Influence of Brewer's Spent Grain Compounds on Glucose Metabolism Enzymes.

With a yearly production of about 39 million tons, brewer's spent grain (BSG) is the most abundant brewing industry byproduct. Because it is rich in fiber and protein, it is commonly used as cattle feed but could also be used within the human diet. Additionally, it contains many bioactive substances such as hydroxycinnamic acids that are known to be antioxidants and potent inhibitors of enzymes of glucose metabolism. Therefore, our study aim was to prepare different extracts-A1-A7 (solid-liquid extraction with 60% acetone); HE1-HE6 (alkaline hydrolysis followed by ethyl acetate extraction) and HA1-HA3 (60% acetone extraction of alkaline residue)-from various BSGs which were characterized for their total phenolic (TPC) and total flavonoid (TFC) contents, before conducting in vitro studies on their effects on the glucose metabolism enzymes α-amylase, α-glucosidase, dipeptidyl peptidase IV (DPP IV), and glycogen phosphorylase α (GPα). Depending on the extraction procedures, TPCs ranged from 20-350 µg gallic acid equivalents/mg extract and TFCs were as high as 94 µg catechin equivalents/mg extract. Strong inhibition of glucose metabolism enzymes was also observed: the IC50 values for α-glucosidase inhibition ranged from 67.4 ± 8.1 µg/mL to 268.1 ± 29.4 µg/mL, for DPP IV inhibition they ranged from 290.6 ± 97.4 to 778.4 ± 95.5 µg/mL and for GPα enzyme inhibition from 12.6 ± 1.1 to 261 ± 6 µg/mL. However, the extracts did not strongly inhibit α-amylase. In general, the A extracts from solid-liquid extraction with 60% acetone showed stronger inhibitory potential towards a-glucosidase and GPα than other extracts whereby no correlation with TPC or TFC were observed. Additionally, DPP IV was mainly inhibited by HE extracts but the effect was not of biological relevance. Our results show that BSG is a potent source of α-glucosidase and GPα inhibitors, but further research is needed to identify these bioactive compounds within BSG extracts focusing on extracts from solid-liquid extraction with 60% acetone.

Inhibition of α-glucosidases by tea polyphenols in rat intestinal extract and Caco-2 cells grown on Transwell.

Inhibition of maltase, sucrase, isomaltase and glucoamylase activity by acarbose, epigallocatechin gallate, epicatechin gallate and four polyphenol-rich tea extract from white, green, oolong, black tea, were investigated by using rat intestinal enzymes and human Caco-2 cells. Regarding rat intestinal enzyme mixture, all four tea extracts were very effective in inhibiting maltase and glucoamylase activity, but only white tea extract inhibited sucrase and isomaltase activity and the inhibition was limited. Mixed-type inhibition on rat maltase activity was observed. Tea extracts in combination with acarbose, produced a synergistic inhibitory effect on rat maltase activity. Caco-2 cells experiments were conducted in Transwells. Green tea extract and epigallocatechin gallate show dose-dependent inhibition on human sucrase activity, but no inhibition on rat sucrase activity. The opposite was observed on maltase activity. The results highlighted the different response in the two investigated model systems and show that tea polyphenols are good inhibitors for α-glucosidase activity.

Synthesis and Evaluation of Novel Iminosugars Prepared from Natural Amino Acids.

Cyclopropanated iminosugars have a locked conformation that may enhance the inhibitory activity and selectivity against different glycosidases. We show the synthesis of new cyclopropane-containing piperidines bearing five stereogenic centers from natural amino acids l-serine and l-alanine. Those prepared from the latter amino acid may mimic l-fucose, a natural-occurring monosaccharide involved in many molecular recognition events. Final compounds prepared from l-serine bear S configurations on the C5 position. The synthesis involved a stereoselective cyclopropanation reaction of an α,ß-unsaturated piperidone, which was prepared through a ring-closing metathesis. The final compounds were tested as possible inhibitors of different glycosidases. The results, although, in general, with low inhibition activity, showed selectivity, depending on the compound and enzyme, and in some cases, an unexpected activity enhancement was observed.

Synthesis and Therapeutic Applications of Iminosugars in Cystic Fibrosis.

Iminosugars are sugar analogues endowed with a high pharmacological potential. The wide range of biological activities exhibited by these glycomimetics associated with their excellent drug profile make them attractive therapeutic candidates for several medical interventions. The ability of iminosugars to act as inhibitors or enhancers of carbohydrate-processing enzymes suggests their potential use as therapeutics for the treatment of cystic fibrosis (CF). Herein we review the most relevant advances in the field, paying attention to both the chemical synthesis of the iminosugars and their biological evaluations, resulting from in vitro and in vivo assays. Starting from the example of the marketed drug NBDNJ (N-butyl deoxynojirimycin), a variety of iminosugars have exhibited the capacity to rescue the trafficking of F508del-CFTR (deletion of F508 residue in the CF transmembrane conductance regulator), either alone or in combination with other correctors. Interesting results have also been obtained when iminosugars were considered as anti-inflammatory agents in CF lung disease. The data herein reported demonstrate that iminosugars hold considerable potential to be applied for both therapeutic purposes.

Anti-glycation effect and the α-amylase, lipase, and α-glycosidase inhibition properties of a polyphenolic fraction derived from citrus wastes.

The advanced glycation end products (AGEs) constitute a wide variety of substances synthesized from interactions between amino groups of proteins and reducing sugars, which excess induces pathogenesis of chronic diseases. Brazil is the major producer of citrus, a low-cost source of hesperidin, which is a polyphenol recognized for its capacity to inhibit AGEs formation. This is the first work to evaluate the effects of a polyphenolic fraction derived from citrus wastes on the antiglycation and on the inhibition properties of digestive enzymes on the possibility to process these wastes in high value-added products. At concentrations of 10, 15 and 20 mg/mL inhibition of AGEs was higher than 60%. The extracts were able to inhibit by 76% the activity of pancreatic lipase and by 98% the activity of α-glucosidase. For the α-amylase the inhibition capacity was lower than 50%. Strong correlation was obtained among anti-glycation with polyphenolic content and antioxidant capacity.

Phytochemical content, antioxidant activity, and enzyme inhibition effect of Salvia eriophora Boiss. & Kotschy against acetylcholinesterase, α-amylase, butyrylcholinesterase, and α-glycosidase enzymes.

Many taxa of Salvia genus have been used in herbal beverages, food flavoring, cosmetics, and pharmaceutical industry. In this paper, chemical compounds of Salvia eriophora (S. eriophora) leaves were determined by LC-MS/MS (Liquid Chromatography tandem Mass Spectrometry). Salvigenin (158.64 ± 10.8 mg/kg), fumaric acid (123.09 ± 8.54 mg/kg), and quercetagetin-3.6-dimethylether (37.85 ± 7.09 mg/kg) were detected as major compounds in the ethanol extract, whereas fumaric acid (555.96 ± 38.56 mg/kg), caffeic acid (103.62 ± 20.51 mg/kg), and epicatechin (83.19 ± 8.43 mg/kg) were detected as major compounds in the water extract. Furthermore, enzyme inhibition of S. eriophora against acetylcholinesterase (AChE), α-amylase (AM), butyrylcholinesterase (BChE), and α-glycosidase (AG) enzymes were detected. AChE, BChE, AG, and AM enzymes were very strongly inhibited by S. eriophora water extract (WES) and S. eriophora methanol extract (MES). Additionally, antioxidant potential of S. eriophora was determined by in vitro analytical methods. IC50 values of WES and MES were performed for radicals. PRACTICAL APPLICATIONS: Metabolic enzymes have crucial functions on living systems due to inhibition or activation of them mainly attributed with some health disorders. AChE, BChE, AM, and AG enzymes have important roles on carbohydrate metabolism or cholinergic pathways. The relation between enzyme inhibition effect and phenolic compounds or antioxidant activity need to be confirmed. Thus, many studies tested to clarify this relation for pure samples or plant extracts. To the best of our knowledge, this is the first report about inhibition effects of Salvia eriophora extracts against AChE, BChE, AM, and AG enzymes as well as their phenolic contents and antioxidant activities.

Synthesis of tricyclic quinazolinone-iminosugars as potential glycosidase inhibitors via a Mitsunobu reaction.

A series of novel tricyclic quinazolinone-iminosugars 1 (a-c) were synthesized from the benzyl protected sugars through three steps. Firstly, the benzyl protected sugar (aldehyde) 5 reacted with o-aminobenzamide by the iodine-induced oxidative condensation to afford the corresponding aldo-quizanolinone 6. Secondly, through the intramolecular cyclization of the unprotected OH and the amide NH in 6, the tricyclic compounds 7 and 8 were constructed by the key Mitsunobu reaction. Finally, removal of the benzyl group gave the target tricyclic quinazolinone-iminosugars 1. The protocol was effective for the preparation of the tricyclic iminosugars in satisfactory yield. Interestingly, an unusual C-2 epimerization was observed with d-mannose and d-ribose compounds under the conditions of the Mitsunobu reaction that generated the products having the trans configuration at the C-2 and C-3 positions. Unfortunately, such tricyclic quinazolinone-iminosugars showed no inhibitory effects on the tested five glycosidases.

Isolation from Stevia rebaudiana of DMDP acetic acid, a novel iminosugar amino acid: synthesis and glycosidase inhibition profile of glycine and ß-alanine pyrrolidine amino acids.

DMDP acetic acid [N-carboxymethyl-2,5-dideoxy-2,5-imino-D-mannitol] 5 from Stevia rebaudiana is the first isolated natural amino acid derived from iminosugars bearing an N-alkyl acid side chain; it is clear from GCMS studies that such derivatives with acetic and propionic acids are common in a broad range of plants including mulberry, Baphia, and English bluebells, but that they are very difficult to purify. Reaction of unprotected pyrrolidine iminosugars with aqueous glyoxal gives the corresponding N-acetic acids in very high yield; Michael addition of both pyrrolidine and piperidine iminosugars and that of polyhydroxylated prolines to tert-butyl acrylate give the corresponding N-propionic acids in which the amino group of ß-alanine is incorporated into the heterocyclic ring. These easy syntheses allow the identification of this new class of amino acid in plant extracts and provide pure samples for biological evaluation. DMDP N-acetic and propionic acids are potent α-galactosidase inhibitors in contrast to potent ß-galactosidase inhibition by DMDP.

A novel chitosan alleviates pulp breakdown of harvested longan fruit by suppressing disassembly of cell wall polysaccharides.

Longan pulp is an excellent source of polysaccharides and other nutrients that have many health benefits. However, longans is susceptible to pulp breakdown after harvest and loses its nutrition values. To solve this problem, this study aimed to study the effects of a novel chitosan, Kadozan, on pulp breakdown index, contents of pectin, cellulose and hemicelluloses, and activities of enzymes in longan pulp relating to disassembly of polysaccharides (XET, PE, PG, ß-Gal, and cellulase). The data illustrated that, compared to the control longans, chitosan-treated longans contained higher amounts of CWM, CSP, ISP, cellulose and hemicelluloses, but exhibited lower pulp breakdown index, lower activities of cell wall-disassembling enzymes, and contained lower WSP amount. These results suggested that Kadozan with a dilution of 1:500 (VKadozan: VKadozan + Water) could significantly decrease activities of disassembling-enzymes and depolymerization of polysaccharides in cell wall, and subsequently alleviate pulp breakdown and prolong storage-life of postharvest longans.

Antidiabetic properties of dietary phenolic compounds: Inhibition effects on α-amylase, aldose reductase, and α-glycosidase.

Aldose reductase (AR), α-amylase, and α-glycosidase are vital enzymes to prevent diabetic complications. Here, AR was purified from sheep kidney using elementary methods with 111.11-purification fold and with 0.85% purification yield. The interactions between some phenolic compounds and the AR, α-glycosidase, and α-amylase enzyme were determined. It was found that phenolic compounds exhibit potential inhibitor properties for these enzymes. For α-amylase, studied phenolic compounds showed IC50 values in the range of 601.56-2,067.78 nM. For α-glycosidase, Ki values were found in the range of 169.25 ± 27.22-572.88 ± 106.76 nM. For AR, Ki values in the range of 8.48 ± 0.56-43.26 ± 7.63 µM. However, genistein showed the best inhibition effect toward AR and α-glycosidase, but delphinidin chloride exhibited the best inhibition effect against α-amylase enzyme. We determined that all compounds showed noncompetitive inhibition effect against AR and α-glycosidase. Also, studied phenolic compounds may be useful in the prevention or treatment of diabetic complications.

Prospection of Enzyme Modulators in Aqueous and Ethanolic Extracts of Lippia sidoides Leaves: Genotoxicity, Digestion, Inflammation, and Hemostasis.

The aqueous and ethanolic extracts of Lippia sidoides Cham. were chemically characterized and tested for their action on enzymes involved in processes such as inflammation, blood coagulation, and digestion. Both extracts potentiated the activity of phospholipases A2 present in the venom of Bothrops atrox in 12 % and completely inhibited the hemolysis induced by B. jararacussu and B. moojeni venoms in the proportions between 1 : 0.5 and 1 : 5 (venom/extracts (w/w)). They inhibited the thrombolysis induced by B. moojeni (10 to 25 %), potentiated the thrombolysis induced by the Lachesis muta muta venom (30 to 80 %), prolonged the coagulation time induced by B. moojeni and L. muta muta venoms, and presented antigenotoxic action. Both extracts reduced the activity of α-glycosidases, the aqueous extract inhibited lipases, and the ethanolic extract inhibited α-amylases. The results demonstrate the modulatory action of the extracts on proteases, phospholipases, and digestive enzymes. In addition, the rich phenolic composition of these extracts highlights their potential for nutraceutical use.

Anti-diabetic effect and mechanism of Kursi Wufarikun Ziyabit in L6 rat skeletal muscle cells.

Kursi Wufarikun Ziyabit (KWZ) is a traditional prescription that used in folk tea drinking for its health care effect in treatment of type 2 diabetes mellitus (T2DM) in central Asia. However, the underlying mechanism of KWZ in T2DM has not been investigated extensively. This study designed to observe the effect of KWZ on glucose consumption and assess the molecular mechanism on associated proteins in insulin signaling and ER stress pathway in L6 rat skeletal muscle cells. The results showed that, KWZ exhibited proteins of PTP-1B and α-glycosidase inhibitory activity in vitro. No cytotoxicity of KWZ was found on L6 cell line. The best effect of glucose consumption of cells was shown at 6.25 µg/mL after KWZ treatment for 12 h. Expression of PTP-1B protein was inhibited by KWZ in L6 moytubes. PI3K-dependent Akt phosphorylation was found to be activated by KWZ. Moreover, the insulin-mediated induction of IRS-1 and GSK-3 were also activated by KWZ. Western blot results indicated that KWZ significantly improved the levels of ER stress proteins, which reduced the expression of GRP78, enhanced the expression of the PERK, eIF2α and XBP1s. The activation of PERK/eIF2α was likely consequence of GRP78 inhibition, and this might be beneficial for improving the stability of ER and alleviating insulin resistance. These results suggest that KWZ might be serving as the potential drug for the prevention and treatment of T2DM.

Polyoxygenated Cyclohexenoids with Promising α-Glycosidase Inhibitory Activity Produced by Phomopsis sp. YE3250, an Endophytic Fungus Derived from Paeonia delavayi.

Seven new polyoxygenated cyclohexenoids, namely, phomopoxides A-G (1-7), were isolated from the fermentation broth extract of an endophytic fungal strain Phomopsis sp. YE3250 from the medicinal plant Paeonia delavayi Franch. The structures of these compounds were established by spectroscopic interpretation. The absolute configurations of compounds 1 and 4 were confirmed by X-ray crystallographic analysis and chemical derivative approach. All isolated compounds showed weak cytotoxic activities toward three human tumor cell lines (Hela, MCF-7, and NCI-H460) and weak antifungal activities against five pathogenic fungi (Candida albicans, Aspergillus niger, Pyricularia oryzae, Fusarium avenaceum, and Hormodendrum compactum). In addition, compounds 1-7 showed a promising α-glycosidase inhibitory activity with IC50 values of 1.47, 1.55, 1.83, 2.76, 2.88, 3.16, and 2.94 mM, respectively, as compared with a positive control of acarbose (IC50 = 1.22 mM).

Improving the antiprotozoal effect of saponins in the rumen by combination with glycosidase inhibiting iminosugars or by modification of their chemical structure.

The antiprotozoal effect of saponins is transitory, as when saponins are deglycosylated to sapogenins by rumen microorganisms they become inactive. We hypothesised that the combination of saponins with glycosidase-inhibiting iminosugars might potentially increase the effectiveness of saponins over time by preventing their deglycosylation in the rumen. Alternatively, modifying the structure of the saponins by substituting the sugar moiety with other small polar residues might maintain their activity as the sugar substitute would not be enzymatically cleaved. The aim of this in vitro study was to evaluate the acute antiprotozoal effect and the stability of this effect over a 24 h incubation period using ivy saponins, a stevia extract rich in iminosugars, ivy saponins with stevia extract, and a chemically modified ivy saponin, hederagenin bis-succinate (HBS). The effects on fermentation parameters and rumen bacterial communities were also studied. Ivy saponins with stevia and HBS had a greater antiprotozoal effect than ivy saponins, and this effect was maintained after 24 h of incubation (P<0.001). The combination of ivy and stevia extracts was more effective in shifting the fermentation pattern towards higher propionate (+39%) and lower butyrate (-32%) and lower ammonia concentration (-64%) than the extracts incubated separately. HBS caused a decrease in butyrate (-45%) and an increase in propionate (+43%) molar proportions. However, the decrease in ammonia concentration (-42%) observed in the presence of HBS was less than that caused by ivy saponins, either alone or with stevia. Whereas HBS and stevia impacted on bacterial population in terms of community structure, only HBS had an effect in terms of biodiversity (P<0.05). It was concluded that ivy saponins with stevia and the modified saponin HBS had a strong antiprotozoal effect, although they differed in their effects on fermentation parameters and bacteria communities. Ivy saponins combined with an iminosugar-rich stevia extract and/or HBS should be evaluated to determine their antiprotozoal effect in vivo.

Anti-hyperglycaemic activity of Moringa oleifera is partly mediated by carbohydrase inhibition and glucose-fibre binding.

Moringa oleifera has potential anti-hyperglycaemic effects that have been reported earlier by different scientific groups using animal models of diabetes. We aimed to explore the possible mechanisms of action of M. oleifera extract through different methods. Primarily, we measured fasting blood glucose and performed glucose tolerance test, in Type 2 diabetic rats. Further, we studied the effects of extracts on pancreatic insulin concentration. Extracts' effect on carbohydrate breakdown was assayed using α-amylase inhibition assays and assay of six different segments of gastrointestinal (GI) tracts. An in situ intestinal perfusion model and a glucose fibre assay were performed to see the potentiality of M. oleifera on glucose absorption. M. oleifera showed no significant change in insulin secretion in vivo Additionally, substantial effect of the extract was seen on retarded glucose absorption and in the in situ perfusion study of rat intestinal model. α-amylase action was inhibited by the extract, yet again, these findings were further confirmed via the Six Segment assay, where sucrose digestion was found to be inhibited throughout the length of the GI tract. A combined in vitro, in vivo and in situ tests justified the potential of anti-hyperglycaemic activity of M. oleifera and its tissue level mechanism is also justified.

Enzymatic assays and molecular modeling studies of Schisandra chinensis lignans and phenolics from fruit and leaf extracts.

Considerable interest has been shown in natural sources and their compounds in developing new therapeutically agents for different diseases. In this framework, investigations performed on this topic play a central role for human health and drug development process. Schisandra chinensis (Turcz.) Baill is a medicinal and edible plant showing highly advantageous bioactivity and nutritional value. The main bioactive compounds from its fruits are lignans, derivatives of dibenzocyclooctadiene whereas concerning its leaves, phenolic acids, and flavonoids are dominant. The purpose of this study was to investigate the enzyme inhibitory potential on selected carbohydrate hydrolases, cholinesterases, and tyrosinase of extracts from fruits and leaves of Schisandra in relation with their main bioactive compounds. Furthermore, the interactions between dominant compounds (schisandrol A, schisandrol B, schisandrin B, and cinnamic acid) from extracts and selected enzymes were investigated by molecular modeling and molecular dynamic studies in order to explain at a molecular level our findings.

Comparison of the Chemical Profiles and Antioxidant and Antidiabetic Activities of Extracts from Two Ganoderma Species (Agaricomycetes).

The objective of this study was to compare the mycochemical profiles, antioxidant activities, and antidiabetic effects of 2 species of genus Ganoderma, the red lingzhi (G. lucidum) and purple lingzhi (G. sinense) mushrooms. In Chinese medicinal practice, hot water and ethanol are used as solvents to extract samples. In this study, a total of 4 extracts (ethanol and hot water extracts from G. lucidum and G. sinense) were prepared for further assays. Hot water extracts presented much higher values for total phenolic content and ferric-reducing antioxidant power than the ethanol extracts. Ethanol (70%) extract of G. lucidum had the strongest α-glycosidase inhibitory capacity, but the lingzhi polysaccharides showed no inhibitory effect. It also had the largest amount of total ganoderic acids. The results indicated that ethanol extracts from both G. lucidum and G. sinense showed better antidiabetic effects than the hot water extracts. Ganoderic acids, rather than polysaccharides, may contribute the antidiabetic effects of both the Ganoderma species.

Hibiscus sabdariffa (Roselle) Extracts and Wine: Phytochemical Profile, Physicochemical Properties, and Carbohydrase Inhibition.

Three varieties of Hibiscus sabdariffa were analyzed for their phytochemical content and inhibitory potential on carbohydrate-digesting enzymes as a basis for selecting a variety for wine production. The dark red variety was chosen as it was highest in phenolic content and an aqueous extract partially inhibited α-glucosidase (maltase), with delphinidin 3-O-sambubioside, cyanidin 3-O-sambubioside, and 3-O-caffeoylquinic acid accounting for 65% of this activity. None of the varieties significantly inhibited α-amylase. Regarding Hibiscus sabdariffa wine, the effect of fermentation temperature (20 and 30 °C) on the physicochemical, phytochemical, and aroma composition was monitored over 40 days. The main change in phytochemical composition observed was the hydrolysis of 3-O-caffeolquinic acid and the concomitant increase of caffeic acid irrespective of fermentation temperature. Wine fermented at 20 °C was slightly more active for α-glucosidase inhibition with more fruity aromas (ethyl octanoate), but there were more flowery notes (2-phenylethanol) at 30 °C.

Quaternary Indolizidine and Indolizidone Iminosugars as Potential Immunostimulating and Glycosidase Inhibitory Agents: Synthesis, Conformational Analysis, Biological Activity, and Molecular Docking Study.

New quaternary indolizidine iminosugars, with hydroxymethyl group at the ring junction, namely, C-8a-hydroxymethyl-1-deoxycastanospermine congeners 1a, 2a, 3a and their 3-oxo analogs 1b, 2b, and 3b were synthesized by using intramolecular reductive aminocyclization/lactamization of d-mannose/D-glucose derived C5-γ-azido esters as a key step wherein both the rings of the indolizidine skeleton were built up in one pot following the cascade reaction pathway. The conformations ((5)C8 or (8)C5) of 1-3 were assigned on the basis of the (1)H NMR studies. All compounds were found to be potent inhibitors of various glycosidase enzymes with Ki and IC50 values in the micromolar/nanomolar concentration range and further substantiated by molecular docking studies. The effect of synthesized iminosugars 1-3 on the cytokine secretion of IL-4, IL-6, and IFN-γ was evaluated. All compounds were found to be TH1 bias increasing the TH1/TH2 cytokines ratio (IL-6 and IL-4) indicating their potency as immunostimulating agents. Our study suggests that immunomodulatory activity of indolizidine iminosugars can be tuned by minor structural/stereochemical alterations.

Synthesis of 2-carboxymethyl polyhydroxyazepanes and their evaluation as glycosidase inhibitors.

A series of diastereomeric tetrahydroxylated azepanes featuring a carboxymethyl group at the pseudo-anomeric position have been synthesized from a common unsaturated intermediate. Syn- and anti-dihydroxylation reactions were achieved to yield the target compounds after efficient one-step deprotection of carbamate, ester and acetonide groups simultaneously. Screening of these polyhydroxylated azepanes toward a range of commercially available glycosidases was performed and one of the stereoisomers showed potent and selective inhibition toward ß-galactosidase (IC50=21 µM).