Patulin formation

The formation of optically active deuteriopatulin (49 R = H) was observed. This result showed that the intermediate formed from the ring fission of gentisaldehyde (53) underwent a stereospedfic reduction during patulin formation. Natural patulin is optically inactive. 

Early biogenetic theories have involved the intermediacy of 6-formylsalicylic acid (5) (Fig. 7) in patulin formation. Hydroxylation of 5 to yield a hypothetical metabolite, 5-hydroxy-6-formylsalicylic acid, and subsequent... 

Note The reagent can be employed on silica gel, kieselguhr, cellulose and polyamide layers. When left exposed to air the whole chromatogram is slowly colored blue because of the formation of the blue cation (3) (see Reaction). The detection limits for patulin, moniliformine and penicillic acid are ca. 50 ng per chromatogram zone. 

Despite the apparent connections between formation of antibiotics and spores, it has become clear that antibiotic production is not obligatory for spore formation [192]. The most damaging evidence to the antibiotic-spore obligatory hypothesis is the existence of mutants which form no antibiotic but still sporulate. Such mutants have been found in the cases of bacitracin (Bacillus licheniformis), myco-bacillin (Bacillus subtilis), linear gramicidin (B. brevis), tyrocidine (B. brevis), gramicidin S (B. brevis), oxytetracycline (Streptomyces rimosus), streptomycin (S. griseus), methylenomycin A (Streptomyces coelicolor), and patulin (Penicillium urticae). 

Norstadt and McCalla (1968) observed the formation of patulin, a potent phytotoxic substance, in soil amended with wheat straw. This was apparently produced by Penicil-lium urtricae Bainier, since the presence of the residues favored growth of the fungus, and phytotoxicity increased with growth. 

Rychlik and Schieberle reported a synthesis of C-labeled patulin (348) in 1998 (303). The synthesis was from L-arabinose (363), as described by Stapleton and coworkers (298), with an initial methyl acetal formation, protection of a 1,2-diol, then... 

To summarize the situation as it exists today, it can be stated that there is no evidence that gramicidin S, bacitracin, linear gramicidin, and patulin are required for the formation of spores. Although spores produced in the cdssence of linear gramicidin appeeur to be abnormal, those produced in the absence of gramicidin S do not. 

Reiss, J. (1976). Mycotoxins in foods inhibition of the formation of mycotoxins (aflatoxins) and patulin and sterigmatocystin in whole wheat bread by sorbic acid and sorboyl palmitate. Dtsch Lebensm Rundsch, 72, 51-54. 

The secondary biosynthesis of the mycotoxin patulin, as described in detail in Chapter 7, begins with the formation of 6-methylsalicylic acid, and the regulation of this first step is therefore rate-limiting overall. However, it is the control of further steps beyond 6-methylsalicylate that determines the extent to which patulin, or other products of the pathway, actually accumulate (Bu Lock et al., 1965). 

Although nutrient restriction is also conducive to the formation of spores (conidia) in P. urticae, there is no direct connection with patulin synthesis (Sekiguchi and Gaucher, 1977). Equally, in other species where the patulin pathway exists alongside independent pathways to other secondary metabolites, such as byssochlamic acid, the optimum conditions for one pathway may be significantly different from those for the other (Escoula, 1975). 

Patulin (Fig. 1) was discovered by Birkinshaw etal. (1943), and its chemical structure elegantly proved and synthesized by Woodward and Singh (1949, 1950). The oxime was independently prepared by another route (Serratosa, 1961). A recent crystallographic study by Hubbard et al (1977) confirmed the structure of patulin and gave the bond distances and angles of the patulin molecule. Patulin isolated from natural sources has one asymmetric center on carbon 1. Patulin is, however, racemic. One explanation could be that the center at C(l) may racemize easily during work-up. Another possibility could be that the hemiacetal formation is not enzyme controlled. 

The formation of patulin (1) from gentisaldehyde (9) is rationalized by cleavage at the site shown in Fig. 28 (0 Rotation around C(2)-C(3) yields... 

Fig. 28. Postulated formation of a different diastereomer of deuterated patulin.

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