In search of photosensitising compounds in the annual forage legume Biserrula pelecinus L. E. Swinny A , C. K. Revell B,C,D , N. Campbell A , E. Spadek A , and C. Russo A A ChemCentre, Resources and Chemistry Precinct, Level 2, South Wing, Building 500, Cnr Manning Road and Townsing Drive, Bentley, WA 6102, Australia. B Department of Agriculture and Food Western Australia, 3 Baron-Hay Court, South Perth, WA 6151, Australia. C Centre for Plant Genetics and Breeding, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia. D Corresponding author. Email: clinton.revell@agric.wa.gov.au Abstract. Biserrula is an annual pasture legume endemic to the Mediterranean basin and has been recently domesticated for use in Mediterranean environments in southern Australia. Over the past 10 years the species has been associated with isolated cases of what appears to be a primary photosensitisation in sheep that graze green pastures in winter and spring. Whole-top samples of biserrula pasture were taken from a range of farmers’ paddocks over 2 years (including paddocks where photosensitisation had been observed) and methanolic extracts were screened by high-performance liquid chromatography and liquid chromatography coupled to mass spectrometry for known primary photosensitising compounds belonging to the classes furanocoumarins and dianthrones. None of these were detected. Pyrrolizidine alkaloids were also not detected and this supports the view that a secondary photosensitisation is not involved. Chlorophyll profiles were relatively unchanged between samples and this suggested that chlorophyll metabolites are unlikely to be responsible for a primary photosensitisation. A series of luteolin and apigenin mono- and diglycosides were identified in the extracts, but these are not regarded as photosensitising compounds. Further work is required to establish the photosensitising agent(s) in biserrula. Additional keywords: chlorophyll,flavones,HPLC,LCMS,photosensitisation. Received2December2014,accepted6May2015,publishedonline8October2015 Introduction Biserrula (Biserrula pelecinus L.) is an annual pasture legume that is found in natural grasslands of the Mediterranean basin, frequently on acidic, sandy soils derived from granite and often as a companion plant to serradella (Ornithopus spp.) and subterranean clover (Trifolium subterraneum L.) (Howieson et al. 1995). It is regarded as a monotypic genus in the Fabaceae family, but some taxonomic keys classify the species in the Astragalus genus as A. pelecinus L. Barneby subsp. pelecinus or subsp. leiocarpus (Encyclopedia of Life 2014). Biserrula was domesticated in Australia on the basis of its acid tolerance, adaptation to pastures grown in rotation with crops, deep root system, grazing tolerance, high hardseed content, high seed production and ease of harvestability (Loi et al. 2005, 2010; Nichols et al. 2007). Two cultivars have been commercialised; cv. Casbah in 1997 and cv. Mauro in 2002 (Nichols et al. 2007) and are estimated to have been sown across 300 000 ha in southern Australia. Sporadic cases of photosensitisation have occurred in sheep grazing both cultivars of biserrula (Revell and Revell 2007; Loi et al. 2010; Quinn et al. 2014) but the causal agent has yet to be identified. Photosensitisation is generally classed as primary or secondary, though four categories have been described (Ginn et al. 2007; The Merck Veterinary Manual 2014). Primary photosensitisation (Type I) occurs when animals graze on plants containing certain fluorescent pigments (polyphenols) that react with sunlight to produce radiant energy that results in the production and release of reactive oxygen intermediates that cause tissue damage. Linear furanocoumarins (as found in Bishop’s weed, Ammi majus L.) and hypericin, a dianthrone derivative (as found in St John’s wort, Hypericum perforatum L.) are some of the better known photosensitising polyphenolic pigments (Ginn et al. 2007; McKenzie 2012; Quinn et al. 2014). Secondary (or hepatogenous) photosensitisation (Type III) occurs more commonly than primary photosensitisation and usually results from liver disease caused by ingesting hepatotoxins in plants (e.g. steroidal saponins in signal grass, Urochloa decumbens (Stapf) R.D. Webster; lantadene in lantana, Lantana camara L.) or fungi (sporidesmin in Pithomyces chartarum (Berl. & Curt.) M.B. Ellis, phomopsins in Diaporthe toxica P.M. Williamson et al.) (Ginn et al. 2007). Pyrrolizidine alkaloids as found in Paterson’s curse (Echium plantagineum L.) have also been linked to hepatotoxic photosensitisation (Quinn et al. 2014). Damaged livers are Journal compilation Ó CSIRO 2015 www.publish.csiro.au/journals/cp CSIRO PUBLISHING Crop & Pasture Science, 2015, 66, 1161–1166 http://dx.doi.org/10.1071/CP14342