Alternaria Metabolites

Erase et al., The Chemistry of Mycotoxins, Progress in the Chemistry of Organic Natural Products, Vol. 97, DOI 10.1007/978-3-7091-1312-7 l 1, 

Less is known about minor AUernaria metabolites, including altenuene 734 (461-463), isoaltenuene 735 (464, 465), neoaltenuene 736 (466), and dehydroaltenusin 737 (467-469), which have been found in infested fruits in sub-milligram amounts (Fig. 11.2). 

The structure of the peiylene metabolite altertoxin I (738), first reported in 1982 by the group of Stinson, and the scaffolds of the other altertoxins, are unusual, since the two aromatic centers in the molecules are completely isolated from each other due to non-conjugated bonding (473). 

Compounds 738-740 belong to the class of perylenequinones (474), but until now, there has been no approach to the total synthesis of altertoxins, based oti the difficulty in formation of two neighboring but separate aromatic centers. 

One of the most toxic components among Alternaria my cotoxins is tenuazonic acid (741) (475) (Fig. 11.4), a tetramic acid derivative, which was first isolated from the culture filtrates of Alternaria tenuis in 1957 by Rosett et al. (476) and shows potent biological activity (475). Tenuazonic acid is biosynthesized from L-fro-leucine and its structure was revealed four years later by Sticicings and his group (477). 

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Griffin G F and Chu F S (1983), Toxicity of the alternaria metabolites altemariol, altemariolmethyl ether, altemuene, and tenuazonic acid in the chicken embryo assay , Appl. Environ. Microbiol., 46, 1420-1421. 

Griffin GF, Chu FS (1983) Toxicity of ths Alternaria Metabolites Altemariol, Altemariol Methyl Ether, Altenuene, and Tenuazonic Acid in the Chicken Embryo Assay. Appl Environ Microbiol 46 1420... 

Stack ME, Prival MJ (1986) Mutagenicity of the Alternaria Metabolites Altertoxins I, n, and III. Appl Environ Microb 52 718... 

The main metabolites of this group of fungi (Fusarium, Aspergillus, Penicillium, and Alternaria) are not only mycotoxins but also hormonally active compounds as well as enzymes, for instance amylase, chitinase, cellulase, glucanase, xylanase, or protease (Pawelzik et al. 1998). 

Zinniol. Zinniol [13] was first described as a phytotoxic metabolite of Alternarla zinniae (21). Zinniol is now known to be produced by many Alternaria spp., including fungal pathogens of weeds and crop plants (21). This compound causes necrosis in plants (21)> S2) and "green island formation, as discussed earlier. 

Alternaria solani, the causal organism of early blight disease of tomato and potato produces several metabolites whose structures have been clarified. It was pointed out that the fungus also secretes host-specific toxins which induce necrotic symptoms typically associated with the disease [50]. Five phytotoxins were isolated, solanapyrones A (67), B (68), C (69), D (70) and E (71), Fig. 17. The diastereomeric... 

While some success has been reported in analogous studies with polyketide assembly intermediates in Streptomyces metabolites, e.g. erythromycin [41] and tylosin [42], similar experiments on fungal polyketides have been more limited. The di- and tetraketide intermediates (44) and (45), variously doubly labelled with and as indicated in Scheme 14, have been incorporated into de-hydro curvular in (46) by cultures of Alternaria cineriae [43]. However, in contrast to the ease of incorporation of assembly intermediates into aspyrone by A. melleus, the experiments in A. cineriae required considerable experimentation to optimise the feeding conditions and the use of the jS-oxidation inhibitors. The initial experiments [43] depended on the use of UV mutants of A. cineriae which had lost the ability to utilise fatty acids and therefore to degrade the fatty... 

Alternaria species are associated with several leaf-spot diseases of plants. Alternaric acid (8.10), produced by A. solani, which is the cause of early blight on potatoes and tomatoes, has a marked phytotoxic activity and may be responsible for many of the symptoms of the plant disease caused by the fungus. It also shows a specific anti-fungal activity. The branched chain structure is biosynthesized from nine acetate units and three Ci units derived from formate. The solanopyrones are another group of phytotoxic metabolites of A. solani. Solanopyrone A (8.11) induced necrotic lesions on the leaves of potatoes typical of this fungal infection. The structures of the solanopyrones were established by... 

A number of Alternaria species are toxic to a wide spectrum of organisms, including bacteria (456, 478), fungi (479), viruses (478), and higher plants (480, 481). Furthermore, it is known that many saprophytic species, associated with agricultural commodities, produce toxic metabolites to mammals (482). 

Visconti A, Bottalico A, Solfrizzo M, Pahnisano F (1989) Isolation and Stracture Elucidation of Isoaltenuene, a New Metabolite of Alternaria alternata. Mycotoxm Res 5 69... 

Pero RW, Posner H, Blois M, Harvan D, Spalding JW (1973) Toxicity of Metabolites Produced by the Alternaria . Environ Health Perspect 4 87... 

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