Cultures of the fungi Aspergillus niger, Cunninghamella verticillata, and P
enicillium simplicissimum, grown in a sucrose/peptone medium, transformed N
-acetylphenothiazine to N-acetylphenothiazine sulfoxide (from 13% to 28% of
the total) and phenothiazine sulfoxide (from 5% to 27%). Phenothiazin-3-on
e (4%) and phenothiazine N-glucoside (4%) were also produced by C. verticil
lata, The probable intermediate, phenothiazine, was detected only in cultur
es of P, simplicissimum (6%).