Inhibition Of Porcine Pancreatic Α-amylase Research Articles

Molecular interactions between polyphenols and porcine α-amylase: An inhibition study on starch granules probed by kinetic, spectroscopic, calorimetric and in silico techniques

Inhibition of α-amylase activity to limit the rise in postprandial glucose is one of the most notable effects of dietary plant (poly)phenols. The rate and extent of inhibition depend on many factors, including the structure of (poly)phenols and the substrate used for the inhibition study. While soluble/gelatinised starch is widely used as a substrate for studying inhibition mechanisms, the formation of (poly)phenol-amylose complexes can reduce susceptibility to α-amylase catalysis. Therefore, the extent of inhibition may not truly represent the inhibition of α-amylase by (poly)phenols. To elucidate mechanisms of interactions between a (poly)phenol and the enzyme, this study compared the inhibition of porcine pancreatic α-amylase (PPA) by three differently structured (poly)phenols: p-coumaric acid, quercetin, and cyanidin-3-glucoside, using solid maize starch as a substrate, that limits the formation of starch-(poly)phenol complexes due to the compact structure of starch granules. The inhibition kinetics were investigated and supported by complementary techniques: in silico analysis (molecular docking and molecular dynamic simulation), fluorescence quenching, circular dichroism and differential scanning calorimetry. Quercetin exhibited the strongest inhibition, followed by cyanidin-3-glucoside and p-coumaric acid, with apparent modes of mixed, mixed, and competitive inhibition, respectively. The specific binding of (poly)phenols to PPA involved hydrogen bonds and hydrophobic interactions, as indicated by in-silico studies. Multi-spectroscopic analysis of the PPA structure unveiled changes or peak shifts due to ligand binding, resulting in structural alterations. These findings were consistent with the kinetic data, emphasising the importance of the structural aspects of each individual (poly)phenol in relation to their interaction with PPA. The study articulated the in-depth mechanism of molecular interaction mechanism between (poly)phenols and enzymes and provided evidence that the structural alterations of enzymes are not a strong indicator of inhibition efficacy, but rather inhibition is due to the binding of (poly)phenols to the enzyme structure limiting the catalysis.

Green-based processes applied for valorization of peanut by-product: In vitro evaluation of antioxidant and enzymatic inhibition capacities

Peanut (Arachis hypogea L.) industrial processing generates underused by-products, which are mostly discharged. In this work, extracts from peanut by-product were obtained by Supercritical Fluid Extraction (SFE), Pressurized Liquid Extraction (PLE) and Subcritical Water Extraction (SWE), and compared to Soxhlet (SOX). Yield values varied from 12.94% to 37.65% for SOX-water and SWE, respectively. The quality of the extracts was evaluated by total phenolic content (TPC), antioxidant and enzymatic inhibition potentials, and fatty acids profile. Best TPC performance and high antioxidant capacity were obtained from samples using ethanol/water by PLE and Soxhlet. High inhibition of human salivary α-amylase was achieved by PLE and Soxhlet samples recovered with ethanol/water mixture. The inhibition of porcine pancreatic α-amylase was higher from samples by SFE and Soxhlet with ethanol. High-pressure methods are appealing alternatives for the recovery of bioactive extracts from peanut by-products, with functional properties and potential inhibitor of digestive enzymes.

Mechanistic study on inhibition of porcine pancreatic α-amylase using the flavonoids from dandelion

This study was designed to investigate quantitatively the inhibition and molecular mechanism of pancreatic α-amylase exhibited by flavonoids from dandelion to reveal its potential use in relieving postprandial hyperglycemia. The results show that the flavonoids reversibly inhibited the α-amylase in a non-competitive manner with Michaelis-Menten constant (Km) and half-inhibitory concentration (IC50) value of 10.51 and 0.0067 mg/mL, respectively. The flavonoids present a strong ability to quench the intrinsic fluorescence of α-amylase through static quenching by forming a complex. The values of the binding site (n) at different temperatures were found to be approximately the unity, indicating the presence of a single class of molecular binding of the dandelion flavonoids on α-amylase. The positive values of enthalpy and entropy change reveal that the binding was predominately driven by hydrophobic interactions. This study suggests a benefit of incorporating the dandelion flavonoids in making functional foods in managing the diet of the diabetes.

Number of galloyl moieties and molecular flexibility are both important in alpha-amylase inhibition by galloyl-based polyphenols.

The inhibition of porcine pancreatic α-amylase (PPA) by 9 galloyl-based polyphenols was evaluated via initial digestion velocity, IC50, inhibition kinetics, fluorescence quenching and molecular docking studies. The results show that the polyphenols with free galloyl moieties (GMs) exhibited a much higher inhibition effect than that with bound GMs. The inhibition was competitive mode and increased with an increase in the number of free GMs. Interestingly, all the constants that indicate the binding affinity of polyphenols to PPA, including the reciprocal of the competitive inhibition constant (1/Kic), fluorescence quenching constant (KFQ) and binding energy (Eb), increased with an increase in the number of free GMs. Besides, the respective order of 1/Kic, KFQ and Eb for the galloyl-based polyphenols was contrary to that of IC50, indicating that the polyphenol-PPA binding interactions resulted in enzyme inhibition. In addition, the binding interactions were suggested to result from the hydrogen bonding and π-π conjugation forces between the free GMs and amino acid residues at the active sites of PPA, whereas the chemical linkage of the GMs with additional polyphenol groups limited these interactions. Furthermore, the hypoglycemic effects of two polyphenols with 5 free GMs indicate that GMs may be considered a functional fragment involved in the alleviation of the symptoms of type II diabetes through α-amylase inhibition.

Effect of Extraction Solvents on Antioxidant and α-amylase Inhibition Activities of Spiced Green Chili Paste: An In Vitro Study

Chili pepper ( Capsicum frutescens L.) is widely produced and consumed as raw or processed products. Spiced green chili paste, locally known as Datta, is hot spicy paste consumed in South Ethiopia. Under this study, total phenolic contents (TPC), total flavonoid contents (TFC), in vitro antioxidant, and α-amylase inhibition activities of different extracts of green Datta paste were investigated. The TPC and TFC of the extracts were determined by the Folin ciocalteu and aluminum chloride methods, respectively. The antioxidant activities were determined by 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging, ferric reducing power, and total antioxidant using phosphomolybdenum methods. In vitro porcine pancreatic α-amylase inhibition activity was evaluated using the dinitrosalicylic acid (DNSA) assay. The acetone extract contained the highest TPC (24.92 ± 2.88 milligram gallic acid equivalent/ gram of dried extract) and TFC (28.05 ± 8.36 milligram catechin equivalent/gram of dried extract). Similarly this extract showed stronger antioxidant capacity, 6.34 ± 1.21 milligram of ascorbic acid equivalent/gram of dried extract, 1.46 ± 0.22 milligram butylated hydroxytoluene equivalent/ gram of dried extract, and 46.99 ± 2.60 mg/mL as determined by ferric reducing power, total antioxidant activity, and DPPH scavenging (IC 50 ) activity, respectively. The same extract also exhibited the strongest α-amylase inhibition activity (IC 50 = 0.45 mg/mL). TPC and TFC were strongly correlated with DPPH (R 2 = 0.99, R 2 = 0.91), reducing power (R 2 = 0.86, R 2 = 0.97), and total antioxidant activity (R 2 = 0.79, R 2 = 0.97), respectively. The α-amylase inhibition activity was strongly correlated with TPC (R 2 = 0.90) but weakly correlated with TFC (R 2 = 0.18). Thus the result indicated promising perspectives for the development and usage of acetone extract of Ethiopian spiced green chili pepper with considerable levels of natural antioxidants which can be used as functional food for preventing oxidative stress mediated human disorders. Keywords: A ntioxidant, chili pastes Datta, α-amylase, Phenolic content. DOI : 10.7176/ALST/77-02 Publication date: January 31 st 2020

In Vitro Antidiabetic, Anti-Obesity and Antioxidant Analysis of Ocimum basilicum Aerial Biomass and in Silico Molecular Docking Simulations with Alpha-Amylase and Lipase Enzymes.

The present study explored phytochemicals, porcine pancreatic α-amylase (PPA) and lipase (PPL) inhibitory activities and antioxidant potential of polar and nonpolar extracts of the leaves and flowers of Ocimum basilicum and the in-silico mode of interaction between these enzymes and the major chemical constituents of the herb. The hexane extract (HE) and hydro-ethanolic extract (EE) obtained sequentially were used to estimate PPA and PPL inhibitory and antioxidant activities, total phenolic content (TPC) and total flavonoid content (TFC). Chemical constituents of the essential oils and HE were determined by GC-MS (Gas Chromatography-Mass Spectrometry). For PPA inhibition, IC50 (µg/mL) of the extracts were 0.27–0.37, which were close to 0.24 of acarbose, while for PPL inhibition, IC50 (µg/mL) of the extracts were 278.40–399.65, and that of Orlistat 145.72. The flowers EE was most potent antioxidant followed by leaves EE. The leaves EE had highest TPC and TFC followed of flowers EE. The essential oil of flowers had higher estragole (55%) than linalool (37%), while the essential oil of the leaves had higher linalool (42%) than estragole (38%). The HE of the flowers contained higher estragole (42%) than linalool (23%), while of the HE of the leaves too had higher estragole (65%) than linalool (18%). The in-silico molecular docking study showed linalool and estragole to have considerable PPA and PPL binding potential, which were further investigated through molecular dynamics simulations and binding free energy calculations. The PPA and PPL inhibitory activities of O. basilicum extracts and their notable antioxidant potential propose the herb as a multi-target complimentary medicine for diabetes, obesity and oxidative stress.

Phytochemical Profiling and Evaluation of Marrubium sivasense Aytaç, Akgül & Ekici for Antioxidant Activity and Inhibition Effects on α-Amylase, Lipoxygenase, Xanthine Oxidase and Tyrosinase Enzymes

Methanol extract of Marrubium. sivasense Aytaç, Akgül & Ekici was analyzed with LC-MS/MS technique. Forsythoside B, verbascoside and leucoseptoside were identified as main compounds. Antioxidant properties of the extract was determined by DPPH free radical scavenging activity (IC50 0.34 mg/mL), trolox equivalent antioxidant capacity (TEAC) (2.3 mM±0.04), xanthine-xanthine oxidase(XO) inhibitory effect (16.54 %). and. B-carotene bleaching (Inh. 43±1.26 %) assays. The extract demonstrated hypoglycemic activity (Inh. 49.67±1.09 %.) via inhibition of porcine pancreatic α-amylase, the antiinflammatory effect of the extract tested via inhibition of 5-LOX was found as Inh 18.71±0.74 %, however no antityrosinase activity was found.

In Vitro Investigation of Potential Anti-Diabetic Activity of the Corm Extract of Hypoxis Argentea Harv. Ex Baker.

The corms of Hypoxis argentea are widely used as a traditional remedy for diabetes mellitus in South Africa. In this study, we investigated the effects of non-toxic concentrations (12.5-100 μg mL-1) of the aqueous extract of H. argentea (HAA) corms on glucose uptake, pancreatic beta cell proliferation, and adipocyte differentiation. HAA stimulated glucose uptake in HepG2 cells up to 19.6 % and 17.0 % in L6 myotubes. Live-cell imaging microscopy revealed significant increases (p < 0.001) in total INS-1 cell numbers exposed to HAA, although no effect was observed on adipogenesis in 3T3-L1 pre-adipocytes. HAA produced weak to moderate inhibition of porcine pancreatic α-amylase, α-glucosidase, porcine pancreatic lipase, dipeptidyl peptidase IV (DPP IV) activities, as well as protein glycation. Our results suggest that the acclaimed anti-diabetic effects of H. argentea could be mediated by its promotion of glucose utilization and preservation of pancreatic beta cell populations while preventing fat accumulation in adipocytes.

Characterization and identification of novel antidiabetic and anti-obesity peptides from camel milk protein hydrolysates

In-vitro inhibitory properties of peptides released from camel milk proteins against dipeptidyl peptidase-IV (DPP-IV), porcine pancreatic α-amylase (PPA), and porcine pancreatic lipase (PPL) were studied. Results revealed that upon hydrolysis by different enzymes, camel milk proteins displayed dramatic increase in inhibition of DPP-IV and PPL, but slight improvement in PPA inhibition was noticed. Peptide sequencing revealed a total of 20 and 3 peptides for A9 and B9 hydrolysates respectively, obtained the score of 0.8 or more on peptide ranker and were categorized as potential DPP-IV inhibitory peptides. KDLWDDFKGL in A9 and MPSKPPLL in B9 were identified as most potent PPA inhibitory peptide. For PPL inhibition only 7 and 2 peptides qualified as PPL inhibitory peptides from hydrolysates A9 and B9, respectively. The present study report for the first time PPA and PPL inhibitory and only second for DPP-IV inhibitory potential of protein hydrolysates from camel milk.

Tea polyphenols enhance binding of porcine pancreatic α-amylase with starch granules but reduce catalytic activity

The effects of tea polyphenols on binding of porcine pancreatic α-amylase (PPA) with normal maize starch granules were studied through solution depletion assays, fluorescence spectroscopy and initial rate kinetics. Only polyphenols which have inhibitory activity against PPA increased the binding of PPA with starch. The results are consistent with a binding equilibrium between polyphenols, starch and PPA. The dissociation constant (Kd) for PPA binding was decreased by tea polyphenols, with the effects greater for theaflavins than catechins and for galloylated than non-galloylated polyphenols. Tea polyphenols were also shown to increase the binding rate of PPA to starch. In addition, there were positive linear correlations between 1/Kd and reciprocal of competitive inhibition constant (1/Kic) and between 1/Kd and fluorescence quenching constant (KFQ). Despite the greater amount of PPA on the granules, starch hydrolysis is reduced because the polyphenol inhibition of PPA persists after binding to starch.

Soluble polysaccharides reduce binding and inhibitory activity of tea polyphenols against porcine pancreatic α-amylase

The effects of three soluble polysaccharides on the inhibitory activity of tea polyphenols against porcine pancreatic α-amylase (PPA) were studied through PPA inhibition, half inhibition concentration (IC50), inhibition kinetics and fluorescence quenching. The results show that citrus pectin, wheat arabinoxylan and oat β-glucan could each increase the IC50 values and competitive inhibition constants (Kic), and decrease the fluorescence quenching constants (KFQ) of tea polyphenols interacting with PPA. The data show a competitive interaction equilibrium among polysaccharides, polyphenols and PPA. For individual polyphenols, there were negative linear correlations between both the values of 1/Kic and KFQ and that of IC50 with and without polysaccharides, indicating that the decreased inhibitory activity of polyphenols induced by the polysaccharides was caused by the reduced binding of polyphenols with PPA. Additionally, the slopes of the linear relationship between IC50 and Kic and that between KFQ and 1/Kic remained stable with and without polysaccharides, suggesting that these constants may be combined to characterize the effects of soluble polysaccharides on the PPA inhibition by polyphenols.

Dietary Flavonoids and Acarbose Synergistically Inhibit α-Glucosidase and Lower Postprandial Blood Glucose.

The inhibition of porcine pancreatic α-amylase and mammalian α-glucosidase by 16 individual flavonoids was determined. The IC50 values for baicalein, (+)-catechin, quercetin, and luteolin were 74.1 ± 5.6, 175.1 ± 9.1, 281.2 ± 19.2, and 339.4 ± 16.3 μM, respectively, against α-glucosidase. The IC50 values for apigenin and baicalein were 146.8 ± 7.1 and 446.4 ± 23.9 μM, respectively, against α-amylase. The combination of baicalein, quercetin, or luteolin with acarbose showed synergistic inhibition, and the combination of (+)-catechin with acarbose showed antagonistic inhibition of α-glucosidase. The combination of baicalein or apigenin with acarbose showed additive inhibition of α-amylase at lower concentrations and antagonistic inhibition at a higher concentration. Kinetic studies of α-glucosidase activity revealed that baicalein alone, acarbose alone, and the combination showed noncompetitive, competitive, and mixed-type inhibition, respectively. Molecular modeling revealed that baicalein had higher affinity to the noncompetitive binding site of maltase, glucoamylase, and isomaltase subunits of α-glucosidase, with glide scores of -7.64, -6.98, and -6.88, respectively. (+)-Catechin had higher affinity to the active sites of maltase and glucoamylase and to the noncompetitive site of isomaltase. After sucrose loading, baicalein dose-dependently reduced the postprandial blood glucose (PBG) level in mice. The combination of 80 mg/kg baicalein and 1 mg/kg acarbose synergistically lowered the level of PBG, and the hypoglycemic effect was comparable to 8 mg/kg acarbose. The results indicated that baicalein could be used as a supplemental drug or dietary supplement in dietary therapy for diabetes mellitus.

3 or 3′-Galloyl substitution plays an important role in association of catechins and theaflavins with porcine pancreatic α-amylase: The kinetics of inhibition of α-amylase by tea polyphenols

The inhibitory activities of three tea extracts (TEs) and individual phenolic compounds in TEs against porcine pancreatic α-amylase (PPA) were studied by measuring their half inhibitory (IC50) concentrations. The kinetics of inhibition by these extracts and compounds were investigated through Dixon, Cornish-Bowden, and Lineweaver–Burk plots. The results showed that green, oolong and black tea extracts, epigallocatechin gallate, theaflavin-3, 3′-digallate and tannic acid were competitive inhibitors of PPA, whereas epicatechin gallate, theaflavin-3′-gallate and theaflavin were mixed-type inhibitors with both competitive and uncompetitive inhibitory characteristics. Only catechins with a galloyl substituent at the 3-position showed measurable inhibition. The competitive inhibition constants (Kic) were lower for theaflavins than catechins, with the lowest value for theaflavin-3, 3′-digallate. The lower Kic than the uncompetitive inhibition constant for the mixed-type inhibitors suggests that they bind more tightly with free PPA than with the PPA–starch complex. A 3 and/or 3′-galloyl moiety in catechin and theaflavin structures was consistently found to increase inhibition of PPA through enhanced association with the enzyme active site.

Comparing morphological, chemical and anti-diabetic characteristics of Puerariae Lobatae Radix and Puerariae Thomsonii Radix

Ethnopharmacological relevancePuerariae Lobatae Radix (PLR) and Puerariae Thomsonii Radix (PTR) are traditional Chinese medicines used for the treatment of diabetes and cardiovascular diseases. These two herbs are used interchangeably in clinical practice, even though they possess significantly different chemical profiles. In the case of Pueraria species, the misidentification is related to the multiple Chinese common names in clinical practice and variable pharmaceutical Latin names in different versions of the Pharmacopoeia of the People׳s Republic of China. In addition, there is lack of evidence demonstrating how the differences in the chemical profile would impact on the pharmacological activity of the two herbs. Therefore, the aim of this study was to compare the microscopic, phytochemical profiles and anti-diabetic activity of PLR and PTR so that the two species can be differentiated. Materials and methodsThe microscopic characteristics of the PLR and PTR were observed and measured by an optical microscope. The major compounds were quantified by ultra-performance liquid chromatography (UPLC) and total flavonoid content (TFC) colorimetric assay. The free radical scavenging capacity was assessed by 2,2-diphenyl-2-picrylhydrazyl (DPPH) antioxidant assays. Anti-diabetic activity was determined by the inhibition of porcine pancreatic α-amylase and rat intestinal α-glucosidase activities. ResultsMicroscopic results illustrated that the size of xylem vessels (PLR: 0.1390±0.0184mm; PTR: 0.0471±0.0109mm), number of fibre per bundle (PLR: 32.6800±2.8780; PTR: 16.5900±0.9982) and the size of fibre (PLR: 0.0075±0.0003mm2; PTR: 0.0025±0.0002mm2) in PLR were significantly greater than that in PTR (p<0.01). PLR possessed a significantly lower total starch content (PLR: 0.5288±1.2559mg starch/g DM; PTR: 76.7954±2.9905mg starch/g DM) and total dietary fibre content (PLR: 4.2886±0.3466g/100g DM; PTR: 12.4148±0.4541g/100g DM) as compared to PTR. Isoflavonoids including puerarin, daidzin, genistin and daidzein were the major chemical constituents in both species. However, the average content of puerarin in PLR was found to be eleven times greater than that in PTR. Furthermore, the TFC, DPPH free radical scavenging capacity, anti-α-amylase and anti-α-glucosidase in the PLR extracts were 4.42, 4.91, 3.10 and 4.22 times greater than in the PTR extracts. ConclusionsThis study provides a comprehensive investigation on the two medicinal valuable Pueraria species and allows differences to be ascertained. This information can be used to update monographs which will help practitioners and dispensers differentiate the herbs. Further study on the interchangeable use of PLR and PTR in clinical practice is urgently warranted.

Potent α-amylase inhibitory activity of Indian Ayurvedic medicinal plants.

BackgroundIndian medicinal plants used in the Ayurvedic traditional system to treat diabetes are a valuable source of novel anti-diabetic agents. Pancreatic α-amylase inhibitors offer an effective strategy to lower the levels of post-prandial hyperglycemia via control of starch breakdown. In this study, seventeen Indian medicinal plants with known hypoglycemic properties were subjected to sequential solvent extraction and tested for α-amylase inhibition, in order to assess and evaluate their inhibitory potential on PPA (porcine pancreatic α-amylase). Preliminary phytochemical analysis of the lead extracts was performed in order to determine the probable constituents.MethodsAnalysis of the 126 extracts, obtained from 17 plants (Aloe vera (L.) Burm.f., Adansonia digitata L., Allium sativum L., Casia fistula L., Catharanthus roseus (L.) G. Don., Cinnamomum verum Persl., Coccinia grandis (L.) Voigt., Linum usitatisumum L., Mangifera indica L., Morus alba L., Nerium oleander L., Ocimum tenuiflorum L., Piper nigrum L., Terminalia chebula Retz., Tinospora cordifolia (Willd.) Miers., Trigonella foenum-graceum L., Zingiber officinale Rosc.) for PPA inhibition was initially performed qualitatively by starch-iodine colour assay. The lead extracts were further quantified with respect to PPA inhibition using the chromogenic DNSA (3, 5-dinitrosalicylic acid) method. Phytochemical constituents of the extracts exhibiting≥ 50% inhibition were analysed qualitatively as well as by GC-MS (Gas chromatography-Mass spectrometry).ResultsOf the 126 extracts obtained from 17 plants, 17 extracts exhibited PPA inhibitory potential to varying degrees (10%-60.5%) while 4 extracts showed low inhibition (< 10%). However, strong porcine pancreatic amylase inhibitory activity (> 50%) was obtained with 3 isopropanol extracts. All these 3 extracts exhibited concentration dependent inhibition with IC50 values, viz., seeds of Linum usitatisumum (540 μgml-1), leaves of Morus alba (1440 μgml-1) and Ocimum tenuiflorum (8.9 μgml-1). Acarbose as the standard inhibitor exhibited an IC50 (half maximal inhibitory concentration)value of 10.2 μgml-1. Phytochemical analysis revealed the presence of alkaloids, tannins, cardiac glycosides, flavonoids, saponins and steroids with the major phytoconstituents being identified by GC-MS.ConclusionsThis study endorses the use of these plants for further studies to determine their potential for type 2 diabetes management. Results suggests that extracts of Linum usitatisumum, Morus alba and Ocimum tenuiflorum act effectively as PPA inhibitors leading to a reduction in starch hydrolysis and hence eventually to lowered glucose levels.

Antioxidant and antidiabetic activity of Dangyuja (Citrus grandis Osbeck) extract treated with Aspergillus saitoi

Dangyuja is a citrus fruit of Cheju Island in Korea, which is known to have a high content of flavanone glycosides, such as naringin and neohesperidin. Flavanone glycosides of Dangyuja (Citrus grandis Osbeck) extract were converted into their aglycones by naringinase and hesperidinase, and into their hydroxylated forms by Aspergillus saitoi. Dangyuja extract treated with A. saitoi had significantly higher antioxidant and antidiabetic activity than both its glycosides and aglycones in oxygen radical absorption capacity (ORAC) and supercoiled DNA strand scission assay, rat intestinal α-glucosidase and porcine pancreatic α-amylase inhibition, suggesting that the fermentation of flavanone aglycones of Dangyuja extract with A. saitoi can increase antioxidant and antidiabetic activity, compared to their glycosides and aglycones. This result suggests that Dangyuja extract prepared with enzymatic and microbial treatments could be used for the development of pharmaceutical foods to control the blood glucose level of diabetic patients by inhibiting α-amylase and α-glucosidase in the intestinal tract.

Inhibition of reduced DP18-maltodextrin and amylose hydrolysis by acarbose: kinetic studies

Kinetics of inhibition of porcine pancreatic α-amylase by acarbose were performed using maltodextrin and amylose as substrates. Similar Lineweaver-Burk primary plots were obtained. Two mixed non-competitive models are proposed. X-ray crystallographic data (Qian, M., Buisson, G., Duée, E., Haser, R. and Payan, F. Biochemistry, 1994; 33: 6284–6294) are in support of the mixed non-competitive inhibition model which involves abortive complexes. Secondary plots are different indicating that in the maltodextrin hydrolysis, one molecule of acarbose is bound per amylase molecule, while using amylose as substrate two molecules of acarbose are bound. These two kinetically determined binding sites might correspond to the two surface sites shown by X-ray crystallography (Qian, M., Haser, R. and Payan, F. Protein Science 1995; 4: 747–755).

Phenomena associated with the disintegration of fuse wires

Puerariae Lobatae Radix (PLR) and Puerariae Thomsonii Radix (PTR) are traditional Chinese medicines used for the treatment of diabetes and cardiovascular diseases. These two herbs are used interchangeably in clinical practice, even though they possess significantly different chemical profiles. In the case of Pueraria species, the misidentification is related to the multiple Chinese common names in clinical practice and variable pharmaceutical Latin names in different versions of the Pharmacopoeia of the People׳s Republic of China. In addition, there is lack of evidence demonstrating how the differences in the chemical profile would impact on the pharmacological activity of the two herbs. Therefore, the aim of this study was to compare the microscopic, phytochemical profiles and anti-diabetic activity of PLR and PTR so that the two species can be differentiated.The microscopic characteristics of the PLR and PTR were observed and measured by an optical microscope. The major compounds were quantified by ultra-performance liquid chromatography (UPLC) and total flavonoid content (TFC) colorimetric assay. The free radical scavenging capacity was assessed by 2,2-diphenyl-2-picrylhydrazyl (DPPH) antioxidant assays. Anti-diabetic activity was determined by the inhibition of porcine pancreatic α-amylase and rat intestinal α-glucosidase activities.Microscopic results illustrated that the size of xylem vessels (PLR: 0.1390±0.0184 mm; PTR: 0.0471±0.0109 mm), number of fibre per bundle (PLR: 32.6800±2.8780; PTR: 16.5900±0.9982) and the size of fibre (PLR: 0.0075±0.0003 mm2; PTR: 0.0025±0.0002 mm2) in PLR were significantly greater than that in PTR (p<0.01). PLR possessed a significantly lower total starch content (PLR: 0.5288±1.2559 mg starch/g DM; PTR: 76.7954±2.9905 mg starch/g DM) and total dietary fibre content (PLR: 4.2886±0.3466 g/100 g DM; PTR: 12.4148±0.4541 g/100 g DM) as compared to PTR. Isoflavonoids including puerarin, daidzin, genistin and daidzein were the major chemical constituents in both species. However, the average content of puerarin in PLR was found to be eleven times greater than that in PTR. Furthermore, the TFC, DPPH free radical scavenging capacity, anti-α-amylase and anti-α-glucosidase in the PLR extracts were 4.42, 4.91, 3.10 and 4.22 times greater than in the PTR extracts.This study provides a comprehensive investigation on the two medicinal valuable Pueraria species and allows differences to be ascertained. This information can be used to update monographs which will help practitioners and dispensers differentiate the herbs. Further study on the interchangeable use of PLR and PTR in clinical practice is urgently warranted.