ANTIBIOTICS 



Fumigatin. — Aspergillus fumigatus, in addition to 

 fumigacin, synthesises the pigment fumigatin which has 

 been shown to be 3-hydroxy-4-methoxy-2 : 5-tohiquinone, 

 



CH3 / \ OH 



, which inhibits the errowth of Gram- 

 " " OCH, 



O 

 positive bacteria at dilutions of 1 in 33,000 to 1 in 50,000, 

 and Gram-negative organisms at 1 in 12,000. It is par- 

 ticularly active against V. comma which is inhibited at 

 a concentration of 1 in 100,000. A number of mono-, 

 di- and tri-methoxy derivatives of toluquinone and of 

 benzoquinone have been tested for activity against 

 Staph, aureus. 4-Methoxy-, 4 : 6-dimethoxy-, 3:4:6- 

 trimethoxy- (spinulosin dimethyl ether), and 6-hydroxy- 

 4-mefchoxy- toluquinones and 2 : 6-dimethoxybenzo- 

 quinone have considerably greater activity than fumigatin. 

 Introduction of the OCH3 grol^p increases the activity 

 whilst an OH group reduces it. The most active is 





 II 



4:6-dimethoxy-toluquinone, jj || , of which 



CH3O V ^ 0CH3, 



o 



10/xg. per ml. is inhibitory. The active structure 

 seems to be =C=C.C0.C(0CH3) = C.CO which is also 

 present in penicillic acid (see p. 170). Replacement of 

 the terminal — CO group by oxygen (as in the methyl 



, . ^. r 1 .. .. rH,0H.C.=CH.C0.C(0CH..)=CH— O. 



derivative 01 kojic acid "1 " I 



(see p. 294) causes a great loss in activity. 



Gigantic Acid. — The growtli of A. giganteus on a 

 2 per cent, malt extract containing 1 per cent, of peptone 



