Porcine pancreatic α-amylase inhibition by the kidney bean (Phaseolus vulgaris) inhibitor (α-AI1) and structural changes in the α-amylase inhibitor complex

Proprietary alpha-amylase inhibitor formulation from white kidney bean (Phaseolus vulgaris L.) promotes weight and fat loss: a 12-week, double-blind, placebo-controlled, randomized trial

White kidney bean (Phaseolus vulgaris L.) extracts can aid weight management by reducing calorie intake from complex carbohydrates through alpha-amylase inhibition. We examined the impact of a proprietary aqueous extract from whole dried white kidney beans standardized by its alpha-amylase inhibitor activity (Phase 2 white kidney bean extract (WKBE)) on weight management in subjects with overweight and moderate obesity. In a randomized, double-blind, placebo-controlled fashion, 81 participants completed the study and ingested either a high dose of Phase 2 (1000 mg, WKBE HIGH), a low dose (700 mg, WKBE LOW), or a matching placebo (microcrystalline cellulose, PLA) three times a day, 30 min before meals, for 12 weeks during a calorie restricted diet. In a dose-dependent manner, Phase 2 significantly reduced body weight, fat mass, BMI, waist, hip and in the WKBE HIGH group thigh circumference. Phase 2 is an effective and safe supplement aiding weight and fat loss. ClinicalTrials.gov identifier NCT02930668.

Natural Inhibitors of Mammalian α-Amylases as Promising Drugs for the Treatment of Metabolic Diseases

α-Amylase is a generally acknowledged molecular target of a distinct class of antidiabetic drugs named α-glucosidase inhibitors. This class of medications is scarce and rather underutilized, and treatment with current commercial drugs is accompanied by unpleasant adverse effects. However, mammalian α-amylase inhibitors are abundant in nature and form an extensive pool of high-affinity ligands that are available for drug discovery. Individual compounds and natural extracts and preparations are promising therapeutic agents for conditions associated with impaired starch metabolism, e.g., diabetes mellitus, obesity, and other metabolic disorders. This review focuses on the structural diversity and action mechanisms of active natural products with inhibitory activity toward mammalian α-amylases, and emphasizes proteinaceous inhibitors as more effective compounds with significant potential for clinical use.

Common bean (Phaseolus vulgaris L.) α-amylase inhibitors as safe nutraceutical strategy against diabetes and obesity: An update review

Overweight and obesity are constantly increasing, not only in Western countries but also in low‐middle‐income ones. The decrease of both the intake of carbohydrates and their assimilation are among the main dietary strategies to counter these conditions. α‐Amylase, a key enzyme involved in the digestion of carbohydrates, is the target enzyme to reduce the absorption rate of carbohydrates. α‐Amylase inhibitors (α‐AIs) can be found in plants. The common bean, Phaseolus vulgaris is of particular interest due to the presence of protein‐based α‐AIs which, through a protein–protein interaction, reduce the activity of this enzyme. Here we describe the nature of the various types of common bean seed extracts, the type of protein inhibitors they contain, reviewing the recent Literature about their molecular structure and mechanism of action. We also explore the existing evidence (clinical trials conducted on both animals and humans) supporting the potential benefits of this protein inhibitors from P. vulgaris, also highlighting the urgent need of further studies to confirm the clinical efficacy of the commercial products. This work could contribute to summarize the knowledge and application of P. vulgaris extract as a nutraceutical strategy for controlling unwanted weight gains, also highlighting the current limitations.

Sensory Characteristics and Nutritional Quality of Food Products Made with a Biofortified and Lectin Free Common Bean (Phaseolus vulgaris L.) Flour

Common beans (Phaseolus vulgaris L.) are an important source of nutrients with beneficial effects on human health. However, they contain lectins, that limit the direct use of flour in food preparations without thermal treatment, and phytic acid, that reduces mineral cation bioavailability. The objectives of this research were: to obtain biofortified snacks and a cream using an untreated common bean flour devoid of active lectins (lec^-) and with reduced content of phytic acid (lpa) and to evaluate the sensorial appreciation for these products. The main results of the present work were: the products with the lpa lec^- flour did not retain residual hemagglutinating activity due to lectins; they showed higher residual α-amylase inhibitor activity (from 2.2 to 135 times), reduced in vitro predicted glycemic index (about 5 units reduction) and increased iron bioavailability compared to the products with wild type flour; products with common bean flour were less appreciated than the reference ones without this flour, but the presence of an intense umami taste can be a positive attribute. Results confirmed that the use of the lpa lec^- flour has important advantages in the preparation of safe and nutritionally improved products, and provide useful information to identify target consumers, such as children and elderly people.

Natural Extracts from White Common Bean (Phaseolus vulgaris L.) Inhibit 3T3-L1 Adipocytes Differentiation

Background: Recent studies have shown that the consumption of common bean (Phaseolus vulgaris L.) foods plays an essential role in the prevention and treatment of obesity. Methods: In this study, different natural extracts that include common bean polyphenol-rich extract (CBP), α-amylase inhibitor-rich extract (α-AIE), and non-starch polysaccharides-rich extract (NSP) were isolated. Their effects on 3T3-L1 adipocytes differentiation were evaluated, respectively. Results: The results showed that CPB reduced the lipid content in the mature adipocytes to 79.29% (150 μg/mL) and 35.13% (300 μg/mL), and α-AIE reduced it to 90.20% (2 mg/mL) and 68.28% (4 mg/mL), while NSP exhibited an auxo-action, suggesting that both CBP and a-AIE inhibited 3T3-L1 adipocytes differentiation. Additionally, CBP significantly suppressed (p < 0.05) the mRNA expression level and the protein expression level of peroxisome proliferator-activated receptor γ (PPARγ), CCAAT-enhancer-binding protein α (C/EBPα), sterol-regulatory element binding proteins 1 c (SREBP-1c), lipoprotein lipase (LPL), and fatty acid binding protein (ap2). Meanwhile, α-AIE only showed significant suppression effects on PPARγ, C/EBPα, and ap2 at the high dose of 4 mg/mL (p < 0.05). Conclusions: These findings indicate that CBP, from white common bean, might be the major component responsible for the inhibitory effects on adipocyte differentiation.

Current Evidence to Propose Different Food Supplements for Weight Loss: A Comprehensive Review

The use of food supplements for weight loss purposes has rapidly gained popularity as the prevalence of obesity increases. Navigating through the vast, often low quality, literature available is challenging, as is providing informed advice to those asking for it. Herein, we provide a comprehensive literature revision focusing on most currently marketed dietary supplements claimed to favor weight loss, classifying them by their purported mechanism of action. We conclude by proposing a combination of supplements most supported by current evidence, that leverages all mechanisms of action possibly leading to a synergistic effect and greater weight loss in the foreseen absence of adverse events. Further studies will be needed to confirm the weight loss and metabolic improvement that may be obtained through the use of the proposed combination.

Molecular determinant for specificity: Differential interaction of α-amylases with their proteinaceous inhibitors

BACKGROUND

α-Amylase inhibitors (α-AIs) belong to the discrete classes, and exhibited differential specificities against α-amylases from various sources. Several α-amylases and their complexes with inhibitors at the molecular level have been studied in detail. Interestingly, some α-AIs depict specific and selective interactions amid different insect α-amylases.

SCOPE OF REVIEW

There are studies to understand evolutionary variability and functional differentiation of insect α-amylases and their cognate inhibitors. We have examined sequence, structural, and interaction diversity between various α-amylases and α-AIs. Based on these analyses, we are providing a potential basis for the functional differentiation among certain insect α-amylases concerning mammalian counterparts and their interactions with different proteinaceous α-AIs.

MAJOR CONCLUSIONS

Insect α-amylases have conserved domain architecture with differences in length, number of disulfide bonds, and secondary structure. Furthermore, few of them exhibit variable characteristics like chloride dependent activity, the presence of N-terminal glutamine residue to protect against proteolytic degradation, and loop variations near the enzyme active site. Conformation of α-AI protein could be an essential factor for their specificity and binding affinities towards target α-amylase(s). Furthermore, variation into the enzyme binding pocket residues might contribute to differential interactions with inhibitors.

GENERAL SIGNIFICANCE

Molecular insights in the interactions between insect α-amylases and plant α-AI will provide the details of mechanisms assisting the inhibitor specificity. Furthermore, this information will help to design potent and effective α-AIs against specific α-amylase.

Amperometric determination of heavy metal using an HRP inhibition biosensor based on ITO nanoparticles-ruthenium (III) hexamine trichloride composite: Central composite design optimization

A novel horseradish peroxidase (HRP) enzyme inhibition biosensor based on indium tin oxide (ITO) nanoparticles, hexaammineruthenium (III) chloride (RUT), and chitosan (CH) modified glassy carbon electrode (GCE) was developed. The biosensor fabrication process was investigated using scanning electron microscopy, energy-dispersive X-ray spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The amounts of ITO nanoparticles and RUT were optimized using a 2² central composite design for the optimization of electrode composition. The detection limits were determined as 8 nM, 3 nM, and 1 nM for Pb²⁺, Ni²⁺, and Cd²⁺, respectively. The inhibition calibration curves of the biosensor were found to be within the range of 0.009-0.301 µM with a sensitivity of 11.97 µA µM^-1 cm^-2 (0.85 µA µM^-1) for Pb²⁺, 0.011-0.368 µM with a sensitivity of 10.84 µA µM^-1 cm^-2 (0.77 µA µM^-1) for Ni²⁺, and 0.008-0.372 µM with a sensitivity of 10.99 µA µM^-1 cm^-2 (0.78 µA µM^-1) for Cd²⁺. The type of HRP inhibition by Pb²⁺, Ni²⁺ and Cd²⁺ was investigated by the Dixon and Cornish-Bowden plots. The effects of possible interfering species on the biosensor response were examined. The analysis of Pb²⁺, Ni²⁺, and Cd²⁺ in tap water was demonstrated using the HRP/ITO-RUT-CH/GCE with satisfactory experimental results. The proposed method agreed with the atomic absorption spectrometry results.

The evaluation of lipid peroxidation and oxidative modification of proteins in blood serum under obesity development and the consumption of aqueous kidney beans Phaseolus vulgaris pods extract

Our interest has focused on the investigation of the anti-obese potential of kidney beans (P. vulgaris) pods extract. In the course of the study, obesity development in rats was induced with high-calorie diet. Control and obese rats then have consumed with aqueous kidney beans (P. vulgaris) pods extract during 6 weeks (200 mg/kg). Results show that the long-term consumption of P. vulgaris pods extract can lead to the reduction of hyperglycemia and insulin resistance development. Furthermore, we saw a normalization of lipid peroxidation parameters and oxidative modification of protein due to the consumption of the kidney beans (P. vulgaris) pods extract. Our experimental data demonstrate the ability of the kidney beans (P. vulgaris) pod extracts to mitigate obesity development but the details of this mechanism remains to be not fully understood.

Regular intake of white kidney beans extract (Phaseolus vulgaris L.) induces weight loss compared to placebo in obese human subjects

Scope

Phaseolus vulgaris L. is rich in alpha-amylase inhibitor and has been used for reducing glycemia and calories absorption through preventing or delaying the digestion of complex carbohydrate. A randomized, double-blinded, placebo-controlled study was conducted on obese volunteers to evaluate the degree of significate weight loss by regular intake Phaseolus vulgaris cultivated from Southwestern region of China.

Method

The volunteers were divided into two groups, homogeneous for age, gender, and body weight. Phaseolus vulgaris extract or placebo was given 2,400 mg per day before each daily meal for 35 consecutive days. Each subject's body weight, fat mass, body mass index, blood biochemical parameters, skinfold fat thickness, and waist/hip circumferences were monitored and analyzed.

Result and conclusion

As a result, the average amount of weight lost by the Phaseolus vulgaris extract group was 2.24 kg (average of 0.448 kg per week), compared with a 0.29 kg weight loss (average of 0.058 kg per week) in placebo group after 35 days. The differences between groups were significant (p < .01). The body mass index decreased by an average of 0.79, and the body fat decreased by 1.53% on average compared to baseline (p < .05). The thickness of subcutaneous fat was significantly reduced at the four measurement points, and the decrease of waist circumference and hip circumference was significant as well. No adverse or side effects were observed during the trial period. The results indicate that Phaseolus vulgaris extract can significantly induce weight loss in a short time period.

The impact of four processing methods on trypsin-, chymotrypsin- and alpha-amylase inhibitors present in underutilised legumes

The global trend in increasing plant-based protein diets due to health and ideological reasons, has created an increased demand for food legumes that exceeds current production. To meet this demand, it is timely to reduce relying solely on soybean, and explore the potential of the underutilised legumes that are cultivated regionally. Underutilised legumes are rich in protein, carbohydrates and other nutrients that are essential for consumer. However, relatively little is known about their anti-nutritional properties and processing methods. Anti-nutritional factors (ANFs) such as enzyme inhibitors are prevalent in legumes and may interfere with digestibility and nutrient absorption. Nevertheless, an optimised food processing method will overcome this challenge and warrant a safe inclusion of legume in plant-based protein diets. Hence current study aimed to optimise the food processing methods (soaking, wet heating, autoclaving and freezing) and evaluate their efficiency in eliminating the enzyme inhibitors [trypsin, chymotrypsin (CIA) and α-amylase (AIA) inhibitors] present in seven underutilised legumes. Current study showed that autoclaving at 121 °C for 15 min reduced the AIA in all underutilised legumes tested. The AIA and CIA of bambara groundnut were successfully inactivated by wet heating at 50 °C for 60 min, and by autoclaving at 121 °C for 15 min. While the CIA of chickpea was successfully inactivated by freezing at - 80 °C for 24 h.

Systematic Review and Meta-Analysis of a Proprietary Alpha-Amylase Inhibitor from White Bean (Phaseolus vulgaris L.) on Weight and Fat Loss in Humans

The aim of this meta-analysis was to examine the evidence for the effectiveness of a proprietary alpha-amylase inhibitor from white bean (Phaseolus vulgaris L.) supplementation interventions in humans on modification of body weight and fat mass. A systematic literature search was performed using three databases: PubMed, the Cochrane collaboration, and Google Scholar. In addition, the manufacturer was contacted for internal unpublished data, and finally, the reference section of relevant original research and review papers were mined for additional studies. Eleven studies were selected for the meta-analysis of weight loss (a total of 573 subjects), and three studies for the meta-analysis of body fat reduction (a total of 110 subjects), as they fulfilled the inclusion criteria. Phaseolus vulgaris supplementation showed an average effect on weight loss difference of −1.08 kg (95% CI (confidence interval), −0.42 kg to −1.16 kg, p < 0.00001), and the average effect on body fat reduction was 3.26 kg (95% CI, −2.35 kg to −4.163 kg, p = 0.02). This meta-analysis found statistically significant effects of Phaseolus vulgaris supplementation on body weight and body fat.

Exploitation of Common Bean Flours with Low Antinutrient Content for Making Nutritionally Enhanced Biscuits

Consumption of legumes is associated with a number of physiological and health benefits. Legume proteins complement very well those of cereals and are often used to produce gluten-free products. However, legume seeds often contain antinutritional compounds, such as phytate, galactooligosaccharides, phenolic compounds, lectins, enzyme inhibitors, whose presence could affect their nutritional value. Screening natural and induced biodiversity for useful traits, followed by breeding, is a way to remove undesirable components. We used the common bean cv. Lady Joy and the lpa1 mutant line, having different seed composition for absence/presence of lectins,α-amylase inhibitor, (α-AI) and phytic acid, to verify the advantage of their use to make biscuits with improved nutritional properties. We showed that use of unprocessed flour from normal beans (Taylor's Horticulture and Billò) must be avoided, since lectin activity is still present after baking, and demonstrated the advantage of using the cv. Lady Joy, lacking active lectins and having active α-AI. To assess the contribution of bean flour to biscuit quality traits, different formulations of composite flours (B12, B14, B22, B24, B29) were used in combinations with wheat (B14), maize (gluten-free B22 and B29), or with both (B12 and B24). These biscuits were nutritionally better than the control, having a better amino acid score, higher fiber amount, lower predicted glycemic index (pGI) and starch content. Replacement of cv. Lady Joy bean flour with that of lpa1, having a 90% reduction of phytic acid and devoid of α-AI, contributed to about a 50% reduction of phytic acid content. We also showed that baking did not fully inactivate α-AI, further contributing to lowering the pGI of the biscuits. Finally, data from a blind taste test using consumers indicated that the B14 biscuit was accepted by consumers and comparable in terms of liking to the control biscuit, although the acceptability of these products decreased with the increase of bean content. The B22 gluten-free biscuits, although received liking scores that were just above the middle point of the hedonic scale, might represent a good compromise between health benefits (absence of gluten and lower pGI), expectations of celiac consumers and likeness.

Nutraceutical properties of dietary plants extracts: prevention of diabetic nephropathy through inhibition of glycation and toxicity to erythrocytes and HEK293 cells

CONTEXT

Glycated albumin is reported to elicit pathobiologic effects in diabetic nephropathy and abrogating its biologic effects has novel therapeutic potential.

OBJECTIVE

This study examines the effects of dietary plants extracts (Laurus nobilis, Carum carvi, Coccinia grandis, Mentha arvensis, Phaseolus vulgaris) against albumin glycation and its toxicity to erythrocytes and HEK293 cells.

MATERIALS AND METHODS

Albumin (10 mg/ml) was incubated with fructose (250 mM) in PBS along with aqueous plant extracts (1% w/v) for 4 d. After incubation, the antiglycation potential of extracts was estimated by measuring AGEs, fructosamine, amyloids, carbonyls, free amino groups, and antioxidant potential of albumin. The glycation extent of the treated samples was determined by boronate affinity chromatography. Effect of extracts against glycation induced cytotoxicity in erythrocytes and HEK 293 cells was assessed by estimating viability, glutathione, and antioxidant capacity. Plant extracts were tested for their phenolic content and antioxidant potential (reducing potential, DPPH, ABTS, NO, and H2O2 radical scavenging activities).

RESULTS

Plant extracts significantly decreased the AGEs formation and amyloid aggregation in glycated BSA (p < 0.001). Further, fructosamine and carbonyls were reduced to 55-72% and 83-89%, respectively. Free amino group and antioxidant activity of albumin were also preserved by 1.25-1.40-fold and 1.75-1.8-fold, respectively. Further, co-incubation of extracts with glycated albumin, protected erythrocytes, and HEK293 cells as they inhibited cellular hemolysis/toxicity (p < 0.001) by upregulating cellular antioxidants.

DISCUSSION AND CONCLUSION

Plant co-incubation reversed many modifications in albumin glycation, cellular dysfunction indicating that dietary sources with antiglycating and antioxidant potential could be considered for the effective management of diabetic nephropathy.

Twenty Traditional Algerian Plants Used in Diabetes Therapy as Strong Inhibitors of α-Amylase Activity

In the present work, we have studied the inhibitory effects of aqueous and alcoholic extracts of six Algerian medicinal plants known by their therapeutic virtues against diabetes. The total phenolic compounds content, assayed using Folin-Ciocalteu’s reagent, of the samples ranged from 0.183 mg/g to 43.088 mg/g and from 1.197 mg/g to 7.445 mg/g, expressed as gallic acid equivalent (GAE), for the, respectively, whereas the total flavonoids concentrations, detected using 2% of the aluminium chloride, ranged from 0.41 mg/g to 11.613 mg/g and from 0.0097 mg/g to 1.591 mg/g, expressed as rutin equivalents (RE), for the aqueous and methanolic extracts, respectively. The major plants were found to inhibit enzymatic activities of Aspergillus oryzae-amylase in a concentration dependent manner. The values of the inhibition constants (Ki) have been determined according to the Dixon and Lineweaver-Burk methods. The results showed that the Ki values were less than 55 ppm for the all extracts. A strong inhibition was found in the phenolic extract of Salvia officinalis with a Ki of 8 ppm.

An in vitro and in vivo study of the α-amylase activity of phaseolamin

We evaluated the polypeptide profiles, inhibition of human salivary α-amylase activity, and hemagglutination properties of a commercial phaseolamin sample. We also performed an in vivo assay to investigate the effects of a commercial phaseolamin treatment (100, 500, or 1500 mg/kg) over 20 days on the glycemia, body weight, and serum biochemical parameters (total cholesterol, triglycerides, alanine aminotransferase, and aspartate aminotransferase) of nondiabetic and streptozotocin-induced diabetic rats. The in vitro evaluation showed defined protein profiles, low hemagglutination activity, and high α-amylase inhibition. None of the experimental groups treated with phaseolamin or acarbose showed decreases in body weight. Our data demonstrate that phaseolamin inhibits amylase activity in vitro, reduces blood glucose levels, decreases or attenuates some of the renal and hepatic effects of diabetes in streptozotocin-induced rats, and could therefore have therapeutic potential in the treatment or prevention of the complications of diabetes.

Weight reduction and maintenance with IQP-PV-101: a 12-week randomized controlled study with a 24-week open label period

OBJECTIVE

The safety and efficacy of IQP-PV-101, a proprietary extract of Phaseolus vulgaris, on weight management in two phases was evaluated here. The weight loss (WL) phase was conducted over 12 weeks and the weight maintenance (WM) phase took 24 weeks.

METHODS

In the double-blind WL phase, subjects were randomized to receive either IQP-PV-101 or placebo. All subjects adhered to a mildly hypocaloric diet. Body weight and other body composition parameters were measured at baseline and every 4 weeks thereafter. During the single arm, open label WM trial, energy intake was ad libitum. Efficacy parameters were measured at baseline, week 12 and week 24.

RESULTS

At the end of the WL study, the IQP-PV-101 group lost a mean of 2.91 ± 2.63 kg in body weight compared with 0.92 ± 2.00 kg in the placebo group (P < 0.001). During the WM phase, 36 out of 49 subjects (73.5%) were able to maintain their weight, even without dietary restrictions. No serious or related adverse events were reported over the combined period of 36 weeks.

CONCLUSIONS

Results indicate that IQP-PV-101 is safe and effective for weight loss and maintenance.

Functional characterization of a vacuolar invertase from Solanum lycopersicum: post-translational regulation by N-glycosylation and a proteinaceous inhibitor

Plant vacuolar invertases, which belong to family 32 of glycoside hydrolases (GH32), are key enzymes in sugar metabolism. They hydrolyse sucrose into glucose and fructose. The cDNA encoding a vacuolar invertase from Solanum lycopersicum (TIV-1) was cloned and heterologously expressed in Pichia pastoris. The functional role of four N-glycosylation sites in TIV-1 has been investigated by site-directed mutagenesis. Single mutations to Asp of residues Asn52, Asn119 and Asn184, as well as the triple mutant (Asn52, Asn119 and Asn184), lead to enzymes with reduced specific invertase activity and thermostability. Expression of the N516D mutant, as well as of the quadruple mutant (N52D, N119D, N184D and N516D) could not be detected, indicating that these mutations dramatically affected the folding of the protein. Our data indicate that N-glycosylation is important for TIV-1 activity and that glycosylation of N516 is crucial for recombinant enzyme stability. Using a functional genomics approach a new vacuolar invertase inhibitor of S. lycopersicum (SolyVIF) has been identified. SolyVIF cDNA was cloned and heterologously expressed in Escherichia coli. Specific interactions between SolyVIF and TIV-1 were investigated by an enzymatic approach and surface plasmon resonance (SPR). Finally, qRT-PCR analysis of TIV-1 and SolyVIF transcript levels showed a specific tissue and developmental expression. TIV-1 was mainly expressed in flowers and both genes were expressed in senescent leaves.

Reducing effect of a combination of Phaseolus vulgaris and Cynara scolymus extracts on food intake and glycemia in rats

Extracts from Phaseolus vulgaris and Cynara scolymus may reduce food intake and/or postprandial glycemia. This study investigated the effect of standardized extracts of P. vulgaris and C. scolymus and their combination on food intake and glycemia in rats. P. vulgaris and C. scolymus extracts, and their 1:2 combination, were administered acutely to rats (a) given access to regular food and water, (b) given access to regular food, water, and a chocolate-flavored beverage, or (c) infused with a starch bolus. P. vulgaris extract and the combination produced comparable reductions in intake of regular food and chocolate-flavored beverage; conversely, C. scolymus extract was ineffective on both parameters. P. vulgaris and C. scolymus extracts additively contributed to the reducing effect of the combination on glycemic rise. These results suggest that a mixture of P. vulgaris and C. scolymus extracts is preferable over each single extract, as it combines the anorectic effect of the P. vulgaris extract with the hypoglycemic effect of both extracts. These data support the recent clinical use of the combination of P. vulgaris and C. scolymus extracts in the control of appetite, food intake, and postprandial glycemia and represent a successful example of translational research in the nutraceutical field.

Multiple cycles of repeated treatments with a Phaseolus vulgaris dry extract reduce food intake and body weight in obese rats

Previous lines of experimental evidence have suggested that Phaseolus vulgaris extracts reduce food intake, body weight, lipid accumulation, hedonic properties of food, carbohydrate absorption and metabolism, and glycaemia in rats. The present study was designed to assess the effect of multiple cycles of repeated treatments with a standardised P. vulgaris dry extract on daily food intake and body weight in genetically obese Zucker fa/fa rats (Expt 1). Additionally, the study tested the effect of acute treatment with P. vulgaris dry extract on postprandial glycaemia in Zucker fa/fa rats (Expt 2). In Expt 1, P. vulgaris dry extract was administered daily, at doses of 50 and 500 mg/kg, in three 5 d treatment periods followed by three 20 d off-treatment periods. Administration of P. vulgaris dry extract resulted in dose-dependent decreases in daily food intake and body weight in each treatment phase. Reductions in food intake were of comparable magnitude in each treatment phase. In Expt 2, food-deprived rats were acutely treated with 50 and 500 mg P. vulgaris dry extract per kg immediately before access to a fixed amount of a starch-enriched chow. Treatment with P. vulgaris dry extract resulted in a dose-dependent suppression of glycaemia. These results extend previous data on the anorectic and hypoglycaemic effects of the P. vulgaris dry extract to a validated animal model of obesity. Together with data published previously in the literature, these results strengthen the hypothesis that potentially effective, novel pharmacotherapies for obesity and related disorders may originate from extracts and derivatives of P. vulgaris.

Bean amylase inhibitor and other carbohydrate absorption blockers: effects on diabesity and general health

Many believe that excessive intake of refined carbohydrates (CHO) plays a major role in the development of obesity/overweight, type 2 diabetes mellitus and insulin resistance, a collection of events commonly referred to as "diabesity," and have sought natural means to overcome these linked perturbations. As a first approach, planned diets with low portions of refined CHO have become popular. However, these diets do not satisfy everyone; and many are concerned over replacing CHO with more fats. As a second option, addition of soluble fiber to the diet can slow absorption of refined CHO, i.e., lower the glycemic index of foods and overcome or at least ameliorate many of the adverse reactions resulting from increased refined CHO ingestion. Unfortunately, the general public does not favor diets high in fiber content, and various fibers can lead to gastrointestinal problems such as gas and diarrhea. A third choice to favorably influence CHO absorption is to use natural dietary supplements that block or slow CHO absorption in the gastrointestinal tract via inhibiting enzymes necessary for CHO absorption -amylase and alpha-glucosidases. Although a number of natural supplements with anti-amylase activity have been recognized, the most studied and favored one is white kidney bean extract. Animal and human studies clearly show that this agent works in vivo and has clinical utility. This paper reviews many aspects of diabesity and the use of "carb blockers" to prevent and ameliorate the situation. In many respects, carb blockers mimic the beneficial effects of fibers.

Biochemical characterization of the alpha-amylase inhibitor in mungbeans and its application in inhibiting the growth of Callosobruchus maculatus

The insect Callosobruchus maculatus causes considerable damage to harvested mungbean seeds every year, which leads to commercial losses. However, recent studies have revealed that mungbean seeds contain alpha-amylase inhibitors that can inhibit the protein C. maculatus, preventing growth and development of the insect larvae in the seed, thus preventing further damage. For this reason, the use of alpha-amylase inhibitors to interfere with the pest's digestion process has become an interesting alternative biocontrolling agent. In this study, we have isolated and purified the alpha-amylase inhibitor from mungbean seeds (KPS1) using ammonium sulfate precipitation, gel filtration chromatography and reversed phase HPLC. We found that the alpha-amylase inhibitor, isolated as a monomer, had a molecular weight of 27 kDa. The alpha-amylase inhibitor was purified 750-fold with a final yield of 0.4 mg of protein per 30 g of mungbean seeds. Its specific activity was determined at 14.5 U (mg of protein)(-1). Interestingly, we found that the isolated alpha-amylase inhibitor inhibits C. maculatus alpha-amylase but not human salivary alpha-amylase. After preincubation of the enzyme with the inhibitor, the mungbean alpha-amylase inhibitor inhibited C. maculatus alpha-amylase activity by decreasing V(max) while increasing the K(m) constant, indicating that the mungbean alpha-amylase is a mix noncompetitive inhibitor. The in vivo effect of alpha-amylase inhibitor on the mortality of C. maculatus shows that the alpha-amylase inhibitor acts on C. maculatus during the development stage, by reducing carbohydrate digestion necessary for growth and development, rather than during the end laying/hatching stage. Our results suggest that mungbean alpha-amylase inhibitor could be a useful future biocontrolling agent.

Development and characterization of lysine based tripeptide analogues as inhibitors of Sir2 activity

Sirtuins are NAD(+) dependent deacetylases that modulate various essential cellular functions. Development of peptide based inhibitors of Sir2s would prove useful both as pharmaceutical agents and as effectors by which downstream cellular alterations can be monitored. Click chemistry that utilizes Huisgen's 1,3-dipolar cycloaddition permits attachment of novel modifications onto the side chain of lysine. Herein, we report the synthesis of peptide analogues prepared using click reactions on Nepsilon-propargyloxycarbonyl protected lysine residues and their characterization as inhibitors of Plasmodiumfalciparum Sir2 activity. The peptide based inhibitors exhibited parabolic competitive inhibition with respect to acetylated-peptide substrate and parabolic non-competitive inhibition with NAD(+) supporting the formation of EI(2) and E.NAD(+).I(2) complexes. Cross-competition inhibition analysis with the non-competitive inhibitor nicotinamide (NAM) ruled out the possibility of the NAM-binding site being the second inhibitor binding site, suggesting the presence of a unique alternate pocket accommodating the inhibitor. One of these compounds was also found to be a potent inhibitor of the intraerythrocytic growth of P.falciparum with 50% inhibitory concentration in the micromolar range.

Potential efficacy of preparations derived from Phaseolus vulgaris in the control of appetite, energy intake, and carbohydrate metabolism

Preclinical data on extracts of and preparations derived from beans of Phaseolus vulgaris are reviewed as potential remedies for use in controlling food consumption, body weight, lipid accumulation, and glycemia. A growing body of evidence suggests that acute and chronic administration of P. vulgaris derivatives reduces food intake (including highly palatable foods), body weight, lipid deposit, and glycemia in rats exposed to multiple experimental procedures. Two possible lectin-mediated mechanisms of action have been proposed: (a) inhibition of α-amylase, resulting in a reduced carbohydrate metabolism and absorption; (b) phytohemoagglutinin-induced modulation of the activity of cholecystokinin and glucagon-like peptides, resulting in a reduced appetite. Preliminary clinical data, as well as reports focusing on the use of several traditional medicines, apparently extend these findings to humans. Should these initial clinical data be confirmed by future surveys, P. vulgaris derivatives might constitute novel remedies for the treatment of obesity and metabolic syndrome. Future studies are also expected to identify active structures leading to the development of new pharmaceutical agents.

The nutraceutical role of thePhaseolus vulgarisα-amylase inhibitor

The present review assesses the potential of thePhaseolus vulgarisα-amylase inhibitor isoform 1 (α-AI1) starch blockers as a widely used remedy against obesity and diabetes. Consumption of the α-amylase inhibitor causes marginal intraluminal α-amylase activity facilitated by the inhibitor's appropriate structural, physico-chemical and functional properties. As a result there is decreased postprandial plasma hyperglycaemia and insulin levels, increased resistance of starch to digestion and increased activity of colorectal bacteria. The efficacy and safety of the amylase inhibitor extracts, however, depend on the processing and extraction techniques used. The extracts are potential ingredients in foods for increased carbohydrate tolerance in diabetics, decreased energy intake for reducing obesity and for increased resistant starch. Research developments in the distribution and biosynthesis of the α-amylase inhibitor, relevant physico-chemical properties, the molecular starch-blocking mechanism, anti-obesity and anti-diabetes effects, safety of extracts and the need for research into their potential anti-colorectal cancer effect are discussed.

Evolutionary analysis of the APA genes in the Phaseolus genus: wild and cultivated bean species as sources of lectin-related resistance factors?

The APA (Arcelin/Phytohemagglutinin/alpha-Amylase inhibitor) gene family is composed of various members, present in Phaseolus species and coding for lectin and lectin-related seed proteins having the double role of storage and defense proteins. Here members of the APA family have been identified by immunological, functional, and molecular analyses and representative genes were sequenced in nine wild species of Phaseolus. All taxa possessed at least one member of the true lectin gene. No arcelin type sequences have been isolated from the species examined. Among the wild species studied, only P. costaricensis contained an alpha-amylase inhibitor (alpha-AI). In addition P. augusti, P. maculatus, P. microcarpus, and P. oligospermus showed the presence of the lectin-related alpha-amylase inhibitor-like (AIL) genes and alpha-AI activity. Data from Southern blot analysis indicated the presence of only one lectin gene in P. parvulus and P. filiformis, while an extensive gene duplication of the APA locus was found in the other Phaseolus species. Phylogenetic analysis carried out on the nucleotide sequences showed the existence of two main clusters and clearly indicated that lectin-related genes originated from a paralogous duplication event preceding the development of the ancestor to the Phaseolus genus. The finding of detectable alpha-AI activity in species containing AIL genes suggests that exploiting APA genes variability in the Phaseolus genus may represent a valuable tool to find new members that may have acquired insecticidal activities.

Inhibition by natural dietary substances of gastrointestinal absorption of starch and sucrose in rats 2. Subchronic studies

Acute oral consumption of various natural inhibitors of amylase (bean and hibiscus extracts) and sucrase (L-arabinose) reduce absorption of starch and sucrose respectively in rats and pigs measured by lessened appearance of circulating glucose levels. The present subchronic study was designed to determine whether these selected inhibitors of gastrointestinal starch and sucrose absorption (so-called "carb blockers") remain effective with continued use and to assess their metabolic influences after prolonged intake. Sprague-Dawley rats were gavaged twice daily over nine weeks with either water or an equal volume of water containing a formula that included bean and hibiscus extracts and L-arabinose. To estimate CHO absorption, control and treated Sprague-Dawley rats were gavaged with either water alone or an equal volume of water containing glucose, rice starch, sucrose, or combined rice starch and sucrose. Circulating glucose was measured at timed intervals over four hours. The ability to decrease starch and sucrose absorption use. No toxic effects (hepatic, renal, hematologic) were evident. Blood chemistries revealed significantly lower circulating glucose levels and a trend toward decreased HbA1C in the nondiabetic rats receiving the natural formulation compared to control. Subchronic administration of enzyme inhibitors was also associated with many metabolic changes including lowered systolic blood pressure and altered fluid-electrolyte balance. We postulate that proper intake of natural amylase and sucrase inhibitors may be useful in the prevention and treatment of many chronic disorders associated with perturbations in glucose-insulin homeostasis secondary to the rapid absorption of refined CHO.

Inhibition by natural dietary substances of gastrointestinal absorption of starch and sucrose in rats and pigs: 1. Acute studies

Rapid gastrointestinal absorption of refined carbohydrates (CHO) is linked to perturbed glucose-insulin metabolism that is, in turn, associated with many chronic health disorders. We assessed the ability of various natural substances, commonly referred to as "CHO blockers," to influence starch and sucrose absorption in vivo in ninety-six rats and two pigs. These natural enzyme inhibitors of amylase/sucrase reportedly lessen breakdown of starches and sucrose in the gastrointestinal tract, limiting their absorption. To estimate absorption, groups of nine SD rats were gavaged with water or water plus rice starch and/or sucrose; and circulating glucose was measured at timed intervals thereafter. For each variation in the protocol a total of at least nine different rats were studied with an equal number of internal controls on three different occasions. The pigs rapidly drank CHO and inhibitors in their drinking water. In rats, glucose elevations above baseline over four hours following rice starch challenge as estimated by area-under-curve (AUC) were 40%, 27%, and 85% of their internal control after ingesting bean extract, hibiscus extract, and l-arabinose respectively in addition to the rice starch. The former two were significantly different from control. L-Arabinose virtually eliminated the rising circulating glucose levels after sucrose challenge, whereas hibiscus and bean extracts were associated with lesser decreases than l-arabinose that were still significantly lower than control. The glucose elevations above baseline over four hours in rats receiving sucrose (AUC) were 51%, 43% and 2% of control for bean extract, hibiscus extract, and L-arabinose, respectively. Evidence for dose-response of bean and hibiscus extracts is reported. Giving the natural substances minus CHO challenge caused no significant changes in circulating glucose concentrations, indicating no major effects on overall metabolism. A formula combining these natural products significantly decreased both starch and sucrose absorption, even when the CHO were given simultaneously. These results support the hypothesis that the enzyme inhibitors examined here at reasonable doses can safely lower the glycemic loads starch and sucrose.

A Dietary supplement containing standardized Phaseolus vulgaris extract influences body composition of overweight men and women

BACKGROUND

More than one billion human adults worldwide are overweight and, therefore, are at higher risk of developing cardiovascular diseases, diabetes, and a variety of other chronic perturbations. Many believe that use of natural dietary supplements could aid in the struggle against obesity. So-called "starch blockers" are listed among natural weight loss supplements. Theoretically, they may promote weight loss by interfering with the breakdown of complex carbohydrates thereby reducing, or at least slowing, the digestive availability of carbohydrate-derived calories and/or by providing resistant starches to the lower gastrointestinal tract.

AIMS

The present research study examines a dietary supplement containing 445 mg of Phaseolus vulgaris extract derived from the white kidney bean, previously shown to inhibit the activity of the digestive enzyme alpha amylase, on body composition of overweight human subjects.

METHODS

A randomized, double-blinded, placebo-controlled study was conducted on 60 pre-selected, slightly overweight volunteers, whose weight had been essentially stable for at least six months. The volunteers were divided into two groups, homogeneous for age, gender, and body weight. The test product containing Phaseolus vulgaris extract and the placebo were taken one tablet per day for 30 consecutive days before a main meal rich in carbohydrates. Each subject's body weight, fat and non-fat mass, skin fold thickness, and waist/hip/thigh circumferences were measured.

RESULTS

After 30 days, subjects receiving Phaseolus vulgaris extract with a carbohydrate-rich, 2000- to 2200-calorie diet had significantly (p<0.001) greater reduction of body weight, BMI, fat mass, adipose tissue thickness, and waist,/hip/ thigh circumferences while maintaining lean body mass compared to subjects receiving placebo.

CONCLUSION

The results indicate that Phaseolus vulgaris extract produces significant decrements in body weight and suggest decrements in fat mass in the face of maintained lean body mass.

Development of four phylogenetically-arrayed BAC libraries and sequence of the APA locus in Phaseolus vulgaris

The APA family of seed proteins consists of three subfamilies, in evolutionary order of hypothesized appearance: phytohaemagglutinins (PHA), alpha-amylase inhibitors (alphaAI), and arcelins (ARL). The APA family plays a defensive role against mammalian and insect seed predation in common bean (Phaseolus vulgaris L.). The main locus (APA) for this gene family is situated on linkage group B4. In order to elucidate the pattern of duplication and diversification at this locus, we developed a BAC library in each of four different Phaseolus genotypes that represent presumptive steps in the evolutionary diversification of the APA family. Specifically, BAC libraries were established in one P. lunatus (cv. 'Henderson: PHA+ alphaAI- ARL-) and three P. vulgaris accessions (presumed ancestral wild G21245 from northern Peru: PHA+ alphaAI+ ARL-; Mesoamerican wild G02771: PHA+ alphaAI+ ARL+; and Mesoamerican breeding line BAT93: PHA+ alphaAI+ ARL-). The libraries were constructed after HindIII digestion of high molecular weight DNA, obtained with a novel nuclei isolation procedure. The frequency of empty or cpDNA-sequence-containing clones in all libraries is low (generally <1%). The Henderson, G21245, and G02771 libraries have a 10x genome coverage, whereas the BAT93 library has a 20x coverage to allow further, more detailed genomic analysis of the bean genome. The complete sequence of a 155 kbp-insert clone of the G02771 library revealed six sequences belonging to the APA gene family, including members of the three subfamilies, as hypothesized. The different subfamilies were interspersed with retrotransposon sequences. In addition, other sequences were identified with similarity to chloroplast DNA, a dehydrin gene, and the Arabidopsis flowering D locus. Linkage between the dehydrin gene and the D1711 RFLP marker identifies a potential syntenic region between parts of common bean linkage group B4 and cowpea linkage group 2.

Mutational Analysis of Target Enzyme Recognition of the β-Trefoil Fold Barley α-Amylase/Subtilisin Inhibitor

The barley alpha-amylase/subtilisin inhibitor (BASI) inhibits alpha-amylase 2 (AMY2) with subnanomolar affinity. The contribution of selected side chains of BASI to this high affinity is discerned in this study, and binding to other targets is investigated. Seven BASI residues along the AMY2-BASI interface and four residues in the putative protease-binding loop on the opposite side of the inhibitor were mutated. A total of 15 variants were compared with the wild type by monitoring the alpha-amylase and protease inhibitory activities using Blue Starch and azoalbumin, respectively, and the kinetics of binding to target enzymes by surface plasmon resonance. Generally, the mutations had little effect on k(on), whereas the k(off) values were increased up to 67-fold. The effects on the inhibitory activity, however, were far more pronounced, and the K(i) values of some mutants on the AMY2-binding side increased 2-3 orders of magnitude, whereas mutations on the other side of the inhibitor had virtually no effect. The mutants K140L, D150N, and E168T lost inhibitory activity, revealing the pivotal role of charge interactions for BASI activity on AMY2. A fully hydrated Ca(2+) at the AMY2-BASI interface mediates contacts to the catalytic residues of AMY2. Mutations involving residues contacting the solvent ligands of this Ca(2+) had weaker affinity for AMY2 and reduced sensitivity to the Ca(2+) modulation of the affinity. These results suggest that the Ca(2+) and its solvation sphere are integral components of the AMY2-BASI complex, thus illuminating a novel mode of inhibition and a novel role for calcium in relation to glycoside hydrolases.

Proteinaceous α-amylase inhibitors

Proteins that inhibit alpha-amylases have been isolated from plants and microorganisms. These inhibitors can have natural roles in the control of endogenous alpha-amylase activity or in defence against pathogens and pests; certain inhibitors are reported to be antinutritional factors. The alpha-amylase inhibitors belong to seven different protein structural families, most of which also contain evolutionary related proteins without inhibitory activity. Two families include bifunctional inhibitors acting both on alpha-amylases and proteases. High-resolution structures are available of target alpha-amylases in complex with inhibitors from five families. These structures indicate major diversity but also some similarity in the structural basis of alpha-amylase inhibition. Mutational analysis of the mechanism of inhibition was performed in a few cases and various protein engineering and biotechnological approaches have been outlined for exploitation of the inhibitory function.