A new 7,8-euphadien-type triterpenoid from Brackenridgea nitida and Bleasdalea bleasdalei that inhibits DNA polymerase beta

Bioassay-guided fractionation of extracts prepared from Brackenridgea nitida and Bleasdalea bleasdalei, using an assay to detect DNA polymerase beta inhibition, resulted in the isolation of the inhibitory principle, (24E)-3beta-hydroxy-7,24-euphadien-26-oic acid (1), a new euphane triterpenoid. The structure of 1 was established on the basis of HRMS and 1D and 2D NMR spectroscopic methods and was confirmed further by X-ray crystallographic analysis. Compound 1 inhibited rat DNA polymerase beta with an IC(50) value of 23 microM in the presence of bovine serum albumin (BSA) and 9.7 microM in the absence of BSA, consistent with the possibility that 1 may be of utility in vivo. This possibility was further supported by the finding that 1 potentiated the inhibitory action of the anticancer drug bleomycin in cultured P-388D(1) cells, reducing the number of viable cells by 48% when employed at a concentration of 25 microM in the presence of an otherwise nontoxic (75 nM) concentration of bleomycin. Compound 1 is the first euphane-type triterpenoid found to inhibit DNA polymerase beta.

Inversion of the cis geometry requirement for cytotoxicity in structurally novel platinum(II) complexes containing the bidentate N,O-donor pyridin-2-yl-acetate

Water soluble platinum(II) complexes have been synthesized that contain the N,O-chelate pyridin-2-yl acetate (PyAc) as a novel structural motif in platinum antitumor complexes. The trans-platinum complex trans-[PtCl(PyAc-N,O)(NH3)] (2) (N-donors are trans) and its isomer cis-[PtCl(PyAc-N,O)(NH3)] (4) (N trans to Cl) were prepared from trans-[PtCl2((NH3)(PyAcH)].H2O (1.H2O) and cis-[PtCl2(NH3)(PyAcMe) (3), respectively, employing the bidentate ligand as its methylester (PyAcMe). 2 and 4 are readily formed from the respective dichloro species, even at low pH and in the presence of extra chloride, indicating a high thermodynamic stability of the PyAc chelate ring. 1.H2O and 2-4 were characterized by 1H NMR and IR spectroscopy and elemental analyses. The solid-state structure of 2 was determined: triclinic, P1 (no. 2), with a = 8.170(2) A, b = 9.274(3) A, c = 7.374(2) A, alpha = 108.68(2) degrees, beta = 113.27(2) degrees, gamma = 74.40(2) degrees, V = 479.7(6) A3, Z = 2. The six-membered metallacyclus in 2 adopts a "boat" form, allowing a strainless coordination of platinum. The most promising cytotoxic properties in the above series of compounds have been established for 2 (and 1, which rapidly transforms into 2 at 37 degrees C and neutral pH). Preliminary ID50 values were 0.88 and 1.26 microM, respectively, in cisplatin-sensitive L1210 leukemia. Both compounds proved to be cross-resistant to the clinical drug. Reactions of 2 and 4 with 5'-guanosine monophosphate (5'-GMP) under physiological conditions gave the monofunctional adducts trans- and cis-[Pt(5'-GMP-N7)(PyAc-N,O)(NH3)] (I and II). Chelate-bound carboxylate was not replaced by guanine-N7 when an excess of nucleotide was applied (NMR). In an analogous reaction, 2 reacts with the oligonucleotide d(TCGT) [5'-T(1)-C(2)-G(3)-T(4)-3'] to give the adduct d(TCGT)-N7(3)-Pt(PyAc-O,N)(NH3) (III), which was characterized by a combination of total correlation spectroscopy, double-quantum-filtered correlation spectroscopy, nuclear Overhauser effect spectrometry, and rotating-frame Overhauser enhancement spectroscopy experiments. Binding of the [Pt(PyAc-N,O)(NH3)]+ fragment to N7 of G(3) causes an increase of N-type character of the T(4) and G(3) deoxyribose residues relative to the unplatinated sequence, while those of T(1) and C(2) remain S-type. An internucleotide nuclear Overhauser effect between H6(4) and H2'(3) indicates stacking between guanine and the 3'-thymine base. The most striking feature proved to be the pronounced upfield shift and broadening of the 1H NMR signals assigned to the base protons H5 and H6 in III. Magnetization transfer between H5(2) and H3 of pyridine suggests that this effect is caused by base-base interactions involving the planar ligand on platinum, which must be situated on the 5' face of guanine. Possible implications for the DNA binding and cytotoxic effect of the compounds are discussed.

Synthesis of unnatural amino acids via Suzuki cross-coupling of enantiopure vinyloxazolidine derivatives

[formula: see text] (R and S)-alpha-Amino alcohols and alpha-amino acids, including 4-methoxyhomophenylalanine, with a variety of unnatural side chains have been synthesized via palladium-catalyzed cross-coupling Suzuki reactions. The key building blocks 1 and 2, synthesized from the common achiral precursor 2-butene-1,4-diol, were made enantiopure utilizing a Pseudomonas cepacia lipase-catalyzed kinetic resolution. The optimal conditions for the Suzuki cross-coupling and the subsequent oxidations of the resultant alpha-amino alcohols are described.

Metal ions in non-complementary DNA base pairs: an ab initio study of Cu(I), Ag(I), and Au(I) complexes with the cytosine-adenine base pair

Ab initio calculations have been carried out to characterize the structure and energetics of a silver(I) complex with the cytosine-adenine DNA base pair and an aqua ligand in the coordination sphere of Ag. In addition, we have also studied analogous complexes with Cu(I) and Au(I), and structures in which adenine has been replaced by purine in order to investigate the structural role of the adenine amino group. The calculations revealed that all metal-modified structures are dominated by the metal-base interactions, while the water-metal ion interaction and many-body interligand repulsion are less important contributions. Nevertheless, the structural role of the water molecule in the complex is quite apparent and in agreement with an earlier crystallographic study. The metal-modified base pairs exhibit large conformational flexibility toward out-of-plane motions (propeller twist and buckle), comparable or, in some cases, even larger than that observed in the base pairs without metal ions. All structures have been optimized within the Hartree-Fock approximation, while interaction energies were evaluated with the inclusion of electron correlation.

Reversal of hyperglycemia in streptozotocin diabetic mice by xenotransplantation of microencapsulated rat islets

Rat pancreatic islets were immunoisolated within alginate capsules with additional polyethyleneimine-protamine-heparin highly biocompatible membrane. Perifusion study in vitro demonstrated satisfactory similarities between the insulin release profiles of encapsulated and free islets. Concordant xenotransplantation of microencapsulated rat islets significantly prolonged mean time of restored normoglycemia (46 +/- 15 days) in streptozotocin-diabetic BALB/c mice recipients comparing to uncoated grafts (7 +/- 2 days).

Experience with pancreas islets separation, immunoisolation and cryopreservation

Experience of Warsaw Pancreas Laboratory is presented. Some improvement in the methods of rat, human and pig pancreases digestion, and in identification of Langerhans islets by means of intravenous injection of I-DTZ was achieved. For immunoisolation of islets, 2 methods were elaborated: capsules containing alginate/polyethyleneimine/protamine/heparin membrane prepared by modified Sun method, and microcapsules based on Zekorn method. Biocompability of hollow fibers, prepared with polypropylene (PP), surface modified PP (PPS) and polysulphone (PS) was assessed in vitro. Only PS fibers were fully compatible. It was shown, that the mixture of exocrine tissue did not influence in vitro insulin secretion, providing that alginate in which islets are embedded remain gelled. The efficacy of 3 methods of islets cryopreservation was compared: freezing in "semicontrolable" conditions, in programmable Kriomedpol machine, and vitrification. The highest percentage of frozen/thawed living cells, and the most reliable results were obtained with Kriomedpol method.

Comparison of two methods of pancreas islets immunoisolation

The efficacy of two methods of Langerhans islets immunoisolation was compared. For this purpose the function of islets encapsulated with alginate/polyethylenimine/protamine/heparin (APPH) or with alginate/poly-L-lisine/alginate (APA) membranes was assessed: in vitro according to their survival and response to glucose challenges, and in vivo according to their capability to provide sufficient insulin delivery to maintain normal fasting blood glucose following xenotransplantation to streptozotocin diabetic mice. In vitro insulin secretion and the response to glucose challenge of APPH and APA encapsulated islets were comparable to free islets. In vivo intraperitoneal concordant xenotransplantation of APA encapsulated rat islets reversed the diabetic state of streptozotocin diabetic mice for a longer period, than APPH islet grafts. This study clearly demonstrated the inadequacy of in vitro methods in the prediction of in vivo results of islets transplantation.

[Experiments with pancreas islet xenotransplantation]

Different methods of human, porcine and rat pancreata digestion Langerhans islets purification, immuno-isolation and cryopreservation were compared. The results obtained were assessed in vitro and in vivo. The longest concordial xenograft survival was observed after transplantation of rats islets immunoisolated by Sun's method to streptozotocin diabetic mice. Due to its simplicity and lesser time consumption using Kriomedpol machine was recommended.

In vitro and in vivo evaluation of protamine-heparin membrane for microencapsulation of rat Langerhans islets

Rat pancreatic islets were microencapsulated with multilayer protamine-heparin (PH) membrane. Basal and stimulatory insulin secretion of microencapsulated islets was similar to the controlled free islets in vitro. During the long-term culture (up to 2 weeks) mean insulin release of encapsulated islets did not significantly differ from the mean of free ones (the ratio of mentioned means was 54-167%). Empty PH microcapsules transplanted into Wistar rats intraperitoneally and under the kidney capsule were generally harmless up to 4 months. In only a few cases traces of fibrotic tissue around capsules entrapped in the omentum were found. No damage of microcapsules structure was observed. The worst results were obtained in the instance of retroperitoneal transplantation. We conclude, therefore, that PH membrane was proved to be highly biocompatible, nontoxic for islets, and did not impair viability and glucose-dependent insulin secretion of Langerhans islets in in vitro culture.

Carbamates of (hydroxyphenoxy)methyl heteroaromatic salts as acetylcholinesterase inhibitors and protective agents against organophosphorus compounds

A series of N,N-dimethylcarbamates of 2-[(2'-, 3'-, and 4'-hydroxyphenoxy)methyl] heteroaromatic salts has been prepared. Pyridine, imidazole, quinoline, benzimidazole, and imidazo-[1,2-alpha]pyridine derivatives were included. Most of the compounds are inhibitors of electric eel acetylcholinesterase and also show prophylactic activity toward a 2LD50 dose of soman in mice.

Developmental effects of impaired breathing in the face of the growing child

Craniofacial morphology and occlusal pattern are evaluated in 71 subjects having impaired breathing as diagnosed by an otolaryngologist, and in an equal number of controls. The impaired group demonstrate characteristic combinations of craniofacial deformities and malocclusions, with the younger individuals demonstrating a lesser expression of malocclusion progression and morphologic deformities. This suggests that early recognition of such facial patterns may be utilized to identify those breathing compromised individuals who have a likely tendency to develop certain types of malocclusion.

Crystal structure of the alpha, beta, gamma-tridentate manganese complex of adenosine 5'-triphosphate cocrystallized with 2,2'-dipyridylamine

The 1:1:1 complex of Mn2+, ATP, and 2,2'-dipyridylamine (DPA) crystallizes as Mn-(HATP)2.Mn(H2O)6.(HDPA)2.12H2O in the orthorhombic space group C222(1) with unit cell dimensions a = 10.234 (3) A, b = 22.699 (3) A, and c = 31.351 (4) A. The structure was solved by the multisolution technique and refined by the least-squares method to a final R index of 0.072 using 3516 intensities. The structure is composed of two ATP molecules sharing a common manganese atom. The metal exhibits alpha, beta, gamma coordination to the triphosphate chains of two dyad-related ATP molecules, resulting in a hexacoordinated Mn2+ ion surrounded by six phosphate groups. The metal to oxygen distances are 2.205 (6), 2.156 (4), and 2.144 (5) A for the alpha-, beta-, and gamma-phosphate groups, respectively. No metal-base interactions are observed. There is a second hexaaqua-coordinated Mn2+ ion that is also located on a dyad axis. The hydrated manganese ions sandwich the phosphate-coordinated manganese ions in the crystal with a metal-metal distance of 5.322 A. The ATP molecule is protonated on the N(1) site of the adenine base and exhibits the anti conformation (chi = 66.0 degrees). The ribofuranose ring is in the 2/3 T conformation with pseudorotation parameters P = 179 (1) degrees and tau m = 34.1 (6) degrees. The adenine bases form hydrogen-bonded self-pairs across a crystallographic dyad axis and stack with both DPA molecules to form a column along the dyad. The structure of the metal-ATP complex provides information about the possible metal coordination, conformation, and environment of the nucleoside triphosphate substrate in the enzyme.

Interaction of adenosine 5'-triphosphate with metal ions X-ray structure of ternary complexes containing Mg(II), Ca(II), Mn(II), Co(II), ATP and 2,2'-dipyridylamine

The X-ray structures of the isomorphous Mg2+, Ca2+, Mn2+ and Co2+ complexes of ATP have been determined. The metal ions are wrapped in hexa-coordination by the alpha, beta and gamma phosphate groups of two ATP molecules thus blocking the interaction of the metal ions with the adenine base. A second metal ion which is fully hydrated, M(H2O)2+(6), is engaged in a strong hydrogen bond with the gamma phosphate group of ATP and suggests a possible step in facilitating the cleavage between the beta and gamma phosphates in phosphoryl transfer reactions.

Similar binding of the carcinostatic drugs cis-[Pt(NH3)2Cl2] and [Ru(NH3)5Cl] Cl2 to tRNAphe and a comparison with the binding of the inactive trans-[Pt(NH3)2Cl2] complex - reluctance in binding to Watson-Crick base pairs within double helix

A comparative study of the binding of square planar cis- and trans-[Pt(NH3)2Cl2] complexes and the octahedral [Ru(NH3)5(H2O)]3+ complex to tRNAphe from yeast was carried out by X-ray crystallography. Both of the carcinostatic compounds, cis-[Pt(NH3)2Cl2] and [Ru(NH3)5(H2O)]3+ show similarities in their mode of binding to tRNA. These complexes bind specifically to the N(7) positions of guanines G15 and G18 in the dihydrouridine loop. [Ru(NH3)5(H2O)]3+ has an additional binding site at N(7) of residue G1 after extensive soaking times (58 days). A noncovalent binding site for ruthenium is also observed in the deep groove of the acceptor stem helix with shorter (25 days) soaking time. The major binding site for the inactive trans-[Pt(NH3)Cl2] complex is at the N(1) position of residue A73, with minor trans-Pt binding sites at the N(7) positions of residues Gm34, G18 and G43. The similarities in the binding modes of cis-[Pt(NH3)2Cl2] and [Ru(NH3)5(H2O)]3+ are expected to be related to their carcinostatic properties.