Raman spectra for the ν(C=C) stretching region of botryococcenes. A, indicated botryococcenes were purified from B. braunii by HPLC, dissolved in n-hexane, analyzed by Raman spectroscopy within the ν(C=C) stretching region, and compared with that for the total hydrocarbon extract and pure squalene. B, structures of squalene and individual botryococcenes analyzed in A.