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The plumage carotenoids of six species from five genera of broadbills (Eurylaimidae) have been examined. These plumages are crimson, violet, purple-maroon, or yellow. Two genera also have brilliant green plumages that are produced by a combination of structural coloration and unknown carotenoids. Six different carotenoids from nine different plumage patches were identified, including two previously unknown molecules, using high-performance liquid chromatography, mass spectrometry, and MS/MS fragment analysis. The yellow pigment in Eurylaimus javanicus and Eurylaimus ochromalus is identified as the novel carotenoid, 7,8-dihydro-3'-dehydro-lutein. The yellow and green plumages of Psarisomus dalhousiae contain the unmodified dietary carotenoids lutein and zeaxanthin. The brilliant green feathers of Calyptomena viridis contain a mixture of lutein and two other xanthophylls that have previously been found only in woodpeckers (Picinae). The crimson and violet colors of Cymbirhynchus, Sarcophanops, and Eurylaimus are produced by a novel pigment, which is identified as 2,3-didehydro-papilioerythrinone. The molecular structure of this carotenoid was confirmed using (1)H nuclear magnetic resonance, correlated two-dimensional spectroscopy, and two-dimensional nuclear Overhauser effect spectroscopy. Resonance Raman (rR) spectroscopy carried out at room and low temperatures was used to probe the configuration and conformation of 2,3-didehydro-papilioerythrinone in situ within crimson C. macrorhynchos and purple-red E. javanicus feathers. The rR spectra reveal that the pigment is in an all-trans configuration and appears to be relatively planar in the feathers. The likely metabolic pathways for the production of broadbill carotenoids from dietary precursors are discussed.

Rhodoxanthin is one of few retro-carotenoids in nature. These chromophores are defined by a pattern of single and double bond alternation that is reversed relative to most carotenoids. Rhodoxanthin is found in the plumage of several families of birds, including fruit doves (Ptilinopus, Columbidae) and the red cotingas (Phoenicircus, Cotingidae). The coloration associated with the rhodoxanthin-containing plumage of these fruit dove and cotinga species ranges from brilliant red to magenta or purple. In the present study, rhodoxanthin is characterized in situ by UV-Vis reflectance and resonance Raman spectroscopy to gain insights into the mechanisms of color-tuning. The spectra are compared with those of the isolated pigment in solution and in thin solid films. Key vibrational signatures are identified for three isomers of rhodoxanthin, primarily in the fingerprint region. Electronic structure (DFT) calculations are employed to describe the normal modes of vibration, and determine characteristic modes of retro-carotenoids. These results are discussed in the context of various mechanisms that change the electronic absorption, including structural distortion of the chromophore or enhanced delocalization of π-electrons in the ground-state. From the spectroscopic evidence, we suggest that the shift in absorption is likely a consequence of perturbations that primarily affect the excited state of the chromophore., (Copyright © 2013 Elsevier Inc. All rights reserved.)

The carotenoids have low-lying triplet excited states and can self-assemble in some solvents to form weakly or strongly coupled aggregates. These qualities make carotenoid aggregates useful for studies of singlet fission, where an outstanding goal is the correlation of interchromophoric coupling to the dynamics and yield of triplet excited states from a parent singlet excited state. Three aggregates of zeaxanthin, two weakly coupled and one strongly coupled, are characterized by steady-state spectroscopic methods including temperature-dependent absorption, fluorescence, and resonance Raman spectroscopy. The absorption spectra for each type of aggregate are distinct; however, an analysis of band positions reveals some important shared characteristics and suggests that the strongly coupled H-aggregate contains a subpopulation of weakly coupled constituents. Temperature-dependent absorption spectroscopy indicates that one of the weakly coupled aggregates can be converted to the other upon heating. The emission spectra of the three aggregates have similar profiles that are overall red-shifted by more than 1000 cm(-1) relative to the monomer. The emission quantum yields of the aggregates are 5 to 30 times less than that of the monomer, with the lowest yield for the strongly coupled aggregate. The vibrational spectra of the chromophores support only slight perturbations from the structure of solvated monomers. Our findings support the conclusion that all three aggregates are best characterized as H-aggregates, in agreement with a prior theoretical study of lutein aggregates.