Search

Objective: This mini-review highlights the highly sensitive ¨soft¨ ionization mass spectrometric methods applied to chlorophyll chemistry. Method: This is a first-hand review of the important developments made over the mass spectrometry of chlorophyll a and chlorophyll b derivatives. Results: The review covers the capacity of the mass spectrometric techniques to solve problems, e.g., assignment of stereochemical configuration at a chiral center, determination of the structures of the chlorophyll b allomers, which are difficult to prepare and purify in larger amounts, and elucidation of the mechanism of Willstatter's allomerization of chlorophylls. Only one example, in which the conventional electron impact mass spectrometry was used, is provided by the characterization of the chlorophyll derivatives found as retinal pigments in the eyes of the remarkable deep-sea fish Malacosteus niger. Other mass spectrometric investigations, dealing with structural properties of chlorophylls, are considered briefly in an end paragraph of this review. Conclusion: Different mass spectrometric techniques have been shown to be very useful in the structural assignments of chlorophyll derivatives.

Wool is dyed for the first time with a mixture of two pure natural anthraquinone carboxylic acids, dermorubin and 5-chlorodermorubin (2:1), by means of the acid dyeing technique. The anthraquinone carboxylic acids are isolated from the fungus Dermocybesanguinea and separated by multiplicative liquid-liquid partition using a stepwise pH gradient. The color of the dyed wool is investigated in terms of the CIELAB L*, a*, and b* parameters, and color-fastnesses to light, washing, and rubbing are tested according to ISO standards. The mixture of dermorubin and 5-chlorodermorubin dyes wool orange-red with good color-fastness properties. Our procedure is equivalent to the industrial winch- technique. The results indicate that wool has a high uptake for the anthraquinone carboxylic acids. Apparently, the ionic bonds between the carboxylate ions of the dye and the protonated amino groups of the wool enhance the color-fastness properties of the dyed fabric. Dermorubin and 5-chlorodermorubin have significant potential as textile dyes. affording useful alternatives to synthetic dyes.

Wool and polyamide are dyed with the pure natural anthraquinones, emodin and dermocybin, using the mordant dyeing technique. The anthraquinones are isolated from the fungus Dennocybe sanguined.Potassiumaluminum sulphate, potassium dichromate, cobaltous sulphate, and ferrous sulphate are used as mordants. The color of each dyed material is investigated in terms of the Cielab L*, a*,and b*values, and color-fastnesses to light, washing, and rubbing are tested according to the ISO standards. Emodin dyes wool and polyamide yellow and red, whereas dermocybin confers purple and violet colors with color-fastness properties from good to moderate. Our procedure is facile and may be considered equivalent to the winch technique. The results show that wool and polyamide have a high uptake for the pure natural anthraquinones. These compounds have significant potential for new dyeing techniques, and they can provide useful alternatives to synthetic dyes.

Preparative-scale separation of substituted anthraquinones by multiple liquid-liquid partition was studied using isopropylmethyl ketone (IM K)/aqueous phosphate buffer (aq.) as the solvent system and the Hietala apparatus with 100 partition units as the partition equipment. The lower (aq.) phase was chosen as mobile, while the upper (IMK) phase remained stationary. Hence, the principle of stepwise pH-gradient elution could be utilized to separate the components in two complex mixtures of hydroxyanthraquinones and hydroxyanthraquinone carboxylic acids, isolated from the fungus Dermocybe sanguinea. In spite of the nonlinearity of the partition isotherm s for these anthraquinones, implying deviations from the Nernst partition law, remarkable separations were achieved for the components in each mixture. Every anthraquinone carboxylic acid showed markedly irregular partition behavior, appearing in the effluent as two more or less resolved concentration zones. Such splitting was attributed to the formation of relatively stable sandwich-dimers, which were in a slow equilibrium with the monomers in the more nonpolar organic phase. At lower pH-values, only the polar monomers were distributed into the mobile aqueous phase and moved forward, whereas the nonpolar sandwich-dimers remained almost entirely in the stationary organic phase and lagged behind. When the pH of the mobile aqueous phase was raised high enough, the firmly linked dimers were monomerized and emerged from the apparatus as a second concentration profile. Intermolecular hydrogen bonding and p-p interaction between the n-systems of two anthraquinone molecules in a parallel orientation were considered responsible for the nonlinear and markedly irregular partition behavior of the natural anthraquinones studied. The nonlinearity of the partition behavior of the hydroxyanthraquinones lacking the carboxyl group, appeared merely as excessive broadening of the experimental concentration profile, which impaired the resolution between the components only insignificantly. Thus, e.g. the main components, dermocybin and emodin, could both be obtained from Separation 1 in a purity of at least 99% .

Pure natural anthraquinones, emodin and dermocybin, isolated from the fungus Dermocybe sanguinea, are for the first time used as disperse dyes for polyester and polyamide fabrics using a high-temperature dyeing method, accompanied with a reference dyeing with CI Disperse Red 60. The color of each dyed material is investigated in terms of the CIELAB L*, a*, and b*values, and color fastness to light, washing, and rubbing are tested according to the ISO standards. Emodin dyes polyester bright yellow and dermocybin bright reddish-orange, and the fabrics show excellent color-fastness results. Emodin and dermocybin successfully dye polyamide brownish-orange and wine-red, respectively, but the fastness results are only moderate. This study shows that pure natural anthraquinone compounds can produce bright hues and color-fastness properties equivalent to those of synthetic disperse dyes, and thus providing useful alternatives to the synthetics.

A new and simple enzymatic method was developed for preparative isolation of anthraquinone pigments from Dermocybe sanguined. The endogenous ß-glucosidase of the fungus was used to catalyze the hydrolysis of the O-glycosyl linkage in emodin- and dermocybin-1-ß-?-glucopyranosides. The developed enzymatic method was found to be effective for the pigment isolation, as the hydrolysis occurred virtually completely, thus leading to a high pigment yield. Two fractions were obtained by the method: Fraction 1 (94% of the total pigment amount), containing almost exclusively the main pigments emodin and dermocybin, and Fraction 2 (6% ), containing the anthraquinone carboxylic acids. A 10.5 kg amount of fresh fungi yielded 56 g of Fraction 1 and 3.3 g of Fraction 2 anthraquinones. The anthraquinones in each fraction were separated by thin-layer chromatography using toluene-ethyl acetateethanol- formic acid (10:8:1:2, v/v/v/v) as eluent. The components on the chromatograms were detected and characterized by measurements on a densitometer-spectrophotometer. Combined gas chromatography-mass spectrometry was applied to determine the anthraquinone derivatives of Fraction 1 after methylation and acetylation.

A novel molecular electron donor−acceptor (DA) dyad, composed of a phytochlorin donor and a [60]fullerene acceptor, was used for the preparation of solid molecular films capable of performing vectorial photoinduced electron transfer (VPET). Being mixed with octadecylamine at concentrations of 50 mol % and lower, the DA compounds form a stable monolayer, which can be transferred onto a solid substrate. Thus prepared Langmuir−Blodgett (LB) monolayer films are characterized by uniform orientation of the DA molecules and, consequently, can undergo VPET. This was confirmed by time-resolved Maxwell displacement charge (TRMDC) measurements. The rate constant for the electron transfer was ca. 10⁹ s^-1 as estimated from the fluorescence lifetime measurements. The majority of the charge transfer states of the DA molecules (>60%) recombined with a time constant of ca. 30 ns, being almost independent of the DA concentration in the concentration range from 2 to 50 mol %, as revealed from TRMDC experiments. Therefore, VPET is most probably an intramolecular reaction. The dependences of the TRMDC signal amplitude on the DA concentration and on the density of the excitation energy indicated that an energy transfer takes place prior to the electron transfer. A variation in the charge recombination rate was observed when a static bias voltage was applied across the films. An estimation of the charge displacement distance across the film gave a value of ca. 0.5 nm.

A new two-dimensional TLC technique was developed to separate substituted anthraquinones on silica plates using n-pentanol-pyridine-methanol (6:4:3, v/v/v) and toluene-ethyl acetate-ethanol-formic acid (10:8:1:2, v/v/v/v) as eluents. The good separation power of the new technique was demonstrated by applying it to the analysis of complex anthraquinone mixtures isolated from the Scandinavian Derm ocybe sanguinea. Emodin, physcion, endocrocin, dermolutein, dermorubin, 5-chlorodermorubin, emodin-1-ß-D-glucopyranoside, dermocybin-1-ß-D-glucopyranoside and dermocybin, and five new, earlier in D. sanguinea unidentified compounds, 7-chloroemodin, 5,7-dichloroemodin, 5,7-dichloroendocrocin, 4-hydroxyaustrocorticone and austrocorticone, were separated and identified on the basis of Rfvalues, UV/Vis spectra and mass spectra.

It is shown that the allomerization of chlorophylls a and b is effectively inhibited by carotenoid pigments. In the light of this finding, two possible mechanisms are considered for the allomerization. One assumes the addition of singlet oxygen to the 9,10-double bond of the chlorophyll (Chl) enolate anion to yield a C-10 hydroperoxide or a dioxetane derivative. The other assumes a free-radical chain reaction involving Chl enolate anion, triplet oxygen, Chl C-10 radicals and peroxide radicals, and Chl C-10 hydroperoxide. The observation that the allomerization and its inhibition by carotenoids occur under carefully controlled dark conditions precluding singlet oxygen formation provides substantial support to the latter mechanism. Further evidence for the free-radical mechanism is obtained by observing the increase of the allomerization rate when air is replaced with pure oxygen from a container. The rate increases to about two-fold in the methanolic Chl solution containing no carotenoid but remains close to zero in the Chl solution containing an equimolar amount of β-carotene. The relevance of the results to photosynthesis and cancer research is briefly discussed.

The electronic absorption (UV/VIS), circular dichroism (CD) and proton magnetic resonance (1H NMR) spectra have been recorded for C-10 epimeric chlorophylls a and a′, pheophytins a and a′ as well as pheophorbides a and a′. Although the epimers in each pair showed virtually identical UV/VIS spectra, their CD spectra were profoundly different and exhibited opposite signs at most wavelengths in the UV region. The differences were interpreted as arising, in part, from different C-10 configurations, and, in part, from conformational alterations induced by the steric strain in the crowded periphery of the macrocycle. The conformational alterations were also clearly indicated by the 1H NMR Δδ-values observed for the α,β and δ methine protons, the C-10 protons and most methyl group protons of the epimers in each pair. This was considered to imply changes in the geometry of the whole macrocycle. The Δδ-values were larger for the Mg-free epimers than for the chlorophyll epimers, which shows that the central Mg-atom makes the macrocycle more rigid. Correlations between the signs of the CD bands and configurations are discussed.

Evidence for the self-aggregation of 10(S)-chlorophyll a ( = chlorophyll a′) in nonpolar solvents has been obtained by means of absorption spectroscopy in the visible and infrared regions. The visible absorption spectrum of chlorophyll a′ exhibits a shoulder at 680 nm in aliphatic hydrocarbon solvents and the infrared spectrum measured in carbon tetrachloride contains an “aggregation peak” at 1650 cm-1. IR spectroscopy shows, in addition, that the C-10 epimers of chlorophyll a are both present as monomers in tetrahydrofuran. However, in the presence of a small amount of aliphatic alcohol or water, the IR spectrum in tetrahydrofuran at lowered temperatures exhibits an intense, wide absorption band at ～ 1650 cm-1which was interpreted as arising from the hydrogen bonding of the hydroxyl group to the C-9 keto carbonyl of the chlorophyll

The solution structures of the P4-epimers of Zn(II)–pyropheophytin–anthraquinone dyads (ZnPQ1 and ZnPQ2) were determined using two-dimensional NMR spectroscopy and molecular modeling. The mutual orientation of the anthraquinone and Zn–pyropheophytin rings was found to be different in the two P4-epimeric dyads on the basis of the ROESY correlations, observed between the quinone and phorbin protons. The anthraquinone ring is situated below the phorbin macrocycle in both dyads, ZnPQ1 and ZnPQ2. In ZnPQ1, the ring planes show tilting, the anthraquinone ring being in a sloping position below subrings B, C and E of the phorbin macrocycle. In ZnPQ2, the two π-systems are almost parallel with the anthraquinone ring being located approximately below the center of the phorbin macrocycle. © 1997 by John Wiley & Sons, Ltd.

We present a femtosecond transient absorption study of chlorophyll b monomers in various solvent environments. Transient absorption spectra and kinetics of chlorophyll b were measured in neat pyridine and acetone. The kinetics were measured also for three samples of chlorophyll b dissolved in 3-methylpentane and titrated with pyridine. Characteristic for all chlorophyll b samples is a very strong excited-state absorption, which significantly affects time-resolved anisotropy values in the wavelength region of our study (600−750 nm). The excited-state absorption spectrum was simulated, and on the basis of time-resolved anisotropy measurements the broad and smooth excited-state absorption band was found to be composed of several transitions to higher excited states. For all of the chlorophyll b samples studied, we observed two fast lifetime components (~100 fs and 1−3 ps). The former component is assigned to transient hole burning of the inhomogeneously broadened ground-state absorption spectrum, while the latter component, which is sensitive to properties of the solvent, is suggested to arise mainly from solvent relaxation.

Transformation of one or both of the methoxycarbonyl groups of dimethyl 3,3′-(3-formyl-2,7,12,18-tetramethyl-21H,23H-porphyrin-13,17-diyl)-dipropionate ( 1) to isopropenyl groups was observed when an excess of ylide was used in the Wittig reaction.

The allomerization of chlorophyll bin methanol produced 13 2( S)-hydroxy-10-methoxychlorophyll bin a yield of ca.8%. The formation of this allomer was totally unexpected, as 10-substituted chlorophylls have never been reported before. The structure of the new chlorophyll bderivative was determined on the basis of UV/Vis, FAB-MS, 1H NMR and 2D ROESY NMR spectra. This letter focuses on the NMR analysis.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.