Two novel aminooligosaccharides isolated from the culture of Streptomyces coelicoflavus ZG0656 as potent inhibitors of alpha-amylase

Acarbose glycosylation by AcbE for the production of acarstatins with enhanced α-amylase inhibitory activity

Acarbose is a potent glycosidase inhibitor widely used in the clinical treatment of type 2 diabetes mellitus (T2DM). Various acarbose analogs have been identified while exploring compounds with improved pharmacological properties. In this study, we found that AcbE from Actinoplanes sp. SE50/110 catalyzes the production of acarbose analogs that exhibit significantly improved inhibitory activity towards α-amylase than acarbose. Recombinant AcbE mainly catalyzed the formation of two new compounds, namely acarstatins A and B, using acarbose as substrate. Using high-resolution mass spectrometry, nuclear magnetic resonance, and glycosidase hydrolysis, we elucidated their chemical structures as O-α-d-maltosyl-(1 → 4)-acarbose and O-α-d-maltotriosyl-(1 → 4)-acarbose, respectively. Acarstatins A and B exhibited 1584- and 1478-fold greater inhibitory activity towards human salivary α-amylase than acarbose. Furthermore, both acarstatins A and B exhibited complete resistance to microbiome-derived acarbose kinase 1-mediated phosphorylation and partial resistance to acarbose-preferred glucosidase-mediated hydrolysis. Therefore, acarstatins A and B have great potential as candidate therapeutic agents for T2DM.

Natural Inhibitors of Mammalian α-Amylases as Promising Drugs for the Treatment of Metabolic Diseases

α-Amylase is a generally acknowledged molecular target of a distinct class of antidiabetic drugs named α-glucosidase inhibitors. This class of medications is scarce and rather underutilized, and treatment with current commercial drugs is accompanied by unpleasant adverse effects. However, mammalian α-amylase inhibitors are abundant in nature and form an extensive pool of high-affinity ligands that are available for drug discovery. Individual compounds and natural extracts and preparations are promising therapeutic agents for conditions associated with impaired starch metabolism, e.g., diabetes mellitus, obesity, and other metabolic disorders. This review focuses on the structural diversity and action mechanisms of active natural products with inhibitory activity toward mammalian α-amylases, and emphasizes proteinaceous inhibitors as more effective compounds with significant potential for clinical use.

Acarbose May Function as a Competitive Exclusion Agent for the Producing Bacteria

Acarbose is a well-known microbial specialized metabolite used clinically to treat type 2 diabetes. This natural pseudo-oligosaccharide (PsOS) shows potent inhibitory activity toward various glycosyl hydrolases, including α-glucosidases and α-amylases. While acarbose and other PsOSs are produced by many different bacteria, their ecological or biological role in microbial communities is still an open question. Here, we show that several PsOS-producing actinobacteria, i.e., Actinoplanes sp. SE50/110 (acarbose producer), Streptomyces glaucescens GLA.O (acarbose producer), and Streptomyces dimorphogenes ATCC 31484 (trestatin producer), can grow in the presence of acarbose, while the growth of the non-PsOS-producing organism Streptomyces coelicolor M1152 was suppressed when starch is the main source of energy. Further investigations using recombinant α-amylases from S. coelicolor M1152 and the PsOS-producing actinobacteria revealed that the S. coelicolor α-amylase was inhibited by acarbose, whereas those from the PsOS-producing bacteria were not inhibited by acarbose. Bioinformatic and protein modeling studies suggested that a point mutation in the α-amylases of the PsOS-producing actinobacteria is responsible for the resistance of those enzymes toward acarbose. Converting the acarbose-resistant α-amylase AcbE to its A304H variant diminished its acarbose-resistance property. Taken together, the results suggest that acarbose is used by the producing bacteria as a competitive exclusion agent to suppress the growth of other microorganisms in their natural environment, while the producing organisms equip themselves with α-amylase variants that are resistant to acarbose.

Novel α-Amylase Inhibitor Hemi-Pyocyanin Produced by Microbial Conversion of Chitinous Discards

α-Amylase inhibitors (aAIs) have been applied for the efficient management of type 2 diabetes. The aim of this study was to search for potential aAIs produced by microbial fermentation. Among various bacterial strains, Pseudomonas aeruginosa TUN03 was found to be a potential aAI-producing strain, and shrimp heads powder (SHP) was screened as the most suitable C/N source for fermentation. P. aeruginosa TUN03 exhibited the highest aAIs productivity (3100 U/mL) in the medium containing 1.5% SHP with an initial pH of 7–7.5, and fermentation was performed at 27.5 °C for two days. Further, aAI compounds were investigated for scaled-up production in a 14 L-bioreactor system. The results revealed a high yield (4200 U/mL) in a much shorter fermentation time (12 h) compared to fermentation in flasks. Bioactivity-guided purification resulted in the isolation of one major target compound, identified as hemi-pyocyanin (HPC) via gas chromatography-mass spectrometry and nuclear magnetic resonance. Its purity was analyzed by high-performance liquid chromatography. HPC demonstrated potent α-amylase inhibitory activity comparable to that of acarbose, a commercial antidiabetic drug. Notably, HPC was determined as a new aAI. The docking study indicated that HPC inhibits α-amylase by binding to amino acid Arg421 at the biding site on enzyme α-amylase with good binding energy (−9.3 kcal/mol) and creating two linkages of H-acceptors.

Determination of the Chemical Composition, Antioxidant, and Enzyme Inhibitory Activity of Onosma mollis DC

Onosma species have long been used traditionally for respiratory tract infections, abdominal pain, wound treatment, burns, and constipation. This study aims to investigate the chemical composition and in vitro antioxidant and enzyme inhibitory activities of ethyl acetate (EtOAc), methanol (MeOH), and water extracts of Onosma mollis DC. MeOH extract was richer in both phenolics and flavonoids than other extracts (44.06 mg GAEs/g and 41.57 mg QEs/g, respectively). The findings obtained from the results of the chromatographic analysis also supported the results of the spectrophotometric analysis. The MeOH extract was the richest in terms of most of the phytochemicals screened. Apigenin 7-glucoside, luteolin 7-glucoside, rosmarinic acid, vanillic acid, and pinoresinol were over 1000.0 μg/g in MeOH extract. The extract in question showed the highest activity in phosphomolybdenum, DPPH, and ABTS radical scavenging and CUPRAC and FRAP reducing power activity assays (2.01, 3.33, 2.30, 1.48, and 0.79 mg/ml, respectively). The water extract presented the highest activity in the ferrous ion chelating assay (1.01 mg/ml). While EtOAc extract showed high activity in acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and α-glucosidase inhibitory activity tests (1.11, 1.49, and 1.07 mg/ml, respectively), MeOH extract showed significant efficacy in tyrosinase and α-amylase inhibitory activity assays (2.94 and 2.08 mg/ml, respectively). There was a high correlation between the total phenolics/flavonoids of the extracts and their antioxidant activities (correlation coefficients were over 0.9). In addition, the phytochemicals mentioned above were found to contribute significantly to the antioxidant activity. It was concluded that a more detailed analysis should be done to determine the compounds responsible for the enzyme inhibitory activities of the extracts.

Microbial Oligosaccharides with Biomedical Applications

Microbial oligosaccharides have been regarded as one of the most appealing natural products attributable to their potent and selective bioactivities, such as antimicrobial activity, inhibition of α-glucosidases and lipase, interference of cellular recognition and signal transduction, and disruption of cell wall biosynthesis. Accordingly, a handful of bioactive oligosaccharides have been developed for the treatment of bacterial infections and type II diabetes mellitus. Given that naturally occurring oligosaccharides have increasingly gained recognition in recent years, a comprehensive review is needed. The current review highlights the chemical structures, biological activities and divergent biosynthetic origins of three subgroups of oligomers including the acarviosine-containing oligosaccharides, saccharomicins, and orthosomycins.

Screening chemical inhibitors for alpha-amylase from leaves extracts of Murraya koenigii (Linn.) and Aegle marmelos L

OBJECTIVES

Aqueous leaves extracts of Murraya koenigii (M. koenigii) and Aegle marmelos (A. marmelos) were prepared and effect of the extracts on inhibiting alpha-amylase playing essential roles on converting starch into glucose have been examined using in vitro assays.

METHODS

Alpha amylase inhibitory assay was used to asses the in vitro antidiabetic activity of the extracts. Gas chromatography-mass spectrometry (GC-MS) analysis was performed to identify the volatile molecules of the extracts. Identified molecule were converted as ligand and docked against human pancreatic α-amylase (0.95 Å; PDB ID: 5U3A) using Autodock tool.

RESULTS

The data analyzes suggested that the alpha-amylase inhibition potential of the extract obtained from M. koenigii was stronger than that of the A. marmelos at low concentrations (<1 mg/mL), whereas both the extracts depicted similar inhibition effects on the enzyme at high concentration (>1 mg/mL). The phytochemicals present in both the plant extracts were identified by using their respective GC-MS data and the data analyzes revealed that the extracts of M. koenigii and A. Marmelos seemed to consist of about 20 and 24 diverse chemical molecules, respectively. Through the molecular docking studies, azulene of M. koenigii and hydroxycyclodecadiene of A. marmelos showed higher binding affinity on alpha-amylase.

CONCLUSIONS

Concentration-dependent alpha-amylase inhibition effects of the extracts were observed and M. koenigii contains more alpha-amylase inhibitory effects due to the presence of azulene. This is primary lead to find out the better anti diabetic natural based drug to the society after clinical trial.

An Insight of Alpha-amylase Inhibitors as a Valuable Tool in the Management of Type 2 Diabetes Mellitus

BACKGROUND

Among the millions of people around the world, the most prevalent metabolic disorder is diabetes mellitus. Due to the drawbacks which are associated with commercially available antidiabetic agents, new therapeutic approaches are needed to be considered. Alpha-amylase is a membrane- bound enzyme which is responsible for the breakdown of polysaccharides such as starch to monosaccharides which can be absorbed.

METHODS

We searched the scientific database using alpha-amylase, diabetes, antidiabetic agents as the keywords. Here in, only peer-reviewed research articles were collected which were useful to our current work.

RESULTS

To overcome the research gap, the alpha-amylase enzyme is regarded as a good target for antidiabetic agents to design the drug and provide an alternate approach for the treatment of type 2 diabetes mellitus. Basically, alpha-amylase inhibitors are classified into two groups: proteinaceous inhibitors, and non-proteinaceous inhibitors. Recently, non-proteinaceous inhibitors are being explored which includes chalcones, flavones, benzothiazoles, etc. as the potential antidiabetic agents.

CONCLUSION

Herein, we discuss various potential antidiabetic agents which are strategically targeted alpha-amylase enzyme. These are having lesser side effects as compared to other antidiabetic agents, and are proposed to prevent the digestion and absorption of glucose leading to a decrease in the blood glucose level.

Inhibitory effects of a sulfated polysaccharide isolated from edible red alga Bangia fusco-purpurea on α-amylase and α-glucosidase

In this study, a sulfated polysaccharide (BFP) was isolated from the edible red alga Bangia fusco-purpurea. Gel-filtration and thin layer chromatographically analyses suggested that BFP was a homogenous polysaccharide. The chemical structural analysis revealed that BFP mainly consisted of galactose together with a small amount of uronic acid, mannose, and glucose. Its molecular mass was estimated to be 133.18 kDa by high-performance liquid chromatography (HPLC) analysis. BFP inhibited α-amylase and α-glucosidase in a concentration-dependent manner. The IC50 values of BFP against α-amylase and α-glucosidase were estimated to be 1.26 ± 0.11 mg/mL and 1.34 ± 0.07 mg/mL, respectively. Kinetic analyses suggested that BFP showed competitive and non-competitive inhibition against α-amylase and α-glucosidase, respectively. Circular dichroism spectral and fluorescence spectral analyses suggested that BFP affects the conformational structures of these enzymes, which may lead to the inhibition of the enzymatic activities.

Abbreviations: Ara: D-arabinose; AnGal: anhydro-L-galactose residues; CD spectroscopy: Circular Dichroism spectroscopy; DNS: dinitrosalicylic acid; FT-IR: fourier transform infrared spectra; Fuc: L-fucose; Gal: D-galactose; Glc: D-glucose; GlcA: D-Glucuronic acid; HPLC: high performance liquid chromatography; Man: D-mannose; pNPG: p-nitrophenyl-α-D-glucoside; TFA: trifluoroacetic acid; TLC: thin-layer chromatography; PMP: 1-phenyl-3-methyl-5-pyrazolone; Xyl: D-xylose

Structural elucidation and bioactivities of a novel arabinogalactan from Coreopsis tinctoria

Coreopsis tinctoria is being widely cultivated in Xinjiang of China, whose consumption is known to prevent diabetes and neurodegenerative diseases. To elucidate the bioactive ingredients responsible for these benefits, the alkaline soluble crude polysaccharide (CTB) was isolated from C. tinctoria. In vitro experiments showed that the inhibition of α-amylase and α-glucosidase by CTB was 13407-fold and 906-fold higher than that by positive control, respectively. Then, a novel arabinogalactan, CTBP-1, was isolated and purified from CTB. Structural analysis showed that CTBP-1 possessed a 1,6-linked β-d-Galp and 1,5-linked α-l-Araf backbone with branches substituted at the C-3 position of the 1,6-linked β-d-Galp, and the side chains included 1,5-linked α-l-Araf, T-linked β-d-Galp and T-linked α-l-Araf. The inhibitory effects of CTBP-1 on α-amylase and α-glucosidase were 2.7 and 17.9 times that of acarbose, respectively. CTBP-1 could avoid indigestion and similar side effects. In addition, CTBP-1 remarkably inhibited the release of nitric oxide (NO), tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in lipopolysaccharide (LPS)-stimulated BV2 microglial cells. In summary, CTBP-1 is a novel arabinogalactan with great potential as a treatment for type 2 diabetes and Alzheimer's disease.

Suppressive effect of ascophyllan HS on postprandial blood sugar level through the inhibition of α-glucosidase and stimulation of glucagon-like peptide-1 (GLP-1) secretion

A sulfated polysaccharide ascophyllan inhibited α-glucosidase in a concentration dependent manner, and >90% activity was inhibited at 1.0 mg/mL. The inhibitory activity was much higher than that of acarbose. No significant inhibitory effect of ascophyllan on α-amylase was observed up to 10.0 mg/mL. Ascophyllan HS, a commercially available ascophyllan preparation showed even higher inhibitory effect on α-glucosidase than ascophyllan. Interestingly, ascophyllan and ascophyllan HS induced the secretion of glucagon-like peptide-1 (GLP-1) from human intestinal NCI-H716 cell line in a concentration dependent manner (10-100 ng/mL). The oral glucose tolerance tests revealed that after continuous 8-week ingestion of ascophyllan HS at 100 mg/day, the glucose area under the curve values of the ascophyllan HS ingested group were significantly lower than placebo ingested group. Serum glycosylated hemoglobin (HbA1c) level in ascophyllan HS ingested group tended to decrease after 8-week ingestion, whereas no significant change was observed in placebo ingested group. This is the first report indicating that ascophyllan can induce the secretion of GLP-1 from human intestinal cell line (NCI-H716), besides the potent inhibitory effect on α-glucosidase. Furthermore, clinical trial suggested that ascophyllan HS may be a practically applicable blood glucose controlling agent in humans.

Acylated Aminooligosaccharides with Inhibitory Effects against α-Amylase from Streptomyces sp. HO1518

Five new acylated aminooligosaccharides (1–5), together with one known related analogue (6), were isolated from Streptomyces sp. HO1518. Their structure was identified by extensive spectroscopic analysis, including 1D and 2D NMR data and high resolution electrospray ionization mass spectrometry (HRESIMS), and by comparison with those reported in the literature. All of the new compounds showed more promising porcine pancreatic α-amylase (PPA) inhibitory activities than the clinical drug acarbose, indicating them as potential pharmaceutical drug leads toward type II diabetes.

Biosynthesis and Metabolic Engineering of Pseudo-oligosaccharides

Pseudo-oligosaccharides are microbial-derived secondary metabolites whose chemical structures contain pseudosugars (glycomimetics). Due to their high resemblance to the molecules of life (carbohydrates), most pseudo-oligosaccharides show significant biological activities. Some of them have been used as drugs to treat human and plant diseases. Because of their significant economic value, efforts have been put into understanding their biosynthesis, optimizing their fermentation conditions, and engineering their metabolic pathways to obtain better production yields. A number of unusual enzymes participating in diverse biosynthetic pathways to pseudo-oligosaccharides have been reported. Various methods and conditions to improve the production yields of the target compounds and eliminate byproducts have also been developed. This review article describes recent studies on the biosynthesis, fermentation optimization, and metabolic engineering of high-value pseudo-oligosaccharides.

Fucoidan - An α-amylase inhibitor from Sargassum wightii with relevance to NIDDM

The present experiment was conducted to screen the α-amylase inhibitory activity of fucoidan extracted from Sargassum wightii collected at the coastal area of Mandapam, Tamil Nadu, India. Fucoidan was extracted from the sporophyll of S. Wightii by ethanol and CaCl2 precipitation method. The average yield was 1.8±0.16% and the extracted fucoidan was found to contain 53±0.52% of fucose and 36±0.60% of sulphate. Structural elucidation (FT-IR and NMR) and in vitro α-amylase activity of purified fucoidon were performed. Fucoidan at the concentration of 62.5, 125 and 250μg exhibited 24.81, 62.50 and 99.24% inhibition against α-amylase, respectively, in a dose dependent manner. Fucoidan from S. wightii also inhibits α-glucosidase which clearly indicates dual inhibitory activity of the compound. The IC50 value against α-amylase of fucoidan is found to be 103.83μg which is more effective than that of acarbose (16mg).

Synthesis and Evaluation of a Series of Oleanolic Acid Saponins as α-Glucosidase and α-Amylase Inhibitors

Sixteen naturally occurring oleanolic acid saponins and their derivatives were synthesized in an efficient and practical strategy, and their inhibitory activities against α-glucosidase and α-amylase were evaluated in vitro. Among all the compounds, 28-O-monoglucoside 8 exhibited remarkably potent inhibitory activity against α-glucosidase with an IC50 value of 87.3 µM, which was fivefold stronger than that of the antidiabetic acarbose. Based on the preliminary structure-activity relationships, for 28-O-monoglucosides, the presence of a terminal α-l-rhamnopyranosyl residue enhanced the α-glucosidase and α-amylase inhibitory activities. Furthermore, for 3,28-O-bidesmosides, sugar-substituted moieties attached to the C-3 and C-28 positions of the oleanolic acid scaffold are helpful to increase the inhibitory activities against α-amylase and α-glucosidase.

Bioactive oligosaccharide natural products

Covering up to December 2013. Oligosaccharide natural products target a wide spectrum of biological processes including disruption of cell wall biosynthesis, interference of bacterial translation, and inhibition of human α-amylase. Correspondingly, oligosaccharides possess the potential for development as treatments of such diverse diseases as bacterial infections and type II diabetes. Despite their potent and selective activities and potential clinical relevance, isolated bioactive secondary metabolic oligosaccharides are less prevalent than other classes of natural products and their biosynthesis has received comparatively less attention. This review highlights the unique modes of action and biosynthesis of four classes of bioactive oligosaccharides: the orthosomycins, moenomycins, saccharomicins, and acarviostatins.

Alpha-amylase and alpha-glucosidase inhibition is differentially modulated by fucoidan obtained from Fucus vesiculosus and Ascophyllum nodosum

Fucoidan is a water-soluble, negatively charged, biologically active polysaccharide found in great abundance in brown marine algae. However, the inhibition of α-amylase and α-glucosidase by fucoidan derived from two algal species (Ascophyllum nodosum and Fucus vesiculosus) harvested at different periods (accounting for seasonal and yearly variations) has never been investigated. It was found that fucoidans inhibited α-glucosidase differently, depending on the algal species from which it was extracted and the algae's season of harvest. Fucoidan extracted from A. nodosum was a more potent inhibitor of α-glucosidase, with an IC50 ranging from 0.013 to 0.047 mg/mL, than the inhibition by fucoidan extracted from F. vesiculosus (IC50=0.049 mg/mL). In contrast, fucoidan extracted from F. vesiculosus did not inhibit α-amylase activity, while fucoidan from A. nodosum decreased α-amylase activity by 7-100% at 5 mg/mL depending upon the algae harvest period. An IC50 of 0.12-4.64 mg/mL for fucoidan from A. nodosum was found for the α-amylase inhibition. The ability of fucoidan to inhibit α-amylase and α-glucosidase thus varies according to the algae species and harvest period. A. nodosum is more suitable than F. vesiculosus as a source of fucoidan to inhibit α-amylase and α-glucosidase activities. Their potential benefits towards Type 2 diabetes management should be further investigated.

Two novel potent α-amylase inhibitors from the family of acarviostatins isolated from the culture of Streptomyces coelicoflavus ZG0656

Two novel aminooligosaccharides were separated from the culture filtrate of Streptomyces coelicoflavus ZG0656. Their chemical structures were determined by acidic hydrolysis, electrospray-ionization tandem mass spectrometry (ESI-MS/MS), and NMR spectroscopy. The compounds were named acarviostatins III0(-1) and III23 according to the nomenclature of this group of metabolites. The two novel acarviostatins were both mixed noncompetitive inhibitors of porcine pancreatic α-amylase (PPA). The inhibition constants (K(i)) for acarviostatins III0(-1) and III23 were 0.009 and 0.026 μM, respectively, 151 and 52 times more potent than acarbose.

Draft genome sequence of Streptomyces coelicoflavus ZG0656 reveals the putative biosynthetic gene cluster of acarviostatin family α-amylase inhibitors

AIMS

The aims of this study are to obtain the draft genome sequence of Streptomyces coelicoflavus ZG0656, which produces novel acarviostatin family α-amylase inhibitors, and then to reveal the putative acarviostatin-related gene cluster and the biosynthetic pathway.

METHODS AND RESULTS

The draft genome sequence of S. coelicoflavus ZG0656 was generated using a shotgun approach employing a combination of 454 and Solexa sequencing technologies. Genome analysis revealed a putative gene cluster for acarviostatin biosynthesis, termed sct-cluster. The cluster contains 13 acarviostatin synthetic genes, six transporter genes, four starch degrading or transglycosylation enzyme genes and two regulator genes. On the basis of bioinformatic analysis, we proposed a putative biosynthetic pathway of acarviostatins. The intracellular steps produce a structural core, acarviostatin I00-7-P, and the extracellular assemblies lead to diverse acarviostatin end products.

CONCLUSIONS

The draft genome sequence of S. coelicoflavus ZG0656 revealed the putative biosynthetic gene cluster of acarviostatins and a putative pathway of acarviostatin production.

SIGNIFICANCE AND IMPACT OF THE STUDY

To our knowledge, S. coelicoflavus ZG0656 is the first strain in this species for which a genome sequence has been reported. The analysis of sct-cluster provided important insights into the biosynthesis of acarviostatins. This work will be a platform for producing novel variants and yield improvement.

Structures of human pancreatic α-amylase in complex with acarviostatins: Implications for drug design against type II diabetes

Human pancreatic α-amylase (HPA) catalyzes the hydrolysis of α-d-(1,4) glycosidic linkages in starch and is one of the major therapeutic targets for type II diabetes. Several acarviostatins isolated from Streptomyces coelicoflavus var. nankaiensis previously showed more potent inhibition of HPA than acarbose, which has been successfully used in clinical therapy. However, the molecular mechanisms by which acarviostatins inhibit HPA remains elusive. Here we determined crystal structures of HPA in complexes with a series of acarviostatin inhibitors (I03, II03, III03, and IV03). Structural analyses showed that acarviostatin I03 undergoes a series of hydrolysis and condensation reactions in the HPA active site, similar to acarbose, while acarviostatins II03, III03, and IV03 likely undergo only hydrolysis reactions. On the basis of structural analysis combined with kinetic assays, we demonstrate that the final modified product with seven sugar rings is best suited for occupying the full active site and shows the most efficient inhibition of HPA. Our high resolution structures reported here identify first time an interaction between an inhibitor and subsite-4 of the HPA active site, which we show makes a significant contribution to the inhibitory effect. Our results provide important information for the design of new drugs for the treatment of type II diabetes or obesity.

Profiling of acarviostatin family secondary metabolites secreted by Streptomyces coelicoflavus ZG0656 using ultraperformance liquid chromatography coupled with electrospray ionization mass spectrometry

Profiling of acarviostatin family secondary metabolites secreted by Streptomyces coelicoflavus ZG0656 was performed by means of a rapid and facile procedure using ultraperformance liquid chromatography coupled with electrospray ionization mass spectrometry (UPLC/ESI-MS). The acarviostatins were separated on a C18 UPLC column with a series of acetonitrile-aqueous ammonia gradients. The target homologues were detected using the multiple reaction monitoring mode, and the chemical structures were confirmed by analyzing the diagnostic fragment ions in their MS/MS spectra. All six known reference acarviostatins (I03, II03, II13, II23, III03, IV03) were thus identified. In addition, at least 74 acarviostatin homologues, including 65 novel compounds, were characterized. Some of the features of the novel structures included having up to five acarviosine moieties, an acarviosine moiety at the reducing terminus, or an incomplete acarviosine moiety at the nonreducing terminus. This type of investigation may be useful for researchers who study secondary metabolomics in microorganisms and plants, especially those who perform metabolic profiling of aminooligosaccharides and other natural products with similar structures.

Four acarviosin-containing oligosaccharides identified from Streptomyces coelicoflavus ZG0656 are potent inhibitors of alpha-amylase

Four aminooligosaccharides were isolated and purified from the culture filtrate of Streptomyces coelicoflavus ZG0656. Their chemical structures were determined by electrospray ionization tandem mass spectrometry (ESI-MS/MS) and two-dimensional nuclear magnetic resonance (NMR) spectroscopy. The names acarviostatins I03, II03, III03, and IV03 were given to the oligomers due to their acarviosin core structures. Acarviostatins III03 and IV03, which contain three and four acarviosin-glucose moieties, respectively, were identified as novel compounds. The four acarviostatins were all mixed noncompetitive inhibitors of porcine pancreatic alpha-amylase (PPA). The inhibition constants (K(i)) for acarviostatins III03 and IV03 were 0.008 and 0.033muM, respectively. Acarviostatin III03 is the most effective alpha-amylase inhibitor known to date, with a K(i) value 260 times more potent than acarbose.