Structural Insights into the TES/TFA Reduction of Differently Substituted Benzofurans: Dihydrobenzofurans or Bibenzyls?

Various polysubstituted benzofurans were reduced by using triethylsilane in trifluoracetic acid. 2,3-Dihydrobenzofurans or bibenzyl compounds were obtained in high yields, depending on the nature of the substituents at C2 and on the benzene ring of the core structure. A p-anisole substituent at C2 of benzofurans always led to the corresponding bibenzyls.

Towards By-Product Utilisation of Pea Hulls: Isolation and Quantification of Galacturonic Acid

In order to evaluate by-products from food processing as alternative raw materials for pectin extraction, their amount of galacturonic acid (GalA) has to be analysed as a marker for pectin content. In the present study, significant differences in GalA release using different digestion methods are shown for pea hulls, as an example of by-products with a high content of cellulose. Complete digestion of the fibre matrix was assumed for Saeman hydrolysis as a reference protocol. Significantly lower GalA release was achieved by a treatment with trifluoracetic acid (TFA). An alternative treatment with ethylenediaminetetraacetic acid (EDTA) at pH 11 followed by an enzymatic digestion at pH 4.5 using a combination of polygalacturonase (Vegazyme M) and cellulase (Celluclast 1.5L) resulted in a similar release of GalA compared to Seaman hydolysis. Pea hull samples, analysed by this alternative protocol, showed on average a GalA content of 11.2%. Therefore, pea hulls may serve as new raw material for pectin extraction.

Synthesis and ROMP of new sulfobetaine and carboxybetaine norbornene

The synthesis of novel norbornene based polyzwitterions via ring opening metathesis polymerization (ROMP) is present. Trifluoracetic acid (TFA) was used as a solvent to provide a homogenous medium for the polymerization reaction of sulfobetaines with the commercially available Hoveyda-Grubbs’ initiator. In order to prevent the competitive complexation via carboxylate functional group of the ruthenium metal center, we carried out the controlled polymerization of ethyl protected carboxybetaines monomers.

DETERMINATION THE CONCENTRATION OF ASIATICOSIDE IN CENTELLA ASIATICA (L.) URB. – APIACEAE AT QUANG DIEN DISTRICT, THUA THIEN HUE PROVINCE

Background: Centella asiatica (L.) Urb. - Apiaceae has been used in traditional medicine to cure many diseases such as cholera dysentery, pimples, discharge, cough, sore throat, hemorrhoids and detoxification. The objective is to determine the amount of active ingredient asiaticoside in Centella asiatica (L.) Urb at Quang Tho 2 cooperatives, Quang Dien District, Thua Thien Hue province. Materials and method: C.asiatica after being harvested, washed and drained was dried in sunlight or in dryer with different temperature. Each 20g of C.asiatica was extracted using various methods with dissolving appropriate solvents. The extracted solution was diluted by extracted solvent. This diluted solution was filtered through 0.45μm membrane filter for the purpose of chromatography. Results: The chromatography condition: mobile phase consisting of methanol: Trifluoracetic acid 1% (60: 40); Column: HiQ Sil C18 (4.6 x 250 mmm) 3μm; flow rate at 0.7 ml/min; The maximum detection wavelength: 215 nm; retention time of asiaticosid (tR): 18.7 minutes. Conclusion: The content of asiaticoside in sample is from 0.09% to 1.35% depending on the initial sample handling and sample extraction method. Keywords: Centella asiatica (L.) Urb. - Apiaceae, asiaticoside, HPLC.

Sample Preparation of Eggs from Laying Hens Using QuEChERS Dispersive Extraction for the Simultaneous Determination of Melamine and Cyromazine Residues by HPLC-DAD

A quick, easy, cheap, effective, rugged, and safe (QuEChERS) dispersive extraction method is proposed herein for the isolation and cleanup of melamine and cyromazine from chicken egg yolk. Analytes are determined by high-performance liquid chromatography using photodiode array detector after separation on a LiChroCART® (250 × 4 mm)–-LiChrospher® RP-8e, 5 µm analytical column using a mobile phase of 0.1% trifluoracetic acid and methanol (80:20 v/v) delivered isocratically at a flow rate of 1 mL/minute. Extraction of isolated compounds was achieved by methanol and acetonitrile mixture (1:1 v/v). Recovery rates ranged between 74.5% and 115.8%. The method was validated in terms of 657/2002/EC decision. The within-laboratory reproducibility, expressed as a relative standard deviation, was <11%. Decision limits (CCalfa) were 2.56 mg/kg for melamine and 0.22 mg/kg-1 for cyromazine, and the corresponding results for detection capability (CCbeta) were 2.8 mg/kg for melamine and 0.24 mg/kg for cyromazine. Ruggedness was estimated according to the Youden approach studying egg yolk mass, sorbent mass, centrifugation time, organic solvents volume, evaporation temperature, and vortex time.

Determination of Organic Acids in Salicornia herbacea by Solid-phase Extraction Combined with Liquid Chromatography

A solid-phase extraction (SPE) method for the determination of procatechuic acid, ferulic acid and caffeic acid in Salicornia herbacea L. (Hamcho) has been developed. The optimal conditions were obtained by using a C18 SPE cartridge. By using ethanol and acetonitrile /water/ trifluoracetic acid as washing and eluting solvents, most interfering compounds originating from the hamcho matrix were eliminated. The extracts were sufficiently clean to be directly injected into the HPLC for further chromatographic analysis. Good linearity was obtained from 0.1 to 200 μg/mL (r > 0.999) for procatechuic acid, 0.2 to 400 μg/mL (r > 0.999) for caffeic acid and 0.3 to 600 μg/mL (r > 0.999) for ferulic acid, with the relative standard deviations being less than 3.6%. The mean recoveries of procatechuic acid, ferulic acid and caffeic acid from hamcho were more than 79.2% and the detection limit (S/N = 3:1) was 0.02 μg/mL for procatechuic acid, 0.01 μg/mL for caffeic acid and 0.04 μg/mL for ferulic acid. This method is a viable alternative to the existing HPLC methods for analyzing the content of procatechuic acid, ferulic acid and caffeic acid in hamcho.

Study on SF Nanofibrous Mats via Electrospun with Different Spinning Solvent as TFA/DCM and FA

Silk fibroin (SF) was regenerated for electrospinning. A mixture solvents Trifluoracetic acid (TFA) and dichloromethane (DCM) was selected as the solvent of regenerated SF. Its spinning properties and characteristics of end nanofibers mats were compared with those of the regenerated SF electrospinning solution dissolved in formic acid (FA). From the comparison of SEM images of regenerated SF electrospinning from the two different solvents solutions, it could be found that the spinning concentration range in TFA&DCM was smaller than that in FA for the solution viscosity was bigger than that in FA. Moreover, from the FTIR spectra of electrospun nanofibers obtained from TFA&DCM and FA was both similar with that of regenerated SF. This meant that there was no new group formed when TFA& DCM was selected as solvents. Therefore, TFA&DCM were also a nice option for the electrospinning of regenerated SF.

Identification of carbohydrate isomers in flavonoid glycosides after hydrolysis by hydrophilic interaction chromatography

A method for carbohydrate isomers (saccharide units) identification in flavonoid glycosides after hydrolysis by an HPLC system with two detectors (diode array UV-VIS detector and evaporative light scattering detector) was set up in this work. Experimental procedure was optimized with two types of model glycosides, namely rutin and hesperidin. The model glycosides were hydrolyzed to saccharide units and aglycone parts; the aglycone was characterized by its UV-VIS spectrum and the saccharide unit was identified by its retention time and elution profile (anomeric signals). Acidic and enzymatic hydrolyses were compared in the first step of the method; in acidic hydrolysis, trifluoracetic acid was used, while glucosidase, galactosidase, and hesperidinase were used in enzymatic hydrolysis. A complete enzymatic hydrolysis was achieved with hesperidin and neohesperidin, but not with 3-O-glycosides. The method was applied for the identification of a glycone from a glycoside isolated from Polygonum lapathifolium (Polygonaceae sp.).