C31-C34 methylated squalenes from a Bolivian strain of Botryococcus braunii

Three new triterpenes, synthesized by a Bolivian strain of the green microalga Botryococcus braunii, were isolated and their chemical structures determined by ID and 2D NMR, and mass spectrometry. These compounds are tri-, di-, and mono-methylsqualenes, co-occurring with the previously identified tetramethylsqualene and some C-30-C-32 botryococcenes. In this strain, methylated squalenes constitute up to 24% of the total hydrocarbons and 4.5% of the dry biomass. The results of a pulse-chase experiment with L-[Me-C-13] methionine provide evidence for the origin of these compounds via methylation of squalene at positions 3, 7, 18 and 22. (C) 2004 Elsevier Ltd. All rights reserved.