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HPLC chromatographs of (a) Standards and (b) RTEtOH. Peaks: (1) betulinic acid; (2) oleanolic acid. Ascentis C18 column (5 μm, 250 cm×4.6 mm, analytical), mobile phase: acetonitrile and 0.2% formic acid (22:78; v/v) in the isocratic mode, low rate: 0.8 mL min−1, UV detection wavelength: 210 nm.
