New dihydrostilbene derivatives from the leaves of Glycyrrhiza glabra and evaluation of their antioxidant activity.

Five new prenylated dihydrostilbenes, alpha,alpha'-dihydro-3,5,4'-trihydroxy-4,5'-diisopentenylstilbene (1), alpha,alpha'-dihydro-3,5,3',4'-tetrahydroxy-4,5'-diisopentenylstilbene (2), alpha,alpha'-dihydro-3,5,4'-trihydroxy-5'-isopentenylstilbene (3), alpha,alpha'-dihydro-3,5,3'-trihydroxy-4'-methoxy-5'-isopentenylstilbene (4), and alpha,alpha'-dihydro-3,5,3',4'-tetrahydroxy-5'-isopentenyl stilbene (5), along with four known flavonoids, glabranin (6), pinocembrin, (7), licoflavone (8), and wighteone (9), were isolated from a lipid extract of the leaves of Sicilian Glycyrrhiza glabra. The structures of the compounds were elucidated by spectroscopic methods. The antioxidant activities of the crude extracts and the isolated compounds were tested.