In vitro inhibitory effects of cranberry bean (Phaseolus vulgaris L.) extracts on aldose reductase, α‐glucosidase and α‐amylase

The in vitro inhibitory activities of different seed extracts prepared from cranberry bean mutant SA‐05 and its wild‐type variety Hwachia against aldose reductase, α‐glucosidase and α‐amylase were examined. The results indicated that the polyphenolics‐rich extracts obtained using 800 g kg^?1 methanol and 500 g kg^?1 ethanol demonstrated inhibitory activities against aldose reductase (IC₅₀ of 0.36–0.46 mg mL^?1) and α‐glucosidase (IC₅₀ of 1.32–1.94 mg mL^?1). The 500 g kg^?1 ethanol extracts also showed α‐amylase inhibitory activities (IC₅₀ of 70.11–80.22 μg mL^?1). Subsequent extracts, prepared further with NaCl and H₂O from precipitates of 800 g kg^?1 methanol or 500 g kg^?1 ethanol extracts, exhibited potent α‐amylase inhibitory activities (IC₅₀ of 17.68–38.68 μg mL^?1). A combination of 500 g kg^?1 ethanol extraction plus a subsequent H₂O extraction produced highest polyphenolics and α‐amylase inhibitors. The SA‐05 α‐amylase inhibitor extracts showed greater inhibitory activities than that of Hwachia. Thus, cranberry bean mutant SA‐05 is an advantageous choice for producing anti‐hyperglycaemic compounds.     

Inhibitory potential of phenylpropanoid glycosides from Ligustrum purpurascens Kudingcha against α‐glucosidase and α‐amylase in vitro

The leaves of Ligustrum purpurascens are used in a Chinese traditional tea called small‐leaved kudingcha, which is rich in phenylpropanoid glycosides (PPGs) and has many beneficial properties. Two critical exoacting glycoside hydrolase enzymes (glucosidases) involved in carbohydrate digestion are α‐glucosidase and α‐amylase. We investigated the properties of PPGs from L. purpurascens for inhibiting α‐amylase and α‐glucosidase activity in vitro and found IC₅₀ values of 1.02 and 0.73 mg mL^?1, respectively. The patterns of inhibiting both α‐amylase and α‐glucosidase were mixed‐inhibition type. Multispectroscopy and molecular docking studies indicated that the interaction between PPGs and α‐amylase and α‐glucosidase altered the conformation of enzymes, with binding at the site close to the active site of enzymes resulting in changed enzyme activity. Our studies may help in the further health use of small‐leaved kudingcha.     

α‐Glucosidase and α‐amylase inhibitory activities of phloroglucinal derivatives from edible marine brown alga,Ecklonia cava

BACKGROUND: Diabetes mellitus (DM) is a chronic metabolic disorder characterized by defects in insulin secretion and action, which can lead to damaged blood vessels and nerves. With respect to effective therapeutic approaches to treatment of DM, much effort has being made to investigate potential inhibitors against α‐glucosidase and α‐amylase from natural products. The edible marine brown alga Ecklonia cava has been reported to possess various interesting bioactivities, which are studied here. RESULTS: In this study, five phloroglucinal derivatives were isolated from Ecklonia cava: fucodiphloroethol G ( 1 ), dieckol ( 2 ), 6,6′‐bieckol ( 3 ), 7‐phloroeckol ( 4 ) and phlorofucofuroeckol A ( 5 ); compounds 1, 3 and 4 were obtained from this genus for the first time and with higher yield. The structural elucidation of these derivatives was completely assigned by comprehensive analysis of nuclear magnetic spectral data. The anti‐diabetic activities of these derivatives were also assessed using an enzymatic inhibitory assay against rat intestinal α‐glucosidase and porcine pancreatic α‐amylase. Most of these phlorotannins showed significant inhibitory activities in a dose‐dependent manner, responding to both enzymes, especially compound 2 , with the lowest IC₅₀ values at 10.8 µmol L^?1 (α‐glucosidase) and 124.9 µmol L^?1 (α‐amylase), respectively. Further study of compound 2 revealed a non‐competitive inhibitory activity against α‐glucosidase using Lineweaver‐Burk plots. CONCLUSION: These results suggested that Ecklonia cava can be used for nutritious, nutraceutical and functional foods in diabetes as well as for related symptoms. Copyright © 2009 Society of Chemical Industry     

Extraction,optimisation and characterisation of phenolics from Thymus vulgaris L.: phenolic content and profiles in relation to antioxidant,antidiabetic and antihypertensive properties

The objectives of this study were to examine varying extraction conditions of Thymus vulgaris L. as related to phenolic content and profiles of the extracts and their antioxidant, antihypertensive and antidiabetic properties. Phenolics were extracted under various conditions pertaining to free and bound phenolics, solvent type and combination of extraction time and temperature, and these extracts were evaluated in terms of their antioxidant activities and inhibitory activities of angiotensin‐converting enzyme (ACE), α‐glucosidase and α‐amylase. The acetone–water solvent mixture (1:1; v/v) produced the extract with the greatest phenolic content, antioxidant activity and inhibitory activities of ACE and α‐glucosidase. The optimal extraction temperature for maximum phenolic content and antioxidant activity associated with methanol extraction was 60 °C, whereas a lower temperature at 40 °C was required to maximise inhibitory activities for ACE, α‐glucosidase and α‐amylase. An inverse relationship was seen between antioxidant and glucosidase inhibitory activities vs. the ACE and α‐amylase inhibitory activities, which suggests the need for extractions to be directed to specific bioactivities of thyme extracts. Generally, the results indicate major differences in phenolic profiles among the tested extraction conditions with thymol as the predominant phenolic seen in most extractions, while gallic acid, rosmarinic acid or diosmin also predominated in other extracts. Extracts with the same predominant phenolic compound and similar phenolic content showed major disparities in their ACE, glucosidase and α‐amylase inhibitory activities, indicating that the major phenolic profiles of thyme extracts may not be necessarily related to the degree of inhibition of ACE, glucosidase and α‐amylase enzymes.     

Interaction of aqueous extracts of two varieties of Yam tubers (Dioscorea spp) on some key enzymes linked to type 2 Diabetes in vitro

This study sought to assess the effect of processing of yam flour [from white yam (Dioscorea rotundata) and water yam (Dioscorea alata)] to paste, on the antioxidant properties and inhibition of key enzymes linked to type‐2 diabetes (α‐amylase and α‐glucosidase). The phenolic content (phenol and flavonoid), antioxidant properties, α‐amylase and α‐glucosidase inhibitory properties of the aqueous extracts of the yam products were determined. Processing into paste caused significant (P < 0.05) percentage decrease in their total phenol and flavonoid content of the yam varieties. However, significant increase (P < 0.05) in the antioxidant properties of the yam varieties was observed after processing. Furthermore, the yam extracts inhibited α‐amylase and α‐glucosidase activities in vitro in a dose‐dependent parttern (1–4 mg mL^?1), however, the pasting process caused significant (P < 0.05) decrease in the α‐amylase inhibitory and α‐glucosidase inhibitory activities. Therefore, processing the yam varieties into paste (browned) could potentially increase their antioxidant capacity as well as decreasing their α‐amylase and α‐glucosidase inhibitory properties.     

α‐Glucosidase Inhibitory Activities of Fatty Acids Purified from the Internal Organ of Sea Cucumber Stichopus japonicas

α‐Glucosidase inhibitory activities of the various solvent fractions (n‐hexane, CHCl₃, EtOAc, BuOH, and water) of sea cucumber internal organ were investigated. 1,3‐Dipalmitolein (1) and cis‐9‐octadecenoic acid (2) with potent α‐glucosidase inhibitory activity were purified from the n‐hexane fraction of sea cucumber internal organ. IC₅₀ values of compounds 1 and 2 were 4.45 and 14.87 μM against Saccharomyces cerevisiae α‐glucosidase. These compounds mildly inhibited rat‐intestinal α‐glucosidase. In addition, both compounds showed a mixed competitive inhibition against S. cerevisiae α‐glucosidase and were very stable at pH 2 up to 60 min. The K_I values of compounds 1 and 2 were 0.48 and 1.24 μM, respectively. Therefore, the internal organ of sea cucumber might be a potential new source of α‐glucosidase inhibitors suitably used for prevention of obesity and diabetes mellitus.     

Phytosterols in banana (Musa spp.) flower inhibit α‐glucosidase and α‐amylase hydrolysations and glycation reaction

Three phytosterols were isolated from Musa spp. flowers for evaluating their capabilities in inhibiting glucosidase and amylase activities and glycation of protein and sugar. The three phytosterols were identified as β‐sitosterol (PS1), 31‐norcyclolaudenone (PS2) and (24R)‐4α, 14α, 4‐trimethyl‐5α‐cholesta‐8, 25(27)‐dien‐3β‐ol (PS3). IC₅₀ values (the concentration of inhibiting 50% of enzyme activity) of PS1, PS2 and PS3 against α‐glucosidase were 283.67, 11.33 and 43.10 μg mL^?1, respectively. For inhibition of α‐amylase, the IC₅₀ values of PS1, PS2 and PS3 were 52.55, 76.25 and 532.02 μg mL^?1, respectively. PS1 was an uncompetitive inhibitor against α‐amylase with K_m at 5.51 μg mL^?1, while PS2 and PS3 exhibited a mixed‐type inhibition with K_m at 52.36 and 2.49 μg mL^?1, respectively. PS1 and PS2 also significantly inhibited the formation of advanced glycation end products (AGEs) in a BSA–fructose model. The results suggest that banana flower could possess the capability in prevention of the diseases associated with abnormal blood sugar and AGEs levels, such as diabetes.     

Total Phenol Content,Antioxidant Activities and α‐Glucosidase Inhibition of Sesame Cake Extracts

Sesame cake, the byproduct obtained after the removal of oil is presently used as cattle field. Present study evaluates the α‐glucosidase, α‐amylase inhibition and antioxidant properties of black sesame cake extracts. For that purpose, defatted seeds were sequentially extracted with ethyl acetate, methanol, methanol‐water 70:30 (v/v) and water. Among the extracts tested, methanol extract demonstrated better antioxidant activities (2,2‐diphenyl‐1‐picrylhydrazyl, hydroxyl and superoxide radical) and total phenol content. But the total flavonoid content and the total reducing power was high for methanol‐water. Most active methanol extract was further screened for α‐glucosidase and α‐amylase inhibition. The extract showed strong α‐glucosidase inhibitory potential and mild α‐amylase inhibition. The study indicated that the extraction yield and the antioxidant activities were strongly dependent on the solvent, antioxidant assays and extract concentration. These results demonstrated that sesame meal can be exploited as source of protein and bioactive for the development of functional food.     

Inhibitory activities of kaempferol,galangin, carnosic acid and polydatin against glycation and α‐amylase and α‐glucosidase enzymes

The activities of four natural phenolics, kaempferol, galangin, carnosic acid and polydatin in scavenging free radicals, inhibiting advanced glycation end‐product (AGE) formation, α‐amylase and α‐glucosidase and trapping methylglyoxal (MGO), were evaluated in this study. Carnosic acid and galangin had the highest activity in scavenging free radicals. Kaempferol and galangin had the greatest activity in preventing bovine serum albumin (BSA) against glycation and reducing glycated proteins. Polydatin had the greatest performance in trapping MGO to reduce glycation reaction. However, there was no significant difference for kaempferol, galangin and carnosic acid in inhibiting AGE formation by BSA‐MGO reaction. Kaempferol, galangin and carnosic acid were the competitive inhibitors for α‐amylase, while kaempferol and carnosic acid were noncompetitive inhibitors for α‐glucosidase. However, polydatin showed as a mixed noncompetitive inhibitor for both α‐amylase and α‐glucosidase. The results indicated that the four natural phenolics have potential in inhibiting AGE production and the digestive enzymatic activity with different mechanisms.     

Molecular Weight Affected Antioxidant,Hypoglycemic and Hypotensive Activities of Cold Water Extract from Pleurotus citrinopileatus

Cold water extract of P. citrinopileatus (CWEPC) was fractioned into 4 fractions, PC‐I (<1 kDa), PC‐II (1‐3.5 kDa), PC‐III (3.5‐10 kDa), and PC‐IV (>10 kDa), by ultrafiltration. The antioxidant activities, the inhibition of pancreatic α‐amylase, intestinal α‐glucosidase, and hypertension‐linked angiotensin converting enzyme (ACE), as well as the contents of polysaccharides, protein, and phenolic compounds of 4 fractions were determined. The results showed that lower MW fractions exerted a higher antioxidant activity, which was correlated to phenolic contents. The high molecular fraction (PC‐IV) exhibited significantly higher inhibitory activity on α‐amylase, α‐glucosidase, and ACE compared to CWEPC and the other 3 lower MW fractions (<10 kDa), which was more related to protein contents. The inhibition capability of CWEPC and PC‐IV on α‐amylase activity was 1/13.4 to 1/2.7 relative to that of acarbose, respectively. Kinetic data revealed that PC‐IV fraction followed a noncompetitive inhibition pattern on α‐glucosidase activity. The study demonstrated that various MW fractions and types of components contribute to different biological functions of P. citrinopileatus and it is protein constituents but not peptides responsible for the hypoglycemic potential of CWEPC.     

A preliminary study of monosaccharide composition and α‐glucosidase inhibitory effect of polysaccharides from pumpkin (Cucurbita moschata) fruit

In this work, crude polysaccharide extracts were extracted from pumpkin (Cucurbita moschata) fruit by hot water. After removal of proteins and purification, polysaccharides of pumpkin fruit (PP1‐1) were subjected to structural identification. Gas chromatography analysis indicated that PP1‐1 comprised of galactose (86.4%), and glucose (13.6%). The molecular weight of PP1‐1 was measured to be 0.87 × 10⁴ Da by gel permeation chromatography. The inhibitory kinetic evaluation showed that it was non‐competitive inhibition of PP1‐1 on the α‐glucosidase‐catalysed hydrolysis of PNPG. The Michaelis–Menten constant (K_m) was 0.106 m , and the inhibitory constants (K_i), 0.435 mg.     

Changes in chemical composition of lupin seeds (Lupinus angustifolius) after selective α‐galactoside extraction

A selective procedure for the extraction of α‐galactosides has been employed in two sweet lupin seeds (Lupinus angustifolius var. Troll and var. Emir) in order to reduce flatulence‐causing factors. Different nutritional parameters (proteins, fat, ash, dietary fibre, starch, sucrose, vitamins B₁, B₂, E and C) and antinutritional factors (α‐galactosides, trypsin inhibitor activity and inositol phosphates) were studied in raw and processed seeds. The α‐galactoside content in both varieties was reduced by 87–100%. The extracted lupins seeds presented a high retention in protein and fat (109–136% and 95–104%, respectively). Sucrose and soluble dietary fibre, however, decreased significantly as a result of processing and retentions ranged between 5 and 29%. The vitamin B₁, B₂, and E contents decreased during selective extraction, the retentions being in the ranges 25–47%, 38–40%, and 48–54%, respectively, for var. Troll and Emir. However extracted lupin seeds still contained important amounts of vitamins and insoluble dietary fibre, compounds with nutritional importance. Raw and processed lupins did not contain starch. TIA and vitamin C were not detected, and total inositol phosphates were modified slightly after extraction. In conclusion, the lupin seeds obtained by the extraction of α‐galactosides can be an adequate proteic ingredient to be incorporated in functional foods. Copyright © 2005 Society of Chemical Industry     

Anti‐acetylcholinesterase,antidiabetic, anti‐inflammatory,antityrosinase and antixanthine oxidase activities of Moroccan propolis

Biological properties of Moroccan propolis have been scarcely studied. In the present work, the total phenols and flavonoids from 21 samples of propolis collected in different places of Morocco or 3 supplied in the market were determined, as well as the in vitro capacity for inhibiting the activities of acetylcholinesterase, α‐glucosidase, α‐amylase, lipoxygenase, tyrosinase, xanthine oxidase and hyaluronidase. The results showed that samples 1 (region Fez‐Boulemane, Sefrou city) (IC₅₀ = 0.065, 0.006, 0.020, 0.050, 0.014 mg mL^?1) and 23 (marketed) (IC₅₀ = 0.018, 0.002, 0.046, 0.037, 0.008 mg mL^?1) had the best in vitro capacity for inhibiting the α‐amylase, α‐glucosidase, lipoxygenase, tyrosinase and xanthine oxidase activities, respectively. A negative correlation between IC₅₀ values and concentration of phenols, flavones and flavanones was found. These activities corresponded to the generally higher amounts of phenols and flavonoids. In the same region, propolis samples have dissimilar phenol content and enzyme inhibitory activities.     

Comparison of Polyphenol Profile and Inhibitory Activities Against Oxidation and α‐Glucosidase in Mulberry (Genus Morus) Cultivars from China

Mulberry (genus Morus) is a significant source of polyphenols, which can promote positive effects on human health. China has various mulberry cultivars, however, many Chinese mulberry cultivars have been only minimally studied. To solve this lack of research, 8 mulberry cultivars (Da10, Tang10, Yueshen74, Yuefenshen, Longsang, Ningxia1hao, Taiwanguosang, and Baiyuwang) from 4 regions of China were assessed to determine their polyphenol profiles using HPLC‐MS/MS and then tested for their antioxidant and anti‐α‐glucosidase activities in vitro. A total of 18 nonanthocyanins and 4 anthocyanins were quantified in mulberry cultivars; among these polyphenols, chlorogenic acid, quercetin 3‐O‐rutinoside, and cyanidin 3‐O‐glucoside were confirmed as the major phenolic acid, flavonol derivative, and anthocyanin, respectively. Two types of stilbene compounds, piceid, and piceatannol, were detected for the 1st time in all mulberry cultivars. Moreover, the methanolic extracts of different mulberry cultivars showed disparate antioxidant and α‐glucosidase inhibitory activities, and this discrepancy was mainly attributed to varying the anthocyanin content. Based on our results, Taiwanguosang is proposed to be a good candidate suitable for further process due to its high level of anthocyanins.     

Identification of α‐glucosidase inhibitors from a new fermented tea obtained by tea‐rolling processing of loquat (Eriobotrya japonica) and green tea leaves

BACKGROUND: A new fermented tea produced by tea‐rolling processing of loquat (Eriobotrya japonica) leaf with green tea leaf (denoted as LG tea) showed a potent antihyperglycaemic effect in maltose‐loaded rats. The aim of this study, therefore, was to identify α‐glucosidase inhibitors in the antihyperglycaemic tea product. RESULTS: LG tea had a threefold higher maltase‐inhibitory activity (IC₅₀ 0.065 mg dried extract mL^?1) than either the constituent loquat leaf or green tea alone. In addition, LG tea favourably inhibited maltase action rather than sucrase action. As a result of bio‐guided high‐performance liquid chromatography separations of LG tea, theasinensin A, theasinensin B, strictinin and 1,6‐digalloylglucose were newly identified as maltase inhibitors with IC₅₀ values of 142, 225, 398 and 337 µmol L^?1 respectively, along with previously identified catechins and theaflavins. CONCLUSION: Judging from the magnitude of the α‐glucosidase‐inhibitory contribution of each isolated compound to the overall inhibition of LG tea, catechins were the main candidates responsible for α‐glucosidase or maltase inhibition in LG tea, followed by theaflavins, theasinensins, strictinin and 1,6‐digalloylglucose. Copyright © 2010 Society of Chemical Industry     

GC‐MS‐Based Metabolite Profiling of Cosmos caudatus Leaves Possessing Alpha‐Glucosidase Inhibitory Activity

Cosmos caudatus, which is known as “Ulam Raja,” is an herbal plant used in Malaysia to enhance vitality. This study focused on the evaluation of the α‐glucosidase inhibitory activity of different ethanolic extracts of C. caudatus. Six series of samples extracted with water, 20%, 40%, 60%, 80%, and 100% ethanol (EtOH) were employed. Gas chromatography‐mass spectrometry (GC‐MS) and orthogonal partial least‐squares (OPLS) analysis was used to correlate bioactivity of different extracts to different metabolite profiles of C. caudatus. The obtained OPLS scores indicated a distinct and remarkable separation into 6 clusters, which were indicative of the 6 different ethanol concentrations. GC‐MS can be integrated with multivariate data analysis to identify compounds that inhibit α‐glucosidase activity. In addition, catechin, α‐linolenic acid, α‐D‐glucopyranoside, and vitamin E compounds were identified and indicate the potential α‐glucosidase inhibitory activity of this herb.     

Isolation of a Recombinant Bacillus sp. TS‐23 α‐Amylase by Adsorption‐Elution on Raw Starch

A Bacillus sp. TS‐23 α‐amylase produced by recombinant Escherichia coli was adsorbed onto raw starch and the adsorbed enzyme was eluted with maltose or maltodextrin in 50 mM Tris/HCl buffer (pH 8.5). The adsorption‐elution procedure resulted in a yield of 53% α‐amylase activity and sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS/PAGE) analysis showed that the eluted α‐amylase had a molecular mass of approximately 64 kDa. Raw starch could be used repeatedly in the adsorption‐ elution cycle with good reproducibility. Scanning electron microscopy of the isolated corn starch exhibited a smooth appearance of the granules before adsorption and only a small change in appearance after three adsorption‐elution cycles. These results suggest that the raw starch adsorption‐elution technique has a great potential in the isolation of Bacillus sp. TS‐23 α‐amylase from the culture broth of recombinant E. coli.     

Glycoalkaloids in potato tubers: the effect of variety and drought stress on the α‐solanine and α‐chaconine contents of potatoes

Six varieties of Solanum tuberosum L potato grown in the Bolivian highlands under drought stress, with and without irrigation, were analysed for their content of glycoalkaloids (GAs). The plant material consisted of three drought‐tolerant varieties from a local breeding programme (PROINPA), Potosina, Chapaquita and Pampeña, and three control cultivated varieties, Malcacho, Sani Imilla and Desiree, either susceptible or relatively tolerant to drought. α‐Solanine and α‐chaconine were quantified in both the peel and flesh of the tubers. A significant increase in GA concentration (α‐solanine + α‐chaconine) was observed under drought stress conditions in most varieties; average concentration increases of 43 and 50% were registered in the improved and control cultivars respectively. In all tested cultivars, however, the GA concentration remained lower than the recommended food safety level (200 mg kg⁻¹ fresh tubers). It ranged from 52.4 to 100 mg kg⁻¹ fresh tubers in the improved cultivars and from 55.6 to 122.3 mg kg⁻¹ fresh tubers in the controls. In the improved and control varieties the α‐solanine content averaged 42.6 and 35.4% of the total potato GAs respectively and was not significantly affected by drought stress, except in Desiree. In all conditions the peel contained the greatest proportion of total GAs. The hybrid variety Pampeña (new drought‐tolerant variety) contained the lowest amounts of GAs, which were lower than those of the control varieties, with and without irrigation. © 2000 Society of Chemical Industry     

Effects of polysaccharides and polyphenolics fractions of Zijuan tea (Camellia sinensis var. kitamura) on α‐glucosidase activity and blood glucose level and glucose tolerance of hyperglycaemic mice

The effects of polysaccharides, theaflavins, thearubigins and theabrownin fractions of Zijuan tea on α‐glucosidase and blood glucose level and intolerance of hyperglycaemic mice were evaluated. The polysaccharides or theaflavins fraction exhibited greater inhibition rate of α‐glucosidase than acarbose positive control, thearubigins fraction or theabrownin fraction. The four fractions were delivered to the treatment mice through oval gavage each day for 15 days. The mice in polysaccharides and theaflavins high‐ and low‐dose and theabrownin high‐dose treatments significantly lowered their blood glucose levels while all the treatment mice gained body weight. The mice in polysaccharides, theaflavins and theabrownin high‐ and low‐dose treatments had greater glucose tolerance as well. Thus, the theaflavins and polysaccharides fractions of Zijuan tea effectively moderated the complications of hyperglycaemic mice. The lower effectiveness of thearubigins and theabrownin fractions may be caused by the highly polymerised polyphenolics which decreased their accessibility to α‐glucosidase and digestibility in mice.     

α‐Amylase inhibitors from an Indonesian medicinal herb,Phyllanthus urinaria

BACKGROUND: Diabetes mellitus and associated diseases are an increasing problem around the world. One of the hyperglycemic remedies is glucose absorption reduction by suppressing carbohydrate digestion due to utilization of α‐amylase inhibitors. RESULTS: Prospective herbs were analyzed by in vitro enzyme assay to evaluate their inhibitory activity against porcine pancreatic amylase (PPA), and it was found that Phyllanthus urinaria and three other herbs to showed a potent inhibitory activity. A 50% aqueous methanol‐soluble extract of the leaves of P. urinaria was chromatographed using a silica gel column. The active fractions were further purified by preparative high‐performance liquid chromatography to isolate active principles against PPA. Structural determination revealed that these isolated compounds were gallic acid, corilagin, and macatannin B, and showed mild activity against PPA (activity in 1 mmol L^?1 concentration: 23%, 21%, 33%, respectively). CONCLUSION: P. urinaria extracts show inhibitory activity against PPA. This activity, together with the information on isolated compounds, may benefit further exploration of P. urinaria utilization in the management of borderline diabetes patients. Copyright © 2011 Society of Chemical Industry