Analysis of scarlet elf cup (Sarcoscypha coccinea) carotenoids in vivo by Raman spectroscopy

Abstract

AbstractRaman spectroscopy, an established optical method of remote diagnostics of pigments and dyes, is applied here for the first time to the cup fungus Scarlet elf cup (Sarcoscypha coccinea or Plectania coccinea or Peziza coccinea) from the order Pezizales (Ascomycota). As‐collected fungi samples are investigated, not subject to any treatment. The dominant vibrational features in the acquired in vivo spectrum, around 1000, 1150, and 1500 cm−1, respectively, clearly indicate it is dominated by carotenoid(s). Contrary to most previous Raman studies of carotenoids, including few studies of fungi, which focused on the latter three strongest fundamental vibrations, we have resolved and analyzed in detail 30 vibrational bands, including rarely studied wavenumber range above 2000 cm−1. We discuss in detail the inferred from our spectral analysis carotenoid species in comparison with those previously reported for Sarcoscypha coccinea by other methods. In particular, we suggest two characteristic ring vibrations, at 1131 and 1283 cm−1, to be used as a measure of the ratio of astaxanthin and plectaniaxanthin to β‐carotene and lycopene in this and similar fungi. In addition, we report the fluorescence spectrum of this fungal species, present as background in the Raman spectrum at visible excitation. The results obtained in this work will facilitate subsequent more quantitative studies of carotenoid composition in other kinds of fungi and other microorganisms using Raman spectroscopy in combination with other techniques.