DERIVATIVES OF PYRONE 



179 



20 



Figure 8. Growth and kojic 

 acid formation by Aspergillus 

 flavus as functions of nitro- 

 gen supply. Drawn from 

 tabular data of May, Moyer, 

 Wells, and Herrick (373). 



Mycelium 



0.1 1.0 10 



Ammonium nitrate, gm per liter 

 (logarithmic scale) 



kojic acid by Aspergillus flavus, but the effect appears to be on the 

 entire metabolism of the organism rather than specifically on kojic 

 acid synthesis (374). 



The very high yields of kojic acid — up to 57 per cent of the glucose 

 consumed by a growing culture (373) and up to 78 per cent of that 

 used by preformed mycelium (319) — -suggest that the acid may be 

 formed directly from glucose. This is borne out by the isotope studies 

 of Arnstein and Bentley (18). Degradation of kojic acid derived from 

 glucose- 1-C 14 shows that the bulk of the acid is formed from glucose 

 without splitting of the carbon chain. The occurrence of small 

 amounts of C 14 in other positions is adequately explained by the 

 postulate that a minor fraction of the carbon of kojic acid is derived 

 from compounds of the phosphogluconate oxidation respiratory path- 

 way (19, 283). 



The details of the conversion of glucose to kojic acid are not known; 

 Arnstein and Bentley (18) discuss some possibilities. The fact that a 

 preformed mycelium does not require added phosphate for kojic acid 

 synthesis (242) is irrelevant to the problem of whether or not phos- 

 phorylative steps are involved in synthesis, since the endogenous phos- 

 phate reserves of the cell would without question be adequate for a 

 cyclic process. 



Patulin is a pyrone derivative, the structure of which is largely 

 known (181, 563). It has been isolated several times independently 

 tinder different names — clavacin, claviformin, expansin, and clavatin 

 — from species of Penicillium and Aspergillus; its history and synonymy 



