Ergochromes

Secaionic acid DJ Toxic ergochrome mycotoxin of CDPK (67), MLCK (60),... 

Revised structures of secalonic acids A. B, C, D Hooper er at., Chem- Commun. 1971, 111 eufem, J. Chem. Soc. (C) 1971, 3580. Crystal and molecular structure of secalonic acid A C. C. Howard er al. J. Chem. Soc. Perkin Trans. I 1976, 1820. Identity of secalonic acid A with mtothein Yoshioka et al, Chem. Pharm. Bull 16, 2090 (1968). Biosynthesis of secalonic acid A I. Kurobane et al., Tetrahedron Letters 1978, 1379. Review of secalonic acids and other ergochromes Franck, Flasch in Fortschr. Chem. Org Naturst. 36, 151-206 (1973). 

In 1983 Holker, Simpson, and O Brien reported the isolation of the diversonolic esters (972, 973) (Fig. 13.15), which they obtained from Penicillium diversum, along with lichexanthone (840a) and several other known compounds (634). The authors performed a structural analysis for these new compounds based on methyl-ation, proton-NMR analysis, chelate ferric effects, and other spectroscopic techniques, which led to the assignment of the structures of these new compounds as 970 and 971. These substances appear reminiscent of hemisecalOTiic acids (ergochrome monomers), but the structures originally proposed were later found to be incorrect (see below). 

The secalonic acids (1034—1046) (Fig. 13.27) are comprised of dimers of the blennolides (vide supra). This class of compounds, also named ergochromes, has been the subject to extensive investigation due to their biological activity. 

A novel ergochrome, neosartorin (1078, Fig. 13.33), was isolated from the mycelium of the soil mold Neosartorya fischeri, and the chemical structure was deduced with a variety of spectroscopic techniques (687). This compound is an isomer of the eumitrins. It was determined that the relative configurations at the C-5, -6 and -10 (and C-5, -6 and -10 ) positions are the same as in secalonic acids A and D. 

Phomoxanthones A and B (1080 and 1081, Fig. 13.34) were isolated from the endophytic fungus, Phomopsis sp., when an extract from this species was found to exhibit in vitro antimalarial activity (688). Phomoxanthone A is a symmetrical homodimer with a 4,4 - (para-para)-]mkage, while phomoxanthmie B has a 2,4 -(ortho-para)-lmkage, as seen with the eumitrins. These structures are similar to those of the ergochromes, however, the carboxymethyl substituents at C-lOa (C-lOa ) have been replaced with acetoxymethyl substituents, and the C-6 (C-6a) hydroxy group moieties are acetylated. The relative configuration of both phomoxanthones A and B was determined by NMR experiments. The compounds proved to be inhibitory in vitro for Plasmodium falciparum, Mycobacterium tuberculosis, and several cancer cell lines (Fig. 13.35). 

Proksa B, Uhrin D, Liptaj T, Sturdikova M (1998) Neosartorin, an Ergochrome Biosynthesized by Neosartorya fischeri. Phytochemistry 48 1161. 

Franck, B., and H. Flasch Die Ergochrome (Physiologie, Isolierung, Struktur und Biosynthese). Fortschr. Chem. organ. Naturstoffe 30, 151 (1973). 

Acetyl CoA 6-Methyl-salicylic acid, acetophenones, lecanoric acid, patulin, coniine, gallic acid (D 3.3.1) Eugenone, citrinin, sepedonin, coumarin derivatives (D 3.3.2) Plumbagin (D 3.3.3) Griseo-fulvin (D 3.3.4) Anthra-quinones, ergochromes (D 3.3.5) Afla-toxins (D 3.3.6)... 

Representatives of this group of polyketides are anthraquinone derivatives and ergochromes. In most of the anthraquinones the nucleus is substituted at C-1 and C-8 with hydroxy groups and may carry an additional hydroxy group at C-3 and a one-carbon side chain at C-6 (Table 34). Anthraquinones are easily reduced to anthrones/anthranols in a reversible reaction ... 

The ergochromes are light yellow dimeric xanthone derivatives resembUng the anthraquinones in their pattern of substitution (Fig. 79). The two xanthone moieties (secalonic acids) are interUnked at the position 2. 

Anthracenes of polyketide origin are built in molds, e.g., Aspergillus and PeniciU lium lichens, Basidiomycetes and higher plants, e.g., Polygonaceae and Rhamna-ceae (see however the formation of anthraquinone derivatives from shikimic acid, D 8.1). Ergochromes have been found in molds and lichens. 

Franck, B. The biosynthesis of ergochromes. In The Biosynthesis of Mycotoxins (P. S. Steyn ed.), pp. 157-191. Academic Press, New York 1980 Leistner, E. Biosynthesis of plant quinones. In The Biochemistry of Plants, Vol. 7, Secondary Plant Products (E. E. Conn, ed.), pp. 403-423. Academic Press, New York 1981 Sankawa, U. The biosynthesis of anthraquinoid mycotoxins from Penicillium islandicum Sopp and related fungi. In The Biosynthesis of Mycotoxins (P. S. Steyn, ed.),pp. 357-394. Academic Press, New York 1980... 

Frank, B. and Flash, H. (1973) Die ergochrome (Pysiologie, Isolierung, Strukture und Biosynthese). In Forsch. Chem. Org. Naturstoffe, 30, pp. 151-206. 

Figure 17 Biphenyl pigments (ergochromes) isolated from genus Claviceps...

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