Collybial, a new antibiotic sesquiterpenoid from Collybia confluens (Basidiomycetes)

A new antibiotic was isolated from fermentations of an american strain of Collybia confluens. Its structure was elucidated by spectroscopic methods as 2,10,10-trimethal-4-oxo-tricyclo[7.2.0.0(2.5)]undec-6- en-carbaldehyde (with the relative stereo chemistry 1S, 2R, 5R, 9R) (1). The inhibitor, which was named collybial, is structurally related to koraiol, a sesquiterpenoid isolated from Pinus koraiensis (Khan V. A. (1979), Khim. Prir. Soedin 5, 652-658). Collybial inhibited the growth of Gram-positive bacteria at concentrations starting from 21.5 microM. The propagation of vesicular stomatitis virus (VSV) in baby hamster kidney (BHK-21) cells was inhibited by 21.5 microM collybial. Cytotoxic effects on BHK cells were observed at 5 fold higher concentrations.