Molecular spectroscopic studies of lichen substances 1: parietin and emodin

The Raman and infrared spectra of the UV-radiation protectant parietin extracted from Xanthoria lichen species are reported and vibrational assignments made of key features which are important for the characterisation of parietin in situ in stress-tolerant living organisms. The spectra of parietin are compared with those of the chemically related emodin, which is of pharmaceutical interest. The key molecular vibrational bands of parietin will be used for the analysis of lichen specimens exposed to high UV-radiation stress growing on Leonie Island, Antarctica, under the 'ozone hole' to better understand the production of UV-protectants in controlled habitats. (C) 2003 Published by Elsevier Science B.V.