Provitamins and vitamins D2 and D3 in Cladina spp. over a latitudinal gradient:: possible correlation with UV levels

Provitamin D-2, vitamin D-2 and vitamin D-3 were identified in the thallus of a lichen species, Cladina arbuscula (Wallr.) Hale and W.L. Culb. The identification of vitamin D-3 was supported by: (1) co-chromatography in both reverse and straight phase HPLC (high performance liquid chromatography), (2) ultraviolet absorption spectrum, and (3) molecular ion peaks demonstrated by ESI (electrospray ionisation) mass spectrometry. The contents of vitamin D-3 range from 0.67 to 2.04 mug g(-1) dry matter in the thalli of C. arbuscula specimens grown under different natural conditions, while provitamin D-3 could not be detected. The ranges for provitamin D-2 and vitamin D-2 were 89-146 and 0.22-0.55 mug g(-1) dry matter, respectively, while the contents of provitamin D-3 were below the detection limit (0.01 mug dry matter). When C. arbuscula thalli collected at different latitudes from northern Finland to Greece were compared, a positive correlation of vitamin D-2 and D-3 contents with modelled UV-B radiation at the collection sites was found. A single sample of C. rangiferina from northern Finland gave much higher values for the vitamins. A possible reason could be the lower content of UV-B absorbing pigment in the latter species. (C) 2001 Elsevier Science B.V. All rights reserved.