tangerines and compare them with the murcott variety grown in Portugal mainland. Using headspace solid-phase microextraction coupled to gas chromatography mass spectrometry (HS-SPME/GC-MS), we identified a total of 128 volatile organic metabolites (VOMs) in the juice and peels, with d-limonene, γ-terpinene, β-myrcene, α- and β-pinene, o-cymene, and terpinolene, the most dominant in both cultivars. In contrast, setubalense juices are richer in terpenes, many of them associated with health protection. Discriminant analysis revealed a pool of VOMs, including β-caryophyllene and E-ocimene, with bioactive properties able to differentiate among tangerines according to variety and sample type (peel vs. juice). This is the first report on the volatile composition of setubalense tangerines grown on Madeira Island revealing that its pungent aroma is constituted by secondary metabolites with specific aroma notes and health properties. This is strong evidence of the higher nutraceutical value of such fruit for the human diet.

Valorisation of kitul, an overlooked food plant: Phenolic profiling of fruits and inflorescences and assessment of their effects on diabetes-related targets

Caryota urens L. has long been valued as a traditional food, the edible fruits being eaten raw and the inflorescences commonly used on sweet sap and flour production. In the current work, the phenolic profile of methanol extracts obtained from the inflorescences and fruits was unveiled for the first time, nine caffeic acid derivatives being identified and quantified. Since kitul products have been reported for their antidiabetic properties, extracts radical scavenging activity and α-amylase, α-glucosidase and aldose reductase inhibitory activity were assessed. The inflorescences' extract was particularly active against yeast α-glucosidase (IC₅₀ = 1.53 μg/mL), acting through a non-competitive inhibitory mechanism. This activity was also observed in enzyme-enriched homogenates obtained from human Caco-2 cells (IC₅₀ = 64.75 µg/mL). Additionally, the extract obtained from the inflorescences showed no cytotoxicity on HepG2, AGS and Caco-2 cell lines. Our data suggest that C. urens inflorescences can support the development of new functional foods with α-glucosidase inhibitory activity.

Inhibitory potential on key enzymes relevant to type II diabetes mellitus and antioxidant properties of the various extracts and phytochemical constituents from Rumex acetosella L

Type II diabetes mellitus is a common and costly disease worldwide, characterized by hyperglycemia. Alpha (α)-amylase and α-glucosidase are important targets in diabetes therapy. Inhibition of these enzymes may lessen hyperglycemia, preventing diabetic complications. Oxidative stress is another factor involved in the disease's etiology. In the present study, we investigated antidiabetic profiles of the various extracts and phytochemicals of Rumex acetosella. Since the plant has been traditionally used for the antidiabetic purposes. α-amylase and α-glucosidase inhibitory studies in addition to DPPH•, ABTS•+, NO 2 - radical scavenging, and phosphomolybdate antioxidant assays were performed to evaluate the antidiabetic property. Specifically, the ethanol and ethanol-water extracts remarkably inhibited α-glucosidase than that of acarbose, unlike their slight/no inhibition on α-amylase. Convincing α-glucosidase inhibitory and antioxidant potential of alcohol-including extracts verified the ethnobotanical use of R. acetosella as an antidiabetic agent. PRACTICAL APPLICATIONS: The incidence of Type II DM is rising globally. Reducing hyperglycemia holds great importance to prevent devastating outcomes of diabetic complications. Ethnobotanical use of natural sources for medical purposes provides a basis for their potential activity against various diseases. The introduction of herbal agents may lead to the development of new drug candidates with convincing activity. Rumex acetosella L. has been traditionally used for the antidiabetic purposes. The research pointed out various extracts and phytochemical constituents from R. acetosella may act as antihyperglycemic agents. Particularly, alcohol-including extracts of R. acetosella may be considered as promising alternatives in the prevention or treatment of type II DM. The study puts emphasis on the therapeutic value of the plants for antidiabetic medication.

Thermoase-hydrolysed pigeon pea protein and its membrane fractions possess in vitro bioactive properties (antioxidative, antihypertensive, and antidiabetic)

Enzymatic hydrolysis can liberate bioactive peptides from protein materials, thus, pigeon pea was hydrolysed using thermoase. Crude hydrolysate (PPHT) was subjected to ultrafiltration using different molecular weight cutoffs to collect <1, 1-3, 3-5, 5-10, and >10 kDa peptide fractions. Fractions were analysed for in vitro antioxidative, antihypertensive, and antidiabetic properties. The peptide fractions had stronger DPPH^• scavenging and renin inhibition when compared to PPHT. In contrast, ACE inhibition was stronger for the PPHT and <1 kDa peptide fraction while activity decreased as peptide size increased. The <1 kDa peptide also showed significantly stronger ferric reducing antioxidant power, OH^• scavenging and inhibition of linoleic acid oxidation when compared to PPHT. α-amylase and α-glucosidase were inhibited by all the peptide fractions, though the 3-5 and >10 kDa had higher values. We conclude that the PPHT and peptide fractions could serve as potential ingredients to formulate antihypertensive and antidiabetic functional foods and nutraceuticals. PRACTICAL APPLICATIONS: Oxidative stress promotes the generation of free radicals, which have a significant impact in the pathogenesis of human chronic diseases such as cardiovascular impairment, cancer, and diabetes. Peptides generated from enzymatic hydrolysis of proteins have been identified to impart beneficial health effects. In this work, we showed that a thermoase digest of pigeon pea protein as well as the fractionated peptides had strong antioxidant properties in addition to exhibiting inhibitory activities against renin and angiotensin converting enzyme, the main therapeutic targets for antihypertensive agents. The peptide products also inhibited α-amylase and α-glucosidase activities, providing potential ingredients that can be used to formulate antidiabetic functional foods.

Glucose lowering and pancreato-protective effects of Abrus Precatorius (L.) leaf extract in normoglycemic and STZ/Nicotinamide - Induced diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Abrus precatorius (L.) leaves are used as folk medicine by the local communities in the western region of Ghana to treat diabetes mellitus; however, this health claim remains unverified scientifically.

OBJECTIVE

The study investigated glucose lowering and pancreato-protective effects of Abrus precatorius leaf extract (APLE) in normoglycemic and STZ/nicotinamide (NIC)-induced diabetic rats.

METHOD

after preparation of APLE, it was subjected to phytochemical screening, proximate composition and elemental assessments by using standard methods. Oral glucose tolerance test (OGTT) and maltose, lactose and sucrose oral challenge were assessed in normoglycemic rats post-APLE. Morphological characteristics of glucose response curve (time of glucose peak and shape of glucose response curve) were determined. Subsequently, diabetes mellitus was experimentally established in normoglycaemic adult Sprague-Dawley rats (weighing 150-250 g) of both sexes by sequential injection of Streptozotocin (STZ, 60 mg/kg ip)-reconstituted in sodium citrate buffer and NIC (110 mg/kg ip)-reconstituted in normal saline (1:1 v/v) for 16 weeks. Except control rats (normal saline 5 ml/kg ip; baseline fasting blood glucose [FBG] of 6.48 mmol/L), rats having FBG (stable at 11.1 mmol/L or ≥ 250 mg/dL) 3 days post-STZ/NIC injection were randomly re-assigned to one of the following groups: model (STZ/NIC-induced diabetic rats), APLE (100, 200 and 400 mg/kg respectively po) and metformin (300 mg/kg po) and treated daily for 28 days. Bodyweight and FBG were measured on weekly basis. FBG was measured by using standard glucometers. On day 28, rats were sacrificed under chloroform anesthesia, blood collected via cardiac puncture; kidney, liver and pancreas surgically harvested. While the pancreas was processed, sectioned and H&E-stained for histological examination, fresh kidney and liver were homogenized for assessment of total anti-oxidant capacity. Median cross-sectional area of pancreatic islets of Langerhans was determined for each group by using Amscope.

RESULTS

Cumulatively, APLE (100, 200 and 400 mg/kg respectively) dose-dependently decreased the initial FBG by 55.22, 76.15 and 77.77% respectively compared to model (-1.04%) and metformin (72.29%) groups. APLE treatment recovered damaged pancreatic β-cells and also increased median cross-sectional area (x10⁶ μm²) of pancreatic islets compared to that of model group. APLE significantly (P < 0.05) increased total anti-oxidant capacity (5.21 ± 0.02 AscAE μg/mL) of plasma, kidney and liver compared to model (4.06 ± 0.04 AscAE μg/mL) and metformin (4.87 ± 0.03 AscAE μg/mL) groups.

CONCLUSION

APLE has demonstrated glucose lowering and pancreato-protective effects in rats and arrested the characteristic loss in bodyweight associated with diabetes mellitus. This finding preliminarily confirms folk use of APLE as an anti-diabetic herbal medicine, whiles providing a rationale for further translational studies on APLE.

Macro- and Micronutrients from Traditional Food Plants Could Improve Nutrition and Reduce Non-Communicable Diseases of Islanders on Atolls in the South Pacific

Pacific Islanders have paid dearly for abandoning traditional diets, with diabetes and other non-communicable diseases (NCD) widespread. Starchy root crops like sweet potato, taro, and cassava are difficult to grow on the potassium-deficient soils of atolls, and high energy, low nutrient imported foods and drinks are popular. Nutritious, leafy food plants adapted to alkaline, salty, coral soils could form part of a food system strategy to reduce NCD rates. This project targeted four atolls south of Tarawa, Kiribati, and was later extended to Tuvalu. Mineral levels in diverse, local leafy food plants were compared to reveal genotype–environment interactions. Food plants varied in ability to accumulate minerals in leaves and in tolerance of mineral-deficient soils. Awareness activities which included agriculture, health, and education officers targeted atoll communities. Agriculture staff grew planting material in nurseries and provided it to farmers. Rejuvenation of abandoned giant swamp taro pits to form diversified nutritious food gardens was encouraged. Factsheets promoted the most suitable species from 24 analyzed, with multiple samples of each. These included Cnidoscolus aconitifolius (chaya), Pseuderanthemum whartonianum (ofenga), Polyscias scutellaria (hedge panax), and Portulaca oleracea (purslane). The promoted plants have been shown in other studies to have anti-NCD effects. Inclusion of the findings in school curricula and practical application in the form of demonstration school food gardens, as well as increased uptake by farmers, are needed. Further research is needed on bioavailability of minerals in plants containing phytates and tannins.

Antihyperglycemic Effects of Annona diversifolia Safford and Its Acyclic Terpenoids: α-Glucosidase and Selective SGLT1 Inhibitiors

Annona diversifolia Safford and two acyclic terpenoids were evaluated to determine their antihyperglycemic activity as potential α-glucosidase and selective SGLT-1 inhibitiors. Ethanolic extract (EEAd), chloroformic (CHCl₃Fr), ethyl acetate (EtOAcFr), aqueous residual (AcRFr), secondary 5 (Fr5) fractions, farnesal (1), and farnesol (2) were evaluated on normoglycemic and streptozocin-induced diabetic mice. EEAd, CHCl₃Fr, Fr5, (1) and (2) showed antihyperglycemic activity. The potential as α-glucosidase inhibitors of products was evaluated with oral sucrose and lactose tolerance (OSTT and OLTT, respectively) and intestinal sucrose hydrolysis (ISH) tests; the potential as SGLT-1 inhibitors was evaluated using oral glucose tolerance (OGTT), intestinal glucose absorption (IGA), and urinary glucose excretion (UGE) tests. In OSTT and OLTT, all treatments showed significant activity at two and four hours. In ISH, half maximal effective concentrations (CE₅₀) of 565, 662 and 590 μg/mL, 682 and 802 μM were calculated, respectively. In OGTT, all treatments showed significant activity at two hours. In IGA, CE₅₀ values of 1059, 783 and 539 μg/mL, 1211 and 327 μM were calculated, respectively. In UGE Fr5, (1) and (2) showed significant reduction of the glucose excreted compared with canagliflozin. These results suggest that the antihyperglycemic activity is mediated by α-glucosidase and selective SGLT-1 inhibition.

Phenylpropanoid-Conjugated Triterpenoids from the Leaves of Actinidia arguta and Their Inhibitory Activity on α-Glucosidase

Actinidia arguta, commonly called hardy kiwifruit or kiwiberry, has cold-resistant properties and can be cultivated in Asia, including Korea. Seven new triterpenoids (2-4 and 8-11) along with eight known triterpenoids were isolated from the leaves of A. arguta through various chromatographic techniques. The new triterpenoids were defined as actiniargupenes A-C (2-4), actinidic acid derivatives with phenylpropanoid constituent units, dehydroisoactinidic acid (8), and actiniargupenes D-F (9-11), asiatic acid derivatives with phenylpropanoid substituents, on the basis of 1D and 2D NMR and MS data. Among the triterpenoids, those with a phenylpropanoid constituent unit showed inhibitory activity on α-glucosidase, which suggested the importance of the phenylpropanoid moiety. Molecular docking analysis demonstrated the interaction between the 4'-OH group of the phenylpropanoid moiety and α-glucosidase.

Polysaccharides from Opuntia milpa alta alleviate alloxan-induced INS-1 cells apoptosis via reducing oxidative stress and upregulating Nrf2 expression

The incidence and progression of type 2 diabetes are closely related to pancreatic β-cell damage. Oxidative stress may be one of the key factors contributing to β-cell apoptosis. Opuntia milpa alta polysaccharides (MAPs) are water-soluble macromolecular polysaccharides that have antidiabetic effects in vivo. Therefore, we hypothesized that MAPs might effectively prevent β-cell apoptosis via the inhibition of oxidative damages. In this study, INS-1 cells were exposed to alloxan with different concentrations of MAPs in vitro, and the cell viability, oxidative enzyme activities, nitric oxide production, reactive oxygen species production, apoptosis, and the expression of proteins in the antioxidant nucleus transcription factor NF-E2-related factor 2 (Nrf2) pathway and proteins related to apoptosis were measured to assess oxidative stress responses and apoptosis. The results indicated that INS-1 cell viabilities and superoxide dismutase and reduced glutathione activities were significantly restored, whereas lactate dehydrogenase releases and reactive oxygen species, nitric oxide, and malondialdehyde levels were greatly decreased after MAPs treatment. We found that MAPs could attenuate alloxan-induced apoptosis by increasing the expression of Bcl-2 and decreasing the expression of Bax and the activities of caspase-3 and caspase-9. The results of Western blot revealed that MAPs suppressed the expression of cleaved caspase-3 and cleaved PARP and upregulated the expression of nucleus Nrf2 and its downstream protein. These findings indicated that MAPs could alleviate alloxan-induced β-cell apoptosis by reducing oxidative stress and upregulating Nrf2 expression.

Bioactive terpenoid constituents from Eclipta prostrata

Chemical fractionation of the ethanolic extract of Eclipta prostrata yielded a series of unreported terpenoid constituents, including a rare 6/6/6/6-fused tetracyclic triterpenoid, a pentacyclic triterpenoid, two pentacyclic triterpenoid saponins, a diterpenoid and a sesquiterpenoid. Structures were assigned to these compounds on the basis of comprehensive spectroscopic analyses, with the absolute configurations of the tetracyclic triterpenoid, the diterpenoid and the sesquiterpenoid being determined via explanation of electronic circular dichroism data. Screening of these isolates in an array of bioassays revealed antibacterial, cytotoxic and α-glucosidase inhibitory activities for selective compounds. Of particular interest, the tetracyclic triterpenoid showed very strong inhibition against α-glucosidase with an IC₅₀ of 0.82 ± 0.18 μM, being 10³-fold as active as the positive control acarbose.

Reduction of blood glucose by plant extracts and their use in the treatment of diabetes mellitus; discrepancies in effectiveness between animal and human studies

ETHNOPHARMACOLOGICAL RELEVANCE

The global problem of diabetes, together with the limited access of large numbers of patients to conventional antidiabetic medicines, continues to drive the search for new agents. Ancient Asian systems such as traditional Chinese medicine, Japanese Kampo medicine, and Indian Ayurvedic medicine, as well as African traditional medicine and many others have identified numerous plants reported anecdotally to treat diabetes; there are probably more than 800 such plants for which there is scientific evidence for their activity, mostly from studies using various models of diabetes in experimental animals.

AIM OF THE REVIEW

Rather than a comprehensive coverage of the literature, this article aims to identify discrepancies between findings in animal and human studies, and to highlight some of the problems in developing plant extract-based medicines that lower blood glucose in patients with diabetes, as well as to suggest potential ways forward.

METHODS

In addition to searching the 2018 PubMed literature using the terms 'extract AND blood glucose, a search of the whole literature was conducted using the terms 'plant extracts' AND 'blood glucose' AND 'diabetes' AND 'double blind' with 'clinical trials' as a filter. A third search using PubMed and Medline was undertaken for systematic reviews and meta-analyses investigating the effects of plant extracts on blood glucose/glycosylated haemoglobin in patients with relevant metabolic pathologies.

FINDINGS

Despite numerous animal studies demonstrating the effects of plant extracts on blood glucose, few randomised, double-blind, placebo-controlled trials have been conducted to confirm efficacy in treating humans with diabetes; there have been only a small number of systematic reviews with meta-analyses of clinical studies. Qualitative and quantitative discrepancies between animal and human clinical studies in some cases were marked; the factors contributing to this included variations in the products among different studies, the doses used, differences between animal models and the human disease, and the impact of concomitant therapy in patients, as well as differences in the duration of treatment, and the fact that treatment in animals may begin before or very soon after the induction of diabetes.

CONCLUSION

The potential afforded by natural products has not yet been realised in the context of treating diabetes mellitus. A systematic, coordinated, international effort is required to achieve the goal of providing anti-diabetic treatments derived from medicinal plants.

Antibacterial, antioxidant and enzyme inhibition activity capacities of Doronicum macrolepis (FREYN&SINT): An endemic plant from Turkey

In the present study, the antioxidant, enzyme inhibition (α-amylase, α-glucosidase, and cholinesterase) and antimicrobial (MIC) activities of three different solvent (ethanol, methanol, or ethyl acetate) extracts of stem, root, and flower of Doronicum macrolepis plant were investigated. In addition to this, the chemical composition and the antimicrobial activity of the essential oil were determined. Antioxidant activity was detected using ABTS and DPPH assays. Antimicrobial activity evaluated by microdilution method against to nineteen microorganisms. Also, enzyme inhibition activities were determined by colorimetric methods. Essential oil of the plant extracted by hydrodistilation and characterized using GC/MS. The antioxidant properties of the flower were determined to be higher than those of the other segments of this plant. Moreover, the total phenolic and flavonoid contents were also found to be higher in the flower parts. The highest enzyme inhibition activity was observed to be α-amylase (221.54 mmol ACAE/g extract) in flower ethylacetate extract, α-glucosidase (15.32 mmol ACAE/g extract) in flower ethanol extract, and cholinesterase (AChE: 2.4 and BChE: 22.35 mg GALE/g extract) in stem ethylacetate extract. Besides them, the antimicrobial activity of the essential oil was found to be higher than the extracts. It showed a high level of inhibition especially on E. coli at 4 µg/ml concentration. Moreover, remarkable inhibition was observed for two candida strains tested. In conclusion, the results suggest that, because of its bioactivity including the antioxidant, antimicrobial, and enzyme inhibition properties, the D. macrolepis can be accepted as a promising and natural source for the industrial applications. The present study is the first study, in which the bioactive components and the antioxidant, antimicrobial, and enzyme inhibition properties of endemic D. macrolepis plant were determined.

Consumption of Cooked Common Beans or Saponins Could Reduce the Risk of Diabetic Complications

Several risks for diseases, such as atherosclerosis, renal diseases, and diabetes, have inextricably been linked with obesity. Nowadays, this health-risk-laden disease is being managed with assorted types of drugs, some of which guarantee modest benefits. The chronic inflammatory effect of obesity has a negative effect in insulin signaling, a situation attributable to insulin resistance that culminates in high blood sugar inputs seen in diseases such as type 2 diabetes and metabolic syndrome. Food such as beans with different bioactive compounds could reduce the risk of diabetic complications. Demand for bean products is growing because of its robust contents of several health-promoting components, eg, saponins. Saponins are characterized by containing lower glucose and cholesterol levels and have been doted with antioxidant activities, as well as anti-inflammatory and anti-diabetic effects. In this writing, the attributes of saponins in providing substantial health and nutritional benefits in humans, as well as in improving and ameliorating diabetic complications, were reviewed.

High performance liquid chromatographic profiling of antioxidant and antidiabetic flavonoids purified from Azadirachta indica (neem) leaf ethanolic extract

Azadirachta indica (neem) is a tropical and semi-tropical tree native to the whole Indian subcontinent. Neem leaves are rich in flavonoids, which exhibit important pharmacological activities targeting almost all human organs. In order to produce a purified extract of neem leaves enriched of antioxidant and antidiabetic flavonoids, the ethanolic extract of neem leaves has been further undergone to liquid-liquid extractions by using three different organic solvents, i.e. dichloromethane, n-butanol and ethyl acetate. Qualitative and quantitative analyses were performed on the extracts obtained by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). Astragalin, quercitrin, isoquercitrin, nicotiflorin and rutin were the only flavonoids found among those screened. By comparing all HPLC chromatograms of purified extracts as obtained with different solvents, it was found that the qualitative-quantitative composition of flavonoids depends upon the extraction solvent used; in particular, dichloromethane allows extraction of 89.5 % quercitrin, 5.3 % isoquercitrin, 5.2 % rutin; n-butanol allows extraction of 6.0 % isoquercitrin, 6.2 % nicotiflorin, 87.8 % rutin; ethyl acetate allows extraction of 4.2 % astragalin, 12.0 % quercitrin, 50.3 % isoquercitrin, 6.7 % nicotiflorin, 26.9 % rutin. Thus, depending on the specific purposes and needs, each of these three extraction solvents has the potential to prepare formulations enriched with the most suitable flavonoids composition.

Plant- and Nutraceutical-based Approach for the Management of Diabetes and its Neurological Complications: A Narrative Review

Diabetes is an important metabolic disease affecting many organs and systems in the body. The nervous system is one of the body systems affected by diabetes and neuropathic complications are troublesome in diabetic patients with many consequences. As diabetes has deleterious influences almost on bodily systems, an integrative approach seems to be necessary accepting the body as a whole and integrating body systems with lifestyle and living environment. Like some traditional health systems such as Ayurveda, integrative approach includes additional modalities to overcome both diabetes and diabetic complications. In general, these modalities consist of nutraceuticals and plant products. Prebiotics and probiotics are two types of nutraceuticals having active ingredients, such as antioxidants, nutrient factors, microorganisms, etc. Many plants are indicated for the cure of diabetes. All of these may be employed in the prevention and in the non-pharmacological management of mildto- moderate diabetes. Severe diabetes should require appropriate drug selection. Being complementary, prebiotics, probiotics, plants and exercise may be additive for the drug therapy of diabetes. Similarly, there are complementary approaches to prevent and cure neurological and/or behavioral manifestations of diabetes, which may be included in therapy and prevention plans. A scheme is given for the prevention and therapy of comorbid depression, which is one of the most common behavioral complications of diabetes. Within this scheme, the main criterion for the selection of modalities is the severity of diseases, so that personalized management may be developed for diabetic patients using prebiotics and probiotics in their diets, plants and drugs avoiding possible interactions.

A colorimetric method for the determination of different functional flavonoids using 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and peroxidase

In many occasions it is necessary to use fast and simple methods, different to the chromatographic techniques, for the quantification of biomolecules such as flavonoids. Also, the flavonoid levels in some foodstuffs can be influenced by industrial extraction processes such as pressing and squeezing, resulting in modification of their functional value. For this purpose, we have developed a rapid method to analyze flavonoids, based on a coupling reaction between ABTS and flavonoid mediated by peroxidase. The present method can be used to detect and measure flavonoids with hydroxyl moieties on A- or B-rings, not adjacent to methoxy or oxo substitutions. The visible spectrum of the ABTS-flavonoid complex, the calibration curve (within the range 5-50 μM) and the molar absorption coefficients for isosakuranetin, isonaringin, rhoifolin, hyperoside, rutin, hesperetin, quercetin, kaempherol and naringenin are given. The method has been applied to complex culture media and is sensitive, accurate, quick and easy to apply. This method can be used in laboratories that do not have sophisticated and expensive techniques such as liquid chromatography and also as a quick, simple and inexpensive technique for student practice laboratories.

Non-Pungent n-3 Polyunsaturated Fatty Acid (PUFA)-Derived Capsaicin Analogues as Potential Functional Ingredients with Antioxidant and Carbohydrate-Hydrolysing Enzyme Inhibitory Activities

N-Eicosapentaenoyl vanillylamine (EPVA) and N-docosahexaenoyl vanillylamine (DHVA), derived from n-3 polyunsaturated eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), respectively, were studied for their potential antioxidant and carbohydrate-hydrolysing enzyme inhibitory activities together with capsaicin and the corresponding n-3 polyunsaturated fatty acids (PUFAs). The antioxidant potential was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) assay, β-carotene bleaching test, and ferric reducing ability power (FRAP). In the ABTS assay the following trend of potency could be observed EPVA > DHVA ≥ capsaicin. In addition, except for the FRAP test, all samples showed a greater activity than the positive controls used as reference compounds in the antioxidant assays. Both EPVA and DHVA showed half maximal inhibitory concentration (IC₅₀) values much lower than acarbose, which was used as the reference drug in the carbohydrate-hydrolysing enzyme inhibitory activity assays. It is interesting to note that structural changes in capsaicin derivatives had higher impacts on α-glucosidase than on α-amylase inhibition. Taken together, our data suggest that both EPVA and DHVA, which are not limited in compliance-related considerations with respect to capsaicin, due to absence of pungency, could be proposed as functional ingredients for the development of products for the management of type II diabetes and border-line hyperglycaemic patients.