Isolation, structural elucidation and in vitro hepatoprotective activity of flavonoids from Glycyrrhiza uralensis

Two new flavonoid glycosides, 2′,4′-dihydroxydihydrochalcone-4-O-β-d-glucopyranoside (1) and medicarpin-3-O-β-d-apiofuranosyl (1 → 2)-β-d-glucopyranoside (2), together with 34 known flavonoids were isolated from the 75% EtOH extract of the dried roots of Glycyrrhiza uralensis Fisch. Their structures were elucidated on the basis of spectroscopic analyses. The flavonoids were classified into ten sub-types, namely, dihydrochalcone (1), pterocarpans (2–4), flavones (5–6), flavanones (7–11), chalcones (12–15), retro-chalcones (16–18), isoflavans (19–21), isoflavones (22–28), 3-arylcoumarins (29–30), and coumestans (31–36). The isolated flavonoids were evaluated for in vitro hepatoprotective activity against d-galactosamine-induced toxicity in human hepatoma HepG2 cells.