Highly Conformationally Restricted Cyclopropane Tethers with Three-Dimensional Structural Diversity Drastically Enhance the Cell Permeability of Cyclic Peptides.

The conformation of cyclic peptides is closely related to their physicochemical and biological properties, but their rational design to obtain a conformation with the desired properties is difficult. Herein, we present a new strategy by using conformationally restricted cyclopropane tethers (CPTs) to control the conformation and improve the cell permeability of cyclic peptides regardless of the amino acid sequence. Newly designed cis- or trans-CPTs with three-dimensional structural diversity were introduced into a model cyclic peptide, and the relationship between the conformation of the cyclic peptides and their cell permeability was analyzed. Peptides containing a CPT exhibited conformational diversity due to the characteristic steric feature of cyclopropane, among which peptides containing a CPT, cis-NfCf had remarkably higher cell permeability than peptides containing other CPTs-even superior to that of cyclosporine A, a known permeable cyclic peptide.

Development of a rapid and detailed structural identification system with an on-line immobilized enzyme reactor integrated into LC-NMR.

Immobilized enzyme reactors (IMERs) integrated into an LC-NMR system were developed for rapid and detailed structural identification of enzymatic reaction products. An on-column enzymatic reaction was achieved for immobilized cytochrome-c and dog microsomes. After the reaction, these products were analyzed by LC-NMR without any work-up processes. The immobilized cytochrome-c column integrated into LC-NMR was used to characterize the reaction product formed on N-demethylation by measurement of (1)H-NMR. In the case of reaction taking place on the microsome column, a glucuronidation product was identified by (1)H-NMR and (1)H-(1)H correlated spectroscopy. The chemical structures of the enzymatic reaction products could be elucidated by IMER-LC-NMR without the need for authentic samples or isolation processes.

Development of an automated synthesis system for preparation of glucuronides using a solid-phase extraction column loaded with microsomes.

An automated synthesis system using a solid-phase extraction (SPE) system and column packed with octadecylsilica (ODS), which was coated with phospholipid and loaded with dog liver microsomes, was developed for synthesis of glucuronides. Preparation of the microsome-immobilized SPE column, glucuronidation of drugs to synthesize the glucuronides and elution of the products were performed by an automated synthesis system. The phospholipid-coated SPE column and then the microsome-immobilized SPE column were readily prepared by allowing a solution containing L-alpha-dipalmitoylphosphatidylcholine to flow through the SPE column, and then by recycling a buffer solution containing dog liver microsomes through the resulting phospholipid-coated SPE column. The microsome-immobilized SPE column exhibiting the uridine diphosphate (UDP)-glucuronosyltransferase activity catalyzed the glucuronidation of mefenamic acid and estradiol to the corresponding glucuronides in the presence of UDP-glucuronic acid, and three glucuronides of mefenamic acid and estradiol were synthesized using the automated synthesis system, by simply recycling a buffer solution containing UDP-glucuronic acid through the microsome-immobilized SPE column loaded with the substrate. We used beta-cyclodextrin as a solubilizing agent for the synthesis of the glucuronides of estradiol that is practically insoluble in aqueous solutions. The productivity of these glucuronides using the microsome-immobilized SPE column was higher than that using the free microsomes (batch method). Furthermore, we developed a fully automated synthesis-isolation system by coupling the automated synthesis system to an automated preparative HPLC system. The automated synthesis system as well as the fully automated synthesis-isolation system should be very useful for synthesizing glucuronides for drug development.

Novel dolabellane-type diterpene alkaloids with lipid metabolism promoting activities from the seeds of Nigella sativa.

[structure: see text] Four new dolabellane-type diterpene alkaloids, nigellamines A(1) (1), A(2) (2), B(1) (3), and B(2) (4), were isolated from the seeds of Nigella sativa. Their absolute stereostructures were determined on the basis of chemical and physicochemical evidence. Nigellamines A(1) (1), B(1) (3), and B(2) (4) were found to show potent lipid metabolism promoting activity in primary cultured mouse hepatocytes, and their activities were equivalent to that of a PPAR-alpha agonist, clofibrate.

Anti-plasticizing effect of amorphous indomethacin induced by specific intermolecular interactions with PVA copolymer.

The mechanism of how poly(vinyl alcohol-co-acrylic acid-co-methyl methacrylate) (PVA copolymer) stabilizes an amorphous drug was investigated. Solid dispersions of PVA copolymer, poly(vinyl pyrrolidone) (PVP), and poly(vinyl pyrrolidone-co-vinyl acetate) (PVPVA) with indomethacin (IMC) were prepared. The glass transition temperature (Tg)-proportion profiles were evaluated by differential scanning calorimetry (DSC). General Tg profiles decreasing with the IMC ratio were observed for IMC-PVP and IMC-PVPVA samples. An interesting antiplasticizing effect of IMC on PVA copolymer was observed; Tg increased up to 20% IMC ratio. Further addition of IMC caused moderate reduction with positive deviation from theoretical values. Specific hydrophilic and hydrophobic interactions between IMC and PVA copolymer were revealed by infrared spectra. The indole amide of IMC played an important role in hydrogen bonding with PVA copolymer, but not with PVP and PVPVA. X-ray diffraction findings and the endotherm on DSC profiles suggested that PVA copolymer could form a semicrystalline structure and a possibility of correlation of the crystallographic nature with its low hygroscopicity was suggested. PVA copolymer was able to prevent crystallization of amorphous IMC through both low hygroscopicity and the formation of a specific intermolecular interaction compared with that with PVP and PVPVA.

Structures of new dammarane-type Triterpene Saponins from the flower buds of Panax notoginseng and hepatoprotective effects of principal Ginseng Saponins.

The saponin fraction from the flower buds of Panax notoginseng exhibited protective effect on liver injury induced by d-galactosamine and lipopolysaccharide. From the saponin fraction with hepatoprotective effect, five new dammarane-type triterpene saponins, notoginsenosides-O (1), -P (2), -Q (3), -S (4), and -T (5), were isolated together with nine known protopanaxadiol oligoglycosides. The structures of the new saponins were elucidated on the basis of chemical and physicochemical evidence. The principal dammarane-type triterpene saponins from the roots and flower buds of Panax notoginseng were found to show potent hepatoprotective effects.

Protective effects of polygodial and related compounds on ethanol-induced gastric mucosal lesions in rats: structural requirements and mode of action.

The methanolic extract from the leaves of Tasmannia lanceolata was found to potently inhibit ethanol-induced gastric lesions in rats. Through bioassay-guided separation, three known sesquiterpenes, polygodial, polygodial 12 alpha-acetal, and polygodial 12 beta-acetal, and a new sesquiterpene, methyl isodrimeninol, were isolated as the active constituents. Among them, polygodial showed very potent gastroprotective effects (ED(50)=0.028 mg/kg, po). From the gastroprotective effects of various reduction and oxidation derivatives of polygodial, the dialdehyde or diacetal structure was found to be essential for the strong activity. Since the gastroprotection of polygodial was attenuated by pretreatment with indomethacin, N-ethylmaleimide, N(G)-nitro-L-arginine methyl ester and ruthenium red, endogenous prostaglandins, sulfhydryl compounds, nitric oxide and vanilloid receptors may be involved in the protective activity.