Caeine: also a fungal metabolite Amauri Bogo, Peter G. Mantle* Biochemistry Department, Imperial College of Science, Technology and Medicine, London SW7 2AY, UK Received 6 January 2000; received in revised form 5 May 2000 Abstract Caeine has been found to occur as a fungal metabolite and to be the principal alkaloid in sclerotia of Claviceps sorghicola,a Japanese ergot pathogen of Sorghum spp. 7 2000 Elsevier Science Ltd. All rights reserved. Keywords: Claviceps sorghicola; Sclerotia; Alkaloid; Sorghum bicolor; Caeine 1. Introduction Caeine, a notable alkaloid in tea (Theaceae) and coee (Rubiaceae) with important physiological, socio- logical and commercial implications, is produced also by some other plants such as mate (Aquifoliaceae), guarana (Sapindaceae) and cola (Sterculiaceae) (Har- borne et al., 1999). Recently, caeine has even been found in anthers of Citrus spp (Kretschmar and Bau- mann, 1999). It is one of a very small group of plant secondary metabolites, including, for example, the cocoa alkaloid theobromine, which are biosynthesised from purine bases. Theobromine occurs with caeine in some plants. Caeine is biosynthesised from adenine and methionine in tea (Suzuki and Takahashi, 1976). Fungi have not previously been recognized as having the genome for such types of alkaloidal secondary metabolites which are unique purine derivatives with- out a pentose, although Turner (1971) quotes a small group of adenosine derivatives containing a pentose, notably including cordycepin from Cordyceps militaris and Aspergillus nidulans. Ergot fungi (Claviceps spp), taxonomically close to Cordyceps, usually produce classical ergot alkaloids based on the tetracyclic ergo- line ring system, all having close biogenetic inter-re- lationships as intermediates or end products of pathways arising from a linking of tryptophan and mevalonate. Two ergot fungi which are notable excep- tions primarily parasitise Sorghum spp. The sclerotia of Claviceps sorghi (Kulkarni et al., 1976), a fungus apparently restricted to the Indian sub-continent, have not been observed naturally for many years. The fun- gus is not alive in any culture collection and may unfortunately now be extinct. However, sclerotia have never been found to contain alkaloid (Frederickson et al., 1991). Also, sclerotia of a sorghum ergot pathogen (Claviceps sorghicola, Tsukiboshi et al., 1999), appar- ently originating in Japan, have only ever been found to produce a trace of an unde®ned clavine-like alkaloid (2 mg from 1 kg of sclerotia; Ohmomo, 1990) with rather polar chromatographic behaviour in TLC. C. sorghicola has been a subject of study at Imperial Col- lege for several years (Hassan, 1996; Mantle, 1999), but no trace of ergoline alkaloid has been found in sclerotia grown experimentally on male-sterile sorghum in England. However, analysis of another polar com- ponent has now revealed caeine, identi®ed by its characteristic electron impact mass spectrum. 2. Results and discussion Chromatograms of the extract at the ®nal stage of the standard extraction process for ergoline alkaloids Phytochemistry 54 (2000) 937±939 0031-9422/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved. PII: S0031-9422(00)00169-2 www.elsevier.com/locate/phytochem * Corresponding author. Tel.: +44-171-594-5245; fax: +44-171- 225-0960. E-mail address: p.mantle@ic.ac.uk (P.G. Mantle).