Lignans from Isatis indigotica roots and their inhibitory effects on nitric oxide production.

Seventeen lignans (1-17) were obtained from the roots of Isatis indigotica (I. indigotica). Among them, isatindigosesquilignans A-C (1-3) were deduced as three undescribed sesquilignans, which possess unusual carbon skeleton of aryltetralin unit connected with a C6-C3 moiety via a five-membered ring of C-3-C-8″-C-7″-O-C-4. Isatindigosesquilignans B and C were determined as the first examples of its glycosides from a natural source and a plausible biosynthetic pathway was proposed. Moreover, all of the isolated lignans were assayed regarding their inhibitory effects on nitric oxide (NO) production in RAW 264.7 cells and compounds 1, 2 and 7 showed inhibitory effects with IC50 values ranging from 19.46 μM to 64.82 μM.