Evaluation of In Vitro α‐Amylase and α‐Glucosidase Inhibitory Potentials of 14 Medicinal Plants Constituted in Thai Folk Antidiabetic Formularies

The sporadic increase in the occurrence and prevalence of diabetes mellitus have compelled and vigorous search for alternative anti‐diabetic therapeutic approach from medicinal plants and its bioactive. One of the major approach employed is the reduction of gastrointestinal glucose levels through the inhibition of carbohydrate digesting enzymes notably α‐amylase and α‐glucosidase. In this study, the ethanol extracts of 14 selected plants from Mor Porn's recipe were screened for their α‐amylase and α‐glucosidase inhibitory activity. The ethanolic extract from the stem of Vitex glabrata displayed the highest percentage inhibitory activity of 84.98 ± 0.59 and 84.71 ± 1.51 against α‐glucosidase and α‐amylase enzymes, respectively. Chemical investigation of the active extract of V. glabrata indicated that pentacyclic triterpenes were the major compounds responsible for the activity. The result obtained from this study suggests the potential use of V. glabrata as an alternative natural source for the treatment of diabetes mellitus.     

IFN‐γ inhibits basal and α‐MSH‐induced melanogenesis

Inflammatory cytokines are closely related to pigmentary changes. In this study, the effects of IFN‐γ on melanogenesis were investigated. IFN‐γ inhibits basal and α‐MSH‐induced melanogenesis in B16 melanoma cells and normal human melanocytes. MITF mRNA and protein expressions were significantly inhibited in response to IFN‐γ. IFN‐γ inhibited CREB binding to the MITF promoter but did not affect CREB phosphorylation. Instead, IFN‐γ inhibited the association of CBP and CREB through the increased association between CREB binding protein (CBP) and STAT1. These findings suggest that IFN‐γ inhibits both basal and α‐MSH‐induced melanogenesis by inhibiting MITF expression. The inhibitory action of IFN‐γ in α‐MSH‐induced melanogenesis is likely to be associated with the sequestration of CBP via the association between CBP and STAT1. These data suggest that IFN‐γ plays a role in controlling inflammation‐ or UV‐induced pigmentary changes.     

5α‐Androst‐16‐en‐3α‐ol β‐D‐Glucuronide,Precursor of 5α‐Androst‐16‐en‐3α‐ol in Human Sweat

5α‐Androst‐16‐en‐3α‐ol (α‐androstenol) is an important contributor to human axilla sweat odor. It is assumed that α‐andostenol is excreted from the apocrine glands via a H₂O‐soluble conjugate, and this precursor was formally characterized in this study for the first time in human sweat. The possible H₂O‐soluble precursors, sulfate and glucuronide derivatives, were synthesized as analytical standards, i.e., α‐androstenol, β‐androstenol sulfates, 5α‐androsta‐5,16‐dien‐3β‐ol (β‐androstadienol) sulfate, α‐androstenol β‐glucuronide, α‐androstenol α‐glucuronide, β‐androstadienol β‐glucuronide, and α‐androstenol β‐glucuronide furanose. The occurrence of α‐androstenol β‐glucuronide was established by ultra performance liquid chromatography (UPLC)/MS (heated electrospray ionization (HESI)) in negative‐ion mode in pooled human sweat, containing eccrine and apocrine secretions and collected from 25 female and 24 male underarms. Its concentration was of 79 ng/ml in female secretions and 241 ng/ml in male secretions. The release of α‐androstenol was observed after incubation of the sterile human sweat or α‐androstenol β‐glucuronide with a commercial glucuronidase enzyme, the urine‐isolated bacteria Streptococcus agalactiae, and the skin bacteria Staphylococcus warneri DSM 20316, Staphylococcus haemolyticus DSM 20263, and Propionibacterium acnes ATCC 6919, reported to have β‐glucuronidase activities. We demonstrated that if α‐ and β‐androstenols and androstadienol sulfates were present in human sweat, their concentrations would be too low to be considered as potential precursors of malodors; therefore, the H₂O‐soluble precursor of α‐androstenol in apocrine secretion should be a β‐glucuronide.     

Synephrine and phenylephrine act as α‐amylase, α‐glycosidase,acetylcholinesterase, butyrylcholinesterase,and carbonic anhydrase enzymes inhibitors

In this paper, synephrine and phenylephrine compounds showed excellent inhibitory effects against human carbonic anhydrase (hCA) isoforms I and II, α‐amylase, α‐glycosidase, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE). Synephrine and phenylephrine had K_i values of 199.02 ± 16.01 and 65.01 ± 5.00 μM against hCA I and 336.02 ± 74.01 and 92.04  ±  18.03 μM against hCA II, respectively. On the other hand, their K_i values were found to be 169.10  ±  80.03 and 88.03  ±  5.01 nM against AChE and 177.06  ±  6.01 and 78.03  ±  3.05 nM against BChE, respectively. α‐Amylase and α‐glycosidase enzymes were easily inhibited by these compounds. α‐Glycosidase inhibitors, generally defined to as starch blockers, are anti‐diabetic drugs that help to decrease post comestible blood glucose levels.     

The importance of starch and sucrose digestion in nutritive biology of synanthropic acaridid mites: α‐Amylases and α‐glucosidases are suitable targets for inhibitor‐based strategies of mite control

The adaptation of nine species of mites that infest stored products for starch utilization was tested by (1) enzymatic analysis using feces and whole mite extracts, (2) biotests, and (3) inhibition experiments. Acarus siro, Aleuroglyphus ovatus, and Tyroborus lini were associated with the starch‐type substrates and maltose, with higher enzymatic activities observed in whole mite extracts. Lepidoglyphus destructor was associated with the same substrates but had higher activities in feces. Dermatophagoides farinae, Chortoglyphus arcuatus, and Caloglyphus redickorzevi were associated with sucrose. Tyrophagus putrescentiae and Carpoglyphus lactis had low or intermediate enzymatic activity on the tested substrates. Biotests on starch additive diets showed accelerated growth of species associated with the starch‐type substrates. The inhibitor acarbose suppressed starch hydrolysis and growth of the mites. We suggest that the species with higher starch hydrolytic activity in feces were more tolerant to acarbose, and α‐amylase and α‐glucosidase of synanthropic mites are suitable targets for inhibitor‐based strategies of mite control. © 2009 Wiley Periodicals, Inc.     

Biotransformation of (−)‐(R)‐α‐Phellandrene: Antimicrobial Activity of Its Major Metabolite

Terpene derivatives converted by microbial biotransformation constitute an important resource for natural pharmaceutical, fragrance, and aroma substances. In the present study, the monoterpene α‐phellandrene was biotransformed by 16 different strains of microorganisms (bacteria, fungi, and yeasts). The transformation metabolites were initially screened by TLC and GC/MS, and then further characterized by NMR spectroscopic techniques. Among the six metabolites characterized, 6‐hydroxypiperitone, α‐phellandrene epoxide, cis‐p‐menth‐2‐en‐1‐ol, and carvotanacetone, which originated from (?)‐(R)‐α‐phellandrene, are reported for the first time in this study. Additionally, the substrate and the metabolite 5‐p‐menthene‐1,2‐diol were subjected to in vitro antibacterial and anticandidal tests. The metabolite showed moderate‐to‐good inhibitory activities (MICs=0.125 to >4 mg/ml) against various bacteria and especially against Candida species in comparison with its substrate (?)‐(R)‐α‐phellandrene and standard antimicrobial agents.     

Anti‐Lipid Peroxidation, α‐Glucosidase and α‐Amylase Inhibitory Effects of the Extract of Capitula of Coreopsis tinctoria Nutt. and Protection Effects on High‐Fat/High‐Sugar and Streptozotocin‐Induced Type 2 Diabetes in Mice

Coreopsis tinctoria capitula (CTC) of the Compositae family has been used traditionally to treat various diseases in China, particularly type 2 diabetes mellitus (T2DM). This study evaluated the anti‐lipid peroxidation, α‐glucosidase and α‐amylase inhibitory effects of CTC extracts, and analyzed its chemical composition by HPLC. Moreover, the antioxidant activity and protection effects of CTC extracts were investigated on high‐fat/high‐sugar and streptozotocin‐induced T2DM mice. In vitro study, the ethyl acetate extract (EAE) and butanol extract (BE) of CTC exhibited anti‐lipid peroxidation (IC₅₀: BHA>BE or EAE>ascorbic acid, p<0.05) and α‐glucosidase inhibitory activity (IC₅₀: BE>EAE, p<0.05). In vivo, the BE at the dose of 600 mg/kg was intragastrically given to T2DM mice, which exhibited a certain extent of repair and improvement of the levels of CAT, GSH, GSH‐P_X, SOD, as well as plasma biomarkers, compared with those in the model group (p<0.05). These results demonstrated that CTC extracts have a positive effect to treat T2DM and it can be used for the treatment of T2DM in the future.     

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.     

Glucocorticoid‐transactivated TSC22D3 attenuates hypoxia‐ and diabetes‐induced Müller glial galectin‐1 expression via HIF‐1α destabilization

Galectin‐1/LGALS1, a newly recognized angiogenic factor, contributes to the pathogenesis of diabetic retinopathy (DR). Recently, we demonstrated that glucocorticoids suppressed an interleukin‐1β‐driven inflammatory pathway for galectin‐1 expression in vitro and in vivo. Here, we show glucocorticoid‐mediated inhibitory mechanism against hypoxia‐inducible factor (HIF)‐1α‐involved galectin‐1 expression in human Müller glial cells and the retina of diabetic mice. Hypoxia‐induced increases in galectin‐1/LGALS1 expression and promoter activity were attenuated by dexamethasone and triamcinolone acetonide in vitro. Glucocorticoid application to hypoxia‐stimulated cells decreased HIF‐1α protein, but not mRNA, together with its DNA‐binding activity, while transactivating TSC22 domain family member (TSC22D)3 mRNA and protein expression. Co‐immunoprecipitation revealed that glucocorticoid‐transactivated TSC22D3 interacted with HIF‐1α, leading to degradation of hypoxia‐stabilized HIF‐1α via the ubiquitin‐proteasome pathway. Silencing TSC22D3 reversed glucocorticoid‐mediated ubiquitination of HIF‐1α and subsequent down‐regulation of HIF‐1α and galectin‐1/LGALS1 levels. Glucocorticoid treatment to mice significantly alleviated diabetes‐induced retinal HIF‐1α and galectin‐1/Lgals1 levels, while increasing TSC22D3 expression. Fibrovascular tissues from patients with proliferative DR demonstrated co‐localization of galectin‐1 and HIF‐1α in glial cells partially positive for TSC22D3. These results indicate that glucocorticoid‐transactivated TSC22D3 attenuates hypoxia‐ and diabetes‐induced retinal glial galectin‐1/LGALS1 expression via HIF‐1α destabilization, highlighting therapeutic implications for DR in the era of anti‐vascular endothelial growth factor treatment.     

Synthesis and antimicrobial activity of α‐aminoboronic‐containing peptidomimetics

A library of 175 dipeptidomimetics and tripeptidomimetics containing an α‐amino boronic acid or boronate has been synthesized, and the activity toward Mycobacterium tuberculosis, Candida albicans, Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli and Pseudomonas aeruginosa has been screened. Although there is no clear structure–activity relationship, several compounds exhibit promising activity against different pathogens. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

α‐Glucosidase Inhibitors from the Fungus Aspergillus terreus 3.05358

One new diketopiperazine alkaloid amauromine B ( 1 ), along with three known meroterpenoids, austalide B ( 2 ), austalides N and O ( 3 and 4 ), and two known steroids ( 5 and 6 ), was isolated and identified from the culture broth of the fungus Aspergillus terreus 3.05358. Their structures were elucidated by extensive spectroscopic techniques, including 2D‐NMR and MS analysis, the absolute configuration of 1 was unambiguously established by single crystal X‐ray diffraction analysis. All the isolates were evaluated for their inhibitory effects on α‐glucosidase. Amauromine B ( 1 ) and austalide N ( 3 ) exhibited more potent α‐glucosidase inhibitory activities than the positive control acarbose.     

Synthesis and Antiproliferative Activities of Novel Substituted 5‐Anilino‐α‐Glucofuranose Derivatives

In order to find novel antitumor candidate agents with high efficiency and low toxicity, 14 novel substituted 5‐anilino‐α‐glucofuranose derivatives have been designed, synthesized and evaluated for antiproliferative activities in vitro. Their structures were characterized by NMR (¹H and ¹³C) and HR‐MS, and configuration (R/S) at C(5) was identified by two‐dimensional ¹H,¹H‐NOESY‐NMR spectrum. Their antiproliferative activities against human tumor cells were investigated by MTT assay. The results demonstrated that most of the synthesized compounds had antiproliferative effects comparable to the reference drugs gefitinib and lapatinib. In particular, (5R)‐5‐O‐(3‐chloro‐4‐{[5‐(4‐fluorophenyl)thiophen‐2‐yl]methyl}anilino)‐5‐deoxy‐1,2‐O‐(1‐methylethylidene)‐α‐glucofuranose ( 9da ) showed the most potent antiproliferative effects against SW480, A431 and A549 cells, with IC₅₀ values of 8.57, 5.15 and 15.24 μm , respectively. This work suggested 5‐anilino‐α‐glucofuranose as an antitumor core structure that may open a new way to develop more potent anti‐cancer agents.     

Integrated Genome and Protein Editing Swaps α‐2,6 Sialylation for α‐2,3 Sialic Acid on Recombinant Antibodies from CHO

Immunoglobin G with α‐2,6 sialylation has been reported to have an impact on antibody‐dependent cellular cytotoxicity and anti‐inflammatory efficacy. However, production of antibodies with α‐2,6 sialylation from Chinese hamster ovary cells is challenging due to the inaccessibility of sialyltransferases for the heavy chain N‐glycan site and the presence of exclusively α‐2,3 sialyltransferases. In this study, combining mutations on the Fc regions to allow sialyltransferase accessibility with overexpression of α‐2,6 sialyltransferase produced IgG with significant levels of both α‐2,6 and α‐2,3 sialylation. Therefore, ST3GAL4 and ST3GAL6 genes were disrupted by CRISPR/Cas9 to minimize the α‐2,3 sialylation. Sialidase treatment and SNA lectin blot indicated greatly increased α‐2,6 sialylation level relative to α‐2,3 sialylation for the α‐2,3 sialyltransferase knockouts when combined with α‐2,6 sialyltransferase overexpression. Indeed, α‐2,3 linked sialic acids were not detected on IgG produced from the α‐2,3 sialyltransferase knockout‐α‐2,6 sialyltransferase overexpression pools. Finally, glycoprofiling of IgG with four amino acid substitutions expressed from an α‐2,3 sialyltransferase knockout‐α‐2,6 sialyltransferase stable clone resulted in more than 77% sialylated glycans and more than 62% biantennary disialylated glycans as indicated by both MALDI‐TOF and LC‐ESI‐MS. Engineered antibodies from these modified Chinese hamster ovary cell lines will provide biotechnologists with IgGs containing N‐glycans with different structural variations for examining the role of glycosylation on protein performance.     

A TLC bioautographic method for the detection of α‐ and β‐glucosidase inhibitors in plant extracts

Introduction – Bioautographic assays using TLC play an important role in the search for active compounds from plants. A TLC assay has previously been established for the detection of β‐glucosidase inhibitors but not for α‐glucosidase. Nonetheless, α‐glucosidase inhibition is an important target for therapeutic agents against of type 2 diabetes and anti‐viral infections. Objective – To develop a TLC bioautographic method to detect α‐ and β‐glucosidase inhibitors in plant extracts. Methodology – The enzymes α‐ and β‐d ‐glucosidase were dissolved in sodium acetate buffer. After migration of the samples, the TLC plate was sprayed with enzyme solution and incubated at room temperature for 60 min in the case of α‐d ‐glucosidase, and 37°C for 20 min in the case of β‐d ‐glucosidase. For detection of the active enzyme, solutions of 2‐naphthyl‐α‐D‐glucopyranoside or 2‐naphthyl‐β‐D‐glucopyranoside and Fast Blue Salt were mixed at a ratio of 1 : 1 (for α‐d ‐glucosidase) or 1 : 4 (for β‐d ‐glucosidase) and sprayed onto the plate to give a purple background colouration after 2–5 min. Results – Enzyme inhibitors were visualised as white spots on the TLC plates. Conduritol B epoxide inhibited α‐d ‐glucosidase and β‐d ‐glucosidase down to 0.1 µg. Methanol extracts of Tussilago farfara and Urtica dioica after migration on TLC gave enzymatic inhibition when applied in amounts of 100 µg for α‐glucosidase and 50 µg for β‐glucosidase. Conclusion – The screening test was able to detect inhibition of α‐ and β‐glucosidases by pure reference substances and by compounds present in complex matrices, such as plant extracts. Copyright © 2009 John Wiley & Sons, Ltd.     

TAPP analogs containing β3‐homo‐amino acids: synthesis and receptor binding

β‐Amino acids containing α,β‐hybrid peptides show great potential as peptidomimetics. In this paper, we describe the synthesis and affinity to μ‐opioid and δ‐opioid receptors of α,β‐hybrids, analogs of the tetrapeptide Tyr‐ d ‐Ala‐Phe‐Phe‐NH₂ (TAPP). Each amino acid was replaced with an l ‐ or d ‐β³‐h‐amino acid. All α,β‐hybrids of TAPP analogs were synthesized in solution and tested for affinity to μ‐opioid and δ‐opioid receptors. The analog Tyr‐β³h‐ d ‐Ala‐Phe‐PheNH₂ was found to be as active as the native tetrapeptide. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.     

Effects of solvent fractions of Allomyrina dichotoma larvae through the inhibition of in vitro BACE1 and β‐amyloid(25–35)‐induced toxicity in rat pheochromocytoma PC12 cells

Amyloid‐β peptide (Aβ) generation initiated by β‐site amyloid precursor protein cleaving enzyme 1 BACE1 is a critical cause of Alzheimer's disease. In the course of our ongoing investigation of natural anti‐dementia resources, the ethyl acetate (EtOAc) fraction exerted strong BACE1‐specific inhibition with the half maximal inhibitory concentration (IC₅₀) value of 9.2 × 10^?5 μg/mL. Furthermore, Aβ(25–35)‐induced cell death was predominantly prevented by the EtOAc fraction of Allomyrina dichotoma larvae through diminishing of cellular oxidative stress and attenuating apoptosis by inhibiting caspase‐3 activity. Taken together, the present study demonstrated that A. dichotoma larvae possess novel neuroprotective properties not only via the selective and specific inhibition of BACE1 activity but also through the alleviation of Aβ(25–35)‐induced toxicity, which may raise the possibility of therapeutic application of A. dichotoma larvae for preventing and/or treating dementia.     

Costus spiralis (Jacq.) Roscoe: A Novel Source of Flavones with α‐Glycosidase Inhibitory Activity

Costus spiralis, a plant used in traditional Brazilian medicine for the treatment of complications in diabetes, was investigated. Assay of hexane, ethyl acetate, methanol, and aqueous fractions obtained by partition of a crude methanol extract of dried leaves of C. spiralis revealed that AGI activity was confined to the ethyl acetate fraction. Purification of this fraction yielded schaftoside and isoschaftoside. The AGI activities of the two flavones were lower than, but comparable with, that of the anti‐diabetic drug acarbose. In contrast, the IC₅₀ value of the ethyl acetate fraction was 1.95‐, 2.34‐, and 2.22‐fold higher than those of acarbose, schaftoside, and isoschaftoside, respectively. The results demonstrate for the first time that schaftoside and isoschaftoside are responsible, in part, for the AGI activity of C. spiralis. Our study suggests that further investigations into C. spiralis may lead to the discovery of additional compounds with antihyperglycemic activity.     

Stereoselective Synthesis of (3R)‐3‐Alkyl‐4,1‐Benzoxazepine‐2,5‐Diones

Novel 3‐alkyl‐4,1‐benzoxazepine‐2,5‐diones were synthesized in good ee exploiting the chiral pool methodology, an economical way of asymmetric synthesis. Various anthranilic acids are coupled with different α‐haloacids to afford N‐acylated anthranilic acid intermediates which undergo cyclization to (3R)‐3‐alkyl‐4,1‐benzoxazepines‐2,5‐diones. Chirality 25:865–870, 2013. © 2013 Wiley Periodicals, Inc.     

Antibacterial Δ1‐3‐Ketosteroids from the South China Sea Gorgonian Coral Subergorgia rubra

Three new Δ¹‐3‐ketosteroids characterized with a 9‐OH, subergosterones A–C ( 1 – 3 ), together with five known analogs 4 – 8 , were obtained from the gorgonian coral Subergorgia rubra collected from the South China Sea. The structures of 1 – 3 , including their absolute configurations, were determined by comprehensive spectroscopic methods and electronic circular dichroism (ECD) experiments. Compounds 2 and 3 exhibited inhibitory antibacterial activities against Bacillus cereus with MIC values of 1.56 μM .     

Conformations of peptides containing a chiral cyclic α, α‐disubstituted α‐amino acid within the sequence of Aib residues

A single chiral cyclic α,α‐disubstituted amino acid, (3S,4S)‐1‐amino‐(3,4‐dimethoxy)cyclopentanecarboxylic acid [(S,S)‐Ac₅c^dOM], was placed at the N‐terminal or C‐terminal positions of achiral α‐aminoisobutyric acid (Aib) peptide segments. The IR and ¹H NMR spectra indicated that the dominant conformations of two peptides Cbz‐[(S,S)‐Ac₅c^dOM]‐(Aib)₄‐OEt ( 1) and Cbz‐(Aib)₄‐[(S,S)‐Ac₅c^dOM]‐OMe (2) in solution were helical structures. X‐ray crystallographic analysis of 1 and 2 revealed that a left‐handed (M) 3₁₀‐helical structure was present in 1 and that a right‐handed (P) 3₁₀‐helical structure was present in 2 in their crystalline states. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.