Glucoregulatory Properties of a Protein Hydrolysate from Atlantic Salmon (Salmo salar): Preliminary Characterization and Evaluation of DPP-IV Inhibition and Direct Glucose Uptake In Vitro.

Metabolic disorders are increasingly prevalent conditions that manifest pathophysiologically along a continuum. Among reported metabolic risk factors, elevated fasting serum glucose (FSG) levels have shown the most substantial increase in risk exposure. Ultimately leading to insulin resistance (IR), this condition is associated with notable deteriorations in the prognostic outlook for major diseases, including neurodegenerative diseases, cancer risk, and mortality related to cardiovascular disease. Tackling metabolic dysfunction, with a focus on prevention, is a critically important aspect for human health. In this study, an investigation into the potential antidiabetic properties of a salmon protein hydrolysate (SPH) was conducted, focusing on its potential dipeptidyl peptidase-IV (DPP-IV) inhibition and direct glucose uptake in vitro. Characterization of the SPH utilized a bioassay-guided fractionation approach to identify potent glucoregulatory peptide fractions. Low-molecular-weight (MW) fractions prepared by membrane filtration (MWCO = 3 kDa) showed significant DPP-IV inhibition (IC50 = 1.01 ± 0.12 mg/mL) and glucose uptake in vitro (p ≤ 0.0001 at 1 mg/mL). Further fractionation of the lowest MW fractions (<3 kDa) derived from the permeate resulted in three peptide subfractions. The subfraction with the lowest molecular weight demonstrated the most significant glucose uptake activity (p ≤ 0.0001), maintaining its potency even at a dilution of 1:500 (p ≤ 0.01).

Potential DPP IV Inhibitory Peptides from Dry-Cured Pork Loins after Hydrolysis: An In Vitro and In Silico Study.

Peptidyl peptidase IV (DPP-IV) is a pharmacotherapeutic target in type 2 diabetes, and inhibitors of this enzyme are an important class of drugs for the treatment of type 2 diabetes. In the present study, peptides (<7 kDa) isolated from dry-cured pork loins after pepsin and pancreatin hydrolysis were identified by mass spectrometry and tested as potential inhibitors of DPP-IV by the in silico method. Two peptides, namely WTIAVPGPPHS from myomesin (water-soluble fraction, A = 0.9091) and FKRPPL from troponin (salt-soluble fraction, A = 0.8333), were selected as the most promising inhibitors of DPP-IV. Both peptides were subjected to ADMET analysis. Fragments of these peptides showed promising drug-likeness properties as well as favorable absorption, distribution, metabolism, excretion, and toxicity functions, suggesting that they are novel leads in the development of DPP-IV inhibitors from food.

Inhibitory evaluation of Curculigo latifolia on α-glucosidase, DPP (IV) and in vitro studies in antidiabetic with molecular docking relevance to type 2 diabetes mellitus.

The inhibition of α-glucosidase and DPP enzymes capable of effectively reducing blood glucose level in the management of type 2 diabetes. The purpose of the present study is to evaluate the inhibitory potential of α-glucosidase and DPP (IV) activity including with the 2-NBDG uptake assay and insulin secretion activities through in vitro studies. The selected of active compounds obtained from the screening of compounds by LC-MS were docked with the targeted enzyme that involved in the mechanism of T2DM. From the results, root extracts displayed a better promising outcome in α-glucosidase (IC50 2.72 ± 0.32) as compared with the fruit extracts (IC50 3.87 ± 0.32). Besides, root extracts also displayed a better activity in the inhibition of DPP (IV), enhance insulin secretion and glucose uptake activity. Molecular docking results revealing that phlorizin binds strongly with α-glucosidase, DPP (IV) and Insulin receptor (IR) enzymes with achieving the lowest binding energy value. The present work suggests several of the compounds have the potential that contribute towards inhibiting α-glucosidase and DPP (IV) and thus effective in lowering post-prandial hyperglycaemia.

Development and validation of an ultrasensitive LC-MS/MS method for the quantification of cetagliptin in human plasma and its application in a microdose clinical trial.

This study established and validated an LC-MS/MS method for the ultrasensitive determination of cetagliptin in human plasma. Sample pretreatment was achieved by liquid-liquid extraction with ethyl acetate, and chromatographic separation was performed on an XB-C18 analytical column (50 × 2.1 mm, 5 µm) with gradient elution (0.1% formic acid in acetonitrile and 0.1% formic acid) at a flow rate of 1.0 mL/min. For mass spectrometric detection, multiple reaction monitoring was used, and the ion transitions monitored were m/z 421.2-86.0 for cetagliptin and m/z 424.2-88.0 for cetagliptin-d3. Method validation was performed according to the U.S. Food and Drug Administration Bioanalytical Method Validation Guidance, for which the calibration curve was linear in the range of 50.0-2000 pg/mL. All of the other results, such as selectivity, lower limit of quantitation, precision, accuracy, matrix effect, recovery, and stability, met the acceptance criteria. The validated method was successfully applied in a microdose clinical trial to systematically investigate the pharmacokinetic profile of cetagliptin in healthy subjects. Both rapid absorption and prolonged duration demonstrate the potential value of cetagliptin for diabetes treatment.

Application of experimental design in HPLC method optimization and robustness for the simultaneous determination of canagliflozin, empagliflozin, linagliptin, and metformin in tablet.

Gliflozins and gliptins represent two different pharmacological drug classes that exert different and potentially complementary glucose-lowering effect in patients with type II diabetes mellitus. A novel, selective, and sensitive HPLC method was developed for the determination of canagliflozin, empaglifozin, linagliptin, and metformin in pure form, in laboratory prepared mixtures, and in pharmaceutical dosage form. Experimental design optimization was applied by using Plackett-Burman and face-centered composite designs to achieve the best resolution with minimum experimental trials. Three significant variables affecting optimization, namely buffer pH, percentage of methanol, and percentage of acetonitrile, were studied. Chromatographic separation was achieved using an Agilent Eclipse C8 column, and column temperature was kept at 45°C. The mobile phase was composed of dipotassium hydrogen phosphate buffer (0.05 M, adjusted to pH 6 using o-phosphoric acid):acetonitrile:methanol (50:25:25, v/v/v) at a flow rate of 1.5 mL/min. Sharp and well-resolved peaks of the cited drugs were obtained. The method was fully validated in terms of linearity, accuracy, precision, selectivity and robustness in agreement with the International Council of Harmonization (ICH) guidelines Q2 (R1). Satisfactory results were obtained by the analysis of tablets through applying the developed method. Therefore, it could be performed for the analysis of the cited drugs in quality control laboratories.

Gouda Cheese with Modified Content of ß-Casein as a Source of Peptides with ACE- and DPP-IV-Inhibiting Bioactivity: A Study Based on In Silico and In Vitro Protocol.

In silico and in vitro methods were used to analyze ACE- and DPP-IV-inhibiting potential of Gouda cheese with a modified content of ß-casein. Firstly, the BIOPEP-UWM database was used to predict the presence of ACE and DPP-IV inhibitors in casein sequences. Then, the following Gouda cheeses were produced: with decreased, increased, and normative content of ß-casein after 1 and 60 days of ripening each (six variants in total). Finally, determination of the ACE/DPP-IV-inhibitory activity and the identification of peptides in respective Gouda-derived water-soluble extracts were carried out. The identification analyses were supported with in silico calculations, i.e., heatmaps and quantitative parameters. All Gouda variants exhibited comparable ACE inhibition, whereas DPP-IV inhibition was more diversified among the samples. The samples derived from Gouda with the increased content of ß-casein (both stages of ripening) had the highest DPP-IV-inhibiting potency compared to the same samples measured for ACE inhibition. Regardless of the results concerning ACE and DPP-IV inhibition among the cheese samples, the heatmap showed that the latter bioactivity was predominant in all Gouda variants, presumably because it was based on the qualitative approach (i.e., peptide presence in the sample). Our heatmap did not include the bioactivity of a single peptide as well as its quantity in the sample. In turn, the quantitative parameters showed that the best sources of ACE/DPP-IV inhibitors were all Gouda-derived extracts obtained after 60 days of the ripening. Although our protocol was efficient in showing some regularities among Gouda cheese variants, in vivo studies are recommended for more extensive investigations of this subject.

Separation and identification of enzyme inhibition peptides from dark tea protein.

Two key enzymes like α-glucosidase and dipeptidyl peptidase-4 (DPP4) play an important role in the development of Type 2 diabetes (T2D), and inhibiting them is a common treatment strategy for T2D. In this study, an ultrafiltration- centrifugation approach was developed to isolate peptides from dark protein extract. Consequently, 6 peptides TAELLPR, CGKKFVR, AVPANLVDLNVPALLK, VVDLVFFAAAK, MSLYPR and QGQELLPSDFK were identified. The four peptides exhibited α-glucosidase inhibition activities with the IC50 values of 0.43 ± 0.03, 0.52 ± 0.09, 1.03 ± 0.13 and 0.04 ± 0.04 mg/mL, respectively, which were lower than the IC50 value of positive drug acarbose (1.51 ± 0.23 mg/mL); the last two peptides had DPP4 inhibition activities with the IC50 values of 1.35 ± 0.15 and 3.89 ± 0.22 mg/mL, respectively. This suggests that dark tea-derived peptides, for the first time, were found to be potential agents for α-glucosidase and DPP4 inhibition.

Simultaneous Natural Deep Eutectic Solvent-Based Ultrasonic-Assisted Extraction of Bioactive Compounds of Cinnamon Bark and Sappan Wood as a Dipeptidyl Peptidase IV Inhibitor.

Cinnamon bark (Cinnamomum burmannii) and sappan wood (Caesalpinia sappan) have been reported to be beneficial for Type-2 Diabetes Mellitus (T2DM) and the combination is commonly used by Indonesian herbal industries. In the present study, the simultaneous extraction of bioactive compounds from both plants was conducted using natural deep eutectic solvent (NADES), their content analyzed using high-performance liquid chromatography (HPLC), and their dipeptidyl peptidase IV (DPP IV) inhibitory activity evaluated. An additional in silico molecular docking analysis was conducted to ensure their activity. The results showed that NADES (with a composition of choline chloride-glycerol) extraction from cinnamon and sappan wood had DPP IV inhibitory activity of 205.0 and 1254.0 µg/mL, respectively. Brazilin as a marker substance from sappan wood was responsible for the DPP IV inhibitory activity, while none of the marker substances chosen for cinnamon bark (trans-cinnamaldehyde, coumarin, and trans-cinnamic acid) were found to have significant DPP IV inhibitory activity. These results were confirmed by molecular docking conducted in brazilin, trans-cinnamaldehyde, coumarin, and trans-cinnamic acid.

A dipyrrole derivative from Aloe vera inhibits an anti-diabetic drug target Dipeptidyl Peptidase (DPP)-IV in vitro.

Aloe vera, a succulent herb, has a long history of use in traditional medicine, including diabetes. Earlier studies from our laboratory demonstrated that the Aloe vera extract has the ability to inhibit the diabetic drug target dipeptidyl peptidase (DPP) IV in vitro. This current study focuses on the isolation of small water soluble active molecule(s) involved in DPP-IV inhibition from Aloe vera extract, and further to characterize its structure and to elucidate the mode of inhibition of the DPP-IV enzyme. Aloe vera gel ethanolic extract was subjected to preparative reverse-phase high-pressure liquid chromatography (RP-HPLC), LH-20 Sephadex gel filtration chromatography, followed by analytical RP-HPLC, to isolate the active molecule involved in DPP-IV inhibition. Based on the spectroscopic studies, the structure of the isolated DPP-IV inhibitor was predicted to be 3, 6-dioxo-3, 3a, 6, 6 a-tetrahydropyrrolo [3, 4-c] pyrrole-1, 4-dicarboxamide with the chemical formula C8H6N4O4, having the molecular weight of 225.175 Da. This molecule inhibited the DPP-IV enzyme in a noncompetitive manner with an IC50 value of 8.59 ± 2.61 µM, with a Ki of 4.7 ± 0.038 µM. Thus, the mechanism of DPP-IV inhibition and the inhibitory constants were determined. The results of our studies suggested that the inhibition of the DPP-IV enzyme as one of the pathways by which the Aloe vera extract may restore the pancreatic islets cell mass in diabetic animal model.

Standardized Emblica officinalis fruit extract inhibited the activities of α-amylase, α-glucosidase, and dipeptidyl peptidase-4 and displayed antioxidant potential.

BACKGROUND: Emblica officinalis, known as amla in Ayurveda, has been used as a folk medicine to treat numerous pathological conditions, including diabetes. However, the novel extract of E. officinalis fruit extract (amla fruit extract, AFE, Saberry®) containing 100 g kg-1 ß-glucogallin along with hydrolyzable tannins has not yet been extensively studied for its antidiabetic potential. OBJECTIVE: The aim of this study was to investigate the antidiabetic and antioxidant activities of AFE and its stability during gastric stress as well as its thermostability. METHODS: The effect of AFE on the inhibition of pancreatic α-amylase and salivary α-amylase enzymes was studied using starch and yeast α-glucosidase enzyme using 4-nitrophenyl α-d-glucopyranoside as substrate. Further, 2,2-diphenyl-1-picrylhydrazyl radical scavenging and reactive oxygen species inhibition assay was performed against AFE. RESULTS: AFE potently inhibited the activities of α-amylase and α-glucosidase in a concentration-dependent manner with half maximal inhibitory concentration (IC50 ) values of 135.70 µg mL-1 and 106.70 µg mL-1 respectively. Furthermore, it also showed inhibition of α-glucosidase (IC50 562.9 µg mL-1 ) and dipeptidyl peptidase-4 (DPP-4; IC50 3770 µg mL-1 ) enzyme activities. AFE is a potent antioxidant showing a free radical scavenging activity (IC50 2.37 µg mL-1 ) and protecting against cellular reactive oxygen species (IC50 1.77 µg mL-1 ), and the effects elicited could be attributed to its phytoconstituents. CONCLUSION: AFE showed significant gastric acid resistance and was also found to be thermostable against wet heat. Excellent α-amylase, α-glucosidase, and DPP-4 inhibitory activities of AFE, as well as antioxidant activities, strongly recommend its use for the management of type 2 diabetes mellitus. © 2019 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Release of multifunctional peptides from kiwicha (Amaranthus caudatus) protein under in vitro gastrointestinal digestion.

BACKGROUND: The multifactorial origin of many chronic diseases provides a new framework for the development of multifunctional foods. In this study, the effect of in vitro simulated gastrointestinal digestion of kiwicha (Amaranthus caudatus) proteins on the release of multifunctional peptides was evaluated. RESULTS: Gastric digest showed higher angiotensin I converting enzyme (ACE) inhibitory activity while 60 min gastroduodenal digest showed the highest antioxidant, dipeptidyl peptidase IV (DPP-IV), α-amylase and Caco-2 cell viability inhibitory activities. Peptides >5 kDa were more effective in inhibiting colon cancer cell viability, whereas peptides <5 kDa were mainly responsible for the antioxidant, ACE, DPP-IV and α-amylase inhibitory activities. Thirteen peptides from amaranth sequenced proteins were identified. Structure-activity relationship analysis of the identified sequences pointed to three amaranth fragments, namely FLISCLL, SVFDEELS and DFIILE, as potential peptides able to concurrently exert antioxidant capacity and ability to inhibit both ACE and α-amylase. CONCLUSIONS: Five of thirteen peptides identified in kiwicha protein digests show high potential to exert multifunctional properties. Thus kiwicha proteins might start to gain importance as ingredients for functional foods for the prevention and/or management of chronic diseases related to oxidative stress, hypertension and/or diabetes. © 2018 Society of Chemical Industry.

Silver Fir (Abies alba) Extracts Inhibit Enzymes Involved in Blood Glucose Management and Protect against Oxidative Stress in High Glucose Environment.

The diet rich in fruits and vegetables reduces the risk of metabolic syndrome, including diabetes development by various mechanisms of action, mainly due to the presence of polyphenolic compounds. Extracts from different conifer species are known to be a rich source of various polyphenols. In the present study we elucidated the in vitro mechanism of anti-diabetic activity of silver fir (Abies alba) wood and bark extracts and compared their activity to non-coniferous sweet chestnut wood extract and standardized maritime pine bark extract. Extracts and lignans were tested for their inhibitory activity of enzymes involved in the regulation of blood glucose in vitro. The ability of extracts to protect against oxidative stress in high glucose environment was tested on mouse myoblast cell line. Silver fir wood and bark extracts were shown to be effective inhibitors of α-glucosidase, α-amylase and dipeptidyl peptidase 4, three enzymes involved in the regulation of blood glucose levels. Coniferous extracts also showed protection against oxidative stress generated in high glucose environment. Lignans, particularly pinoresinol diglucoside, isolariciresinol and secolariciresinol were shown to be important contributors of antihyperglycemic activity through inhibition of dipeptidyl peptidase 4. This corroborates previously published in vivo results on blood glucose level obtained with silver fir wood extract and supports the use of silver fir wood and bark extracts as food supplements or functional foods in borderline diabetes.

Macrocarpal C isolated from Eucalyptus globulus inhibits dipeptidyl peptidase 4 in an aggregated form.

Dipeptidyl peptidase 4 (DPP-4) inhibitors are used for the treatment of type-2 diabetes mellitus. Various synthetic inhibitors have been developed to date, and plants containing natural DPP-4 inhibitors have also been identified. Here, 13 plant samples were tested for their DPP-4 inhibitory activity. Macrocarpals A-C were isolated from Eucalyptus globulus through activity-guided fractionation and shown to be DPP-4 inhibitors. Of these, macrocarpal C showed the highest inhibitory activity, demonstrating an inhibition curve characterised by a pronounced increase in activity within a narrow concentration range. Evaluation of macrocarpal C solution by turbidity, nuclear magnetic resonance spectroscopy and mass spectrometry indicated its aggregation, which may explain the characteristics of the inhibition curve. These findings will be valuable for further study of potential small molecule DPP-4 inhibitors.

Identification of dipeptidyl peptidase-IV inhibitory peptides from mare whey protein hydrolysates.

Inhibition of dipeptidyl peptidase-IV (DPP-IV) activity is a promising strategy for treatment of type 2 diabetes. In the current study, DPP-IV inhibitory peptides were identified from mare whey protein hydrolysates obtained by papain. The results showed that all the mare whey protein hydrolysates obtained at various hydrolysis durations possessed more potent DPP-IV inhibitory activity compared with intact whey protein. The 4-h hydrolysates showed the greatest DPP-IV inhibitory activity with half-maximal inhibitory concentration of 0.18 mg/mL. The 2 novel peptides from 4-h hydrolysate fractions separated by successive chromatographic steps were characterized by liquid chromatography-electrospray ionization tandem mass spectrometry. The novel peptides Asn-Leu-Glu-Ile-Ile-Leu-Arg and Thr-Gln-Met-Val-Asp-Glu-Glu-Ile-Met-Glu-Lys-Phe-Arg, which corresponded to ß-lactoglobulin 1 f(71-77) and ß-lactoglobulin 1 f(143-155), demonstrated DPP-IV inhibitory activity with half-maximal inhibitory concentrations of 86.34 and 69.84 µM, respectively. The DPP-IV inhibitory activity of the 2 peptides was retained or even improved after simulated gastrointestinal digestion in vitro. Our findings indicate that mare whey protein-derived peptides may possess potential as functional food ingredients in the management of type 2 diabetes.

Identification and characterization of a dipeptidyl peptidase IV inhibitor from aronia juice.

Aronia berries have many potential effects on health, including an antioxidant effect, effect for antimutagenesis, hepatoprotection and cardioprotection, an antidiabetic effect and inhibition of cancer cell proliferation. Previous human studies have shown that aronia juice may be useful for treatment of obesity disorders. In this study, we found that aronia juice has an inhibitory effect against dipeptidyl peptidase IV (DPP IV) (EC 3.4.14.5). DPP IV is a peptidase that cleaves the N-terminal region of incretins such as glucagon-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). Inactivation of incretins by DPP IV induces reduction of insulin secretion. Furthermore, we identified that cyanidin 3, 5-diglucoside as the DPP IV inhibitor in aronia juice. DPP IV was inhibited more strongly by cyanidin 3, 5-diglucoside than by cyanidin and cyanidin 3-glucoside. The results suggest that DPP IV is inhibited by cyanidin 3, 5-diglucoside present in aronia juice. The antidiabetic effect of aronia juice may be mediated through DPP IV inhibition by cyanidin 3, 5-diglucoside.

Separation of alogliptin enantiomers in cyclodextrin-modified capillary electrophoresis: a validated method.

The single enantiomer drug, alogliptin (Alo, Nesina®) is a novel, orally available and selective dipeptidyl peptidase-4 inhibitor used for the treatment of type II diabetes. Following its pKa determination by CE-pH titration, a validated chiral CE method has been developed to separate Alo enantiomers. Preliminary screening of the native CDs and their ten derivatives revealed that sulfopropylated-γ-CD, sulfopropylated-ß-CD and sulfopropylated-γ-CD, sulfobutyl-ether-ß-CD (SBE-ß-CD) and sulfobutyl-ether-γ-CD enabled enantioresolution. Furthermore, cavity size dependent enantiomer migration order reversal was observed between γ- and ß-CD derivatives. To improve enantioseparation, buffer composition and pH, CD concentration, applied voltage, temperature, and injection parameters were optimized for the Alo/ SBE-ß-CD system, yielding a resolution of 8.34. RSD percentage of the resolution value, migration times, and corrected peak areas were below 3 and 5% during testing repeatability and intermediate precision. LOD and LOQ values were found to be 2 and 6 µg/mL, respectively, for each enantiomer. Calibration lines ranging from 6 to 250 µg/mL were constructed with r(2) > 0.9997. Robustness could be successfully verified by using the Plackett-Burman statistical experimental design. The optimized system containing 5 mM SBE-ß-CD in a 25 mM acetate buffer at pH 4.75 was found promising to detect 0.1% distomer in the presence of the API.

A molecular connection of Pterocarpus marsupium, Eugenia jambolana and Gymnema sylvestre with dipeptidyl peptidase-4 in the treatment of diabetes.

CONTEXT: Pterocarpus marsupium (PM) (Leguminosae), Eugenia jambolana (EJ) (Myrtaceae) and Gymnema sylvestre (GS) (Asclepiadaceae) are the most important medicinal plants in the Indian system of traditional medicine for the treatment of hyperglycemia. OBJECTIVES: Dipeptidyl peptidase-4 (DPP-4) inhibitors are the emerging class of anti-diabetic agents. However, only few compounds are commercially available. Therefore, in the present study we tried to explore the naturally occurring PM, EJ and GS semi-standardized extracts for their potential DPP-4 inhibition in vitro and in vivo. MATERIALS AND METHODS: DPP-4 inhibition was evaluated by in vitro inhibitory assay, and enzyme kinetics were calculated using one-phase exponential decay equation. Glucose load (2 g/kg) was administered to control and diabetic rats 30 min following extract administration (100, 200 and 400 mg/kg) orally once, and blood samples were withdrawn at 0, 0.5, 1, 1.5, 2 and 3 h to measure plasma active glucagon-like peptide-1 (GLP-1) levels. RESULTS: PM and EJ inhibit DPP-4 potently with IC50 values of 273.73 ± 2.96 and 278.94 ± 6.73 µg/mL, respectively, compared to GS (773.22 ± 9.21 µg/mL). PM, EJ and GS exhibit long duration of action with enzyme inhibitory half-lives of 462.3, 317.2 and 153.8 min, respectively. Extracts significantly increase GLP-1 levels compared to negative control groups and peak GLP-1 level was observed at 2 h for PM and EJ, whereas for GS it was at 1.5 h DISCUSSION AND CONCLUSION: Taken together, results suggest the extracts may have potent DPP-4 inhibitory action, and their hypoglycemic action attributed through an increase in plasma active GLP-1 levels.

Bioassay-guided isolation of DPP-4 inhibitory fractions from extracts of submerged cultured of Inonotus obliquus.

Inonotus obliquus is a medicinal mushroom used in Russian and Eastern European folk medicine for the treatment of gastrointestinal cancer, cardiovascular disease and diabetes. Previous studies in our laboratory have demonstrated that the mycelium powders of I. obliquus possess significant antihyperglycemic effects in a mouse model of diabetic disease induced by alloxan. However, the active ingredients of mycelium powders responsible for the diabetes activity have not been identified. This study aims to identify the active ingredients of I. obliquus mycelium powders by a bioassay-guided fractionation approach and explore the mechanism of action of these active ingredients by using a well-established DPP-4 (an important enzyme as a new therapeutic target for diabetes) inhibitory assay model. The results showed the chloroform extract of mycelium was potential inhibitory against DPP-4. Bioactivity guided fractionation led to the identification of 19 compounds using UPLC-Q-TOF-MS. Molecular docking between the compounds and DPP-4 revealed that compounds 5, 8, 9, 14, 15 may be the active components responsible for the DPP-4 inhibitory activity.

Inhibitory effect of verbascoside isolated from Buddleja brasiliensis Jacq. ex Spreng on prolyl oligopeptidase activity.

The phenylpropanoid glycoside verbascoside [2-(3,4-dihydroxyphenylethyl)-1-O-α-L-rhamnopyranosyl-(1→3)-ß-D-(4-O-caffeyl)-glucopyranoside] (1) has been isolated as the main constituent of the crude extract of Buddleja brasiliensis Jacq. ex Spreng from Southern Brazil. The crude extract, main fractions and the compound 1 were evaluated for inhibition of the enzymes acetylcholinesterase (AChE), dipeptidyl peptidase-IV (DPP-IV) and prolyl oligopeptidase (POP). Compound 1 showed weak activity against DPP-IV with an IC(50) >> 150 µM and was inactive against AChE, with a pMIQ determined by bioautography of 9.6. In contrast, 1 displayed significant inhibition of POP in a dose-dependent manner with an IC(50) value of 1.3 ± 0.2 µM, similar to the positive control, baicalin, with a POP IC(50) of 12 ± 3 µM.

Discovery of potent dipeptidyl peptidase IV inhibitors derived from ß-aminoamides bearing substituted [1,2,3]-triazolopiperidines for the treatment of type 2 diabetes.

A series of novel [1,2,3]-triazolopiperidine derivatives 5a-5y were synthesized and evaluated as inhibitors of dipeptidyl peptidase IV (DPP-4) for the treatment of type 2 diabetes, most of the compounds exhibited excellent in vitro potency (IC(50)<50n M) against DPP-4. Among these, compound 5d with potent in vitro activity against DPP-4 and good pharmacokinetic profiles exhibited pronounced in vivo efficacy in an oral glucose tolerance test (OGTT) in ICR mice. On the base of these properties, compound 5d was selected as a potential new candidate for the treatment of type 2 diabetes.