Synthesis and vasorelaxant activity of new 1,4-benzoxazine derivatives potassium channel openers

As part of a search for new potassium channel openers, the synthesis and vasorelaxant activity of new 1,4-benzoxazine derivatives derived from transformation of the benzopyran skeleton of cromakalim were described. Several new 1,4-benzoxazine derivatives were provided with significant vasorelaxant activity with an overall pharmacological behavior similar to CRK (1f, 1i, 2d, 2e, 2f and 2i).     

1,4-Benzothiazine and 1,4-benzoxazine imidazole derivatives with antifungal activity: a docking study

We have recently described the synthesis and antifungal activity of a series of 1,4-benzothiazine and 1,4-benzoxazine imidazole derivatives that mainly showed in vivo activity against a murine experimental model of candidiasis but that very often lacked in vitro activity. Here, we report a docking study of a representative set of our molecules in a 3D model of CYP51 of Candida albicans (CA-CYP51). The model was constructed on the basis of the sequence homology relationship with the recently reported crystal structure of the CYP51 of Mycobacterium tuberculosis (MT- CYP51).     

Design, synthesis, and preliminary biological evaluation of 2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine derivatives

We synthesized a series of novel small molecules, 2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine derivatives, by tandem reduction-oxirane opening of 2-nitroaroxymethyloxiranes in moderate or excellent yields. We investigated the effects of all of the compounds on HUVEC apoptosis and A549 cell growth. The results showed that 6,8-dichloro-2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine was the most effective small molecule in promoting HUVEC apoptosis and inhibiting A549 cell proliferation, but 6-amino-2,3-dihydro-3-hydroxymethyl-1,4-benzoxazine could remarkably inhibit HUVEC apoptosis and might induce the formation of microvessel.     

Inhibition of PrPSc formation in scrapie infected N2a cells by 5,7,8-trimethyl-3,4-dihydro-2H-1,4-benzoxazine derivatives

Prion diseases are fatal, neurodegenerative diseases characterized by the structural conversion of the normal, cellular prion protein, PrP^C into an abnormally structured, aggregated and partially protease-resistant isoform, termed PrP^Sc. Although substantial research has been directed toward development of therapeutics targeting prions, there is still no curative treatment for the disease. Benzoxazines are bicyclic heterocyclic compounds possessing several pharmaceutically important properties, including neuroprotection and reactive oxygen species scavenging. In an effort to identify novel inhibitors of prion formation, several 5,7,8-trimethyl-1,4-benzoxazine derivatives were evaluated in vitro for their effectiveness on the expression levels of normal PrP^C and its conversion to the abnormal isoforms of PrP^Sc in a scrapie-infected cell culture model. The most potent compound was 2-(4-methoxyphenyl)-5,7,8-trimethyl-3,4-dihydro-2H-1,4-benzoxazine, with a diminishing effect on the formation of PrP^Sc, thus establishing a class of compounds with a promising therapeutic use against prion diseases.     

Inhibition of PrPSc formation in scrapie infected N2a cells by 5,7,8-trimethyl-3,4-dihydro-2H-1,4-benzoxazine derivatives

Prion diseases are fatal, neurodegenerative diseases characterized by the structural conversion of the normal, cellular prion protein, PrP^C into an abnormally structured, aggregated and partially protease-resistant isoform, termed PrP^Sc. Although substantial research has been directed toward development of therapeutics targeting prions, there is still no curative treatment for the disease. Benzoxazines are bicyclic heterocyclic compounds possessing several pharmaceutically important properties, including neuroprotection and reactive oxygen species scavenging. In an effort to identify novel inhibitors of prion formation, several 5,7,8-trimethyl-1,4-benzoxazine derivatives were evaluated in vitro for their effectiveness on the expression levels of normal PrP^C and its conversion to the abnormal isoforms of PrP^Sc in a scrapie-infected cell culture model. The most potent compound was 2-(4-methoxyphenyl)-5,7,8-trimethyl-3,4-dihydro-2H-1,4-benzoxazine, with a diminishing effect on the formation of PrP^Sc, thus establishing a class of compounds with a promising therapeutic use against prion diseases.     

Two new 1,4-naphthoquinone derivatives from Impatiens balsamina L. flowers

Two new 1,4-naphthoquinone derivatives, balsaminone D (1), balsaminone E (2) along with two known compounds (3 and 4) were discovered from Impatiens balsamina L. flowers. Their structures were identified with spectroscopic methods including HR–EI–MS, 1D and 2D NMR, as well as the absolute configuration was determined by ECD calculation. In addition, new compounds 1 and 2 with IC₅₀ value of 30.54 and 40.67 μg/mL exhibited better activities against activated t-HSC/Cl-6 cells than positive control Silymarin and Fufang Biejia Ruangan Pian, of which the IC₅₀ value were 202.34 and 231.56 μg/mL, respectively.     

Isoprenylhydroquinone glucoside: a new non-antioxidant inhibitor of peroxynitrite-mediated tyrosine nitration.

Three hydroquinone glucosides and four caffeoylquinic esters were examined for their effect on tyrosine nitration, as well as on the oxidation of dihydrorhodamine (DHR) 123 and cytochrome c(2+) induced by peroxynitrite. All these phenolics, which had previously been characterized as the active principles of the plant Phagnalon rupestre, were fairly active in preventing the oxidation of DHR 123, though inefficient in the cytochrome c test. While their antioxidant potency is associated with the presence of a caffeoyl moiety, not so an obvious chemical character was correlated to a greater activity against nitration of tyrosine. Here, the highest potency corresponded to 2-isoprenylhydroquinone-1-glucoside. On the basis of the fact that the susceptibility to nitration of given aromatic compound confers to it inhibitory activity of tyrosine nitration, the analysis of ultraviolet and nuclear magnetic resonance spectral shifts provides valuable information for explaining the ability of natural phenolics to interfere with that reaction.     

Synthesis and antimycobacterial activity of new quinoxaline-2-carboxamide 1,4-di-N-oxide derivatives

As a continuation of our research and with the aim of obtaining new antituberculosis agents which can improve the current chemotherapeutic antituberculosis treatments, new series of quinoxaline-2-carboxamide 1,4-di-N-oxide derivatives were synthesized and evaluated for in vitro antituberculosis activity against Mycobacterium tuberculosis strain H(37)Rv, using the radiometric BACTEC 460-TB methodology. Active compounds were also screened by serial dilution to assess toxicity to a VERO cell line. The results indicate that some compounds exhibited a good antituberculosis activity and the arylcarboxamide analogues 3, 8, and 9 were the most active compounds (EC(90)/MIC1). Also, the cytotoxic effects indicate that these compounds have a good Selectivity Index (SI).     

Accumulation of tyrosol glucoside in transgenic potato plants expressing a parsley tyrosine decarboxylase

As part of the response to pathogen infection, potato plants accumulate soluble and cell wall-bound phenolics such as hydroxycinnamic acid tyramine amides. Since incorporation of these compounds into the cell wall leads to a fortified barrier against pathogens, raising the amounts of hydroxycinnamic acid tyramine amides might positively affect the resistance response. To this end, we set out to increase the amount of tyramine, one of the substrates of the hydroxycinnamoyl-CoA:tyramine N-(hydroxycinnamoyl)-transferase reaction, by placing a cDNA encoding a pathogen-induced tyrosine decarboxylase from parsley under the control of the 35S promoter and introducing the construct into potato plants via Agrobacterium tumefaciens-mediated transformation. While no alterations were observed in the pattern and quantity of cell wall-bound phenolic compounds in transgenic plants, the soluble fraction contained several new compounds. The major one was isolated and identified as tyrosol glucoside by liquid chromatography-electrospray ionization-high resolution mass spectrometry and NMR analyses. Our results indicate that expression of a tyrosine decarboxylase in potato does not channel tyramine into the hydroxycinnamoyl-CoA:tyramine N-(hydroxycinnamoyl)-transferase reaction but rather unexpectedly, into a different pathway leading to the formation of a potential storage compound.     

Dorycnioside, a new phenylbutanone glucoside from Dorycnium pentaphyllum subsp. herbaceum

A new phenylbutanone glucoside, dorycnioside, was isolated from the methanol extract of the aerial parts of Dorycnium pentaphyllum subsp. herbaceum Vill. (Rouy) and identified as 4-(4'-O-beta-D-glucopyranosyl-3',5'-dimethoxyphenyl)-2-butanone (1). In addition, two known phenylbutanone glucosides, five flavonoids, one cyanogenic glucoside, one cyclitol and one hydroquinone glucoside were also isolated and identified. The major constituent of the methanol extract was found to be myricitrin. The structure of 1 was elucidated on the basis of its spectroscopic data. It is the first time that derivatives of phenylbutanone are isolated from the Leguminosae family.     

Synthesis and SAR studies of 1,4-benzoxazine MenB inhibitors: Novel antibacterial agents against Mycobacterium tuberculosis

Menaquinone is an essential component of the electron transport chain in many pathogens and consequently enzymes in the menaquinone biosynthesis pathway are potential drug targets for the development of novel antibacterial agents. In order to identify leads that target MenB, the 1,4-dihydroxy-2-naphthoyl-CoA synthase from Mycobacterium tuberculosis, a high-throughput screen was performed. Several 1,4-benzoxazines were identified in this screen and subsequent SAR studies resulted in the discovery of compounds with excellent antibacterial activity against M. tuberculosis H37Rv with MIC values as low as 0.6 μg/ml. The 1,4-benzoxazine scaffold is thus a promising foundation for the development of antitubercular agents.     

Dolichyl monophosphate and its sugar derivatives in plants.

A glucose acceptor was isolated from soya beans by extraction with chloroform/methanol (2:1, v/v), followed by DEAE-cellulose column chromatography of the extract. This acceptor could not be distinguished from liver dolichyl monophosphate by t.l.c. It could replace dolichyl monophosphate as a mannose acceptor with a liver enzyme and its glucosylated derivative could replace dolichyl monophosphate glucose as a glucose donor in the same system. These results, together with those already reported [Pont Lezica, Brett, Romero Martinez & Dankert (1975) Biochem, Biophys. Res. Commun. 66, 980-987], indicate that the acceptor from soya bean is a dolichyl monophosphate. Gel filtration of its glucosylated derivative on Sephadex G-75 in the presence of sodium deoxycholate indicated that the acceptor contained 17 or 18 isoprene units. An enzyme preparation from pea seedlings was shown to use endogenous acceptors to form lipid phosphate sugars containing mannose and N-acetylglucosamine from GDP-mannose and UDP-N-acetylglucosamine. Chromatographic and degradative techniques indicated that the compounds formed were lipid monophosphate mannose, lipid pyrophosphate N-acetylglucosamine, lipid pyrophosphate chitobiose and a series of lipid pyrophosphate oligosaccharides containing both mannose and N-acetylglucosamine. None of these compounds was degraded by catalytic hydrogenation, and so the lipid moiety in each case was probably an alpha-saturated polyprenol. The endogenous acceptors for mannose and N-acetylglucosamine in peas may therefore be dolichyl monophosphate, as has been found in mammalian systems.     

Short-term measurement of carbon isotope fractionation in plants

Combustion-based studies of the carbon-13 content of plants give only an integrated, long-term value for the isotope fractionation associated with photosynthesis. A method is described here which permits determination of this isotope fractionation in 2 to 3 hours. To accomplish this, the plant is enclosed in a glass chamber, and the quantity and isotopic content of the CO₂ remaining in the atmosphere are monitored during photosynthesis. Isotope fractionation studies by this method give results consistent with what is expected from combustion studies of C₃, C₄, and Crassulacean acid metabolism plants. This method will make possible a variety of new studies of environmental and species effects in carbon isotope fractionation.     

Sulphur fractionation in calcareous soils and bioavailability to plants

Sulphur fractionation and availability to plants are poorly understood in calcareous soils. Sixty-four calcareous soils containing varying amounts of CaCO₃ were collected from ten provinces in China and their S fractions determined. Organic S was the predominant fraction of S, accounting for on average 77% of the soil total S. The amounts of adsorbed sulphate were found to be negligible. 1 M HCl extracted substantially more sulphate than either 0.01 M CaCl₂ or 0.016 M KH₂PO₄, indicating the existence of water-insoluble but acid-soluble sulphate, probably in the form of sulphate co-precipitated with CaCO₃. The concentrations of water-insoluble sulphate correlated positively with the contents of CaCO₃ and accounted for 0.03–40.3% (mean 11.7%) of soil total S. To test the bioavailability of water-insoluble sulphate, a sulphate-CaCO₃ co-precipitate labelled with ³⁵S was prepared and added to a calcareous soil in a pot experiment with either NH₄⁺ or NO₃^– as the N source. In 29 days, wheat plants took up 10.6% and 3.0% of the ³⁵S added to the soil in the NH₄⁺ and NO₃^– treatments, respectively. At the end of the pot experiment, the decrease of water-insoluble, acid-soluble, sulphate was more apparent in the NH₄⁺ than in the NO₃^– treatment. The results indicate that sulphate co-precipitated with CaCO₃ in calcareous soils may become partly available for plant uptake, depending on rhizosphere pH, if the field precipitate is similar to the laboratory prepared sample studied.     

Synthesis and biological activity of new 1,4-benzodioxan-arylpiperazine derivatives. Further validation of a pharmacophore model for alpha(1)-adrenoceptor antagonists.

A series of WB4101 (1)-related benzodioxanes (2-17) have been synthesized by replacing the phenoxyethyl moiety of 1 with a N-alkyl piperazine bearing a cyclic substituent (a substituted or unsubstituted phenyl group, a pyridine or pyridazinone ring, a furoyl moiety) at the second nitrogen atom. The binding profile of these compounds has been assessed by radioligand receptor binding assay at alpha(1)- and alpha(2)-adrenoceptors, in comparison to prazosin and rauwolscine, respectively. Moreover, structure-activity relationships have been derived for compounds 2-17 based on their fitting to a pharmacophore model for alpha(1)-adrenoceptor antagonists recently proposed by our research group. In a parallel way, the same compounds have been used to further test the predictive power and statistical significance of the model itself. The accuracy of the results obtained also in this case revealed the robustness of the calculated pharmacophore model and led to the identification of the molecular structural moieties which are thought to contribute to the biological activity.     

Synthesis and antimalarial evaluation of new 1,4-bis(3-aminopropyl)piperazine derivatives

Synthesis and evaluation of the activity of a new family of 1,4-bis(3-aminopropyl)piperazine derivatives against a chloroquine-resistant strain of Plasmodium falciparum, and as inhibitors of beta-hematin formation, are described. The highest antimalarial activities were obtained for compounds displaying the highest predicted vacuolar accumulation ratios and the best potencies as inhibitors of beta-hematin formation. The most potent compound displayed an activity 3-fold better than chloroquine for a comparable selectivity index upon MRC-5 cells. Therefore, in this series, the replacement of the 7-chloroquinoline group can constitute a strong rationale for further investigation.