Dipole-dipole transfer between acetone solvates of chlorophyll a and chlorophyll a dihydrate dimers in water/acetone mixtures. A model for P680 sensitized excitation

We describe a simple model for P680 sensitized excitation in photosynthesis. Chl a fluorescence quenching effects observed when water is added to Chl a solutions in acetone are shown to be the result of resonant transfer between acetone solvates of monomeric Chl a, Chl a·Ac, and dimers of Chl a dihydrate. The presence of (Chl a·2H₂O)₂ is evidenced by a 678 nm difference absorbance (ΔA band obtained on conversion of a 680 nm absorption shoulder to polycrystalline Chl a precipitate, (Chl a·H₂O)_n. The equilibration between (Chl a·2H₂O)₂ and Chl a·Ac as a principal mechanism for Chl a·Ac fluorescence quenching is supported by theoretical fits of the data.     

THE CHLOROPHYLL a AGGREGATE ABSORBING NEAR 685 nm IS SELECTIVELY FORMED IN AQUEOUS TETRAHYDROFURAN*

An aqueous solution of 2–12% (vol/vol) tetrahydrofuran (THF) induced the selective aggregation of chlorophyll a (Chl a) to form a novel species, A-685, absorbing near 685 nm. The formation of A-685 was closely correlated with a decrease in water activity of the solution. A Raman spectrum of the Chl a species formed in the presence of 6% THF suggests a unique interaction among Chl a, solvent THF and water molecules to give a stacked aggregate (Chl a.THF.H₂O.THF.Chl a). The circular dichroic spectrum of the Chl a species formed in the 6% THF aqueous solution showed an intense signal that had negative and positive wings with about 100-fold larger molar ellipticity for the A-685 than for monomer. However, Chl a', the C10 epimer of Chl a, and chlorophyllide, with a phytyl chain replaced by an ethyl group, did not form A-685 in 6% THF. These clearly indicate that 10-methylcarboxylate and the phytyl chain have a significant role in stabilizing A-685. A possible structure for A-685 is proposed as a novel in vitro model for the P-680 Chl a dimer.     

STUDIES OF CHLOROPHYLL-CHLOROPHYLL AND CHLOROPHYLL-LIGAND INTERACTIONS BY VISIBLE ABSORPTION AND INFRARED SPECTROSCOPY AT LOW TEMPERATURES

Abstract— A comparison of the visible absorption and infrared spectra of various chlorophyll-chlorophyll (Chl) and Chi-nucleophile aggregates at room temperature and at low temperatures has been made. The IR data provide structural information indispensable for the interpretation of the visible spectra. As a necessary preliminary, it is shown that Chl a solutions in nonpolar solvents can be prepared by appropriate drying techniques that contain at a conservative estimate ≤ 3 mol % of water (i.e. Chl a/H₂O > 30:1). Very dry solutions of Chl a or Pyrochl a(≥ 10 mM) in toluene or methylcyclohexane-isopentane solution show only slight changes in visible spectra on cooling to 77 K. From IR, additional Chl-Chl aggregation occurs on cooling in methylcyclohexane-isopentane but not to a significant extent in toluene. Dilute (10 μM) solutions of Chl a or Pyrochl a in nonpolar solvents form a new absorption peak near 700 nm at low temperatures, which we attribute to traces of water in the solvent or other residual nucleophiles not removed during the Chl purification. Addition of stoichiometric amounts of water increases the size of the ?700 nm peak even in dilute Chl solutions. Chlorophyll a, Pyrochl a, but not pheophytin a are shown to interact with nucleophiles of the general type RXH (where R= H or alkyl, and X = O, N, or S). Such nucleophiles can coordinate to the Mg atom of one Chl molecule by lone pairs on O, N, or S, and hydrogen bond to oxygen donor functions in another Chl molecule. A ?0.1 M solution of Chl a or Pyrochl a in toluene containing 1.5 equivalents of ethanol is converted almost entirely to a species absorbing at ?700 nm at 77 K. Infrared spectroscopy shows conclusively that it is the keto C=O function that is involved in the cross-linking by hydrogen bonding, a conclusion supported by the observation that Pyrochl a forms a very similar red-shifted species at low temperatures, despite the absence of a carbomethoxy C=O function. n-Butylamine and ethanethiol interact in much the same way as does ethanol to form species red shifted to ?700 nm. A variety of possible structures for the low temperature forms is discussed, and the use of these red shifted species as paradigms for photoreaction center Chl is described.     

The enolate anions of chlorophylls a and b as ambident nucleophiles in oxidations with (−)- or (+)-(10-camphorsulfonyl)oxaziridine. Synthesis of 13(S/R)-hydroxychlorophylls a and b

The enolate anions of chlorophylls (Chl) are ambident nucleophiles that are of considerable organic chemical interest in relation to the theory of electron delocalization (aromaticity) and charge-transfer in large conjugated π-systems, as well as for their chemical reactivity. Under deaerated conditions, the (−)- and (+)-enantiomers of (10-camphorsulfonyl)oxaziridine (CSOAI) are effective oxidants for the enolate anions of Chl a and Chl b, when 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) serves as a base. In this study, the use of these sterically hindered reagents to hydroxylate Chl a and Chl b is described for the first time. The total yield of 13²(S/R)-HO-Chl a was 71 and 90% for the oxidations of Chl a with (−)-CSOAI and (+)-CSOAI, respectively. Chl b, however, behaved clearly differently from Chl a. The total yield of 13²(S/R)-HO-Chl b was 40% in the oxidation with (−)-CSOAI and 60% in the reaction with (+)-CSOAI. A competing side-reaction, which resulted in the 15²-methyl, 17³-phytyl ester of Mg-15¹(S/R)-unstable rhodin, was found to lower the yields of the desired main products. The formation of the side-products was largely avoided and the yield of 13²(S/R)-HO-Chl b was improved by increasing the volume of hexane and using phosphate buffer in the first step of the work-up. With (−)-CSOAI, a 94% diastereomeric excess (de) was achieved for 13²(R)-HO-Chl a, whereas the de for 13²(R)-HO-Chl b was 66%. With (+)-CSOAI, the de was 10% for 13²(R)-HO-Chl a and 8% for 13²(R)-HO-Chl b. The results were interpreted in terms of a nucleophilic reaction mechanism, kinetically controlled by steric hindrance, originating on the one hand in the 17-propionate phytyl ester side-chain, protruding over the isocyclic ring E of the Chl enolate ion, and on the other hand in the bulky camphorsulfonyl unit of CSOAI. Possible reasons for the different results from the Chl b oxidations as compared with those of the Chl a oxidations are discussed. Comparison of the differences in the NMR δ_C-values between 13²(S)- and 13²(R)-HO-Chl a as well as those between 13²(S)- and 13²(R)-HO-Chl b, indicated that the change of stereochemical configuration at C-13² induces only slight differences in the δ_C-values. Of special interest are the δ_C-values of C-13², which are at ca. 91 ppm for the a- and b-series diastereomers. This carbon is deshielded by ca. 25 ppm relative to the C-13² of 13²(R)-Chl a (δ_C=65.5). Owing to this, ¹³C NMR spectroscopy is a good method to distinguish the 13²-hydroxylated chlorophylls from the intact, naturally occurring chlorophylls.     

Spectroelectrochemical behaviour of water bounded Chl a in the presence of various acceptors

The spectroelectrochemical behaviour of non-aqueous solutions containing (Chl a·H₂O)₂ and (Chl a·2 H₂O)_n, used as models for P 700 and P 680, respectively, is reported. The potential associated with the electron-transfer processes and the kind of electrode reactions in the presence of substances (benzylviologen and dichlorophenolindophenol) used as a specific acceptor for photosystems I and II were studied. To carry out the measurements, a thin-layer spectroelectrochemical cell with a platinum optically transparent electrode was used.     

439 — Photoelectrochemical and spectral properties of chlorophyll and its analogues in artificial membranes and liposomes

The results of spectral and photoelectrochemical investigations of artificial pigment—lipid membranes and liposomes are given, as well as data on the liposomal membrane structure obtained by electron microscopy.Chlorophyll (Chl) of artificial membranes is shown to be in monomeric (λ_abs = 670 nm) and crystalline (λ_abs = 740 nm) forms. The line with (δH_pp) of the e.p.r. signal of monomeric Chl cation-radical is within 8–9 G and that of crystalline is 1.7 G with g-factor = 2.0024. It was shown that about 22–28 Chl molecules were incorporated in the aggregates.The value of photoresporises generated by the membrane depends on the availability of electron donors and acceptors on the opposite sides of the membrane, the pH gradient via the membrane, as well as the external applied voltage. The membranes with incorporated Chl and pheophytin generate photopotentials of opposite signs.     

CHLOROPHYLL a AND CAROTENOID AGGREGATES AND ENERGY MIGRATION IN MONOLAYERS AND THIN FILMS

Abstract— The spectra of absorption, fluorescence and excitation of monolayers and thin films containing chlorophyll a together with a carotenoid (cis-β-carotene, trans-β-carotene, fucoxanthin, or zeaxanthin), were measured at — 196°C. The concentration ratios used, (Chl)/(Car), were 6:1, 4:1, 3:1, 2:1, 1:1 and 1:3, and the area densities, 3·70, 2·55, 1·76, 0·71, 0·37 and 0·17 nm²/pigment molecule. In dilute monolayers, (3·70 nm²/molecule), with a constant concentration ratio (Chl)/(Car) = 3:1, evidence of three β-carotene forms, with absorption bands at 460, 500 and 520 nm (C₄₆₀, C₅₀₀ and C₅₂₀), and of a chlorophyll a form with an absorption band at 669–672 (Chl_669–672) was found. On increasing the density to 0·2–0·3 nm²/molecule, a conversion of C₄₆₀ and C₅₂₀ into C₅₀₀, was observed, and several more additional (probably more strongly aggregated) chlorophyll a forms appeared, with absorption bands at 672–733 nm. With excess carotene [(Chi)/(Car) = 1:3] the forms C₄₆₀, C₅₀₀, C₅₂₀ and Chl_669–672 were present even in the most dense films (0·2–0·3 nm²/molecule). The same was found with other carotenoids: if one of the pigments was in excess, aggregated forms of the other tended to disappear. In the transfer of energy from carotenoids to chlorophyll a, C₅₀₀ was found to be the main donor. In layers with a concentration ratio (Chl)/(Car) = 3:1, the efficiency of transfer was less than 10 per cent at the lowest density used (3·70 nm²/molecule); it increased to 50 per cent, as the density was increased to 0·20 nm²/molecule. When the relative concentration of the carotenoid was increased to (Chl)/(Car) = 1:1, the efficiency of energy transfer dropped to 25 per cent even at 0·20 nm²/molecule. It seems that the efficiency of energy transfer between carotene molecules (prior to its transfer to chlorophyll a) is low, and effective transfer occurs only between β-carotene and immediately adjacent chlorophyll a molecules.     

CHLOROPHYLL a FLUORESCENCE OF GONYAULAX POLYEDRA GROWN ON A LIGHT-DARK CYCLE AND AFTER TRANSFER TO CONSTANT LIGHT

Abstract— The chlorophyll a fluorescence properties of Gonyaulax polyedra cells before and after transfer from a lightdark cycle (LD) to constant dim light (LL) were investigated. The latter display a faster fluorescence transient from the level ‘I’ (intermediary peak) to ‘D’ (dip) to ‘P’ (peak) than the former (3 s as compared to 10 s), and a different pattern of decline in fluorescence from ‘I’ to ‘D’ and from ‘P’ to the steady state level with no clearly separable second wave of slow fluorescence change, referred to as ‘s' (quasi steady state)→‘M’ (maximum) →‘T’ (terminal steady state). The above differences are constant features of cells in LD and LL, and are not dependent on the time of day. They are interpreted as evidence for a greater ratio of photosystem II/photosystem I activity in cells in LL. After an initial photoadaptive response following transfer from LD to LL, the cell absorbance at room temperature and fluorescence emission spectra at 77 K for cells in LL and LD are comparable. The major emission peak is at 685–688 nm (from an antenna Chl a 680, perhaps Chl a-c complex), but, unlike higher plants and other algae, the emission bands at 696–698 nm (from Chl a_II complex, Chl a 685, close to reaction center II) and 710–720 nm (from Chl a₁, complexes, Chl a 695, close to reaction center I) are very minor and could be observed only in the fluorescence emission difference spectra of LL minus LD cells and in the ratio spectra of DCMU-treated to non-treated cells. Comparison of emission spectra of cells in LL and LD suggested that, in LL, there is a slightly greater net excitation energy transfer from the light-harvesting peridinin-Chl a (Chl a 670) complex, fluorescing at 675 nm, to the other antenna chlorophyll a complex fluorescing at 685–688 nm, and from the Chl a., complex to the reaction center II. Comparison of excitation spectra of fluorescence of LL and LD cells, in the presence of DCMU, confirmed that cells in LL transfer energy more extensively from the peridinin-Chl a complex to other Chl a complexes than do cells in LD.     

Raman spectra of chlorophyll forms

The Raman spectra of chlorophyll a (Chl) forms in aqueous poly(vinyl alcohol) (PVA) and in dimethyl sulfoxide (DMSO)—water mixtures were recorded at 457.9 nm excitation and their structures were characterized by comparison with the spectra of the following well-known chlorophyll forms: (1) monomers (Chl)₁ in the polar solvents of group (A), i.e., diethyl ether, tetrahydrofuran, acetone, N,N-dimethylformamide and DMSO, of which the oxygen atom is expected to coordinate to the central magnesium atom; (2) monomers (Chl)₁ in the polar solvents of group (B), i.e., methanol, ethanol, 1-propanol, 2-propanol and 1-butanol, which are supposed to form a hydrogen-bond to the C₉=O group in addition to the coordination-bond to the Mg atom; (3) dehydrated aggregates (Chl)_n in dry non-polar solvents, i.e., carbon tetrachloride, n-hexane and n-octane; and (4) hydrated aggregates (Chl·2H₂O)_n in wet non-polar solvents, i.e., n-hexane and n-octane. The frequency of the C₉ = O stretching Raman line of each of the above chlorophyll forms was: (1) 1702—1680 cm⁻¹; (2) 1673—1668 cm⁻¹; (3) around 1655 cm⁻¹; (4) around 1645 cm⁻¹. The frequency proved to be a marker of intermolecular interaction of the Chl molecules. The spectral patterns in the 1650—700 cm⁻¹ region of (1), (2) and (3) were similar. However, the relative intensities of Raman lines of (4), which was ascribed to a one-dimensional, regular stacking of the Chl macrocycles, were quite different from those of (1)—(3).The chlorophyll form in PVA aqueous solution was identified as (Chl·2H₂O)_n by spectral comparison. The chlorophyll forms present in the DMSO—water mixtures were highly dependent on the DMSO content. It is suggested that (Chl)₁ having hydrogen-bonded H₂O should be present in 10% DMSO solution, and that a new chlorophyll form (Chl·DMSO)_n having (a) a stoichiometric intermolecular interaction with DMSO and (b) a regular stacking of the chlorophyll macrocycles, should be predominant in 50% DMSO aqueous solution.     

High performance liquid chromatographic analysis of phytoplankton pigments using a C16-amide column

In this study, a reverse-phase HPLC method incorporating a ternary solvent system was developed to analyze most polar and non-polar chlorophylls and carotenoids present in phytoplankton. The method is based on an RP-C₁₆-Amide column and provided excellent peak resolution of most taxonomically important pigments and an elution profile different than C₈ or C₁₈ columns provide. Analysis of mixed pigment standards, extracts of phytoplankton monocultures, and field samples showed that this method was able to resolve more than sixty pigments, ranging from very polar acidic chlorophylls to the non-polar hydrocarbon carotenes in less than 36 min. This included chlorophylls c₁, c₂ and c₃, divinyl chlorophylls a and b, the carotenoids lutein and zeaxanthin and some recently discovered pigments. The ability of this method to resolve divinyl chl b from monovinyl chl b and divinyl chl a from monovinyl chl a is particularly important for the quantification and identification of the marine cyanobacteria Prochlorococcus spp. in oceanic waters. The described protocol is sensitive and reproducible and can be used to assess the distribution and dynamics of major phytoplankton groups in marine and freshwater ecosystems.     

Synthesis and application of an efficient calix[4]arene-based anion receptor bearing imidazole groups for Cr(VI) anionic species

We synthesized the new calix[4]arene amines bearing two and four imidazole or tert-butylamine moieties (9a,b/10a,b) by the reaction of di- or tetra-tosylated calix[4]arene derivatives (7 and 8, respectively) with 1-(3-aminopropyl)imidazole and/or tert-butylamine, respectively. After the characterization of 9a,b/10a,b their extraction abilities toward Cr(VI) anionic species (CAS) was evaluated and compared by the liquid–liquid extraction method. The extraction results revealed that calix[4]arene amine having four imidazole groups (10a) was an efficient anion receptor for CAS. Moreover, the extraction of CAS by 10a in the presence of other anions such as Cl^?, NO₃^?, and PO₄^3? showed that 10a could be a selective anion receptor for CAS in the presence of those anions.     

Structure‐Dependent Demetalation Kinetics of Chlorophyll a Analogs under Acidic Conditions

Demetalation of chlorophyll (Chl) a and its analogs is an important reaction in oxygenic photosynthetic organisms, which produces the primary electron acceptors in photosystem II reaction centers and is crucial in the Chl degradation. From these viewpoints, demetalation reactions of four Chl a analogs, 3,8‐divinyl‐Chl a (DV‐Chl a), 3‐devinyl‐3‐ethyl‐Chl a (mesoChl a), 13²‐demethoxycarbonyl‐Chl a (pyroChl a) and protochlorophyll a (PChl a), were kinetically analyzed under weakly acidic conditions, and were compared with that of Chl a. DV‐Chl a exhibited slower demetalation kinetics than did Chl a, whereas demetalation of mesoChl a was faster than that of Chl a. The difference in demetalation kinetics of the three chlorophyllous pigments originates from the electron‐withdrawing ability of the vinyl group as the peripheral substituent compared with the ethyl group. Removal of the electron‐withdrawing and homoconjugating 13²‐methoxycarbonyl group in Chl a (Chl a → pyroChl a) accelerated demetalation kinetics by two‐fold. PChl a possessing the porphyrin‐type skeleton exhibited slower demetalation kinetics than Chl a. The structure‐dependent demetalation properties of Chl a analogs will be useful for understanding in vivo Chl demetalation reactions in oxygenic photosynthetic organisms.     

Synthesis and crystal structures of novel glycoluril carboxylic acids conglomerates

The two novel conglomerates were obtained by crystallization of racemic (2'S,3aS,6aR)/(2'R,3aR,6aS) (glycoluril-1-yl)-3-methylbutanoic acid and (2'R,3aR,6aR)/(2'S,3aS,6aS) (4,6-dimethylglycoluril-1-yl)pentanoic acid synthesized by highly diastereoselective condensation of 4,5-dihydroxy- imidazolidin-2-ones with racemic ureido acids. The differences in the molecular geometry of synthesized racemates were studied by X-ray diffraction that showed them to crystallize as conglomerates in non-centrosymmetric space groups Pna2₁ and P2₁2₁2₁, respectively     

New pentacyclic ring systems: intramolecular cyclization of o,o′-disubstituted bibenzothiazoles

Efficient methods for the preparation of isomeric o,o′-diaminobibenzothiazoles (8a and 11a) and o,o′-diamino-2,2′-dimethylbibenzothiazoles (8b and 11b), potentially valuable building blocks for construction of hitherto unknown dithiazolo annulated pentacyclic heterocycles, have been developed. The dithiazolo annulated benzo[c]cinnolines 9a, 9b, and 12a were prepared from the corresponding diamines by oxidation with PhI(OAc)₂ in good yield. The dithiazolo annulated carbazoles 13 and 14 were efficiently prepared from the corresponding diamines by thermal cyclization in H₃PO₄. The unusual course of reduction and product formation of o,o′-dinitrosubstituted bibenzothiazoles 6a and 6b with SnCl₂ under acidic conditions was rationalized by DFT quantum-mechanical calculations. It was suggested that cyclic products are formed from dinitroso derivatives and open-shell species immediately following on a reduction path.     

On the existence of arbitrary four-body (or quasi-four-body) molecules

At wavelengths near 1 mm three rotational transitions of²⁰⁵Tl¹⁹F and²⁰³Tl¹⁹F have been observed. The analysis including previous measurements on rotational transitions at larger wavelengths resulted in sets of the Dunham coefficientsY ₀₁,Y ₁₁,Y ₂₁,Y ₃₁,Y ₀₂,Y ₁₂, andY ₀₃ of the two isotopic species. With these microwave data the constantsY ₁₀ ≈ ω _e and ?Y ₂₀ ≈ ω_e x_e were determined. The parameters of the Dunham potentiala ₀,a ₁,a ₂,a ₃,B _e andr _e are given. The Dunham coefficientsY _mn with the smallest relative experimental error show deviations from the general mass relations between isotopic species indicating a violation of the Born-Oppenheimer approximation.     

Pulse radiolysis study of redox reactions of safranine T in aqueous solutions: One electron oxidation

One electron oxidation of safranine T by specific oxidizing radicals such as Cl^-₂, Tl²⁺, Tl(OH)⁺, N^.₃, Br^-₂ etc. has been studied using the nanosecond pulse radiolysis technique. Reaction of free Br^. atom has also been investigated at neutral pH. The semioxidized safranine species formed by these reactions have been shown to exist in two conjugate acid-base forms with pK_a=4.0. Their spectral and kinetic parameters have been evaluated. Using N^.₃/N^-₃ and I^-₂/2I^- as reference couples, the one electron reduction potential of the semioxidized safranine has been determined to be 1.13±0.02 V vs NHE. The absorption spectra, second order decay rate constant and the pK_a of the OH-reaction product revealed features quite different from that of the semioxidized species suggesting that the mode of OH reaction is not via electron abstraction.     

Circular and Linear Dichroism of Aggregates of Chlorophyll a and Chlorophyll b in 3-Methylpentane and Paraffin Oil

A circular (CD) and linear dichroism (LD) study of the water adducts of the green plant chlorophylls a (Chl a) and b (Chl b) in hydrocarbon solvents 3-methylpentane and paraffin oil is presented. A strong red shift of the Q_y-absorption band from 663 to 746 nm (1678 cm^?1) is observed as the water adduct of Chl a is formed. The Chl a-water adduct shows a strong, nonconservative CD signal, which is characterized by a positive peak at 748 nm and two negative peaks at 720 and 771 nm. The maximum CD (A_L - A_R) is only one order of magnitude smaller than the isotropic absorption maximum. We propose that this exceptionally strong signal is the so-called psi-type CD. The LD spectrum was measured in a flow of paraffin oil. The isotropic absorption maximum peaks at 742 nm in paraffin oil, whereas the maximum of the LD signal is at 743 nm. The LD signal is positive over the whole water-adduct absorption band indicating that the transition dipole of the 742 nm transition is preferentially oriented along the long axis of the aggregate. The structure of the Chl b-water adduct is less well defined. The preparations of the Chl b-water adduct are unstable. The Chl b-water adduct absorption band maximum is at 683 nm. The CD signal of the Chl a-water adduct is about 200-fold the CD of the Chl b-water adduct. We could not orient the Chl b-water adducts by flow, which suggests that the adducts are small or disordered.     

Antioxidant,Antibacterial and Dyeing Potential of Crude Pigment Extract of Gonatophragmium triuniae and Its Chemical Characterization

Filamentous fungi synthesize natural products as an ecological function. In this study, an interesting indigenous fungus producing orange pigment exogenously was investigated in detail as it possesses additional attributes along with colouring properties. An interesting fungus was isolated from a dicot plant, Maytenus rothiana. After a detailed study, the fungal isolate turned out to be a species of Gonatophragmium belonging to the family Acrospermaceae. Based on the morphological, cultural, and sequence-based phylogenetic analysis, the identity of this fungus was confirmed as Gonatophragmium triuniae. Although this fungus grows moderately, it produces good amounts of pigment on an agar medium. The fermented crude extract isolated from G. triuniae has shown antioxidant activity with an IC₅₀ value of 0.99 mg/mL and antibacterial activity against Gram-positive bacteria (with MIC of 3.91 μg/mL against Bacillus subtilis, and 15.6 μg/mL and 31.25 μg/mL for Staphylococcus aureus and Micrococcus luteus, respectively). Dyeing of cotton fabric mordanted with FeSO₄ using crude pigment was found to be satisfactory based on visual observation, suggesting its possible use in the textile industry. The orange pigment was purified from the crude extract by preparative HP-TLC. In addition, UV-Vis, FTIR, HRMS and NMR (¹H NMR, ¹³C NMR), COSY, and DEPT analyses revealed the orange pigment to be “1,2-dimethoxy-3H-phenoxazin-3-one” (C₁₄H₁₁NO₄, m/z 257). To our understanding, the present study is the first comprehensive report on Gonatophragmium triuniae as a potential pigment producer, reporting “1,2-dimethoxy-3H-phenoxazin-3-one” as the main pigment from the crude hexane extract. Moreover, this is the first study reporting antioxidant, antibacterial, and dyeing potential of crude extract of G. triuniae, suggesting possible potential applications of pigments and other bioactive secondary metabolites of the G. triuniae in textile and pharmaceutical industry.     

The absolute configuration of the palmarumycins C9, C10, and C12 by quantum-mechanical calculations of CD spectra

The absolute configurations of the palmarumycins C₉ 1a, C₁₀ 2, and C₁₂ 3 were assigned by comparison of the quantum-mechanically calculated with the experimental CD spectra as (2R,3S,4aS,8aR), (2R,3R,4S,4aS,8aR), and (2R,3R,4R), respectively.