The chemistry of cyclohexenediones produced by the blackleg fungus

Abstract

Several oxidation products of metabolites produced by avimlent isolates of Phoma lingam, the blackleg fungus, are reported; in addition, the profile of metabolites common to P. lingam and P. wasabiae is clarified.Key words: cyclohexenedione, Phoma lingam, P. wasabiae.Resume : On a LtudiC plusieurs produits d'oxydation tires des metabolites produits par des isolats avimlents du Phoman lingam, un champignon; de plus, on a clarifiC le profil des metabolites communs au P. lingam et au P. wasabiae.Mots clis : cyclohex~nedione, Phoma lingam, P. wasabiae. [Traduit par la redaction]Recent work on the so-called weakly virulent, avirulent, or nonaggressive isolates of the blackleg fungus (Leptosphaeria maculans (Desm.) Ces. et de Not., asexual stage Phoma lingum (Tode ex Fr.) Desm.) led to the isolation of several metabolites having a cyclohexenone ring as a common structural feature (1-3). Most importantly, this work revealed an unknown relationship between P. lingam and P. wasabiae. This unforeseen relationship2 was also supported by analysis of particular DNA sequences of isolates of both species (3). As a consequence of that work, it was proposed that the avirulent isolates of P. lingam be formally reclassified (4).As part of our continuing studies of the chemistry of the blackleg fungus,3 it was important to determine the phytotoxicity of the cyclohexenones 1, 2, 5-8 produced by avirulent isolates. During the purification of these metabolites, unexpected products resulting from the slow oxidation of 5 d 5 b and 6 were identified. Here is reported the transformation of phomaligadiones 5 and 6 and phomaligin A (7) to phomaligols 1 and 2, and the intermediates of these oxidative transformations, as well as the products of reaction of phomaligadiones 5 and 6 with diazomethane. These results allow an important clarification regarding the structures of metabolites common to P. wasabiae and P. lingam. In addition, the implications of these findings on the biogenesis of the cyclohexenone-containing metabolites is discussed and the structures of metabolites common to P. wasabiae and P. lingam are noted.

α-Pyrones and Yellow Pigments from the Sponge-Derived Fungus Paecilomyces lilacinus

“…Compounds 7, 8, 11, and 12 were previously isolated from Phoma lingam and Phoma wasabiae, while compounds 9 and 10 were reported as synthetic analogues. [16][17][18][19] The relative configurations of C-2 and C-6 in compounds Table 1). The remaining six carbon signals were attributed to a sec-butyl (δ C 11.7/C-10, 16.9/C-11, 28.0/C-9, and 41.9/C-8) and two methyl groups (δC 20.3/C-14, 7.1/C-13).…”

Phytotoxins, Elicitors and Other Secondary Metabolites from Phytopathogenic “Blackleg” Fungi: Structure, Phytotoxicity and Biosynthesis

“…While ergosterol (39) comprised 95% of the total sterols, several other minor sterols were detected, as well 24-methylene dihydrolanosterol (56) and phomenin B (57) had been previously isolated from A. infectoria [48] and Phoma tracheiphila [49], respectively. Because of the limited amount of phomapyrones isolated, only phomapyrones A (49) and D (52), and phomenin B (57) were tested for phytotoxicity. None of these pyrones caused visible necrosis, even at high concentrations (10 -3 M); however, other 2-pyrones isolated from some pathogenic fungi have displayed phytotoxicity, cytotoxicity, and antibiotic activity [50].…”

“…In further work to find the yellow pigments produced by L. biglobosa, three yellow metabolites, phomaligin A (62) and wasabidienones B (63) and E (64), were isolated [25,52] (Figure 10). These metabolites were also found in P. wasabiae Yokogi, a pathogen of W. japonica M., which suggested a similarity between these two pathogens.…”

“…(iii) Leptosphaeria species / unknown asexual (Polish and Canadian isolates Laird 2 and Mayfair 2, virulent on brown mustard) producing as characteristic metabolites various polanrazines (17)(18)(19)(20)(21)(22), phomapyrones (49)(50)(51)(52)(53)(54)(55) and phomalairdenones (28)(29)(30)(31) in MM ( Figure 21 It is worthy to note that so far only an Australian isolate of L. maculans (IBCN 18) was found to produce substantial amounts of sirodesmin PL (1) (and related metabolites), together with phomalairdenones A (28), B (29) and C (30) [43]. Isolate IBCN 18 was reported to be virulent on both canola and brown mustard.…”