New prenylated isoflavanones from the roots of Glycyrrhiza glabra

Abstract

547.972Two new prenylated isoflavanones have been isolated from the roots of Glycyrrhiza glabra L. along with the known compounds cetoleic acid, β-sitosterol, stigmasterol, lanast-5,24-dien-3β-D-glucuronopyranoside, and glucuronic acid. The structures of the prenylated isoflavanones have been established as 8-isoprenyl-7,4′-dihydroxylicoisoflavanone (glabraisoflavanone A) and 7,3′-dihydroxy-8-isoprenyl-4′-cyclogeranioloxyisoflavanone (glabraisoflavanone B) on the basis of spectral data analyses and chemical reactions.Glycyrrhiza glabra L. (Fabaceae), commonly known in trade as liquorice, is a perennial herb distributed in subtropical and warm temperate regions of the world [1]. The roots are reported to have anti-inflammatory, demulcent, expectorant, and tonic properties and are prescribed to treat sore throat, bronchial catarrh, cough, gastric and duodenal ulcers, dyspepsia, allergic reactions, arthritis, rheumatism, tuberculosis, and liver toxicity [1, 2]. The important phytoconstituents isolated from the roots included glycyrrhizin, liquiritic acid, glabranins A and B, glycyrrhetol, glabrolide, formononetin, liquiritin, isoliquertin, and other phenolic compounds [3][4][5][6][7][8][9]. This present paper describes the isolation and characterization of the known compounds cetoleic acid (1), β-sitosterol (2), stigmasterol (3), lanast-5,24-dien-3β-D-glucuronopyranoside (6), glucuronic acid (7) and of two new prenylated isoflavanones (4, 5) from the roots of G. glabra of northern India.Compound 4, designated as glabraisoflavanone A, was obtained as a pale yellow crystalline product from chloroform eluates. Its UV λ max at 211, 294 nm and the presence of the O-CH 2 -CH-CO sequence in its 1 H and 13 C NMR spectra (Table 1) accounted for its isoflavanone structure. The presence of a bathochromic shift after addition of sodium acetate in the UV spectrum indicated a free hydroxyl group at C-7. It was assigned a molecular formula of C 25 H 28 O 4 (m/z 392.1652) from HREIMS. A set of three AMX patterns of double doublets in the 1 H NMR spectrum at δ 4.45 (J = 10.5, 7.5 Hz), 4.62 (J = 11.3, 5.2 Hz), and 3.91 (J = 5.2, 10.5 Hz) for the aliphatic proton signals and carbon signals at δ 70.83 (C-2), 51.12 (C-3), and 196.89 (C-4) were consistent with compound 4 being an isoflavanone derivative [10,11]. The 1 H and 13 C NMR spectra indicated the presence of one 3-methylbut-2-enyl, one hydroxyl, and dimethyl pyranosyl substituents on the isoflavanone skeleton.

Glycyrrhiza Genus: Enlightening Phytochemical Components for Pharmacological and Health‐Promoting Abilities

“…Moreover, 49 phenolic compounds and 15 different saponins have been identified from licorice roots [ 62 ]. Saponins (licorices A3, G2, and J2), chalcones (isoliquiritin, licochalcone B, and neolicuroside) [ 63 ], coumarins (glycycoumarin) [ 64 ], and flavonoids (glychionides A and B, glabrene, glabrone, glabraisoflavanones A and B, isoviolanthin, 5,7-dihydroxyflavanone, and rhamnoliquiritin) [ 24 , 65 – 67 ] have also been reported in licorice. Glucoliquiritin apioside, prenyl licoflavone A, shinflavanone, shinpterocarpin, and 1-methoxy phaseolin are also present in licorice roots [ 68 ].…”

Isoflavonoids of the Leguminosae

“…134 In one of two studies on Glycyrrhiza glabra roots, which are traded commercially as licorice, MeOH extracts of marketsourced material (New Delhi, India) afforded glabraiso-avanones A (118) and B (119). 135 The structure of the latter is remarkable for its cyclised O-geranyl substituent at C-4 0 of the isoavanone B-ring. Kuroda et al obtained the 3-hydroxyiso-avanone 120 as a racemate by bioassay-guided fractionation of wild-collected (northwestern China) G. glabra roots.…”

Isoflavanones from Desmodium oxyphyllum and their cytotoxicity

“…A 70% aqueous acetone extract prepared from dry powder of the whole D. oxyphyllum plant was subjected repeatedly to column chromatography on silica gel, Sephadex LH-20, RP-18, and preparative HPLC to afford compounds 1-9, including two new isoflavanones, named (3R)-7-hydroxy-4 0 -methoxy-5-methoxycarbonyl-isoflavanone (1) and (3R)-8-hydroxy-4 0 -methoxy-7-methoxy-carbonyl-isoflavanone (2), together with seven known isoflavanones, uncinanone D (3) [10], (3R)-7,2 0 ,4 0 -trihydroxy-3 0 -methoxy-5-methoxycarbonyl-isoflavanone (4) [11], 3,5,7,4 0 -tetrahydroxy-coumaronochromone (5) [12], desmodianone E (6) [13] grabraisoflavanone A (7) [14], licoisoflavone (8) [15], and desmodianone F (9) [16]. The structures of compounds 1-9 are shown in Figure 1, and the 1 H and 13 C NMR spectral data of 1 and 2 are listed in Table 1.…”