Complete assignments of 1H and 13C NMR data for seven arylnaphthalide lignans from Justicia procumbens

Three new arylnaphthalide lignans named 6'-hydroxy justicidin A (1), 6'-hydroxy justicidin B (2) and 6'-hydroxy justicidin C (3) have been isolated from the whole plant of Justicia procumbens, together with four known ones, neojusticin A (4), chinensinaphthol methyl ester (5), isodiphyllin (6) and taiwanin C (7). The complete assignments of H-1 and C-13 NMR chemical shifts for the new lignans and the C-13 NMR chemical shifts for the known lignans were obtained for the first time by means of 2D NMR techniques, including HSQC and HMBC. Copyright (c) 2006 John Wiley & Sons, Ltd.