Gas Chromatography-Mass Spectrometry (GC-MS) is utilised for analysis of polar metabolites following chemical derivatisation and volatiles using headspace analysis.

Liquid Chromatography-Mass Spectrometry (LC-MS) is capable of analysing a range of polar and semi-polar compounds for which no chemical derivatisation is required. Nuclear Magnetic Resonance (NMR) Spectroscopy and Fourier Transform Infrared (FTIR) Spectroscopy are also utilised to structurally characterise small molecules however due to a combination of cost and complexity of the resulting data they are not as common as GC and LC-MS. These techniques enable identification and quantification Inhibitors,research,lifescience,medical of metabolites, which through carefully designed biological experiments, can be utilised to unravel the complex metabolite responses of plants to pathogens. An advantage Inhibitors,research,lifescience,medical of these metabolomics

approaches over genomic and proteomic approaches is the ability to determine the exact metabolic state of the plant after pathogen infection. This review will describe secondary metabolites involved in mediating the outcome of plant-pathogen Inhibitors,research,lifescience,medical interactions in cereals. Secondary metabolites will be discussed in the context of chemical class rather than their roles as phytoanticipan or phytoalexins as a number of compounds fall into both these categories in different species. Inhibitors,research,lifescience,medical These secondary metabolites offer tremendous potential for plant breeding and metabolic engineering in agriculture to aid in controlling existing disease losses [11,12]. 2. Benzoxazinoids Benzoxazinoids (Bxs) are a class of secondary metabolites find more widely distributed in cereals discovered in the 1950′s and since found to have a range of biological Inhibitors,research,lifescience,medical roles including alleopathy, resistance to insects and defence against pathogens [13-15]. Bxs are synthesised from the amino acid tryptophan in the shikimate pathway (Figure 1). They are present in maize; wheat, rye and certain

wild barley species however have not been found in cultivated barley varieties, oat or rice [15,16]. These compounds are found in all parts of the plants but are present at higher levels in younger leaves [15]. Bxs are stored in an inactive glucoside form in plant vacuoles or plastids to avoid toxicity to the plant itself; they undergo enzymatic and chemical degradation Isotretinoin upon tissue disruption to form the active benzoxazinoid [16,17]. The mechanism by which these compounds exert phytotoxic activity may be due to: their mutagenic effects on DNA, ability to react with amino acids and perhaps therefore disrupt proteins [18]. Figure 1. Simplified diagram illustrating the biosynthetic pathways of the discussed plant secondary metabolites involved in pathogen defence. Cyanogenic glucosides, flavonoids and benzoxazanoids are all synthesised from the aromatic amino acids derived from shikimate. …