Marine sponge melanin: a new source of an old biopolymer
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Various types of melanin have already been found in the majority of organisms, being this biopolymer considered as one of the major pigments present in nature. The presence of this pigment in marine sponges (Phylum Porifera, one of the simplest multicellular organisms) was postulated, but never characterized. In this context this work aims the extraction and characterization of a dark pigment observed in four different marine sponges species (Erylus mamillaris, Erylus discophorus var. deficiens, Pachymatisma johnstonia, Dercitus bucklandi). Characterization of the extracted biopolymer was performed using solid state analytical techniques, due to the characteristic non-solubility of melanin. Therefore, characterization techniques like SEM–EDS, IR, UV–vis, MALDI-MS, elemental analysis and X-ray powder diffraction (XRD) were used to identify the biopolymer. The results showed that the extracted material was obtained with high purity, being identified as melanin. The results also emphasize a large structure variability present in this pigment, showing different structure arrangements and composition depending on its source, which influences the UV behaviour. The structural characterization of this class of pigments is fundamental, allowing a better understanding of melanin properties.
KeywordsMelanin Porifera Biopolymer Photoprotection
The authors thank FCT, POCI and FEDER (project POCI/QUI/71576/2006) and the Portuguese National Mass-Spectrometry Network (REDE/1501/REM/2005). J.R. Xavier research is funded by FCT-Portugal (Grant no. SFRH/BPD/62946/2009). We also thank Universidade Lusófona (Portugal), for the opportunity to participate in the Luso Expedição 2006 and Reserva Natural da Berlenga (Instituto da Conservação da Natureza) for all the facilities granted. A warm thank to all colleagues and friends that helped in several campaigns.
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