Biomedical subjects

Rudolf Galensa

Publications and source records attributed to Rudolf Galensa.

4 recordsLinked to original sources

PubMed2006

Stereoisomeric separation of flavanones and flavanone-7-O-glycosides by capillary electrophoresis and determination of interconversion barriers.

The stereoisomeric separation of several flavanones and flavanone-7-O-glycosides has been achieved with capillary electrophoresis by adding native cyclodextrins or cyclodextrin derivatives to the background electrolyte. As an alternative method, micellar electrokinetic chromatography with sodium cholate as a chiral surfactant has been used for the epimeric separation of two flavanone-7-O-glycosides. The effect of buffer systems containing mixtures of cyclodextrin with either sodium dodecyl sulfate or sodium cholate upon the chiral recognition of flavanones and flavanone-7-O-glycosides as well as the variation of the background electrolyte (concentration of buffer and surfactant, pH value, organic modifier), and its influence on the resolution factor Rs was investigated. Temperature- and pH-dependent enantiomerization or epimerization barriers of several flavanones (naringenin, homoeriodictyol) and flavanone-7-O-glycosides (naringin, neohesperidin, prunin, narirutin) in basic media (pH values of 9-11) have been observed. Interconversion profiles featuring characteristic plateau formation of the elution pattern were observed at high pH and evaluated with the simulation software ChromWin to determine rate constants k(T) and Eyring activation parameters, DeltaG#(T), DeltaH#, and DeltaS#.

Cyclodextrins↗

PubMed2004

Identification and quantification of polyphenols in carob fruits (Ceratonia siliqua L.) and derived products by HPLC-UV-ESI/MSn.

The polyphenolic patterns of carob pods (Ceratonia siliqua L.) and derived products were identified and quantified using high-performance liquid chromatography-UV absorption-electrospray ion trap mass spectrometry after pressurized liquid extraction and solid-phase extraction. In carob fiber, 41 individual phenolic compounds could be identified. In addition, spectrophotometric quantification using the Folin-Ciocalteu and vanillin assays was performed, and the antioxidative activity was determined as the 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity. Carob pods contain 448 mg/kg extractable polyphenols comprising gallic acid, hydrolyzable and condensed tannins, flavonol-glycosides, and traces of isoflavonoids. Among the products investigated, carob fiber, a carob pod preparation rich in insoluble dietary fiber (total polyphenol content = 4142 mg/kg), shows the highest concentrations in flavonol-glycosides and hydrolyzable tannins, whereas roasted carob products contain the highest levels of gallic acid. The production process seems to have an important influence on the polyphenolic patterns and quantities in carob products.

Antioxidants↗

PubMed2003

Chiral separation of diastereomeric flavanone-7-O-glycosides in citrus by capillary electrophoresis.

The 2S- and 2R-diastereomers of major flavanone-7-O-glycosides found in sweet orange (Citrus sinensis), mandarine (Citrus deliciosa), grapefruit (Citrus paradisi), lemon (Citrus limon), and sour or bitter orange juice (Citrus aurantium) were separated for the first time by chiral capillary electrophoresis (CE) employing various buffers with combined chiral selectors. Native cyclodextrins (CDs), neutral and charged CD derivatives were examined as chiral additives to the background electrolyte (BGE). Separation efficiency has not proved satisfactory with one single CD as chiral selector in the buffer, a full and simultaneous separation could often be achieved only by using combined buffer with two different CDs. Chiral separation of major flavanones in sweet orange, mandarine and grapefruit juices raised more difficulties than in lemon and sour orange juices as narirutin will not readily build complexes with most CDs. Diastereomeric flavanones of mature and immature grapefruits were compared and some differences were found: naringin showed different diastereomeric ratio and 2S-prunin appeared only in immature grapefruit. Marmalade was also examined by chiral CE. Its major flavanones corresponded to flavanone pattern of mixed sour and sweet oranges.

Citrus↗

PubMed2002

Online coupling of pressurized liquid extraction, solid-phase extraction and high-performance liquid chromatography for automated analysis of proanthocyanidins in malt.

A new instrumental setup for automated extraction of solid samples by online coupling of pressurized liquid extraction, automated SPE (solid-phase extraction) and HPLC is presented. From the extraction to the chromatogram no manual sample handling is required. The application to the determination of proanthocyanidins in malt reduces time and manual work to a minimum compared to former manual methods. Twenty samples can be processed within 24 h in respect to eight samples with the manual method. Using the features of the instrumental coupling, an optimized strategy for SPE of proanthocyanidins from natural samples was developed, requiring no evaporation step, using commercial cartridges and delivering concentrated eluates. The recovery of five main malt proanthocyanidins was 97%, with a reproducibility of 5%. This new instrumental coupling is thought to reduce time and costs along with improved results for a broad range of solid sample materials.

Anthocyanins↗