Effect of Counterions on Physicochemical Properties of Prazosin Salts

This study evaluated the effect of counterions on the physicochemical properties of prazosin salts. Salt forms of prazosin, namely, mesylate, besylate, tosylate, camsylate, oxalate, and maleate, were prepared and compared with the marketed anhydrous and polyhydrate forms of prazosin hydrochloride. Physicochemical characterization was performed in the order of crystallinity, hygroscopicity, solubility, and stability to select the optimal salt(s). Permeability study in Caco-2 cell lines and in vivo bioavailability study in rat model were investigated to ascertain their biopharmaceutical advantage. All salt forms were crystalline, nonhygroscopic (except the anhydrous hydrochloride salt), and had solubility in the range of 0.2 to 1.6 mg/ml. All salts were physically and chemically stable at 40°C/75% relative humidity, but degraded in UV-visible light, except the anhydrous hydrochloride salt. Prazosin mesylate was selected as the optimal salt, as it possessed higher solubility, permeability, and bioavailability, compared to the commercial hydrochloride salts. Hydrochloride salt is reported to have poor bioavailability that is partially attributed to its low solubility and extensive common-ion effect in the gastric region. Factors like hydrophilicity of the counterion, hydration state of the salt, and melting point of the salt contribute to the physicochemical properties of the salts. This study has implications in the selection of an optimal salt form for prazosin, which is suitable for further development.     

Reduced Wall Acetylation Proteins Play Vital and Distinct Roles in Cell Wall O-Acetylation in Arabidopsis

The Reduced Wall Acetylation (RWA) proteins are involved in cell wall acetylation in plants. Previously, we described a single mutant, rwa2, which has about 20% lower level of O-acetylation in leaf cell walls and no obvious growth or developmental phenotype. In this study, we generated double, triple, and quadruple loss-of-function mutants of all four members of the RWA family in Arabidopsis (Arabidopsis thaliana). In contrast to rwa2, the triple and quadruple rwa mutants display severe growth phenotypes revealing the importance of wall acetylation for plant growth and development. The quadruple rwa mutant can be completely complemented with the RWA2 protein expressed under 35S promoter, indicating the functional redundancy of the RWA proteins. Nevertheless, the degree of acetylation of xylan, (gluco)mannan, and xyloglucan as well as overall cell wall acetylation is affected differently in different combinations of triple mutants, suggesting their diversity in substrate preference. The overall degree of wall acetylation in the rwa quadruple mutant was reduced by 63% compared with the wild type, and histochemical analysis of the rwa quadruple mutant stem indicates defects in cell differentiation of cell types with secondary cell walls.Plant cell walls are multifunctional viscoelastic networks mainly composed of polysaccharides. Many of these polysaccharides, including xylans, (gluco)mannans, xyloglucans (XyGs), and pectins, have various degrees and patterns of acetyl esterification (Gille and Pauly, 2012; Pawar et al., 2013). The biological role of cell wall acetylation is not well understood, but it is believed to be important for pathogen resistance and plant development, and the acetylation of pectin also impacts upon the mechanical properties of cell walls (Manabe et al., 2011; Orfila et al., 2012; Pogorelko et al., 2013). In vitro, acetyl groups influence susceptibility to enzymatic degradation of pectin and xylan (Selig et al., 2009; Chen et al., 2012; Gou et al., 2012; Orfila et al., 2012; Pogorelko et al., 2013), and therefore acetylation may constitute a barrier to cell wall deconstruction. Alkali treatment of wall materials, which hydrolyzes the ester bonds, is broadly used to make polysaccharides more extractable. The treatment does not only facilitate the degradation of xylan and pectins, but also improves the deconstruction of cellulose, as the depolymerization of noncellulosic polymers results in a better accessibility to cellulose by degrading enzymes (Selig et al., 2009). Low levels of acetylated polysaccharides in plant feedstocks would be desirable for downstream processing in biorefineries, firstly, because the cell wall material of plant feedstocks with low level of acetylation is expected to be more easily extracted and, secondly, because less acetate, which is highly toxic to microorganisms such as yeast (Saccharomyces cerevisiae), would be released during extraction (Manabe et al., 2011; Gille and Pauly, 2012; Pawar et al., 2013). However, although reducing the O-acetylation level of xylan by approximately 60%, as observed in the walls of the Arabidopsis (Arabidopsis thaliana) eskimo1 mutant, enhances enzymatic degradation of isolated xylan (Yuan et al., 2013), enzymatic hydrolysis yields of whole wall materials have been reported to actually be decreased (Xiong et al., 2013). This presumably results from a tighter association between these now lowly substituted xylan polymers and cellulose (Xiong et al., 2013).Recently, we reported REDUCED WALL ACETYLATION2 (RWA2), the first protein to be involved in cell wall acetylation in planta (Manabe et al., 2011). RWA2 is a member of a small family consisting of four proteins in Arabidopsis, and its loss-of-function mutants display 20% reduction of acetylation in a range of polysaccharides that include XyG and pectins. We have hypothesized, based on phylogenetic analysis, expression pattern, moderate reduction in acetylation, and the absence of morphological phenotype, that RWA proteins have redundant functions in a biochemical reaction that occurs prior to the actual acetylation of specific polysaccharides. Independently to our research, a quadruple mutant of RWA has been reported to display reduction in xylan acetylation, secondary cell wall thickness, and mechanical strength of the stem (Lee et al., 2011). Meanwhile, Gille et al. (2011) have discovered a new family of proteins involved in the acetylation of specific polysaccharides: the plant-specific DOMAIN OF UNKNOWN FUNCTION (DUF) 231 family (also known as TRICHOME BIREFRINGENCE-LIKE [TBL] family). The loss-of-function mutants altered xyloglucan4 (axy4)/tbl27 and axy4L/tbl22 lack O-acetylation specifically of XyG in certain tissues, while eskimo1/tbl29 mutants contain reduced O-acetylation of xylan (Xiong et al., 2013; Yuan et al., 2013). The TBL/DUF231 family proteins and the RWA proteins have sequence similarity to the N-terminal and C-terminal regions of the fungal protein Cas1p, respectively (Anantharaman and Aravind, 2010). This could suggest that the TBL and RWA proteins function in protein complexes where the determinants of substrate specificity reside in the TBL partner (Manabe et al., 2011). However, because there are many more TBL proteins than RWA proteins (e.g. 46 TBL proteins versus four RWA proteins in the genome of Arabidopsis), it is likely that they do not form discrete and invariable complexes. Crossing of rwa2-3 and a leaky allele of axy4, axy4-1, resulted in a double mutant with partially additive phenotype (Gille et al., 2011). Its XyG acetylation is lower compared with either single mutant. From this analysis, RWA2 and AXY4 have been hypothesized to work in synergy, although the function of RWA2 might be substituted by other RWAs (Gille et al., 2011). Here, we have generated all the combinations of double, triple, and quadruple mutants of all four members of RWA family to further investigate the functional diversity and redundancy and to explore the function of cell wall acetylation and the role of RWAs in the network of acetylation-related enzymes. The triple and quadruple mutants we have obtained displayed severe and distinct phenotypes such as extreme dwarfism. This contrasts with the very mild phenotypes reported by Lee et al. (2011). Taken together, RWAs have partially redundant functions in the process of cell wall acetylation and show distinct impacts upon different cell wall polysaccharides.     

Alginate esters via chemoselective carboxyl group modification

Alginates are (1 → 4) linked linear copolysaccharides composed of β-d-mannuronic acid (M) and its C-5 epimer, α-l-guluronic acid (G). Several strategies for synthesis of carboxyl modified alginate derivatives exist in the literature. Most of these however employ aqueous chemistries, such as carbodiimide coupling reactions. Based on our recently discovered method for homogeneous dissolution of tetrabutylammonium (TBA)-alginate, we now describe use of tetrabutylammonium fluoride (TBAF)-based two component solvent systems as media for synthesis of carboxyl-modified alginate esters. Partially and fully esterified benzyl, butyl, ethyl, and methyl alginates were synthesized via reaction with the corresponding alkyl halides. The newly synthesized derivatives were soluble in polar aprotic solvents without the addition of TBAF. Saponification was performed to demonstrate that alkylation was completely regioselective for carboxylate groups in preference to hydroxyl groups to form esters. We demonstrate the utility of these alginate esters to enhance aqueous solubility of the flavonoid naringenin by formation of solid dispersions.     

Alishewanella solinquinati sp. nov., Isolated from Soil Contaminated with Textile Dyes

A novel Gram-negative, motile, rod-shaped, facultative anaerobic bacterial strain, KMK6^T, was isolated from soil contaminated with textile dyes from an industrial estate located at Ichalkaranji, Maharashtra, India, and its taxonomical position was established by using a polyphasic approach. The major cellular fatty acids included C_17:1ω8c, summed feature 3 (C_16:1ω7c and/or iso-C_15:0 2-OH), C_17:0, C_16:0, and C_18:1ω7c. The DNA G+C content of strain KMK6^T was 48.8 mol %. 16S rRNA gene sequence analysis confirmed its placement in the genus Alishewanella, and exhibited sequence similarity levels of below 97 % to the type strains of validly published Alishewanella species. On the basis of genotypic and phenotypic evidence, strains KMK6^T is considered to be a novel species of the genus Alishewanella, for which we propose that strain KMK6^T (=NCIM 5295^T =BCRC 17848^T) is assigned to a novel species, Alishewanella solinquinati sp. nov.     

Influence of abiotic elicitation on production of dipyranocoumarins in suspension cultures of <Emphasis Type="Italic">Calophyllum inophyllum</Emphasis> L.

Effects of elicitation with heavy metals such as copper, cadmium, chromium (abiotic elicitation) and supplementation of CaCl₂ on production of dipyranocoumarins (inophyllums) in suspension cultures of leaf and stem callus of Calophyllum inophyllum were studied. The optimum timing for elicitor introduction was found to be the 10th day after initiating the suspension cultures. Cadmium as abiotic elicitor in suspension cultures of stem callus was found best to elicit maximum production of inophyllums A, C, and calophyllolide while cadmium in suspension cultures of leaf callus was found best for eliciting maximum production of inophyllums B and P. Inophyllum D was the only dipyranocoumarin whose highest production was achieved when 1.0 mM chromium was used as abiotic elicitor in suspension cultures of stem callus. Out of the three abiotic elicitors used, none could result biomass growth. Only incorporation of CaCl₂ in suspension cultures resulted biomass growth. A maximum of 35.26-fold biomass growth was achieved when suspension cultures of stem callus were incorporated with 2.0 mM CaCl₂. CaCl₂ was noted to have no positive influence on production of most of the dipyranocoumarins under study.     

Association between chemical and genetic variation in Calophyllum inophyllum, a medicinally important tree of the Western Ghats of India

Intersubspecific autotetraploid rice hybrids have high heterosis in both vegetative and reproductive growth, but low seed set hinders commercial utilization of autotetraploid rice. Autotetraploid rice hybrids with high and low pollen fertility were used in the present study to compare microtubule distribution patterns and chromosome behavior during pollen mother cell (PMC) meiosis, using indirect immunofluorescence laser scanning confocal microscopy. Microtubule distribution patterns of autotetraploid hybrids were similar to diploid rice, but many different kinds of abnormalities were found in the hybrid with low pollen fertility and seed set. Abnormal microtubule organization including structurally distorted microtubules at pachytene, loosely knitted perinuclear microtubules at diakinesis during prophase?I, and abnormal spindles, viz. multipoles, loss of spindle pole focus, abnormal size of spindles, and so on, were found at metaphase?I and metaphase?II. Some cells developed into triad with no formation of tetrad. Abnormal chromosome behaviors included high percentage of multivalents, chromosome lagging, chromosome bridges, and micronuclei. All these abnormalities were found more frequently in low-fertile hybrid than in high-fertile hybrid. These results suggest that abnormal microtubule distribution pattern is an important factor which affects pollen fertility and percentage seed set in autotetraploid rice, and may also have a close relationship with chromosome behavior.     

Imidazopyridazinones as novel PDE7 inhibitors: SAR and in vivo studies in Parkinson's disease model

The synthesis and structure-activity relationship studies of a series of compounds from imidazopyridazinone scaffold as PDE7 inhibitors are disclosed. Potent analogs such as compounds 7 (31nM), 8 (27nM), and 9 (12nM) were identified. The PDE selectivity and pharmacokinetic profile of compounds 7, 8 and 9 are also disclosed. The adequate CNS penetration of compound 7 in mice allowed it to be tested in the MPTP induced PD model and haloperidol induced catalepsy model to probe the differential pharmacology of PDE7 in the striatal pathway.