Characterization of stress processes of Phaffia rhodozyma stress-resistant mutant.

A carotenoid-less Phaffia rhodozyma mutant (MCP 325) exhibited significantly higher resistance to oxidative stressors such as menadione, H2O2 and K2Cr2O7 than its astaxanthin-producing parental strain (MCP 324). The absence of carotenoids in the mutant did not explain this phenomenon. The cause of the decreased superoxide, hydroxyl radical and glutathione contents, the increased peroxide concentration and the elevated specific activity of catalase under uninduced conditions may be a second mutation. Peroxide treatment induced specific catalase activity in the mutant but not in the parental strain. Regulation of these processes led to the result that, in spite of the mutations, the two strains exhibited the same multiplication rate and generation time.

Reversal of multidrug resitance by natural substances from plants.

The multidrug resistance (MDR) proteins that belong to the ATP-binding cassette superfamily such as P-glycoprotein (P-gp) and MRP1, are present in a majority of human tumors and constitute an important cause of therapeutic failure. Selective inhibitors of the MDR-efflux proteins may improve the effectiveness of cancer chemotherapy. Their mechanism of action was believed to be a competition between resistance modifiers and drugs for the same binding site of P-gp. In our previous work we studied modulation of MDR in cancer cells expressing P-gp or MRP1 by selected carotenoids, flavonoids and extracts from medically important Chinese plants. Capsanthin and capsorubin, carotenoids isolated from paprika, were identified as potent P-gp inhibitors, while lycopene, lutein, antheraxanthin and violaxanthin induced moderate effects. Among flavonoids, effective modulators were rotenone, chrysin, phloretin and sakuranetin. Some chloroform extracts of Chinese herbs were also found to inhibit MDR efflux pumps. The effects of the modulators on P-gp activity were studied by measuring rhodamine 123 uptake in several cancer cells such as the human MDR1 gene-transfected mouse lymphoma cells (L1210) and human breast cancer cells MDA-MB-231 expressing the MRP1 pump (HTB26). Additionally, the ability to alter biophysical properties of lipid bilayers by selected carotenoids was studied by differential scanning calorimetry. The antiproliferative effects as well as the MDR reversal activity of the studied compounds, applied in combination with anticancer drugs, were also discussed.

Effect of polar and non-polar carotenoids on Xanthophylomyces dendrorhous membranes by EPR.

The red yeast Xanthophyllomyces dendrorhous is one of the microbiological production systems for natural carotenoids. High-performance liquid chromatography (HPLC) and electron paramagnetic resonance spectroscopy (EPR) experiments were performed on X. dendrorhous membranes in order to study the effect of incorporation rates of different type of carotenoids. In the case of fluid-phase membranes, it was found that polar carotenoids, such as astaxanthin and cis-astaxanthin, increased the EPR order parameter and decreased the motional freedom and phase-transition temperature. In contrast the non-polar carotenoids beta-cryptoxanthin and beta-carotene decreased the EPR order parameter and increased motional freedom and phase-transition temperature. A noteworthy coherence was observed between the polarities of the strains and the phase-transition temperatures.

Relationship of retinoid and carotenoid metabolism with caecotrophy in rabbits.

The relationship of retinoid and carotenoid metabolism with caecotrophy was studied in adult female New Zealand White rabbits kept in individual metabolic cages. Caecotrophy was prevented by the use of plastic collars. The dry matter, crude protein, fibre, fat and ash contents of hard and soft faecal samples were determined. The retinoid (retinol and retinyl palmitate) and carotenoid (canthaxanthin, beta-carotene, beta-cryptoxanthin, lutein and zeaxanthin) levels of the blood, liver, kidney, caecal content and faeces were also measured by high-performance liquid chromatography (HPLC). The prevention of caecotrophy resulted in a significant decrease of blood retinol (P < 0.001) and retinyl palmitate (P < 0.01) concentration but it did not cause any significant change in the retinol and retinyl palmitate contents of the liver and kidney. The caecal content (25.78 +/- 6.87 microg/g) and the soft faeces (34.52 +/- 10.48 microg/g) contained the retinoids in similar amounts. Various carotenoids were found in considerable amounts in different types of faeces, while in the tissues (blood, liver and kidney) these pigments did not occur in substantial amounts. Total carotenoid concentration was similar in the caecal content (11.23 microg/g) and in the caecotroph (13.85 microg/g). On the basis of the results it can be assumed that the retinoid content of rabbit feed could be lowered in the presence of adequate caecal function and caecotrophy.

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.

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.

(9Z)-capsanthin-5,6-epoxide, a new carotenoid from the fruits of Asparagus falcatus.

From the fruits of Asparagus falcatus a novel minor (Z)-carotenoid has been isolated and, on the basis of spectral data interpretation, characterized as (9Z)-capsanthin-5,6-epoxide [(9Z,3S,5R,6S,3'S,5'R)-5,6-epoxy-3,3'-dihydroxy-5,6-dihydro-beta,kappa-caroten-6'-one, (1)]. In addition, seven other (Z)-carotenoids [namely, (9Z)-, (9'Z)-, (13Z)-, and (13'Z)-capsanthins, (9Z)- and (13Z)-capsorubins, and (9Z)-violaxanthin], which have been previously described from other plants, were isolated and identified.

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.

Carotenoid composition in the fruits of red paprika (Capsicum annuum var. lycopersiciforme rubrum) during ripening; biosynthesis of carotenoids in red paprika.

The changes in the carotenoid pigments of the Capsicum annuum var. lycopersiciforme rubrum during maturation have been investigated quantitatively by means of a HPLC technique. In all of the chromatograms, 40 peaks were detected; 34 carotenoids were identified. The total carotenoid content of the ripe fruits was about 1.3 g/100 g of dry weight, of which capsanthin constituted 37%, zeaxanthin was 8%, cucurbitaxanthin A was 7%, capsorubin constituted 3.2%, and beta-carotene accounted for 9%. The remainder was composed of capsanthin 5,6-epoxide, capsanthin 3,6-epoxide, 5,6-diepikarpoxanthin, violaxanthin, antheraxanthin, beta-cryptoxanthin, and several cis isomers and furanoid oxides. The possible biosynthetic routes for the formation of minor carotenoids containing 3,5,6-trihydroxy-beta-, 3,6-epoxy-beta-, and 6-hydroxy-gamma-end groups are described.

[Carotenoid contents of herbal teas]. / Gyógyteafüvek karotinoid tartalmának vizsgálata.

Carotenoid composition of 14 herbal tea consumed by Herbaria was investigated by HPLC method. The main components were lutein (36-49%) cis-luteins (2-20%) and beta-carotene (3-25%). alpha- and beta-cryptoxanthin, alpha-carotene and some 5,6-epoxy-carotenoids (neoxanthin, violaxanthin, antheraxanthin) were detected. The chlorophyll content was also measured.

Carotenoid composition in the fruits of Asparagus officinalis.

The carotenoid pigments of the ripe and unripe fruits of Asparagus officinalis were investigated by means of an HPLC technique. Capsanthin, capsorubin, capsanthin 5,6-epoxide, antheraxanthin, violaxanthin, neoxanthin, mutatoxanthin epimers, zeaxanthin, lutein, beta-cryptoxanthin, beta-carotene, and some cis isomers were found. Carotenoids with 3,5,6-trihydroxy and 3,6-epoxy beta-end groups could not be deleted.

[Potentially bioactive pyrimidine derivatives. 1. 2-Amino-4-aryl-8-arylidene-3,4,5,6,7,8-hexahydroquinazoline]. / Potentiell bioaktive Pyrimidinderivate. 1. Mitteilung: 2-Amino-4-aryl-8-aryliden-3,4,5,6,7,8-hexahydrochinazoline.

Six condensed 2-amino-4-arylpyrimidines (1a-f) were synthesized by the base catalyzed reaction of some monoarylidenecycloalkanones and guanidine. The reaction of 2,6-diarylidenecyclohexanones with guanidine yielded 2-amino-4-aryl-3,4,5,6,7,8-hexahydroquinazolines which were stable only as salts 3a-j. The oxidation of 3a-j led to 2-amino-4-aryl-8-arylidene-5,6,7,8-tetrahydroquinazolines 4a-j.