Colour diversification in octocorals based on conjugated polyenes: A Raman spectroscopic view

Abstract

Polyenic pigments in octocorals have been investigated by Raman spectroscopy using laser excitation at 532, 785 and 1064 nm. The spectral features suggest the structural nature of carotenoids from Phyllogorgia dilatata, Leptogorgia punicea, Muricea atlantica, Carijoa riisei and conjugated polyenals from L. punicea, L. setacea, Muricea flamma and Renilla muelleri. The observed vibrational bands at ca. 1540–1520 ν1(C=C), 1159 ν2(C–C) and 1005 cm−1 ρ3(C–CH3) were assigned to carotenoids, whereas the identification of non‐methylated conjugated polyenals have been proposed due to two major Raman bands at ca. 1500 and 1120 cm‐1, assigned to ν(C=C) and ν(C–C), respectively. Copyright © 2012 John Wiley & Sons, Ltd.

Conjugated polyenes as chemical probes of life signature: use of Raman spectroscopy to differentiate polyenic pigments

“…[21,25]. Previous works from Maia et al [27,29] and comparison with the literature data [13] have demonstrated that the red octocoral L. punicea may contain 11 conjugated double bonds due to the presence of ν(C=C) modes at ca 1509 cm −1 . However, deconvolution of the in situ Raman spectra using the 1064 nm laser line for vibrational modes ranging from 1550 to 1480 cm −1 and from 1040 to 980 cm −1 showed two distinct bands.…”

“…Raman spectra of polyenals identified from certain octocorals, such as Leptogorgia setacea, M. flamma, R. muelleri, L. punicea (figure 2), Chromonephthea braziliensis and Phyllogorgia dilatata (not shown) [27][28][29], presented spectral features resembling those of Corallium spp. [21,25].…”

“…However, deconvolution of the in situ Raman spectra using the 1064 nm laser line for vibrational modes ranging from 1550 to 1480 cm −1 and from 1040 to 980 cm −1 showed two distinct bands. Based on these data along with Raman analyses previously reported for the yellow L. setacea, pink-orange Chromonephthea braziliensis [29] and coloured pearls [36], it can be suggested that the pigmentation of such organisms is composed of a mixture of polyenals with various numbers of conjugated double bonds. Moreover, in figure 2a,b, the matrix effect can also be seen, which promoted a shift of the Raman bands when L. punicea tissues were demineralized.…”

“…Raman spectroscopic analysis of polyenals or unsubstituted polyacetylenes has revealed that the position of the ν(C=C) and ν(C−C) bands are chain-size and matrix-effect dependent (figures 2 and 3) [27,29,40]. The wavenumber position of δ(C−CH 3 ) at ca 1020 cm −1 presents different behaviour from that of methyl groups arranged as in terpene units; in carotenoids, there is a significant contribution of the δ(C−CH 3 ) to the ν(C−C) mode [41].…”

New Strategies for Identifying Natural Products of Ecological Significance from Corals

“…Studies involving marine organisms are emerging, and Raman analysis has been applied to animals, algae, and dinoflagellates, which have identified carotenoids, sterols, nonsubstituted conjugated polyenals, chromophores of green fluorescent proteins (GFPs), chlorophylls, melanins, and mycosporine-like amino acids (MAAs). Carotenoids have been identified from corals [140][141][142], mollusks [143,144], lobster carapace [145,146], fish [147], brown algae [148] and dinoflagellates [149]. Polyenals are a recently described class of polyenes identified from shells of mollusks [143,144] and octocorals [140][141][142][150][151][152][153].…”