A toxic substance from Aspergillus viridi-nutans

Abstract

A compound toxic to mice has been extracted from mycelia of Aspergillus viridi-nutans NRRL 4365, a member of the A. fumigatus group. After 2 weeks of growth on a Raulin-Thom medium in static culture at 28C, up to 2 g of toxin could be recovered from 300 g (wet weight) of mycelium. After the compound was isolated by chromatographic separation on activated magnesium silicate columns, the purified fraction was readily crystallized from cold benzene. A suspension of the substance in propylene glycol (administered intraperitoneally) had an LD50 of 2.8 mg/kg in 20-g mice. The toxin was highly fluorescent, exhibiting a 382-nm excitation band and an emission maximum at 450 nm. In thin-layer chromatographic analyses the crystalline compound appeared as a single fluorescent spot in two different solvent systems. The ultraviolet spectrum of the metabolite showed absorption maxima at 380 and 266 nm. Distinctive features of the infrared spectrum were the presence of chelated hydroxyl groups and a carbonyl ester function. Mass spectrometry demonstrated that the molecular weight of the toxin was 662 with a molecular formula of C34H30O14. Chemical microanalysis verified the formula and provided evidence of four methoxyl groups.