The antifungal activity of cysteine (2-amino-3-mercaptopropionic acid) on mycelial growth and the production of lanosterol, 3,
-hydroxy-lanosta-8,24-dien-21-al, 3,
-21,dihydroxy-lanosta-8,24-diene, trametenolic acid and ergosterol were investigated in solid and liquid cultures of
Inonotus obliquus at cysteine concentrations of 0.9 and 9.0 mm by means of thinlayer chromatography densitometry. Cysteine elicited the production of ergosterol in all the cultures and at a concentration of 0.9 mm distinctly elicited the production of 3,
-hydroxy-lanosta-8,24-dien-21-al. At 9.0 mm, cysteine had greater antifungal activity than at 0.9 mm, decreasing growth and the production of metabolities.