Novel methoxy-carotenoids from the burgundy-colored plumage of the Pompadour Cotinga Xipholena punicea

Abstract

Recent advances in the fields of chromatography, mass spectrometry, and chemical analysis have greatly improved the efficiency with which carotenoids can be extracted and analyzed from avian plumage. Prior to these technological developments, Brush (1968) [1] concluded that the burgundy-colored plumage of the male pompadour Cotinga Xipholena punicea is produced by a combination of blue structural color and red carotenoids, including astaxanthin, canthaxanthin, isozeaxanthin, and a fourth unidentified, polar carotenoid. However, X. punicea does not in fact exhibit any structural coloration. This work aims to elucidate the carotenoid pigments of the burgundy color of X. punicea plumage using advanced analytical methodology. Feathers were collected from two burgundy male specimens and from a third aberrant orange-colored specimen. Pigments were extracted using a previously published technique (McGraw et al. (2005) [2]), separated by high-performance liquid chromatography (HPLC), and analyzed by UV/Vis absorption spectroscopy, chemical analysis, mass spectrometry, nuclear magnetic resonance (NMR), and comparison with direct synthetic products. Our investigation revealed the presence of eight ketocarotenoids, including astaxanthin and canthaxanthin as reported previously by Brush (1968) [1]. Six of the ketocarotenoids contained methoxyl groups, which is rare for naturally-occurring carotenoids and a novel finding in birds. Interestingly, the carotenoid composition was the same in both the burgundy and orange feathers, indicating that feather coloration in X. punicea is determined not only by the presence of carotenoids, but also by interactions between the bound carotenoid pigments and their protein environment in the barb rami and barbules. This paper presents the first evidence of metabolically-derived methoxy-carotenoids in birds.

Non-destructive descriptions of carotenoids in feathers using Raman spectroscopy

“…The purple feather with cotingin as the major pigment had the highest PC1 score: the conjugated system of cotingin has 11 conjugated subunits (C] C-C) in the backbone, which are cross-conjugated with subunits in the beta rings (conjugation is bridged by keto groups in the 4 and 4 0 positions in the beta rings). 11 The slightly lower PC1 scores from canthaxanthin are attributed to a slightly shorter effective conjugation length, where 11 conjugated subunits in the backbone are continuous with 4 and 4 0 keto groups in the beta rings (i.e. no cross-conjugation).…”

Structure and optical function of amorphous photonic nanostructures from avian feather barbs: a comparative small angle X-ray scattering (SAXS) analysis of 230 bird species

“…In bird species with both non-iridescent blue and structural green plumage patches, the respective absence or presence of cortical pigments in the barb appears to be the general mechanism by which plumage reflectance differences arise between blue and green patches of sexually monomorphic species (e.g. [73] or phaeo-melanins complements a shorter wavelength (violet to blue) single or double structural peaks, producing distinct extra-spectral colours including vivid shades of violets and purples to blue hues with hints of lilac (e.g. Acryllium vulturinum, Numididae, figure 7b; C. maynana, figure 7m; Malurus coronatus, Maluridae; Sitta oenochlamys, Sittidae).…”

Variation in carotenoid–protein interaction in bird feathers produces novel plumage coloration

“…Carotenoids were extracted from the feathers, as previously described by LaFountain et al [36]. An HPLC analysis was conducted using a Waters 600E multi-solvent delivery system with an (a) (b) (c) Figure 1.…”