Hanspeter Pfander

Biosynthesis of C20-carotenoids in Crocus sativus

Abstract Phytoene, phytofluene, tetrahydrolycopene, β-carotene, zeaxanthin and crocetin were isolated from Crocus sativus . The absence of C 20 -hydrocarbon precursors of crocetin supports a degradation pathway for the biosynthesis of crocetin.

[1] Carotenoids: An overview

Publisher Summary This chapter discusses carotenoids. Among the various classes of pigments, carotenoids are among the most widespread and important ones, especially because of their most varied functions. Carotenoids are a class of hydrocarbons (carotenes) and their oxygenated derivatives (xanthophylls). They consist of eight isoprenoid units joined in such a manner that the arrangement of isoprenoid units is reversed at the center of the molecule so that the two central methyl groups are in a 1,6-position relationship and the remaining nonterminal methyl groups are in a 1,5-position relationship. The best-known function of carotenoids is the long-established role of β-carotene and other carotenoids with an unsubstituted β-ring as provitamin A. β-carotene also enhances immunity and is used in livestock for enhancing fertility. Because of their ubiquitous occurrence, different functions, and interesting properties carotenoids are the subject of interdisciplinary research in chemistry, biochemistry, biology, medicine, physics, and many other branches of science. The industrial production of carotenoids has also contributed to knowledge in this field..

DEINOXANTHIN : A NEW CAROTENOID ISOLATED FROM DEINOCOCCUS RADIODURANS

Abstract We have previously demonstrated that carotenoids which support the color of the red pigmented strains of Deinococcus radiodurans could be responsible for the antioxidant activity of these bacteria submitted to hydroxy radicals. Here we report on the isolation and identification of the major carotenoid of this bacterium. Based on UV/Vis-, 1 H NMR- and mass spectra as well as the chemical properties the carotenoid was identified as (all- E )-2,1′-dihydroxy-3′-4′-didehydro-1′,2′-dihydro-β,ψ-carotene-4-one 1 . This carotenoid has never been isolated before and we propose the name deinoxanthin for this new compound. The constitution of a new carotenoid 1 was determined by chemical and spectroscopic methods.

Glycosylation of encapsulated crocetin by a Crocus sativus L. cell culture

Crocus sativus cell suspension culture converted crocetin into several glycosyl esters when the culture was fed with the encapsulated substrate. Glycosylated pigments were stored in vacuoles. Crocetin did not affect the cell growth at concentrations up to 30 mg 100 ml−1. The major pigment has been identified as the crocetin di-neapolitanosyl ester, a new pigment not yet reported in Crocus sativus plant. The other pigments were mixed forms of neapolitanosyl, gentiobiosyl, and glucosyl esters. Glucosyltransferase activity was measured during the culture cycle and indicated that the bioconversion capacity was higher at the end of the exponential phase. The formation of glycosyl esters was highest during the first 24 h of incubation and the maximal concentration of products was achieved after 4 days. The culture had the capacity to form up to 9 mg g−1 dry wt. glycosyl esters with 30 mg substrate per 100 ml culture. Glucose and 2,4-dichlorophenoxyacetic acid added to a 12-day-old culture enhanced the glucosyltransferase activity but did not affect the yield. The formation of glycosyl esters was higher when the substrate was added by steps each day rather than supplied all at once at the beginning of the incubation period, indicating the occurrence of impediment to crocetin uptake.

Separation of crocetin glycosyl esters by high-performance liquid chromatography

Abstract Different methods for the separation of crocetin glycosyl esters from the ethanolic extract of saffron by high-performance liquid chromatography are discussed. After a clean-up by gel filtrationl on Sephadex G-50, best results were obtained with LiChrosorb SI 60 as stationary phase and ethyl acetate-isopropanol-water (56:34:10) as mobile phase.

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.

Carotenoid synthesis: A progress report

The present review covers the progress in chemical synthesis of carotenoids over the period 1990 - 1996 and is a continuation of the review given at the 9th International Symposium on Carotenoids held in Kyoto. Highlights presented at previous symposia will be reported briefly and some reflections on possible future developments in the field are made. HIGHLIGHTS PRESENTED AT PREVIOUS CAROTENOID SYMPOSIA

SYNTHESIS OF CAROTENOID GLYCOSYLESTERS AND OTHER CAROTENOIDS

Abstract: The naturally occurring crocetin di(β-D-glucosyl)ester can be synthesised from crocetin diimidazolide or crocetin di-(1,2,4-triazolide) and β-D-glucose in pyridine in presence of a base. The application of this new method to other carboxylic acids (8′ -apo-β-carotene-8′-oic acid, vitamin A acid, benzoic acid and stearic acid) and carbohydrates (galactose, lactose) shows that this new method, using unprotected carbohydrates and azolides proceeds with a high degree of regioselectivity and stereoselectivity and is of general importance. The synthesis of the three chiral C 30 -apocarotenoids β-citraurin, β-citraurol and β-citraurinene, isolated from orange peel, was carried out with (3R)-3-hydroxy-β-ionone as starting material. Furthermore, C 30 -apocarotenoids with one methyl group shifted by one carbon atom (= diapocarotenoids) were prepared as model compounds. According to the scheme C 10 + C 20 + C 10 , starting with trans-citral via geraniol epoxide, the corresponding C 15 -epoxy Wittig salt and crocetin dialdehyde 1,2-epoxy-lycopene, 1,2,1′,2′-di-epoxy-lycopene and a 1,2-epoxy-C 30 -apocarotinal were synthesised.

Distribution of Carotenoids in Fruits and Vegetables as a Criterion for the Selection of Appropriate Chemopreventive Agents

Common fruits and vegetables contain approximately 40 to 50 carotenoids. Carotenoid-containing fruits and vegetables can be classified into three groups: greens, yellow/red, and yellow/orange. The carotenoids present in greens comprise carotenoid epoxides, lutein, α-carotene, and β-carotene. The yellow/red group contains mostly hydrocarbon carotenoids such as lycopene, neurosporene, y-carotene, ζ-carotene, a-carotene, β-carotene, phytofluene, and phytoene. Yellow/orange fruits and vegetables, in addition to the carotenoids in the other two categories, contain a complex mixture of carotenoids including carotenol fatty acid esters. The effect of various methods of food preparation on qualitative and quantitative distribution of carotenoids in common fruits and vegetables is described. An approach to selection of a mixture of carotenoids as chemopreventive agents based on absorption and relative abundance of these compounds in human serum is discussed.

Synthesis of optically active trans-cyclononenes A possible approach to xenicanes

Abstract Two optically active substituted trans -cyclononenes ( 13a, 13b ) were synthesized from the (−)-Hajos-Parrish diketone. This procedure provides a possible approach for the total synthesis of xenicanes, biologically active compounds isolated from marine organisms.