3',8''-biisokaempferide, a cytotoxic biflavonoid and other chemical constituents of Nanuza plicata (Velloziaceae)

A novel biflavonoid, named 3',8''-biisokaempferide (1), along with the known compounds amentoflavone (2), patagonic acid (3), (4aR,5S,6R,8aR)-5-[2-(2,5-Dihydro-5-methoxy-2-oxofuran- 3-yl)ethyl]-3,4,4a,5,6,7,8,8a-octahydro-5,6,8a- trimethylnaphthalene-1-carboxylic acid (4), 5-caffeoylquinic acid methyl ester (5), 3,5-di-caffeoylquinic acid (6) and luteolin (7), were isolated of the leaves from Nanuza plicata. The compounds 3, 4, 5 and 6 are reported for the first time in Velloziaceae. The structures of the compounds were elucidated on the basis of spectroscopic methods, especially NMR and MS analyses. The cytotoxicity of 3',8''-biisokaempferide was studied in cultures of human glioblastoma GL-15 cells. The effective concentration, which killed 50 % of cells after 72 h was 36.5 μmol L-1. Changes in cellular morphology, including retraction and degradation of cytoplasm, were observed when cells were treated with concentrations from 20 μmol L-1 of 3',8''-biisokaempferide for 72 h. (author)