Stephacidin B, the dimer of avrainillamide, is a green pigment isolated from Aspergillus ochraceus and other Aspergillus sp.. Stephacidin B was reported as a potent antitumor active by Bristol Myers Squibb in 2002 against testosterone-independent PC3 and testosterone-sensitive LNCaP prostate cell lines with IC50 of 0.47 and 0.06 µM, respectively. Stephacidin is active against sensitive and resistant ovarian, colon and breast cell lines. Stephacidin B is more potent and selective than its monomeric analogue, stephacidin A. Stephacidin B is rapidly converted to avrainillamide in cell culture.