Screening of ionic liquids for extraction of flavonoids from heather

Room temperature ionic liquids are novel solvents with the specific properties that makes them of interest for application for extraction for a wide range of compounds. In this work extraction efficiency of flavonoids from heather flowers using ionic liquids based on imidazolium cation were evaluated and compared with organic solvents. It was found that the anion of ionic liquid significantly influence the extraction yields. Flavonoid content as well as antioxidant activity based on radical scavenging on 1,1-diphenul-2-pirylhydrazyl radicals and cupric reducing antioxidant capacity increased in the order: [Bmim]PF₆ < [Bmim]BF₄ < [Bmim]Cl. The obtained extraction yield using [Bmim]Cl were higher than reported for 60% ethanol and ethyl acetate under similar conditions, thus, may be helpful for better utilization of heather flowers as the potential pharmaceutical and nutraceutical ingredients.     

Phytochemical analysis of non-polar solvent extracts of the Wisteria sinensis leaves

A comparative study on the phytochemical composition of the n-hexane and chloroform extracts from Wisteria sinensis leaves collected in June and October is described. Continuous extraction in Soxhlet apparatus, as well as ultrasound-assisted technique, was used for the preparation of the extracts. All the extracts were analysed by GC/MS method. As a result, α-tocopherol was identified as the main component (56%) of the extracts from October leaves, whereas, β-sitosterol was identified as the main compound (47%) in the extracts from the June leaves. Additionally, pure α-tocopherol was isolated from n-hexane extract of the October leaves using column chromatography. A total of 6.25 mg of α-tocopherol was isolated from 1 g of dried leaves. The presence of the vitamin E in extracts from W. sinensis leaves is described here for the first time.     

Ethylethanolammonium 4-nitrobenzoate

Journal of Thermal Analysis and Calorimetry - In the present studies, the thermal behaviour of NaUO2BO3 has been investigated. This compound is a potential product of interaction between the...     

Synthesis and Characterization of the New Copper Tetraphosphonate Cu2[(HO3PCH2)4C6H2]·2H2O

Following the strategy of using polyfunctional phosphonic acids for the synthesis of three‐dimensional metal phosphonates, the ethyl ester of a tetraphosphonic acid, i. e. 1,2,4,5‐(Et₂O₃PCH₂)₄C₆H₂, was used in the hydrothermal synthesis of the new copper tetraphosphonate, Cu₂[(HO₃PCH₂)₄C₆H₂]·2H₂O ( 1 ). The in situ hydrolysis of the ethyl ester leads to the acid (1,2,4,5‐(H₂O₃PCH₂)₄C₆H₂) which reacts with the Cu²⁺ ions to form the green coarse‐crystalline product. The title compound is the first fully characterized copper tetraphosphonate. Its structure was solved from single crystal data ( 1 : triclinic, , a = 4.9262(10), b = 8.1890(16), c = 11.800(2) Å, α = 71.17(3), β = 89.15(3), γ = 88.56(3)°, V = 450.39(16) ų, Z = 2, R1 = 0.0284, wR₂ = 0.0682). The structure is built up from edge‐sharing CuO₅ polyhedra each containing a single H₂O molecule. Thus, dimeric [Cu₂O₈] units are formed. In the second coordination sphere of each of the Cu²⁺ ions four HO₃PCH₂R units are observed. The [Cu₂O₈] polyhedra are connected to eight other [Cu₂O₈] polyhedra by these organic linkers and a three‐dimensional framework structure is formed. Thermogravimetric, magnetic, and temperature dependent powder XRD measurements and the Raman‐spectrum are also presented.     

Elucidation of the Streptomyces coelicolor pathway to 2-undecylpyrrole, a key intermediate in undecylprodiginine and streptorubin B biosynthesis

The red gene cluster of Streptomyces coelicolor directs production of undecylprodiginine. Here we report that this gene cluster also directs production of streptorubin B and show that 2-undecylpyrrole (UP) is an intermediate in the biosynthesis of undecylprodiginine and streptorubin B. The redPQRKL genes are involved in UP biosynthesis. RedL and RedK are proposed to generate UP from dodecanoic acid or a derivative. A redK(-) mutant produces a hydroxylated undecylprodiginine derivative, whereas redL(-) and redK(-) mutants require addition of chemically synthesized UP for production of undecylprodiginine and streptorubin B. Fatty acid biosynthetic enzymes can provide dodecanoic acid, but efficient and selective prodiginine biosynthesis requires RedPQR. Deletion of redP, redQ, or redR leads to an 80%-95% decrease in production of undecylprodiginine and an array of prodiginine analogs with varying alkyl chains. In a redR(-) mutant, the ratio of these can be altered in a logical manner by feeding various fatty acids.     

Competition between the albumin and three histidine fragment of amyloid precursor protein sites to bind Cu(II)

The aim of this work was to check experimentally the relationship between the five-nitrogen donor system {3 × N_imid, 2 × N⁻} seen e.g. in the peptide fragments of the cysteine-rich amyloid precursor protein (APP) region and the albumin-like {NH₂, 2 × N⁻, N_imid} coordination site. The protected and unprotected octadecapeptides DAHQERMDVSETHLHWHT and Ac-DAHQERMDVSETHLHWHT-NH₂ were synthesized and potentiometric and spectroscopic studies were performed. A comparison of both metal-binding sites that occur in both peptides clearly shows that in the unprotected ligand albumin-like binding is much more efficient than the three His site, although around pH 5 both sites have a comparable ability to bind the Cu(II) ion. However, a comparison of the protected and unprotected peptides with their metal binding sites clearly shows that the three His site is very efficient in binding Cu(II) although less effective than the albumin-like motif.     

Mechanistic studies of UV assisted [4 + 2] cycloadditions in synthetic efforts toward vibsanin E

Quantum chemical DFT calculations at the B3LYP/6-31G(d) level have been used to study the stereochemical course of the photochemical cycloaddition of enone 9 with dienes. The observed products of this photochemically induced cycloaddition showed a stereoselectivity, which is opposite to what would be expected by FMO considerations. The quantum chemical calculations revealed that the unusual stereoselectivity of the reaction can be rationalized by assuming a stereospecific photochemical cis-trans isomerization of enone 9 to trans isomer 9a followed by a thermal Diels-Alder reaction of the diene onto the highly reactive trans enone. The photochemical reaction step involves the selective formation of a twisted triplet intermediate, which accounts for the selectivity of the reaction.     

An unknown coordination mode of the phosphite unit and a carbon-free heterocycle in two different heterobimetallic alumophosphites

The unique alumophosphite reagent LAl(SH)(mu-O)P(OEt)2 was prepared and used for the synthesis of the heterobimetallic alumophosphites [{kappa2-S,P-LAl(S)(mu-O)P(OEt)2}2Zn] and [{kappa4-S,O,O-LAl(SLi)(mu-O)P(OEt)2}2]. The first contains a rare example of two carbon-free five-membered heterocycles (Al-S-Zn-P-O) connected in a spiro fashion through the zinc atom, whereas the second possesses an unknown example of a coordination environment of a phosphite unit M-O-P(mu-OEt)2M with an uncoordinated lone electron pair on the phosphorus center.