Provitamins and vitamins D 2 and D 3 in Cladina spp. over a latitudinal gradient: possible correlation with UV levels Ting Wang a,b , Göran Bengtsson c , Ingvar Kärnefelt d , Lars Olof Björn a* a Department of Plant physiology, Lund University, Box 117, SE-22100 Lund, Sweden b Department of Biochemistry, School of Life Sciences, Zhongshan (Sun Yat-sen) University, Guangzhou,51275, China c Chemical Ecology and Ecotoxicology, Department of Ecology, Ecology Building, Lund University, SE-22362 Lund, Sweden d Department of Systematic Botany, Lund University, SE-223 61 Lund, Sweden Received 11 November 2000; accepted 7 June 2001 *Corresponding author. Tel.: 146-46-2227797; fax: 146-46-222-4113. E-mail address: lars olof.Björn@fysbot.lu.se (L.O. Björn). Abstract Provitamin D 2 , vitamin D 2 2 and vitamin D 3 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 mg/g dry matter in the thalli of C. arbuscula specimens grown under different natural conditions, while provitamin D could not be detected. The ranges for provitamin D and vitamin D 2 were 89–146 and 0.22–0.55 mg/g dry matter, respectively, while the contents of provitamin D were below the detection limit (0.01 mg/[g dry matter]). When C. arbuscula thalli collected at different latitudes from northern Finland to Greece were compared, a positive correlation of vitamin D 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. Keywords: Cholecalciferol; Cladina rangiferina, Cladina arbuscula; ESI-MS; Provitamin D, Vitamin D; UV-B 1. Introduction Since provitamin D 3 (7-dehydrocholesterol) was initially isolated from swine skin and was postulated to be the precursor of vitamin D 3 (cholecalciferol) [1], much research has been conducted to isolate, identify and understand the physiological functions of vitamin D 3 in mammals. Vitamin D 3 (OH) 2 plays an important role in the regulation of intestinal calcium and phosphorus absorption, calcium mobilization from bone and renal reabsorption of calcium and phosphorus. With the discovery of a vitamin D receptor, some new functions of vitamin D 3 have been found, such as modulation of osteoclast differentiation, suppression of parathyroid cell growth and parathyroid hormone gene expression, and effects on the growth and differentiation of keratinocytes in skin [2–4]. As vitamin D 3 is the form synthesized by vertebrates, it is often referred to as ‘animal vitamin D’, in contrast to vitamin D 2 , ‘plant vitamin D’. Actually, this is a misconception; vitamin D 3 and vitamin D 3 -like substances have been found in a variety of plants. Vitamin D 3 has been identified in the leaves of Cestrum diurnum, Lycopersicon