We describe the isolation and characterisation of novel non-benzoquinone ansamycin metabolites related to geldanamycin from a culture of Streptomyces sp. S6699. The compounds possess potent inhibitory activity in a cell-based assay measuring inhibition of oncostatin M signalling in a reporter cell line utilising a secreted placental alkaline phosphatase (sPAP) readout. In this paper we report the isolation and structure elucidation of the compounds and describe some of their biological properties.
Two new classes of inhibitors of LpPLA2 have been identified in fermentations of Pseudomonas fluorescens. The two structurally isomeric series differ in the geometry of closure of the bicyclic carbamate and comprise a range of compounds varying only in length of their lipophilic sidechain. The most abundant species were extracted from the cells and purified by silica and C18 chromatography. Members of the more stable class were shown to be potent and selective competitive inhibitors of LpPLA2.
A series of novel inhibitors of lipoprotein associated phospholipase A2 were, isolated from the culture broths of Pseudomonas fluorescens strain DSM11579. The inhibitors fall into two structurally isomeric classes each of which comprise compounds incorporating glycosylated hydrocarbon chains. The structure elucidation for the major member of each structural class is reported. The crystal structure of a non-glycosylated analogue of the 5, 5-series, produced through biotransformation, is also reported.
Two novel compounds, kodaistatin A, C35H34O11, molecular weight 630, and kodaistatin C, C35H34O12, molecular weight 646, have been isolated from cultures of Aspergillus terreus Thom DSM 11247 by solid-phase extraction, size-exclusion chromatography, and various preparative HPLC steps. The use of a range of 2D NMR measurements, in particular 13C-13C correlation measurements, has led to the clarification of the structure of kodaistatin A. Kodaistatin C is a hydroxylated derivative of kodaistatin A. Both natural products contain hydroxylated aspulvinones and identical highly substituted polyketide units. An X-ray single crystal structure analysis of aspulvinon E demonstrated the z-configuration at the central double bond. The kodaistatins are effective inhibitors of the glucose-6-phosphate translocase component of the glucose-6-phosphatase system (EC 18.104.22.168), an enzyme system which is important for the control of blood glucose levels. The IC50 is 80 nM for kodaistatin A and 130nM for kodaistatin C.
New cytotoxic substances, designated BE-52440A and B, were isolated from the mycelium of Streptomyces sp. A52440. The active principles were extracted from the mycelium by methanol and purified by silica gel column chromatography. BE-52440A and B exhibited cytotoxic activity against murine and human tumor cell lines.
Twelve new milbemycins have been isolated and characterized from some strains derived from Streptomyces hygroscopicus subsp. aureolacrimosus SANK 60286 and SANK 60526. The metabolites 1-4 and 9-11 were produced by strain RM28D-688 SANK 60797 as minor products. The metabolites 5-8 were obtained from a broth of strain 57-338 SANK 61796. Strain MK-1391 SANK 62896 was used for the production of metabolite 12. The new metabolites, eight α-class and four β-class compounds, have new structural features. For example, milbemycins α26 and α27, have the 26-hydroxy moiety, and other derivatives (milbemycins α20-23) have different side cnams at the C-26 position from those of milbemycins α11 and α14. In addition, 5-hydroxylmilbemycin β7 (β12), involved in the major biosynthetic pathway of 25-methyl and 25-ethyl milbemycins, was discovered.
15-Deoxyspergualin (DSG) inhibited growth of mouse EL-4 lymphoma cells with an IC50 0.02 μg/ml. Even though the cells were treated with DSG for only 4 hours and then washed, the antiproliferative effect lasted long with an IC50 0.4μg/ml. DSG has spermidine and guanidine moieties in its structure. One decomposed element containing guanidine moiety inhibited the growth at higher doses than DSG, but the effect did not last long unlike DSG. While another element containing spermidine moiety did not affect the growth, it diminished the long-lasting antiproliferative effect of DSG by pretreatment of the cells. Pretreatment with polyamines such as putrescine, spermidine, and spermine also diminished the effect of DSG. Furthermore, N-alkylation of spermidine moiety in DSG abolished the antiproliferative effect. These results suggested that DSG binds to the cells through its spermidine moiety and exerts its long-lasting antiproliferative effect.