A new antioxidant stilbene and other constituents from the stem bark of Morus nigra L.

A new stilbene, 2',3,4',5,5'-pentahydroxy-cis-stilbene (1), along with 13 known compounds, resveratrol (2), oxyresveratrol (3), norartocarpetin (4), kuwanon C (5), morusin (6), cudraflavone A (7), kuwanon G (8), albafurane C (9), mulberrofuran G (10), 3-O-acetyl-α-amyrin (11), 3-O-acetyl-β-amyrin (12) ursolic acid-3-O-acetate (13) and uvaol (14), were isolated from the barks of Morus nigra. Compounds 2, 8, 10, 12 and 14 are reported for the first time from this plant. The isolated compounds were elucidated by means of 1D and 2D NMR, UV, IR and MS, as well as by comparison with the literature data. The isolated compounds and the different extracts were evaluated for their potential antioxidant activity using 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid)(+) radical-scavenging capacity assay and compared with ascorbic acid. The new stilbene (1) exhibited remarkable antioxidant capacity with IC50 of 4.69 μM.