Biomedical subjects

F Zsila

Publications and source records attributed to F Zsila.

7 recordsLinked to original sources

PubMed2001

Five unique compounds: xyloketals from mangrove fungus Xylaria sp. from the South China Sea coast.

Five unique metabolites, xyloketals A (1), B (2), C (3), D (4), and E (5), and the known 6 were isolated from mangrove fungus Xylaria sp. (no. 2508), obtained from the South China Sea. The structures of these compounds were elucidated by spectroscopic and X-ray diffraction experiments. Xyloketal A is a ketal compound with a C(3) symmetry and xyloketals B-E are its analogues. It was found that xytoketal C slowly rearranged to xytoketal B in DMSO-d(6)() solution at room temperature. Xyloketal A exhibited the activity of inhibiting acetylcholine esterase.

Acetylcholinesterase↗

PubMed2001

Supramolecular assemblies of carotenoids.

Carotenoid self-assemblies were formed by aqueous dilution of ethanolic solutions. The four 3',6'-epimers of capsanthol ((all-E,3R,5'R)-3,3',6'-trihydroxy-beta,kappa-carotene) give rise to right- and left-handed card-pack and head-to-tail types of self-assemblies detected by exciton couplets appearing in the CD spectra. Slow kinetics of formation followed for some of the aggregates indicate the complexity of the process. The exciton signals do not appear from equimolar mixtures of related compounds that produce identical type of aggregates of opposite sense on their own. Transformation of self-assembly may reflect the population of kappa-ring rotamers.

Carotenoids↗

PubMed2001

Chiral detection of carotenoid assemblies.

Carotenoid assemblies were produced by aqueous dilution of ethanolic solutions. UV/VIS and CD spectroscopy revealed the formation of J- and H-types of aggregates of both right- and left-handed kinds. Simulation of UV/VIS spectra of the aggregates showed characteristic differences between the two types. 6'-Epimers of capsanthol ((all-E,3R,3'S,5'R)-beta,kappa-carotene-3,3',6'-triols) formed assemblies with increased chirality in dilute solution. While the absorption of 6'R-capsanthol giving H-type aggregate does not depend on the concentration, 6'S-capsanthol yielding J-type assembly showed concentration-dependent absorption intensity. Dilute aggregate of 6'R-capsanthol is characterized by an extremely large A value of -6,600. The transformation of J- to H-type assembly was observed in the mixtures of the epimers producing an intermediate kind of aggregate. A hypothetical structure for H-type assemblies is proposed.

Carotenoids↗

PubMed2001

Color and chirality: carotenoid self-assemblies in flower petals.

As a novel phenomenon, optical activity--often very strong--has been detected by circular dichroism (CD) spectroscopy in carotenoid-containing living flowers of several species belonging to different families. Using natural pure xanthophyll esters, very similar CD spectra were obtained in vitro, proving the ability of these molecules to form chiral self-assemblies. The relationship between the ultrastructure of the chromoplast, its chemical composition and the optical activity is discussed. The applicability of CD spectroscopy for studying intact plant tissue is emphasized.

Carotenoids↗

PubMed2000

Stereochemical study of tolperisone, a muscle relaxant agent, by circular dichroism and ultraviolet spectroscopy.

The stereochemistry of tolperisone, a chiral aryl-alkyl basic ketone was investigated by means of circular dichroism (CD) and ultraviolet (UV) spectroscopy. The unusually high optical activity of tolperisone hydrochloride in the n-->pi* region is interpreted by the presence of a chiral conformer in solution. For stereochemical reasons, the C = O group and the aromatic moiety lack coplanarity by forming an inherently dissymetric chromophore, of M helicity. Similar helicity prevails in the crystal phase, according to the solid-state CD spectrum of (-)-tolperisone HCl salt. The chirality rule proposed by Snatzke for nonplanar benzoyl chromophores predicts the absolute configuration of (-)-tolperisone hydrochloride to be R, in agreement with other alpha-methyl-beta-amino-ketones.

Circular Dichroism↗

PubMed1999

Determination of absolute configuration of ketamine enantiomers by HPLC-CD-UV technique.

Recognizing that the stereochemical structure of NMDA receptor antagonist ketamine provides valuable data about the relationship between its conformation and absolute configuration by CD-UV analysis, a method for the identification of ketamine enantiomers is proposed which avoids the need for authentic samples of the enantiomers. The ketamine enantiomers were separated by HPLC using Chiralcel OJ stationary phase. The in situ registration of CD and UV spectra, together with the application of the octant rule for cyclohexanone derivatives, makes possible the direct assignment of the eluted ketamine enantiomers.

Analgesics↗

PubMed1999

[Novel chiroptical methods in pharmaceutical analysis].

Chiroptical spectroscopy, and its double and triple hyphenated combinations with UV-VIS spectroscopy and/or separation techniques constitute great progress in pharmaceutical analysis, of which five recently developed methods are surveyed here, as follows: The determination of enantiomeric purity by double, CD/UV detection without, and with the latter one provides enhanced sensitivity and selectivity. The determination of chromatographic peak homogeneity, by double detection, and peak slicing by recording. The separation, identification and four stereoisomers of doubly chiral compounds, by HPLC separation on chiral column, and optical-chiroptical detection.

Chromatography, High Pressure Liquid↗