No abstract

Manumycin(1), produced by Streptomyces parvulus (strain Tu 64), was isolated from the mycelium by extraction with acetone and could easily be purified chromatographically. Chemical degradation of 1 (C8iH38N2O7) gave 2-acetamino-3-hydroxycyclopent-2-enone (2) by acetolysis, 2,4,6-trimethyl-2,4-decadienoic acid (3) by alkaline hydrolysis, and 2-(2,4,6-trimethyl-2,4-decadienoylamino)-5,6-epoxy-l ,4-benzoquinone (5) by mild chromic acid oxidation. In connection with a detailed spectroscopic analysis, the structure of 1 could be elucidated and the (^-configuration of the double bonds in the triene and diene chain was established.Manumycin exhibits biological activity against Gram-positive bacteria and fungi and furthermore, an inhibition of the developmental processes of someinsects.Streptomyces parvulus (strain Tu 64) produces the pale yellow antibiotic manumycin0in association with more lipophilic red pigments, which were identified as C25-prodigiosms2), and the colorless hydrophilic amino acid antagonist L-2,5-dihydrophenylalanine3). Previous reports1»4) have already described the isolation and structure of manumycin, whose structural elements could not be classified with a known group of antibiotics. In the meantime similar compounds such as asukamycin5'6), U-621627) and U-56,4078) have been discovered, which could be added to the manumycin group. Structural features incline us to consider these antibiotics as broken chain ansamycins9). To verify this hypothesis, biosynthetic studies of manumycin and asukamycin are in progress10*n). In our preliminary report0, chemical degradation reactions have been described to prove the structure of manumycin.Getting more information from subsequent spectra, we are nowable to derive the structure of manumycinby a detailed spectroscopic analysis in connection with only a few chemical derivatization reactions. In this full paper we describe the fermentation of strain Tu 64 as well as a simpler isolation method, more biological data and a detailed chemical and spectroscopic characterization of manumycin. Fermentation and Isolation Streptomyces parvulus (strain Tii 64) is unstable as its phenotype, and a good logarithmic growth phase is not a reliable indication for producing an identical spectrum of secondary metabolites. The production of the red prodigiosins, starting 36~40 hours after inoculation, does however indicate the formation of manumycin,because these compoundsappear simultaneously. The strain Tii 64 was cultivated in 1-liter, 10-liter and 120-liter fermentors, using soybean meal 2% and mannitol 2% as a culture medium.Inoculum was prepared in Erlenmeyer flasks containing the same mediumand shaken for 60 hours at 28°C. Fig. 1 shows a typical time course of the fermentation in a 10-liter fermentor. The production of manumycinstarts after the log-phase, reaching its maximum76 hours

Aims/hypothesis Inspired by recent speculation about the potential utility of α 2A -antagonism in the treatment of type 2 diabetes, the study examined the contribution of α 2 -antagonism vs other mechanisms to the antihyperglycaemic activity of the imidazoline (±)-efaroxan. Methods Effects of the racemate and its pure enantiomers on isolated pancreatic islets and beta cells in vitro, as well as on hyperglycaemia in vivo, were investigated in a comparative manner in mice. Results In isolated perifused islets, the two enantiomers of efaroxan were equally potent in counteracting inhibition of insulin release by the ATP-dependent K + (K ATP ) channelopener diazoxide but (+)-efaroxan, the presumptive carrier of α 2 -antagonistic activity, was by far superior in counteracting inhibition of insulin release by the α 2 -agonist UK14,304. In vivo, (+)-efaroxan improved oral glucose tolerance at 100-fold lower doses than (−)-efaroxan and, in parallel with observations made in vitro, was more effective in counteracting UK14,304-induced than diazoxide-induced hyperglycaemia. The antihyperglycaemic activity of much higher doses of (−)-efaroxan was associated with an opposing pattern (i.e. with stronger counteraction of diazoxide-induced than UK14,304-induced hyperglycaemia), which implicates a different mechanism of action. Conclusions/interpretation The antihyperglycaemic potency of (±)-efaroxan in mice is almost entirely due to α 2 -antagonism, but high doses can also lower blood glucose via another mechanism. Our findings call for reappraisal of the possible clinical utility of α 2A -antagonistic compounds in recently identified subpopulations of patients in which a congenitally higher level of α 2A -adrenergic activation contributes to the development and pathophysiology of type 2 diabetes.

Starting off with a structure derived from the natural compound multiflorine, a derivatisation program aimed at the discovery and initial characterisation of novel compounds with antidiabetic potential. Design and discovery of the structures was guided by oral bioactivities obtained in oral glucose tolerance tests in mice. 55P0110, one among several new compounds with distinct anti-hyperglycaemic activity, was further examined to characterise its pharmacology and mode of action. Whereas a single oral dose of 55P0110 did not affect basal glycaemia, it markedly improved the glucose tolerance of healthy and diabetic mice (peak blood glucose in glucose tolerance test, mmol/l: healthy mice with 90 mg/kg 55P0110, 17.0±1.2 vs. 10.1±1.1; diabetic mice with 180 mg/kg 55P0110, 23.1±0.9 vs. 11.1±1.4; p<0.001 each). Closer examination argued against retarded glucose resorption from the gut, increased glucose excretion in urine, acute insulin-like or insulin sensitising properties, and direct inhibition of dipeptidyl peptidase-4 as the cause of glucose lowering. Hence, 55P0110 seems to act via a target not exploited by any drug presently approved for the treatment of diabetes mellitus. Whereas the insulinotropic sulfonylurea gliclazide (16 mg/kg) distinctly increased the circulating insulin-per-glucose ratio under basal conditions, 55P0110 (90 mg/kg) lacked such an effect (30 min. after dosing, nmol/mol: vehicle, 2.49±0.27; 55P0110, 2.99±0.35; gliclazide, 8.97±0.49; p<0.001 each vs. gliclazide). Under an exogenous glucose challenge, however, 55P0110 increased this ratio to the same extent as gliclazide (20 min. after glucose feeding: vehicle, 2.53±0.41; 55P0110, 3.80±0.46; gliclazide, 3.99±0.26; p<0.05 each vs. vehicle). By augmenting the glucose stimulated increase in plasma insulin, 55P0110 thus shows distinct anti-hyperglycaemic action in combination with low risk for fasting hypoglycaemia in mice. In summary, we have discovered a novel class of fully synthetic substituted quinazolidines with an attractive pharmacological profile that recommends the structures for further evaluation as candidates for the treatment of diabetes mellitus.

The cardiovascular consequences of endothelin (ET) blockade with the ETA-receptor antagonist FR 139317 were evaluated by determining the long-term effects of the drug on hemodynamic, hormonal, renal and structural parameters in stroke-prone spontaneously hypertensive rats (SHR-SP). Young SHR-SP on a high-sodium diet develop malignant hypertension accompanied by renovascular and cerebrovascular lesions. In control SHR-SP the systolic blood pressure increased from 196 +/- 3 to 260 +/- 4 mm Hg, whereas in animals treated with FR 139317 (20 mg/kg intraperitoneally, twice daily) it increased only from 196 +/- 4 to 212 +/- 3 mm Hg during a treatment period of 6 weeks. There was also an increase in heart weight. At the end of the experiment the plasma levels of atrial natriuretic peptide and brain natriuretic peptide were significantly lower in the group treated with FR 139317 than in the controls. The endothelin plasma levels were significantly higher and the plasma renin activity was lower in the group treated with the endothelin receptor antagonist. These data indicate that endothelin is involved in the maintenance of high blood pressure and cardiac hypertrophy in malignant hypertension, as exemplified by SHR-SP.