Figure 5From: Evaluation and differentiation of the Betulaceae birch bark species and their bioactive triterpene content using analytical FT-vibrational spectroscopy and GC-MS High (top) and low (bottom) wavenumbers spectral range of the FT-Raman spectra of the betulinic acid (a), betulin (b), lupeol (c) and BC1 extract (d). Excitation: 350 mW, 1064 nm. The molecular structure of the three lupan skeleton compounds is shown in the right. Back to article page