During the screening of Aspereillus strains for toxin producers, a ccmpound toxic to mice was extracted from mycelia of A_. viridi-nutans Ducker and Thrower NFUU 4365 grown in Raulin-Thorn medium (1). After the compound, trivially named, viriditoxin, was extracted witi chloroforwnmethanol (80:20) and isolated by chromatographic separation on activated magnesium silicate columns with chloroform:acetonitrile:formic acid (95:4:1) as eluting solvent, the purified fraction was readily crystallized from cold benzene. The yield was 0.7$ based on wet mycelial weight. A suspension of the green substance in propylene glycol (I.P.) had an IDso of 2.8 mg/kg in 20-g mice.
Elemental and mass spectral analyses of viriditoxin (mp 242-245' dec, La -Z80 -2c.P in Cl-K&) established the molecular formula as C3&so01+. The IR spectrum exhibited a band at 1740 cm' attributed to an ester carbonyl and a band at 1635 cm-i that shifted to 1720 cm-l upon acetylation and was assigned to a hydrogen-bonded six-membered la&one.
Because We NMR spectrum (2) of viriditoxin showed only 15 protons, the structure for the new toxin was probably that of a synnnetrical dimer. Two exchangeable protons appeared at 69.72 and 13.70. The position of these peaks indicated that phenolic hydroxyl was present and, in addition, that the lowest field hydroxyl was hydrogen-bonded to a carbonyl. function.
Methoxyl resonances at 63.66 and 3.74 account for an additional six protons. Two aromatic protons appear as singlets at6.6.24 and 6.78. When viriditoxin was acetylated, the aromatic proton resonances were shifted to lower field (66.79, 7.11) and peaks representing the acetate methyls were observed at62.48 and 2.51. The rather large downfield shifts of 0.55 and 0.33 ppm were indicative of a m relationship between the hydroxyl groqs and the aromatic protons.