Absolute stereostructure of potent alpha-glucosidase inhibitor, Salacinol, with unique thiosugar sulfonium sulfate inner salt structure from Salacia reticulata

A most potent alpha-glucosidase inhibitor named salacinol has been isolated from an antidiabetic Ayurvedic traditional medicine, Salacia reticulata WIGHT, through bioassay-guided separation. The absolute stereostructure of salacinol was determined on the basis of chemical and physicochemical evidence, which included the alkaline degradation of salacinol to 1-deoxy-4-thio-D-arabinofuranose and the X-ray crystallographic analysis, to be the unique spiro-like configuration of the inner salt comprised of 1-deoxy-4-thio-D-arabinofuranosyl sulfonium cation and 1'-deoxy-D-erythrosyl-3'-sulfate anion. Salacinol showed potent inhibitory activities on several alpha-glucosidases, such as maltase, sucrase, and isomaltase, and the inhibitory effects on serum glucose levels in maltose- and sucrose-loaded rats (in vivo) were found to be more potent than that of acarbose, a commercial alpha-glucosidase inhibitor.     

A novel alpha-glucosidase inhibitor from pine bark

Inhibitors of carbohydrate-hydrolysing enzymes play an important role for the treatment of diabetes. To our knowledge, a number of inhibitors such as, 1-deoxynojirimycin, acarbose and voglibose have been identified as a result of screening of secondary metabolites up to now. In this note, we report the inhibitory effect on carbohydrate hydrolysis of ethanol extracts from more than 1400 species of plants with the aim of identifying a potential antihyperglycemic drug. Pinus densiflora bark extracts showed the highest inhibition activity against several carbohydrate-hydrolysing enzymes.     

Hypoglycemic activity of the antioxidant saponarin, characterized as alpha-glucosidase inhibitor present in Tinospora cordifolia

Tinospora cordifolia, used in anti-diabetic herbal drug preparations, was reported [12] to contain an alpha-glucosidase inhibitor, characterized as saponarin (apigenin-6-C-glucosyl-7-O-glucoside). The leaf extract had appreciable antioxidant and hydroxyl radical scavenging activities and contained the flavonoid in the range of 32.1 +/- 1.5-45.5 +/- 3.5 mg/g of dry solid. Saponarin showed mixed competitive inhibition on activities of alpha-glucosidase and sucrase of different origins. IC(50), Ki and ki' values determined were 48 muM, 8 muM and 19.5 microM respectively for intestinal maltase and 35 microM, 6 microM and 13 microM respectively for intestinal sucrase. When given orally to maltose-fed rat, saponarin showed hypoglycemic activity in the range of 20-80 mg/kg compared to 100-200 mg/kg for acarbose as reported.     

Synthesis of novel 4'-substituted 16-membered ring macrolide antibiotics derived from leucomycins

A series of novel 4'-substituted 16-membered ring macrolides was synthesized by the cleavage of the mycarose sugar and subsequent modification of 4'-hydroxyl group. This new class of macrolides antibiotics is acid stable. The synthetic methodology described here is expected to find application in the synthesis of new generation of macrolides that target the emerging bacterial resistance.     

Synthesis and properties of oligonucleotides containing a 7-membered (oxepane) sugar ring

Herein we describe the synthesis of novel 7-membered ring (oxepane) thymine and adenine nucleosides (oT and oA) and their corresponding 5'-O-phosphoramidite derivatives. Two homopolymeric sequences (oT(15) and oA(15)) were prepared via conventional solid-phase synthesis. The mutually complementary strands had the ability to form a duplex (oT(15):oA(15)) exhibiting a transition temperature of 12 degrees C. The oxepane oligonucleotides were also found to associate with their respective complementary RNA strands thus forming oT(15):rA(15) (13 degrees C) and oA(15):rU(15) (12 degrees C) hybrids. The corresponding native duplexes, namely dT(15):dA(15), dT(15):rA(15) and dA(15):rU(15) had melting temperatures of 37 degrees C, 32 degrees C and 16 degrees C, respectively. The CD spectrum of oT(15):rA(15) closely resembled that of the native dT(15):rA(15) hybrid and, in fact, both were found to be substrates for E. Coli RNase H. Thus the oxepane nucleic acids reported here are one of only a handful of DNA mimics capable of activating RNase H when bound to RNA.     

Genistein, a soy isoflavone, is a potent alpha-glucosidase inhibitor.

Genistein is an isoflavone that is known to be contained in soybean. It was proved that genistein plays a pivotal role in homeostasis in the human body. In the course of screening for useful alpha-glucosidase inhibitors, we isolated and identified genistein as a candidate for alpha-glucosidase inhibitor from fermentation broths of a Streptomyces sp. Genistein was shown to be a reversible, slow-binding, non-competitive inhibitor of yeast alpha-glucosidase with a K(i) value of 5.7x10(-8) M when the enzyme mixture was pretreated with genistein. These results show a possibility that genistein could be a useful tool for metabolic disorders.     

Caffeoylsophorose, a new natural alpha-glucosidase inhibitor, from red vinegar by fermented purple-fleshed sweet potato

The suppressive effect on the postprandial blood glucose rise through alpha-glucosidase (AGH) inhibition was investigated in this study in order to clarify an antihyperglycemic function of 6-O-caffeoylsophorose (CS) from diacylated anthocyanin. The administration of CS (100 mg/kg) following maltose (2 g/kg) to Sprague-Dawley rats resulted in the maximal blood glucose level after 30 min being significantly decreased by 11.1% compared to the control. A reduction in the serum insulin secretion was also observed in parallel to the decrease in blood glucose level. No blood glucose change was apparent when sucrose or glucose was ingested, suggesting that the antihyperglycemic effect of CS was achieved by maltase inhibition, rather than by sucrase or glucose transport inhibition. An AGH inhibitory assay demonstrated that the non-competitive maltase inhibition of CS was partly due to acylation by phenolic acid with sugar, the presence of hydroxyl groups in the aromatic ring, and the presence of an unsaturated alkyl chain in the acylated moiety.     

Identification of novel, exosite-binding matrix metalloproteinase-13 inhibitor scaffolds

Matrix metalloproteinase-13 (MMP-13) has been implicated as the protease responsible for collagen degradation in cartilage during osteoarthritis (OA). Compounds that inhibit the metalloproteinase at the Zn binding site typically lack specificity among MMP family members. Analogs of the low-micromolar lead MMP-13 inhibitor 4, discovered through high-throughput screening, were synthesized to investigate structure-activity relationships in this inhibitor series. Systematic modifications of 4 led to the discovery of MMP-13 inhibitors 20 and 24 which are more selective than 4 against other MMPs. Compound 20 is also approximately fivefold more potent as an MMP-13 inhibitor than the original HTS-derived lead compound 4.     

Hypoglycemic activity of a novel anthocyanin-rich formulation from lowbush blueberry,Vaccinium angustifolium Aiton

Blueberry fruits are known as a rich source of anthocyanin components. In this study we demonstrate that anthocyanins from blueberry have the potency to alleviate symptoms of hyperglycemia in diabetic C57b1/6J mice. The anti-diabetic activity of different anthocyanin-related extracts was evaluated using the pharmaceutically acceptable self-microemulsifying drug delivery system: Labrasol. Treatment by gavage (500 mg/kg body wt) with a phenolic-rich extract and an anthocyanin-enriched fraction formulated with Labrasol lowered elevated blood glucose levels by 33 and 51%, respectively. The hypoglycemic activities of these formulae were comparable to that of the known anti-diabetic drug metformin (27% at 300 mg/kg). The extracts were not significantly hypoglycemic when administered without Labrasol, demonstrating its bio-enhancing effect, most likely due to increasing the bioavailability of the administered preparations. The phenolic-rich extract contained 287.0±9.7 mg/g anthocyanins, while the anthocyanin-enriched fraction contained 595±20.0 mg/g (cyanidin-3-glucoside equivalents), as measured by HPLC and pH differential analysis methods. The greater hypoglycemic activity of the anthocyanin-enriched fraction compared to the initial phenolic-rich extract suggested that the activity was due to the anthocyanin components. Treatment by gavage (300 mg/kg) with the pure anthocyanins, delphinidin-3-O-glucoside and malvidin-3-O-glucoside, formulated with Labrasol, showed that malvidin-3-O-glucoside was significantly hypoglycemic while delphinidin-3-O-glucoside was not.     

Hypoglycemic effect of copper(II) acetate imidazole complexes

The effect of copper(II) complexes on glucose metabolism was studied in normal and streptozotocin-induced diabetic rats. The copper(II) complexes used were bis(acetato)tetrakis(imidazole) copper (II), [Cu(OAc)₂(Im)₄], bis(acetato)bis(2-methylimidazole) copper(II), [Cu(OAc)₂(1,2dmIm)₂], and bis)acetato)bis(μ-acetato)tetrakis(N-methylimidazole) copper(II) hexaaquo, [Cu₂(OAc)₄-(NmIm)₄]·6H₂O. Intramuscular administration of various doses of Cu(OAc)₂(Im)₄ ranging from 10 to 100 mg/kg body mass to overnight fasted rats decreased blood glucose levels in a dose-dependent manner. Maximum hypoglycemic effect was observed 3 h after administration and lasted for at least 6 h. Treatment with 100 mg/kg body mass of Cu(OAc)₂(Im)4 caused hypoglycemic shock, which was irreversible and even lethal. Blood insulin levels were reduced sharply during this hypoglycemic shock. Similar changes in blood glucose level were achieved using Cu(OAc)₂)2mIm)₂. The same pattern of hypoglycemia, although less pronouned, was observed for Cu₂(OAc)₄(NmIm)₄·6H₂O and Cu (OAc)₂(1,2dmIm)₂. Binary copper(II) acetate complex, the ligand imidazole, and the inorganic form of copper, such as copper(II) chloride, had no significant effect on blood glucose level. These results indicate that the hypoglycemic activity of these complexes varies with the imidazole ligand and structure of the complex. Intramuscular administration of Cu(OAc)₂(Im)₄ to diabetic rats caused a reduction in blood glucose levels and improved their tolerance for glucose.     

Anti-breast cancer activity of LFM-A13, a potent inhibitor of Polo-like kinase (PLK)

Molecular modeling studies led to the identification of LFM-A13 (alpha-cyano-beta-hydroxy-beta-methyl-N-(2,5-dibromophenyl)propenamide) as a potent inhibitor of Polo-like kinase (Plk). LFM-A13 inhibited recombinant purified Plx1, the Xenopus homolog of Plk, in a concentration-dependent fashion, as measured by autophosphorylation and phosphorylation of a substrate Cdc25 peptide. LFM-A13 was a selective Plk inhibitor. While the human PLK3 kinase was also inhibited by LFM-A13 with an IC(50) value of 61 microM, none of the 7 other serine/threonine kinases, including CDK1, CDK2, CDK3, CHK1, IKK, MAPK1 or SAPK2a, none of the 10 tyrosine kinases, including ABL, BRK, BMX, c-KIT, FYN, IGF1R, PDGFR, JAK2, MET, or YES, or the lipid kinase PI3Kgamma were inhibited (IC(50) values >200-500 microM). The mode of Plk3 inhibition by LFM-A13 was competitive with respect to ATP with a K(i) value of 7.2 microM from Dixon plots. LFM-A13 blocked the cell division in a zebrafish (ZF) embryo model at the 16-cell stage of the embryonic development followed by total cell fusion and lysis. LFM-A13 prevented bipolar mitotic spindle assembly in human breast cancer cells and glioblastoma cells and when microinjected into living epithelial cells at the prometaphase stage of cell division, it caused a total mitotic arrest. Notably, LFM-A13-delayed tumor progression in the MMTV/neu transgenic mouse model of HER2 positive breast cancer at least as effectively as paclitaxel and gemcitabine. LFM-A13 showed a favorable toxicity profile in mice and rats. In particular there was no evidence of hematologic toxicity as documented by peripheral blood counts and bone marrow examinations. These results establish LFM-A13 as a small molecule inhibitor of Plk with in vitro and in vivo anti-proliferative activity against human breast cancer.     

TLXI, a novel type of xylanase inhibitor from wheat (Triticum aestivum) belonging to the thaumatin family

Wheat (Triticum aestivum) contains a previously unknown type of xylanase (EC 3.2.1.8) inhibitor, which is described in the present paper for the first time. Based on its >60% similarity to TLPs (thaumatin-like proteins) and the fact that it contains the Prosite PS00316 thaumatin family signature, it is referred to as TLXI (thaumatin-like xylanase inhibitor). TLXI is a basic (pI> or =9.3 in isoelectric focusing) protein with a molecular mass of approx. 18-kDa (determined by SDS/PAGE) and it occurs in wheat with varying extents of glycosylation. The TLXI gene sequence encodes a 26-amino-acid signal sequence followed by a 151-amino-acid mature protein with a calculated molecular mass of 15.6-kDa and pI of 8.38. The mature TLXI protein was expressed successfully in Pichia pastoris, resulting in a 21-kDa (determined by SDS/PAGE) recombinant protein (rTLXI). Polyclonal antibodies raised against TLXI purified from wheat react with epitopes of rTLXI as well as with those of thaumatin, demonstrating high structural similarity between these three proteins. TLXI has a unique inhibition specificity. It is a non-competitive inhibitor of a number of glycoside hydrolase family 11 xylanases, but it is inactive towards glycoside hydrolase family 10 xylanases. Progress curves show that TLXI is a slow tight-binding inhibitor, with a K(i) of approx. 60-nM. Except for zeamatin, an alpha-amylase/trypsin inhibitor from maize (Zea mays), no other enzyme inhibitor is currently known among the TLPs. TLXI thus represents a novel type of inhibitor within this group of proteins.     

A remarkable new species of Salacia (Celastraceae: Salacioideae) from the Western Ghats,India

A new species of Salacia is described from Karnataka and Kerala states of the Western Ghats, India. It is unique within the genus on account of its obliquely dehiscing anthers and 7–10 cm long, prolate to broadly ellipsoid or ovoid, keeled, greenish-yellow 5- to 8-seeded fruit with thin epicarp and dry mesocarp. Salacia megacarpa sp. nov. can be grouped with S. fruticosa Heyne ex M.A.Lawson and S. oblonga Wight & Arn. which are the only other species from the sub-continent which exhibit axillary, ramiflorous, dichotomously branched cymes.     

Hypoglycemic, diuretic and hypocholesterolemic effect of winter cherry (Withania somnifera, Dunal) root

Hypoglycemic, diuretic and hypocholesterolemic effects of roots of W. somnifera (ashvagandha) were assessed on human subjects. Six mild NIDDM subjects and six mild hypercholesterolemic subjects were treated with the powder of roots of W. somnifera for 30 days. Suitable parameters were studied in the blood and urine samples of the subjects along with dietary pattern before and at the end of treatment period. Decrease in blood glucose was comparable to that of an oral hypoglycemic drug. Significant increase in urine sodium, urine volume, significant decrease in serum cholesterol, triglycerides, LDL (low density lipoproteins) and VLDL (very low density lipoproteins) cholesterol were observed indicating that root of W. somnifera is a potential source of hypoglycemic, diuretic and hypocholesterolemic agents. Clinical observations revealed no adverse effects.     

Hypoglycemic activities of MTP-3631, a novel thiopyranopyrimidine derivative.

MTP-3631 is a novel thiopyranopyrimidine derivative structurally different from any existent hypoglycemic agents. MTP-3631 markedly decreased basal blood glucose and improved glucose intolerance in genetically diabetic C57BL/6J ob/ob mice, which was not affected by tolbutamide. MTP-3631 also caused hypoglycemic effects in normal rats, but no change was observed in plasma insulin level. Unlike buformin, MTP-3631 did not change plasma lactate level in ob/ob mice. These results suggest that the hypoglycemic mechanism of MTP-3631 may be essentially different from those of sulfonylureas and biguanides.     

Tetrapetalone A, a novel lipoxygenase inhibitor from Streptomyces sp

A simple new assay was designed for lipoxygenase inhibitors. This assay was used to find the novel lipoxygenase inhibitor, tetrapetalone A (1). Tetrapetalone A (1), C26H33NO7, was isolated from Streptomyces sp. USF-4727 strain. Its planar structure was determined by spectroscopic evidence and by methylating with diazomethane to show the presence of a novel tetracyclic skeleton and a beta-D-rhodinosyl moiety. The stereochemistry of 1 was investigated by the coupling constant in the 1H-NMR spectrum, NOE correlations, modified Mosher's method and derivation. We have reported the structural elucidation of 1 in our previous paper. However, further investigation gave another structure for 1, which is described in this paper. Tetrapetalone A showed similar inhibitory activity against soybean lipoxygenase to the two well-known lipoxygenase inhibitors, kojic acid and NDGA, while methylated tetrapetalone A (2) showed little inhibitory activity, even at a concentration of 1 mM.