α-Glucosidase inhibitors isolated from medicinal plants

Bioactive compounds in plant materials for the prevention of diabetesand obesity

Plant materials have been widely studied for their preventive and therapeutic effects for type 2 diabetes mellitus (T2DM) and obesity. The effect of a plant material arises from its constituents, and the study of these bioactive compounds is important to achieve a deeper understanding of its effect at the molecular level. In particular, the study of the effects of such bioactive compounds on various biological processes, from digestion to cellular responses, is required to fully understand the overall effects of plant materials in these health contexts. In this review, I summarize the bioactive compounds we have recently studied in our research group that target digestive enzymes, dipeptidyl peptidase-4, myocyte glucose uptake, and lipid accumulation in adipocytes.

Abbreviations: AC: adenylyl cyclase; AMPK: AMP-activated protein kinase; βAR: β-adrenergic receptor; CA: catecholamine; cAMP: cyclic adenosine monophosphate; cGMP: cyclic guanosine monophosphate; DPP-4: dipeptidyl peptidase-4; ERK: extracellular signal-regulated kinase; GC: guanylyl cyclase; GH: growth hormone; GLP-1: glucagon-like peptide-1; GLUT: glucose transporter; HSL: hormone-sensitive lipase; IR: insulin receptor; IRS: insulin receptor substrate; MAPK: mitogen-activated protein kinase; MEK: MAPK/ERK kinase; MG: maltase-glucoamylase; NP: natriuretic peptide; NPR: natriuretic peptide receptor; mTORC2: mechanistic target of rapamycin complex-2; PC: proanthocyanidin; PI3K: phosphoinositide 3-kinase; PKA: cAMP-dependent protein kinase; PKB (AKT): protein kinase B; PKG: cGMP-dependent protein kinase; PPARγ: peroxisome proliferator-activated receptor-γ; SGLT1: sodium-dependent glucose transporter 1; SI: sucrase-isomaltase; T2DM: type 2 diabetes mellitus; TNFα: tumor necrosis factor-α.

Is Chickpea a Potential Substitute for Soybean? Phenolic Bioactives and Potential Health Benefits

Legume seeds are rich sources of protein, fiber, and minerals. In addition, their phenolic compounds as secondary metabolites render health benefits beyond basic nutrition. Lowering apolipoprotein B secretion from HepG2 cells and decreasing the level of low-density lipoprotein (LDL)-cholesterol oxidation are mechanisms related to the prevention of cardiovascular diseases (CVD). Likewise, low-level chronic inflammation and related disorders of the immune system are clinical predictors of cardiovascular pathology. Furthermore, DNA-damage signaling and repair are crucial pathways to the etiology of human cancers. Along CVD and cancer, the prevalence of obesity and diabetes is constantly increasing. Screening the ability of polyphenols in inactivating digestive enzymes is a good option in pre-clinical studies. In addition, in vivo studies support the role of polyphenols in the prevention and/or management of diabetes and obesity. Soybean, a well-recognized source of phenolic isoflavones, exerts health benefits by decreasing oxidative stress and inflammation related to the above-mentioned chronic ailments. Similar to soybeans, chickpeas are good sources of nutrients and phenolic compounds, especially isoflavones. This review summarizes the potential of chickpea as a substitute for soybean in terms of health beneficial outcomes. Therefore, this contribution may guide the industry in manufacturing functional foods and/or ingredients by using an undervalued feedstock.

A new glucoside with a potent α-glucosidase inhibitory activity from Lycium schweinfurthii

A new glucoside, 3-methoxy-4-O-β-D-glucopyranosyl-methyl benzoate, has been isolated from Lycium schweinfurthii along with five known compounds through bioactivity guided fractionation of the total plant methanolic extract towards α-glucosidase inhibitory activity. All the isolated compounds were tested for their inhibitory effect on α-glucosidase enzyme. As a result, four of them showed a potent inhibitory activity and thus constitute a therapeutic approach to decrease postprandial hyperglycemia in diabetic patients.

Molecular Insight and Mode of Inhibition of α-Glucosidase and α-Amylase by Pahangensin A from Alpinia pahangensis Ridl

The inhibition of carbohydrate-hydrolyzing enzymes in human digestive organs is crucial in controlling blood sugar levels, which is important in treating type 2 diabetes. In the current study, pahangensin A (1), a bis-labdanic diterpene characterized previously in the rhizomes of Alpinia pahangensis Ridl., was identified as an active dual inhibitor for α-amylase (IC₅₀ =114.80 μm) and α-glucosidase (IC₅₀ =153.87 μm). This is the first report on the dual α-amylase and α-glucosidase inhibitory activities of a bis-labdanic diterpene. The Lineweaver-Burk plots of compound 1 indicate that it is a mixed-type inhibitor with regard to both enzymes. Based on molecular docking studies, compound 1 docked in a non-active site of both enzymes. The dual inhibitory activity of compound 1 makes it a suitable natural alternative in the treatment of type 2 diabetes.

Antioxidant, α-Amylase and α-Glucosidase Inhibitory Activities and Potential Constituents of Canarium tramdenum Bark

The fruits of Canarium tramdenum are commonly used as foods and cooking ingredients in Vietnam, Laos, and the southeast region of China, whilst the leaves are traditionally used for treating diarrhea and rheumatism. This study was conducted to investigate the potential use of this plant bark as antioxidants, and α-amylase and α-glucosidase inhibitors. Five different extracts of C. tramdenum bark (TDB) consisting of the extract (TDBS) and factional extracts hexane (TDBH), ethyl acetate (TDBE), butanol (TDBB), and water (TDBW) were evaluated. The TDBS extract contained the highest amount of total phenolic (112.14 mg gallic acid equivalent per g dry weight), while the TDBB extract had the most effective antioxidant capacity compared to other extracts. Its IC₅₀ values were 12.33, 47.87, 33.25, and 103.74 µg/mL in 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis (ABTS), reducing power (RP), and nitric oxide (NO) assays, respectively. Meanwhile, the lipid peroxidation inhibition of the four above extracts was proximate to that of butylated hydroxytoluene (BHT) as a standard antioxidant. The result of porcine pancreatic α-amylase inhibition showed that TDB extracts have promising effects which are in line with the commercial diabetic inhibitor acarbose. Interestingly, the inhibitory ability on α-glucosidase of all the extracts was higher than that of acarbose. Among the extracts, the TDBB extract expressed the strongest activity on the enzymatic reaction (IC₅₀ = 18.93 µg/mL) followed by the TDBW extract (IC₅₀ = 25.27 µg/mL), TDBS (IC₅₀ = 28.17 µg/mL), and TDBE extract (IC₅₀ = 141.37 µg/mL). The phytochemical constituents of the TDB extract were identified by gas chromatography–mass spectrometry (GC-MS). The principal constituents included nine phenolics, eight terpenoids, two steroids, and five compounds belonging to other chemical classes, which were the first reported in this plant. Among them, the presence of α- and β-amyrins were identified by GC-MS and appeared as the most dominant constituents in TDB extracts (1.52 mg/g). The results of this study revealed that C. tramdenum bark possessed rich phenolics and terpenoids, which might confer on reducing risks from diabetes. A high quantity of α- and β-amyrins highlighted the potentials of anti-inflammatory, anti-ulcer, anti-hyperlipidemic, anti-tumor, and hepatoprotective properties of C. tramdenum bark.

Momilactones A and B Are α-Amylase and α-Glucosidase Inhibitors

Momilactones A (MA) and B (MB) are the active phytoalexins and allelochemicals in rice. In this study, MA and MB were purified from rice husk of Oryza sativa cv. Koshihikari by column chromatography, and purification was confirmed by high-performance liquid chromatography, thin-layer chromatography, gas chromatography-mass spectrometry, liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS), and ¹H and ¹³C nuclear magnetic resonance analyses. By in vitro assays, both MA and MB exerted potent inhibition on α-amylase and α-glucosidase activities. The inhibitory effect of MB on these two key enzymes was greater than that of MA. Both MA and MB exerted greater α-glucosidase suppression as compared to that of the commercial diabetic inhibitor acarbose. Quantities of MA and MB in rice grain were 2.07 ± 0.01 and 1.06 ± 0.01 µg/dry weight (DW), respectively. This study was the first to confirm the presence of MA and MB in refined rice grain and reported the α-amylase and α-glucosidase inhibitory activity of the two compounds. The improved protocol of LC-ESI-MS in this research was simple and effective to detect and isolate MA and MB in rice organs.

Anti-hyperglycemic and genotoxic studies of 1-O-methyl chrysophanol, a new anthraquinone isolated from Amycolatopsis thermoflava strain SFMA-103

The compound 1-O-methyl chrysophanol (OMC) which belongs to a class of hydroxyanthraquinones was isolated from Amycolatopsis thermoflava strain SFMA-103 and studied for their anti-diabetic properties. OMC was evaluated as an anti-diabetic agent based on in silico studies which initially predicted the binding energy with α-amylase (-188.81 KJ mol^-1) and with α-glucosidase (70.53 KJ mol^-1). Further, these results were validated based on enzyme inhibition assays where OMC demonstrated enzyme inhibitory activity towards α-amylase (IC₅₀ 3.4 mg mL^-1) and α-glucosidase (IC₅₀ 38.49 μg mL^-1). To confirm the anti-diabetic activity, in vivo studies (oral dose in Wistar rats) revealed that OMC inhibited significantly the increase in glucose concentration at 100 mg/kg as compared to starch control (p < 0.05). Further, to understand the safety of OMC as a therapeutic agent, the genotoxic analysis was performed in both in vitro Chinese Hamster Ovary cells (250, 500, and 1000 µM/mL) and in vivo Swiss albino mice (250, 500, and 1000 mg/kg). In vitro results showed that OMC concentration of up to 250 µM/mL did not elicit significant changes in CAs, MI, and MN counts in CHO cells. Similarly, in mice experiments (i.p. injection), no significant changes in CAs, MI, and MN induction were observed till 500 mg/kg of OMC when compared with chrysophanic acid (Cy) (200 mg/kg). In addition, mice that received the lowest dose of OMC (250 mg/kg) did not show any histological changes in liver, kidney, and heart. The study concluded that five times higher therapeutic dose (100 mg/kg) of OMC can be utilized against hyperglycemia with no genotoxic effects.

A new method for the in situ assay of α-glucosidase activity and inhibitor screening through an enzyme substrate-mediated DNA hybridization chain reaction

The strategy is based on small molecule-mediated hybridization chain reaction.

Rapidly screening of α-glucosidase inhibitors from Dioscorea opposita Thunb. peel based on rGO@Fe3O4 nanocomposites microreactor

Present study aimed to immobilise the α-glucosidase on suitable supports to construct enzymatic microreactors and their subsequent applicability in efficient inhibitor screening from the Chinese Yam (Dioscorea opposita Thunb.) peel. A type of lamellar and porous composites (rGO@Fe3O4) were synthesised with a facile one-step solvothermal method and employed as carriers to construct enzymatic microreactors for screening α-glucosidase ligand from the Chinese Yam peel in league with the high performance liquid chromatography and mass spectrometry (HPLC-MS). The immobilisation amount of α-glucosidase on rGO@Fe3O4 under the optimised conditions was about 40 μg α-glucosidase/mg carriers. Furthermore, the binding capacities of screened inhibitors, 2,4-dimethoxy-6,7-dihydroxyphenanthrene and batatasin I, were 35.6 and 68.2%, respectively. Hence, considering their high screening efficiency and excellent magnetic separation ability, these as-prepared nanocomposite consisting of rGO and Fe3O4 may be potential supports for the enzyme (such as α-glucosidase) immobilisation for rapid α-glucosidase inhibitors screening from the diverse nature resources.

Polyphenolic profile and antioxidant activity of meristem and leaves from "chagual" (Puya chilensis Mol.), a salad from central Chile

The Bromeliaceae Puya chilensis Mol. is a native monocotyledonous food plant that can be found in central Chile. It is traditionally known as chagual. The tender basal part of the leaves, just starting from the meristem, are consumed as a salad. The aim of this work was to describe the phenolic content and composition of the meristem and leaves of chagual, as well as their antioxidant capacity and inhibitory activity against metabolic syndrome-associated enzymes. Samples of chagual, including two cultivated and three wild growing plants, were analyzed and compared for composition and bioactivity. From the phenolic enriched extract of the plant (PEE), 26 compounds were tentatively identified by HPLC-DAD-ESI-MSⁿ, including 12 hydroxycinnamic acids and 14 flavonoids. The main compounds were identified as diferuloyl hexaric acid isomers and 5-p-Coumaroylquinic acid. The compounds were quantified in both meristem and leaves. The PEE content was up to ten times higher in the meristem than in the leaves, ranging from 0.18 to 124.08 mg/g PEE. The samples inhibited α-glucosidase, but did not show effect on α-amylase and pancreatic lipase. This is the first report on the polyphenol composition and bioactivity of the edible components of the chagual food plant.

α-Glucosidase Inhibitors From the Coral-Associated Fungus Aspergillus terreus

Nine novel butenolide derivatives, including four pairs of enantiomers, named (±)-asperteretones A-D (1a/1b-4a/4b), and a racemate, named asperteretone E (5), were isolated and identified from the coral-associated fungus Aspergillus terreus. All the structures were established based on extensive spectroscopic analyses, including HRESIMS and NMR data. The chiral chromatography analyses allowed the separation of (±)-asperteretones A-D, whose absolute configurations were further confirmed by experimental and calculated electronic circular dichroism (ECD) analysis. Structurally, compounds 2-5 represented the first examples of prenylated γ-butenolides bearing 2-phenyl-3-benzyl-4H-furan-1-one motifs, and their crucial biogenetically related metabolite, compound 1, was uniquely defined by an unexpected cleavage of oxygen bridge between C-1 and C-4. Importantly, (±)-asperteretal D and (4S)-4-decarboxylflavipesolide C were revised to (±)-asperteretones B (2a/2b) and D (4), respectively. Additionally, compounds 1a/1b-4a/4b and 5 were evaluated for the α-glucosidase inhibitory activity, and all these compounds exhibited potent inhibitory potency against α-glucosidase, with IC50 values ranging from 15.7 ± 1.1 to 53.1 ± 1.4 μM, which was much lower than that of the positive control acarbose (IC50 = 154.7 ± 8.1 μM), endowing them as promising leading molecules for the discovery of new α-glucosidase inhibitors for type-2 diabetes mellitus treatment.

Inhibition of α-Glucosidase, Intestinal Glucose Absorption, and Antidiabetic Properties by Caralluma europaea

Many medicinal plants around the world are used for therapeutic purposes against several diseases, including diabetes mellitus. Due to their composition of natural substances that are effective and do not represent side effects for users, unlike synthetic drugs, in this study, we investigated the inhibitory effect of Caralluma europaea (CE) on α-glucosidase activity in vitro; then the kinetics of the enzyme were studied with increasing concentrations of sucrose in order to determine the inhibition type of the enzyme. In addition, this effect of Caralluma europaea (CE) was confirmed in vivo using rats as an experimental animal model. Among the five fractions of CE, only the ethyl acetate fraction of C. europaea (EACe) induced a significant inhibition of α-glucosidase and its inhibition mode was competitive. The in vivo studies were conducted on mice and rats using glucose and sucrose as a substrate, respectively, to determine the oral glucose tolerance test (OGTT). The results obtained showed that the EACe and the aqueous extract of C. europaea (AECe) have significantly reduced the postprandial hyperglycemia after sucrose and glucose loading in normal and diabetic rats. AECe, also, significantly decreased intestinal glucose absorption, in situ. The results obtained showed that Caralluma europaea has a significant antihyperglycemic activity, which could be due to the inhibition of α-glucosidase activity and enteric absorption of glucose.

Bioactive Phenolics of the Genus Artemisia (Asteraceae): HPLC-DAD-ESI-TQ-MS/MS Profile of the Siberian Species and Their Inhibitory Potential Against α-Amylase and α-Glucosidase

Artemisia genus of Asteraceae family is a source of medicinal plants known worldwide and used as ethnopharmacological remedies for the treatment of diabetes in Northern Asia (Siberia). The aim of this study was to determine the phenolic profile of 12 Siberian Artemisia species (A. anethifolia, A. commutata, A. desertorum, A. integrifolia, A. latifolia, A. leucophylla, A. macrocephala, A. messerschmidtiana, A. palustris, A. sericea, A. tanacetifolia, A. umbrosa) and to test the efficacy of plant extracts and pure compounds for antidiabetic potential. Finally, by HPLC-DAD-ESI-TQ-MS/MS technique, 112 individual phenolic compounds were detected in Artemisia extracts in a wide range of concentrations. Some species accumulated rare plant phenolics, such as coumarin-hemiterpene ethers (lacarol derivatives) from A. latifolia and A. tanacetifolia; melilotoside from A. tanacetifolia; dihydrochalcones (davidigenin analogs) from A. palustris; chrysoeriol glucosides from A. anethifolia, A. sericea, and A. umbrosa; eriodictyol glycosides from A. messerschmidtiana; and some uncommon flavones and flavonols. The predominant phenolic group from Artemisia species herb was caffeoylquinic acid (CQAs), and in all species, the major CQAs were 5-O-CQA (20.28-127.99 μg/g) and 3,5-di-O-CQA (7.35-243.61 μg/g). In a series of in vitro bioassays, all studied Artemisia extracts showed inhibitory activity against principal enzymes of carbohydrate metabolism, such as α-amylase (IC₅₀ = 150.24-384.14 μg/mL) and α-glucosidase (IC₅₀ = 214.42-754.12 μg/mL). Although many phenolic compounds can be inhibitors, experimental evidence suggests that the CQAs were key to the biological response of Artemisia extracts. Mono-, di- and tri-substituted CQAs were assayed and showed inhibition of α-amylase and α-glucosidase, with IC₅₀ values of 40.57-172.47 μM and 61.08-1240.35 μM, respectively, and they were more effective than acarbose, a well-known enzyme inhibitor. The results obtained in this study reveal that Siberian Artemisia species and CQAs possess a pronounced inhibitory activity against α-amylase and α-glucosidase and could become a complement to synthetic antidiabetic drugs for controlling blood glucose level.

Potential of Potentilla inclinata and its polyphenolic compounds in α-glucosidase inhibition: Kinetics and interaction mechanism merged with docking simulations

In the present study we aimed to identify the α-glucosidase enzyme inhibitory potential of Potentilla inclinata Vill. MeOH and n-BuOH extracts which possessed remarkable α-glucosidase enzyme inhibitory effects with IC₅₀ values of 1.06±0.02 and 0.93±0.01μg/ml respectively, compared to that of acarbose (IC₅₀ 31.92±0.17). Thus, BuOH extract was chosen for further phytochemical investigations. A phenolic acid, six flavonol glycosides, and two hydrolysable tannins were isolated from the most active n-BuOH extract of the title plant. Structures of the isolated compounds were elucidated by 1D- and 2D-NMR experiments. All the compounds exhibited remarkable α-glucosidase inhibitory activity compared to the positive control, acarbose. Rutin (2) showed the highest activity with an IC₅₀ value of 26.31±0.02μg/ml. An enzyme kinetics analysis revealed that compounds 5 and 7 were competitive, 4 and 6 noncompetitive, and 3 was uncompetitive inhibitors of α-glucosidase enzyme. Molecular docking studies were performed to get insights into inhibition mechanisms of the isolates considering their inhibition type using various binding sites of the enzyme model we previously reported.

Evaluation of Asteraceae herbal extracts in the management of diabetes and obesity. Contribution of caffeoylquinic acids on the inhibition of digestive enzymes activity and formation of advanced glycation end-products (in vitro)

The study was performed to assess, for the first time, the in vitro anti-diabetic potential of ten Asteraceae plant extracts to inhibit the activity of digestive enzymes (α-amylase, α-, β-glucosidases and lipase) responsible for hydrolysis/digestion of sugar and lipids. Prevention of advanced glycation end-products (AGEs) formation was evaluated in bovine serum albumin/ribose glycation reaction model. The phytochemical profiles and caffeoylquinic acids (CQAs) contents were determined for the methanolic extract of each plant. Analyzed plant extracts exhibited significant inhibitory activity against key digestive enzymes linked to type II diabetes and obesity. A strong inhibition was observed for glucosidases and mild activity towards amylase and lipase (compared to reference compounds). Moreover, some extracts exhibited potent ability to prevent formation of AGEs, implicated in some diabetic complications. Caffeoylquinic acids were dominant in all plant extracts and findings demonstrate that these compounds are the most relevant hypoglycemic and anti-glycation agents. From the obtained results, Argyranthemum pinnatifidum, Helichrysum melaleucum, and Phagnalon lowei are good candidates for further development of phyto-pharmaceutical preparations as complementary therapy for diabetes and obesity control.

A novel library of -arylketones as potential inhibitors of α-glucosidase: Their design, synthesis, in vitro and in vivo studies

α-glucosidase is an essential enzyme located at the brush border of intestines. It is an important therapeutic target for type II diabetes. Herein we have designed a library of novel α-arylketones as inhibitors of α-glucosidase (yeast origin) via scaffold hopping and bioisosteric modification of known inhibitors of α-glucosidase. The design was validated through molecular docking that revealed strong binding interactions of the newly designed compounds against α-glucosidase. A library comprising of 15 compounds was synthesized in a combinatorial fashion, where the advanced amide intermediates were accessed through “shot gun” synthesis. The final compounds were characterized by ¹H, ¹³C-NMR and with high resolution mass spectroscopy. In vitro screening of the compounds against yeast α-glucosidase revealed substantial inhibition with IC₅₀s in the range of 4–10 μM (the standard drug acarbose inhibits α-glucosidase with an IC₅₀ of 9.95 μM). Reaction kinetics suggested mixed type inhibition. Finally, in vivo studies of the most active compound 3c against Streptozotocin induced male albino Wistar rats revealed that its administration in the rats for about 4 weeks lead to a highly significant (P < 0.001) decrease in the fasting blood glucose (FBG) compared to the untreated diabetic rats. Moreover, lower dose of 3c had better control over FBG in contrast to high-dose.

The Native Fruit Geoffroea decorticans from Arid Northern Chile: Phenolic Composition, Antioxidant Activities and In Vitro Inhibition of Pro-Inflammatory and Metabolic Syndrome-Associated Enzymes

The native tree Geoffroea decorticans (chañar) grows in the arid lands of northern Chile. It has been used as a food plant since prehistoric times. Phenolic-enriched extracts (PEEs) of Chilean chañar fruits were assessed for their chemical composition, antioxidant properties and inhibition of pro-inflammatory and metabolic syndrome-associated enzymes. Phenolic profiles were determined by HPLC-DAD-MS/MS. The PEEs of G. decorticans showed a strong effect towards the enzymes COX-1/COX-2, with inhibition percentages ranging from inactive to 92.1% and inactive to 76.0% at 50 µg PEE/mL, respectively. The IC50 values of the PEEs towards lipoxygenase and phospholipase A2 inhibitory activity were between 43.6-96.8 and 98.9-156.0 μg PEE/mL, respectively. Samples inhibited α-glucosidase (IC50 0.8-7.3 μg PEE/mL) and lipase (9.9 to >100 μg PEE/mL). However, samples did not inhibit α-amylase. The HPLC-DAD-MS analysis of the PEEs allowed the tentative identification of 53 compounds, mainly flavonol glycosides and procyanidins. The procyanidin content of the Chilean G. decorticans pulp was positively correlated with the antioxidant activity and the inhibition of the enzyme α-glucosidase. These results indicate that the Chilean chañar fruit contains bioactive polyphenols with functional properties.

Acute and sub-chronic toxicity studies of the aqueous extract from leaves of Cistus ladaniferus L. in mice and rats

ETHNOPHARMACOLOGICAL RELEVANCE

Cistus ladaniferus L. (C.ladaniferus) (Cistaceae) is an aromatic shrub native to the Mediterranean region. The leaves are widely used in traditional medicine throughout Morocco for the treatment of various diseases including, diabetes, diarrhea, inflammation, and skin ailments. However, to the best of our knowledge, no systematic study concerning its toxicity profile has been reported.

AIM OF THE STUDY

The study carried out evaluates the potential toxicity of the aqueous extract from leaves of the C.ladaniferus (CL extract) shrub, through the method of acute and sub-chronic oral administration in mice and rats.

MATERIALS AND METHODS

During the acute toxicity study, male and female mice were orally administrated with CL aqueous extract at single doses of 500, 1000, 2000, 3000 and 5000mg/kg (n = 5/group/sex). Abnormal behavior, toxic symptoms, weight, and death were observed for 14 consecutive days to assess the acute toxicity. During the sub-chronic toxicity study, the aqueous extract was administered orally at doses of 500, 700 and 1000mg/kg (n = 6/group) daily to Wistar rats of both sexes for 90 days. The general behavior of the rats was observed daily, and their body weight was recorded weekly. A urinalysis, biochemical analysis, hematological analysis, macroscopic examination and histopathological examination of several organs were conducted at the end of the treatment period.

RESULTS

During the acute toxicity test, when mice were administered doses of 3000 and 5000mg/kg, the CL extract produced a 10-30% mortality rate, respectively, and induced signs of toxicity. However, no mortality or adverse effect was noted at the doses of 1000 and 2000mg/kg. The median lethal dose (LD50) of the extract was estimated to be more than 5000mg/kg. In the subchronic study, the CL extract induced no mortality or treatment-related adverse effects with regard to body weight, general behavior, relative organ weights, urine, hematological, and biochemical parameters. Histopathological examination of vital organs showed normal architecture suggesting no morphological alterations. Moreover, the CL extracts improved lipid profile and exhibited a significant hypoglycemic effect in all doses tested in rats.

CONCLUSION

The results of the present study suggest that treatment with the CL extract for 13 weeks does not appear to produce significant toxicity, except at high dose. Therefore, the use of appropriate levels of the CL extract as a traditional medicine remedies should have a wide margin of safety for its therapeutic use.

Differential α-amylase/α-glucosidase inhibitory activities of plant-derived phenolic compounds: a virtual screening perspective for the treatment of obesity and diabetes

Recently, due to their biological properties, polyphenol-rich functional foods have been proposed to be unique supplementary and nutraceutical treatments for diabetes mellitus. Inhibition of α-amylase and α-glucosidase enzymes using natural products (especially polyphenols) is a novel oral policy to regulate carbohydrate metabolism and hyperglycemia. The present study aims to evaluate the α-amylase and α-glucosidase inhibitory activity of 26 polyphenols using molecular docking and virtual screening studies. The results speculate that among selected compounds caffeic acid, curcumin, cyanidin, daidzein, epicatechin, eridyctiol, ferulic acid, hesperetin, narenginin, pinoresinol, quercetin, resveratrol and syringic acid can significantly inhibit the α-glucosidase enzyme. In addition, catechin, hesperetin, kaempferol, silibinin and pelargonidin are potent α-amylase inhibitors. Therefore the primary structure of polyphenols can change the inhibitory effect versus the α-amylase and α-glucosidase enzymes. Finally, we speculate that consumption of polyphenol-rich functional foods (by considering the best dose of each compound and assessing their possible side effects) in diabetic patients may be useful for regulating carbohydrate metabolism and related disorders. The findings of the current study may also shed light on a way of generating a new class of amylase/glucosidase inhibitors that will discriminately inhibit the on-target enzymes with negligible undesired off-target side effects.

Procoagulant Substance and Mechanism of Myristica fragrans

The effect and mechanisms of Myristica fragrans on blood clotting were evaluated by evaluating blood coagulation time and the fibrinolytic system. The compounds 2 and 5 were isolated from the herbal extract and their activities were assessed for the first time. None of the tested compounds had fibrinolytic activity, but could inhibit the fibrinolytic activity of urokinase. Compound 2 showed the highest inhibitory activity (IC₅₀ = 1.747 mg·mL^-1) followed by compounds 4 (IC₅₀ = 1.818 mg·mL^-1) and 1 (IC₅₀ = 2.407 mg·mL^-1), which were higher than that of the compound in Danshen drug tablets (IC₅₀ = 6.577 mg·mL^-1) used in China. Moreover, compounds 1 and 2 showed strong α-glucosidase inhibitory activity in a dose-dependent manner with IC₅₀ values 21.76 ± 0.59 and 21.31 ± 0.00 μg·mL^-1, respectively. These results demonstrated that the compounds are promising candidates as procoagulant and antidiabetic agents.

In vitro antioxidant and, α-glucosidase inhibitory activities and comprehensive metabolite profiling of methanol extract and its fractions from Clinacanthus nutans

BACKGROUND

This study was aimed to evaluate antioxidant and α-glucosidase inhibitory activity, with a subsequent analysis of total phenolic and total flavonoid content of methanol extract and its derived fractions from Clinacanthus nutans accompanied by comprehensive phytochemical profiling.

METHODS

Liquid-liquid partition chromatography was used to separate methanolic extract to get hexane, ethyl acetate, butanol and residual aqueous fractions. The total antioxidant activity was determined by 2,2-diphenyl-1-picrylhydrazy (DPPH) radical scavenging and ferric reducing antioxidant power assay (FRAP). The antidiabetic activity of methanol extract and its consequent fractions were examined by α-glucosidase inhibitory bioassay. The chemical profiling was carried out by gas chromatography coupled with quadrupole time-of-flight mass spectrometry (GC Q-TOF MS).

RESULTS

The total yield for methanol extraction was (12.63 ± 0.98) % (w/w) and highest fractionated value found for residual aqueous (52.25 ± 1.01) % (w/w) as compared to the other fractions. Significant DPPH free radical scavenging activity was found for methanolic extract (63.07 ± 0.11) % and (79.98 ± 0.31) % for ethyl acetate fraction among all the fractions evaluated. Methanol extract was the most prominent in case of FRAP (141.89 ± 0.87 μg AAE/g) whereas most effective reducing power observed in ethyl acetate fraction (133.6 ± 0.2987 μg AAE/g). The results also indicated a substantial α-glucosidase inhibitory activity for butanol fraction (72.16 ± 1.0) % and ethyl acetate fraction (70.76 ± 0.49) %. The statistical analysis revealed that total phenolic and total flavonoid content of the samples had the significant (p < 0.05) impact on DPPH free radical scavenging and α-glucosidase inhibitory activity.

CONCLUSION

Current results proposed the therapeutic potential of Clinacanthus nutans, especially ethyl acetate and butanol fraction as chemotherapeutic agent against oxidative related cellular damages and control the postprandial hyperglycemia. The phytochemical investigation showed the existence of active constituents in Clinacanthus nutans extract and fractions.

Biosynthesis of α-Glucosidase Inhibitors by a Newly Isolated Bacterium, Paenibacillus sp. TKU042 and Its Effect on Reducing Plasma Glucose in a Mouse Model

Paenibacillus sp. TKU042, a bacterium isolated from Taiwanese soil, produced α-glucosidase inhibitors (aGIs) in the culture supernatant when commercial nutrient broth (NB) was used as the medium for fermentation. The supernatant of fermented NB (FNB) showed stronger inhibitory activities than acarbose, a commercial anti-diabetic drug. The IC50 and maximum α-glucosidase inhibitory activities (aGIA) of FNB and acarbose against α-glucosidase were 81 μg/mL, 92% and 1395 μg/mL, 63%, respectively. FNB was found to be strongly thermostable, retaining 95% of its relative activity, even after heating at 100 °C for 30 min. FNB was also stable at various pH values. Furthermore, FNB demonstrated antioxidant activity (IC50 = 2.23 mg/mL). In animal tests, FNB showed remarkable reductions in the plasma glucose of ICR (Institute of Cancer Research) mice at a concentration of 200 mg/kg. Combining FNB and acarbose enhanced the effect even more, with an added advantage of eliminating diarrhea. According to HPLC (High-performance liquid chromatography) fingerprinting, the Paenibacillus sp. TKU042 aGIs were not acarbose. All of the results suggest that Paenibacillus sp. TKU042 FNB could have potential use as a health food or to treat type 2 diabetes.

Antioxidative and Anti-Inflammatory Activities of Galloyl Derivatives and Antidiabetic Activities of Acer ginnala

Chromatographic isolation of the 80% MeOH extract of Acer ginnala (AG) yielded seven galloyl derivatives: gallic acid (1), ginnalin B (2), acertannin (3), maplexin D (4), maplexin E (5), quercetin-3-O-(2''-galloyl)-α-L-rhamnopyranoside (6), and kaempferol-3-O-(2''-galloyl)-α-L-rhamnopyranoside (7). This is the first study to report the isolation of compounds 4 and 5 from AG. Galloyl derivatives 3-7 exhibited potent radical scavenging activities, with 5 and 7 showing particularly strong inhibitory activities against nitric oxide production in lipopolysaccharides- (LPS-) stimulated RAW264.7 cells. In addition, oral administration of AG extract (500 mg/kg b.w.) improved symptoms of hyperglycemia and blunted the increases in serum GOT/GPT levels in a rat model of streptozotocin-induced diabetes. These results suggest that galloyl derivatives (1-7) are antioxidant and anti-inflammatory agents and that AG extract has potential as a functional material or novel herbal medicine for treating diabetes mellitus.