Kinetic investigation of a new inhibitor for human salivary α-amylase

Multispectroscopy analysis of polystyrene nanoplastic interaction with diastase α-amylase

The digestive enzyme of plant are generally α-amylase. They functions enzyme that breakdown starch into maltose and sugars. This happens in the endosperm of the seed. Due to pollutants, this process get happened one of emergent xenobiotics are micro and nano plastics. This study involves the interaction 100 nm size of polystyrene nano plastic (PSNPs) on α-amylase. The hyperchromism of α-amylase - PSNPs conjugate's revealed that ground-state complex in a microenvironment. Fluorescence quenching happened when the concentration of PSNPs was increased. The Stern Volmer plot revealed binding constant (K_a) was 1.904 × 1019 M^-1. S^-1 while the quenching constant (K_q) was 1.036 × 1011 M^-1, the blue shift of the peak showed static quenching. The binding constant was K_A = 4.2 × 1012, the number of binding site on PSNPs for α-amylase was n = 1.12. The synchronous result showed a gradual reduction in the intensity of Trp residues because when the α-amylase interacts with PSNPs short-range π-π interaction happens around the Trp163 residues. The enzyme activity of α-amylase by 44 % and its IC₅₀ value was found to be 100 µg/mL. The enzyme kinetics (Vmax) analysis showed the type of inhibition with and without PSNPs Vmax 769 and Vmax 303 µg/mL/min, uncompetitive inhibition respectively. The effect of PSNPs on the enzymatic activity of α-amylase showed structural alterations of the protein. Therefore the in vitro and in silico studies were shown evidence of interaction between α-amylase and PSNPs leads to conformational structural changes in α-amylase.

Isolation of Polysaccharides from Trichoderma harzianum with Antioxidant, Anticancer, and Enzyme Inhibition Properties

In this work, a total of six polysaccharides were isolated from culture filtrate (EPS1, EPS2) and mycelia (IPS1-IPS4) of Trichoderma harzianum. The HPLC analysis results showed that EPS1, EPS2, IPS1, and IPS2 were composed of mannose, ribose, glucose, galactose, and arabinose. The FT-IR, 1H, and 13C NMR chemical shifts confirmed that the signals in EPS1 mainly consist of (1→4)-linked α-d-glucopyranose. EPS1 and IPS1 showed a smooth and clean surface, while EPS2, IPS2, and IPS3 exhibited a microporous structure. Among polysaccharides, EPS1 displayed higher ABTS+ (47.09 ± 2.25% and DPPH (26.44 ± 0.12%) scavenging activities, as well as higher α-amylase (69.30 ± 1.28%) and α-glucosidase (68.22 ± 0.64%) inhibition activity than the other polysaccharides. EPS1 exhibited high cytotoxicity to MDA-MB293 cells, with an IC50 of 0.437 mg/mL, and this was also confirmed by cell staining and FACS assays. These results report the physicochemical and bioactive properties of polysaccharides from T. harzianum.

Metabolite Profiling of Methanolic Extract of Gardenia jaminoides by LC-MS/MS and GC-MS and Its Anti-Diabetic, and Anti-Oxidant Activities

In this study, the methanolic extract from seeds of Gardenia jasminoides exhibited strong antioxidant and enzyme inhibition activities with less toxicity to NIH3T3 and HepG2 cells at the concentration of 100 µg/mL. The antioxidant activities (DPPH and ABTS), α-amylase, and α-glucosidase inhibition activities were found higher in methanolic extract (MeOH-E) than H₂O extract. Besides, 9.82 ± 0.62 µg and 6.42 ± 0.26 µg of MeOH-E were equivalent to 1 µg ascorbic acid for ABTS and DPPH scavenging, respectively while 9.02 ± 0.25 µg and 6.52 ± 0.15 µg of MeOH-E were equivalent to 1 µg of acarbose for inhibition of α-amylase and α-glucosidase respectively. Moreover, the cell assay revealed that the addition of MeOH-E (12.5 µg/mL) increased about 37% of glucose uptake in insulin resistant (IR) HepG2 as compared to untreated IR HepG2 cells. The LC- MS/MS and GC-MS analysis of MeOH-E revealed a total of 54 compounds including terpenoids, glycosides, fatty acid, phenolic acid derivatives. Among the identified compounds, chlorogenic acid and jasminoside A were found promising for anti-diabetic activity revealed by molecular docking study and these molecules are deserving further purification and molecular analysis.

Provenance effect on bioactive phytochemicals and nutritional and health benefits of the desert date Balanites aegyptiaca

Balanites aegyptiaca L. is a multipurpose tree distributed in Africa and Middle East. Several parts of B. aegyptiaca have been suggested to have medicinal uses. So far the effect of ecological origin on the nutritional values and biological activities of B. aegyptiaca genotypes is rarely investigated. Further, metabolic profiling and assessment of the functional food value of B. aegyptiaca leaves are far from complete. In this study, biological activities and profiling of primary and secondary metabolites were investigated in the leaves of five B. aegyptiaca provenances collected from Egypt, Sudan, Saudi Arabia, and Yemen. Interestingly, all provenances showed notable antidiabetic, antioxidant, antiprotozoal, antibacterial, antifungal, and anticancer activities. Hierarchical clustering analysis revealed significant variability in the concentrations of individual sugars, organic acids, amino acids, fatty acids, vitamins, phenolics, and minerals among the provenances and these variations were provenance dependent. Medina provenance showed the heights diphenylpicrylhydrazyl (DPPH) scavenging and antifungal activities and was the most powerful against embryonic kidney adenocarcinoma and urinary bladder carcinoma cells. The highest inhibition against Escherichia coli and colon carcinoma cells was observed by Sudan and Cairo provenances. El-Kharga and Yemen provenances showed the greatest activity against Trypanosoma cruzi and hepatocellular and urinary bladder carcinoma. Therefore, leaves of B. aegyptiaca possess good nutritive and biological capacities and might have potential applications in the food and medical industries. However, the strength of such activities is significantly affected by the provenance. PRACTICAL APPLICATIONS: According to the national Research Council (NRC) of United States, Balanites aegyptiaca L. is recognized among the 24 priority lost crops of Africa. B. aegyptiaca leaves contain considerable amounts of primary metabolites (e.g., sugars, EAAs, USFAs) and secondary (e.g., phenolic acids and flavonoids) metabolites, vitamins, and macro and microelements. The obvious existence of these nutritionally and medicinally related compounds supports the functional food value of B. aegyptiaca leaves. Moreover, the present results revealed that B. aegyptiaca is not only a foliage dietary plant, but also could be considered as a valuable source for neutraceuticals, which support its pharmacological value. So far, this is the first report to explore, in detail, the functional food value of B. aegyptiaca leaves by presenting a clear image about its metabolic profiling and biological activities, and how the provenance factor could affect these values.

Inhibition of glycosidase by ursolic acid: in vitro, in vivo and in silico study

BACKGROUND

Controlling the blood glucose level is an effective method to reduce type 2 diabetes and prevent diabetes-related complications. Ursolic acid is a plant extract that can reduce postprandial hyperglycemia effectively. This study aimed to explore the inhibitory effect and interaction mechanism of ursolic acid against α-amylase and α-glucosidase.

RESULTS

In this study, the effect of ursolic acid on glycosidase was studied in vitro, in vivo, and in silico. The half-maximal inhibitory concentration (IC50 ) of ursolic acid on α-amylase and α-glucosidase was 0.482 ± 0.12 mg mL-1 and 0.213 ± 0.042 mg mL-1 , respectively. The results of enzymatic kinetics showed that ursolic acid inhibited α-amylase and α-glucosidase activity in a non-competitive manner. The fluorescence spectrum showed that the combination of ursolic acid and glycosidase caused the intrinsic fluorescence quenching of glycosidase. The observation of starch granules revealed that the activity of α-amylase was inhibited and the hydrolysis of starch granules was prevented in the presence of ursolic acid. Molecular docking results showed that ursolic acid bound to the inactive site of α-amylase and α-glucosidase through the formation of ursolic acid-glucosidase complex. Ursolic acid interacted with α-amylase and α-glucosidase mainly through hydrogen bonding. The postprandial hypoglycemic effect of ursolic acid in C57BL/6J mice showed that the high concentration of ursolic acid could quickly reduce postprandial blood glucose level.

CONCLUSION

Ursolic acid can be considered as a natural ingredient in functional foods to control postprandial blood glucose levels and prevent diabetes by delaying the digestion of starch in foods. © 2019 Society of Chemical Industry.

Enzyme-assisted modification of flavonoids from Matricaria chamomilla: antioxidant activity and inhibitory effect on digestive enzymes

Matricaria chamomilla L. contains antioxidant flavonoids that can have their bioactivity enhanced by enzymatic hydrolysis of specific glycosyl groups. This study implements an untargeted metabolomics approach based on ultra-performance liquid chromatography coupled with electrospray ionisation quadrupole time-of-flight mass spectrometry technique operating in MS^E mode (UPLC-QTOF-MS^E) and spectrophotometric analysis of chamomile aqueous infusions, before and after hydrolysis by hesperidinase and β-galactosidase. Several phenolic compounds were altered in the enzymatically treated infusion, with the majority being flavonoid derivatives of apigenin, esculetin, and quercetin. Although enzymatically modifying the infusion only led to a small increase in antioxidant activity (DPPH• method), its inhibitory effect on pancreatic lipase was of particular interest. The enzymatically treated infusion exhibited a greater inhibitory effect (EC₅₀ of 35.6 µM) than unmodified infusion and kinetic analysis suggested mixed inhibition of pancreatic lipase. These results are of great relevance due to the potential of enzymatically treated functional foods in human health.

Revealing the Amylase Interactome in Whole Saliva Using Proteomic Approaches

Understanding proteins present in saliva and their function when isolated is not enough to describe their real role in the mouth. Due to protein-protein interactions, structural changes may occur in macromolecules leading to functional modulation or modification. Besides amylase's function in carbohydrate breakdown, amylase can delay proteolytic degradation of protein partners (e.g., histatin 1) when complexed. Due to its biochemical characteristics and high abundance in saliva, amylase probably interacts with several proteins acting as a biological carrier. This study focused on identifying interactions between amylase and other proteins found in whole saliva (WS) using proteomic approaches. Affinity chromatography was used, followed by gel electrophoresis methods, sodium dodecyl sulfate and native, tryptic in-solution and in-gel digestion, and mass spectrometry. We identified 66 proteins that interact with amylase in WS. Characterization of the identified proteins suggests that acidic (pI < 6.8) and low molecular weight (MW < 56 kDa) proteins have preference during amylase complex formation. Most of the identified proteins present biological functions related to host protection. A new protein-amylase network was constructed using the STRING database. Further studies are necessary to investigate individualities of the identified amylase interactors. These observations open avenues for more comprehensive studies on not yet fully characterized biological function of amylase.

Salicylic acid elicitation during cultivation of the peppermint plant improves anti-diabetic effects of its infusions

Peppermint (Mentha piperita) infusions represent an important source of bioactive compounds with health benefits, which can be enhanced by applying salicylic acid (SA) during plant cultivation.

Metabolite profile, antioxidant capacity, and inhibition of digestive enzymes in infusions of peppermint (Mentha piperita) grown under drought stress

Peppermint (Mentha piperita) infusions represent an important source of antioxidants, which can be enhanced by inducing abiotic stress in plants. The aim of this study was to evaluate the effect of drought stress on peppermint cultivation as well as the metabolite profile, antioxidant capacity, and inhibition of digestive enzymes of resulting infusions. At 45 days after planting, irrigation was suppressed until 85 (control), 65, 35, 24, and 12% soil moisture (SM) was reached. The results showed that 35, 24, and 12% SM decreased fresh (20%) and dry (5%) weight. The 35 and 24% SM treatments significantly increased total phenolic and flavonoid contents as well as antioxidant capacity. Coumaric acid, quercetin, luteolin, and naringenin were detected only in some drought treatments; however, in these infusions, fewer amino acids and unsaturated fatty acids were identified. The 24 and 12% SM treatments slightly improved inhibition of pancreatic lipase and α-amylase activity. Therefore, induction of moderate water stress in peppermint is recommended to enhance its biological properties.

Effects of Oolong tea polyphenols, EGCG, and EGCG3″Me on pancreatic α-amylase activity in vitro

In order to investigate the inhibitory effects and possible mechanisms of Oolong tea polyphenols, (-)-epigallocatechin gallate (EGCG) and (-)-epigallocatechin 3-O-(3-O-methyl) gallate (EGCG3″Me) on pancreatic α-amylase, the inhibition, enzyme kinetics, ultraviolet (UV) absorption spectrum and fluorescence spectrum of α-amylase were investigated. The results showed that Oolong tea polyphenols, EGCG, and EGCG3″Me all exhibited inhibitory effects against α-amylase, and their half inhibitory concentration (IC50) values were 0.375, 0.350, and 0.572 mg/mL, respectively. The results of Lineweaver-Burk double reciprocal plot indicated that the inhibitory types of Oolong tea polyphenols and EGCG were competitive, whereas EGCG3″Me was in a noncompetitive pattern. Oolong tea polyphenols, EGCG, and EGCG3″Me all induced red-shift of UV absorbance and quenching of fluorescence of α-amylase, suggesting possible changes in the conformation of α-amylase. The differences of inhibitory effects and inhibition types for EGCG and EGCG3″Me might be due to their structural difference (the hydroxyl group at C-3 in D ring of EGCG substituted by methoxy group, forming EGCG3″Me).

In vitro inhibitory effects of cyandin-3-rutinoside on pancreatic α-amylase and its combined effect with acarbose

The inhibitory activity on pancreatic α-amylase by cyanidin-3-rutinoside was examined in vitro. The IC₅₀ value of cyanidin-3-rutinoside against pancreatic α-amylase was 24.4 ± 0.1 μM. The kinetic analysis revealed that pancreatic α-amylase was inhibited by cyanidin-3-rutinoside in a non-competitive manner. The additive inhibition of a combination of cyanidin-3-rutinoside with acarbose against pancreatic α-amylase was also found. These results provide the first evidence for the effect of cyanidin-3-rutinoside in a retarded absorption of carbohydrates by inhibition of pancreatic α-amylase which may be useful as a potential inhibitor for prevention and treatment of diabetes mellitus.

Evaluation of alpha-glucosidase, alpha-amylase and protein glycation inhibitory activities of edible plants

The present study was to investigate in vitro alpha-glucosidase, pancreatic alpha-amylase and protein glycation inhibitory activities of nine edible plants. The results indicated that total phenolics, flavonoids, and condensed tannins of nine edible plants showed marked variations, ranging from 12.2 to 80.1 mg gallic acid equivalent/g extract, 2.34 to 13.65 mg quercetin equivalent/g extract, and 97.2 to 460.1 mg catechin equivalent/g extract, respectively. Our findings showed that grape seed, Cat's whiskers and Sweetleaf extract were the most effective pancreatic alpha-amylase, intestinal maltase, and sucrase inhibitor with IC(50) values of 0.29 +/- 0.01 mg/ml, 0.97 +/- 0.10 mg/ml and 0.86 +/- 0.01 mg/ml, respectively. All extracts (1 mg/ml) markedly inhibited the glycation of bovine serum albumin in fructose-mediated non-enzyme glycation by 50-30% at week 1. It was found that Pennywort maintained the high percentage inhibition among those of the extracts during the 4 weeks of experiment. These edible plants may be used for controlling blood glucose level and prevention of the development of type 2 diabetes.

alpha-Glucosidase inhibitory activity of cyanidin-3-galactoside and synergistic effect with acarbose

Cyanidin-3-galactoside, a natural anthocyanin, was investigated for its alpha-glucosidase inhibitory activity. The IC(50) value of cyanidin-3-galactoside was 0.50 +/- 0.05 mM against intestinal sucrase. A low dose of cyanidin-3-galactoside showed a synergistic inhibition on intestinal alpha-glucosidase (maltase and sucrase) when combined with acarbose. A kinetic analysis showed that cyanidin-3-galactoside gave a mixed type inhibition against intestinal sucrase. The results indicated that cyanidin-3-galactoside was an alpha-glucosidase inhibitor and could be used in combination with acarbose for treatment of diabetes.

Aleppo tannin: structural analysis and salivary amylase inhibition

The effectiveness and specificity of a tannin inhibition on human salivary amylase (HSA) catalyzed hydrolysis was studied using 2-chloro-4-nitrophenyl 4-O-beta-D-galactopyranosyl-alpha-maltoside (GalG(2)-CNP) and amylose substrates. Aleppo tannin was isolated from the gall nut of Aleppo oak. This tannin is a gallotannin, in which glucose is esterified with gallic acids. This is the first kinetic report, which details the inhibitory effects of this compound on HSA. A mixed non-competitive type inhibition has been observed on both substrates. The extent of inhibition is markedly dependent on the substrate-type. Kinetic constants were calculated from Lineweaver-Burk secondary plots for GalG(2)-CNP (K(EI) 0.82 microg mL(-1), K(ESI) 3.3 microg mL(-1)). This indicates a 1:1 binding ratio of inhibitor-enzyme and/or inhibitor-enzyme-substrate complex. When amylose was the substrate the binding ratio of inhibitor to enzyme-substrate complex was found to be 2:1, with the binding constants of K(EI) 17.4 microg mL(-1), K(ESI) 14.9 microg mL(-1), K(ESI(2)) 9.6 microg mL(-1). Presumably, the tannin inhibitor can bind not only to HSA, but to the amylose substrate, as well. Kinetic data suggest that Aleppo tannin is a more efficient amylase inhibitor than the recently studied other tannin with quinic acid core (GalG(2)-CNP: K(EI) 9.0 microg mL(-1), K(ESI) 47.9 microg mL(-1)).

De novo design of alpha-amylase inhibitor: a small linear mimetic of macromolecular proteinaceous ligands

We report a low molecular weight inhibitor of alpha-amylases based on a linear peptidic scaffold designed de novo through the use of combinatorial chemistry. The inhibitory motif denoted PAMI (peptide amylase inhibitor) was selected by using L-peptide libraries and was fine-tuned by the introduction of unnatural modifications. PAMI specifically inhibits glycoside hydrolases of family 13. Its interaction with porcine pancreatic alpha-amylase was characterized by inhibition kinetics, fluorescence competition assays with natural alpha-amylase inhibitors, and isothermal titration calorimetry. We demonstrate that the critical amino acid residues in PAMI are shared with those in the macromolecular proteinaceous inhibitors that, however, bind to alpha-amylases through a spatially scattered set of intermolecular contacts. Thus, natural molecular evolution as well as combinatorial evolution selected the same alpha-amylase binding determinants for completely different spatial frameworks.