EIMS m/z 239 (40, M + ), 238 (100), 210 To understand the structural features of the new metabolites, the crude extracts were chemically derivatized and then analyzed by GCMS. First, it was hypothesized that the mass difference of 2 Da between the major compounds in B. petasata (3 and 5) and B. producta (4 and 6) is indicative of a loss of a degree of unsaturation-either the elimination of one of the olefins or a loss of one of the rings. The former is a typical post-modification event therefore