Volatile Fungal Metabolites Containing Sulfur

Several sulfur compounds have been detected as volatile constituents of truffles. 2,4-Dithiapentane is a major component of the volatile aromatic compounds of the Italian white truffle, Tuber magnatum. Over 120 compounds have been detected in the black Perigord truffle, T. melanosporum. These include dimethyl sulfide, 2-methylbutanol, 2-methylpropanal and2-methylpropan-l-ol. The nutty and earthy flavour is attributed to anisoles and polymethoxybenzenes. Truffles also produce a volatile steroid, androst-16-en-3-one (7.67), which when more concentrated has an unpleasant smell. The combination of these compounds produces an odour that is a powerful animal attractant. The capacity of animals to detect the presence of underground black truffles by these substances has been evaluated by burying samples of the different compounds. The animals located the dimethyl sulfide lure as well as the black truffle flavouring. 

Dimethyl disulfide and dimethyl trisulfide, together with hydrogen sulfide and methanethiol, are major components of the odour of the stink horn. Phallus impudicus. Other volatile compounds include linalool, /ran -ocimene and phenylacetaldehyde. These compounds attract flies to the stinkhorn. The spores of the stink horn stick to the fly and are then dispersed to potential sites 

Volatile fungal metabolites contribute to the organoleptic properties of several other foodstuffs. Surface mould ripened cheeses such as Brie and Camembert are produced using Penicillium camembertii and, more commonly, P. caseicolum. Oct-l-en-3-ol accompanied by smaller amounts of octa-l,5-dien-3-ol and 3-one are major contributors to the aroma. These organisms also have the ability to produce 2-alkanones from fatty acids and these contribute to the odour of the cheese. 2-Methylisoborneol (7.70) and 2-methoxy-3-isopropylpyrazine (7.71) have been detected in mature cultures. An unpleasant earthy flavour encountered in some aged cultures has been attributed to the excessive produetion of 7.71. 

Diseases of plants may arise from attack by fungi, bacteria, viruses, insects or parasitic plants. Insects may also act as the vectors of plant diseases and provide routes for pathogens to enter plants. The disease may be manifest by decayed or swollen roots, shrivelled or lost fruit, chlorotic or wilting leaves, necrotic lesions on the stems, leaves or fruit, excessive gum formation or the formation of cankers. In this chapter we are eoncerned with the chemistry of the fungal attack on plants that lead to these symptoms. 

Fungal diseases of crops have had a major impact on history. The devastating effect of Phytophthora infestans on the Irish potato crop and the resultant famine in 1845 led to a significant emigration to the United States. 

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