[Separation and purification and structural characterization of baicalein].

The root of scutellaria baicalensis georgi that contains a variety of flavonoids is a very old and well-known drug in traditional Chinese medicine, which is widely used for treatment of bronchitis, tumors and inflammatory diseases. The baicalein is the main active component from traditional Chinese medicine-scutellaria baicalensis georgi. It is a very significance research work that the baicalein was separated and purified, and its composition and molecular structure are analyzed and determined for the pharmacology study of Chinese medicine-scutellaria baicalensis georgi. The main works in this paper are as follows. Powdered roots (100 g) were extracted with methanol by three times, each time for 48 hours. The crude extracts were purified by polyamide column chromatography and CH3Cl-C2H5OH gradient desorption. A short yellow prismatic crystal was acquired by recrystallizing technique and its composition and molecular structure were characterized by color reactions and spectral analysis methods as FTIR, UV-Vis, MS and 1H NMR, 13C-NMR. The FTIR spectrum appears the absorption bands for hydroxyls, pyrone carbonyl, aromatic C=C bond and singly substituted phenyl. The characteristic absorption peaks and the vibration modes in FTIR spectrum were identified as corresponding groups. The UV-Vis spectrum in methanol solution and the mix solution of methanol with 5 diagnostic reagents, NaOMe, NaOAc, NaOAc/H3BO3, AlCl3, AlCl3/HCl, respectively indicate that the yellow prismatic crystal is flavone with 5-hydroxyl, 4-carbonyl and 5,6,7- or 5,7,8-trihydroxyls on ring A. The structure of the crystal was characterized by three different MS. The results of FAB-, ESI- and EI-MS show that it is not a flavone glocuside but the flavone with three phenyl hydroxyls on ring A, and no OH group and other substituted groups on ring B. The molecular ion and fragment ions are identified by MS, which include such as m/z 270 M+, m/z 242 [M-CO]+, m/z 168 A, m/z 140 [A1-CO]+, m/z 105 B, m/z 102 B, m/z 77 [B2-CO]+, respectively. 13C-NMR (DMSO-d6) exhibits the signals of the fifteen carbon atoms, nine oxygenous aromatic C, five non-oxygenous aromatic C and a carbonyl C. 1H-NMR(DMSO-d6 + D2O, DMSO-d6 )indicates the presence of C-5, C-6, C-7 hydroxyl protons, which is consistent with the results of UV spectrum. The signals for C-2',6' hydroxyls appear at delta = 8.055 as a doublet peak with spin-spin coupling constant 6.0 Hz. The other signals were ascribed to the corresponding H or C atoms in the compound. The results of FTIR, UV-Vis, MS, 1H NMR, 13C-NMR spectroscopy characterization show that crystal is the 5,6,7-trihydroxy-flavone, that is baicalein, and the molecular formula is C15H10O5.