Notably, the known anthraquinone dimer , as well as two new isomers of anthraquinone dimer , were also isolated from A. glaucus . However, compound 21 was not evaluated for any relevant bioactivity, the trans isomer of emodin-physcion bianthrone showed good cytotoxicity against the cell lines; A-549 and HL-60 with IC50 values of 9.2 and 7.8 μM, respectively. On the other hand, its cis isomer was less active as its IC50 values were 14.2 and 44.0 μM, respectively , suggesting that isomerization slightly affected the cytotoxicity of the compound .