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Crystal structures of the flavonoid Oroxylin A and the regioisomers Negletein and Wogonin
Author(s) -
De Grano Ruel Valerio Robles,
Vashchenko Elena V.,
Nisar Madiha,
Sung Herman H.-Y.,
Vashchenko Valerii V.,
Williams Ian D.
Publication year - 2020
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229620005550
Subject(s) - wogonin , structural isomer , chemistry , flavonoid , crystal structure , stereochemistry , organic chemistry , medicine , scutellaria baicalensis , alternative medicine , pathology , traditional chinese medicine , antioxidant
The flavonoid Oroxylin A (6‐methoxychrysin or 5,7‐dihydroxy‐6‐methoxy‐2‐phenyl‐4 H ‐chromen‐4‐one, C 16 H 12 O 5 ) and its regioisomers are of increasing interest for a variety of bioactive functions and their pharmaceutical formulation is of importance. Previous difficulties in the separation and misidentification of Oroxylin A from its regioisomers Wogonin (8‐methoxychrysin or 5,7‐dihydroxy‐8‐methoxy‐2‐phenyl‐4 H ‐chromen‐4‐one) and Negletein (5,6‐dihydroxy‐7‐methoxyflavone or 5,6‐dihydroxy‐7‐methoxy‐2‐phenyl‐4 H ‐chromen‐4‐one) render its full structural and powder X‐ray characterization highly desirable. The low‐temperature (100 K) crystal structures of Oroxylin A, Negletein and Wogonin sesquihydrate are reported for the first time. Wogonin crystallizes in two related but distinct hydrated forms. These have very similar powder diffractograms, indicating that such issues need to be addressed for its pharmaceutical formulation.