József Deli

Reversal of Multidrug Resistance 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.

HPLC study on the carotenoid composition of Calendula products

The authors report on the HPLC investigation of the carotenoid composition of the steams, leaves, petals and pollens of Calendula officinalis L. In the petals and pollens, the main carotenoids were flavoxanthin and auroxanthin while the stem and leaves mostly contained lutein and beta-carotene. Five different herbal tea and two tinctures made from the flower of C. officinalis L. were also investigated and the carotenoid composition of the industrial products was compared to the starting material.

Color and chirality: carotenoid self-assemblies in flower petals

Abstract. 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.

Isolation and characterization of 3,5,6-trihydroxy-carotenoids from petals ofLilium tigrinum

SummaryReinvestigation by HPLC of the petals ofLilium tigrinum and the isolation of some minor compounds is reported. Using HPLC-controlled, preparative-column chromatography, 5,6-diakarpoxanthin (6), 6-epikarpoxanthin (2), 5,6-diacapsokarpoxanthin (8), and 9Z-antheraxanthin (9Z-13) were isolated and characterized. Based on spectroscopic data the absolute configurations of6 and8 were identical with those originating from paprika, thus the 5,6-diakarpoxanthin (6) and 5,6-diacapsokarpoxanthin (8) have the 3S, 5S, 6S configuration and 6-epikarpoxanthin (2) has the 3S, 5R, 6S configuration.

Carotenoids with anti‐Helicobacter pylori activity from Golden delicious apple

Previously it was reported that hypophasic carotenoids of Golden delicious apple peel showed potent anti‐H. pylori activity (MIC50 = 36 µg/mL), comparable to metronidazole (MIC50 = 45 µg/mL). To further investigate the involved active carotenoids of the apple peel extracts, seven carotenoids were isolated for the current study: (all‐E)‐luteoxanthin, (all‐E)‐neoxanthin, (9′Z)‐neoxanthin, (all‐E)‐antheraxanthin, (all‐E)‐violaxanthin, (9Z)‐violaxanthin and (all‐E)‐lutein. The MIC50 values of (all‐E)‐luteoxanthin, (all‐E)‐neoxanthin and (9′Z)‐neoxanthin were 7.9, 11 and 27 µg/mL, respectively. Other carotenoids and β,β‐carotene did not exhibit potent anti‐H. pylori activity (MIC50 > 100 µg/mL). An examination of structure and function suggested that active carotenoids contained a monofuranoid ring or an allenic bond in addition to an epoxy group and an additional two or three hydroxyl substituents on the side group. Copyright

Hydrophilic carotenoids: Recent progress

Carotenoids are substantially hydrophobic antioxidants. Hydrophobicity is this context is rather a disadvantage, because their utilization in medicine as antioxidants or in food chemistry as colorants would require some water dispersibility for their effective uptake or use in many other ways. In the past 15 years several attempts were made to synthetize partially hydrophilic carotenoids. This review compiles the recently synthetized hydrophilic carotenoid derivatives.

Capsoneoxanthin, a new carotenoid isolated from the fruits of Asparagus falcatus

Abstract From the ripe fruits of Asparagus falcatus capsoneoxanthin, a minor carotenoid was isolated and, based on its spectral data, identified as (all-E,3S,5R,6R,3′S,5′R)-6,7-didehydro-5,6-dihydro-3,5,3′-trihydroxy-β,κ-caroten-6′-one.

Analysis of carotenoids in the fruits of Asparagus falcatus: Isolation of 5,6-diepikarpoxanthin

SummaryIn an investigation of carotenoids present in the fruits ofAsparagus falcatus capsanthin (1), capsorubin (2), 5,6-diepikarpoxanthin (7), capsanthin 5,6-epoxide (18), capsochrome (17), mutatoxanthin (19), antheraxanthin (11), and capsanthone (20) (Figure 1) have been isolated by preparative CLC and characterized by spectroscopic methods. On the basis of spectroscopic data the absolute configuration of 5,6-diepikarpoxanthin (7) was determined as 3S,5S,6S, which is identical with that occurring in samples originating from paprika andLilium.

Configuration of a single centre determines chirality of supramolecular carotenoid self-assembly

Abstract Card-pack and head-to-tail types of self-assembly are formed upon aqueous dilution of capsantholon 6′-epimers dissolved in water-miscible organic solvents. Slow transformation of head-to-tail assembly into card-pack type is observed. Induced supramolecular chirality is seen upon addition of achiral β-carotene, as judged from the increased intensity of exciton signal detected in circular dichroism spectra.

Isolation and purification of acid-labile carotenoid 5,6-epoxides on modified silica gels

INTRODUCTION The acid-labile carotenoid 5,6-epoxides occur in all green plants and in most fruits, but their isolation or purification is complicated and expensive because they decompose on normal silica gels. Alkaline stationary phases in open column chromatography (OCC) have low capacities, which makes them unsuitable for preparative scale. OBJECTIVE To find a simple high-capacity stationary phase for OCC that does not induce transformations of acid-labile compounds. METHODOLOGY Commercially available silica gel was treated with aqueous sodium bicarbonate solution to neutralise its slightly acidic character, and was then washed and dried. The effect of the treated gel (named silica-9) on violaxanthin was studied. The modified gel was also applied to the OCC of different complex natural extracts (maple leaves and fruits of yellow paprika). Carotenoids were examined by HPLC-PAD both before and after chromatography on the modified gel. RESULTS Violaxanthin decomposed rapidly on normal silica gels but not on the modified gel. Chromatography of plant extracts showed that the modified gel had a similar capacity to the untreated gel but did not effect epoxy-carotenoids, which could be separated or enriched readily on a large scale. CONCLUSION The modified gel does not induce any transformation or decomposition of epoxy-carotenoids but still exhibits a high capacity, suggesting that it can be used in preparative organic chemistry as an additional and convenient tool in the OCC for the separation of other acid-labile compounds.