Structures of Six Isoprenoid-substituted Flavonoids, Gancaonins F, G, H, I, Glycyrol, and Isoglycyrol from Xibei Licorice (Glycyrrhiza Sp.)

Abstract

Four new isoprenoid-substituted flavonoids, gancaonins F, G, H, and I, along with two known compounds, glycyrol and isoglycyrol, were isolated from the Xibei licorice (Glycyrrhiza s p . 1. Structures of gancaonins F, G, H, and I were shown to be 3-6, respectively, on the basis of spectral evidence.From the X-ray crystalloqraphic analysis, spectroscopic data, and chemical evidence, the structures 1" and 2 ' for isoglycyrol and glycyrol should be revised to the structures 1 and 2, respectively.Licorice, the root of various species of Glycyrrhiza (Legurninosae), has been used for a long time as one of the most important crude drugs.On the constituents of phenolic compounds of Xibei licorice (Glycyrrhiza sp., Seihoku Kanzo in Japanese), many investigators reported a series of isoprenoid-substituted fla~onoids.~.~We have also reported prenylated flavonoids from Xibei licorice7 and the aerial parts of Glycyrrhiza uralensis FISCH .lIn continuation of these studies, we examined the phenolic constituents of Xibei licorice, and describe here the characterization of four new isoprenoid-substituted flavonoids, gancaonins F (31, G ( 4 ) .H (51, and I (6) together with the revised structures of two known compounds, isoglycyrol ( 1 ) and glycyrol ( 2 ) . 8 From the benzene extract of the crude drug, four kinds of new isoprenoid-substi-* : Compounds 1-6 and 11 were measured at 60 C, digital resolution, 1: 0.52 Hz, 2-6, 11: 0.73 Hz, 5: the number of carbons; according to D.M. Dewick (ref.25) and J.L. Ingham (ref.261, a): data from K.R. Markham g G. (ref.12