The anthraquionone mycotoxin, skyrin, is produced by Penicillium islandicum. DF-100 which was extracted from grapfruit seed extract and is a natural organic complex inhibited the biosynthesis of skyrin by Penicillium islandicum. This study way carried out to determine the potential of DF-100 to support Penicillium islandicum and skyrin production. DF-100 inhibited the growth of the fungus at 750ppm or less and caused complete inhibition of skyrin production at 500ppm or less. DF-100 appears to block the incorporation of emodinathrone into skyrin and an enzymatic step in the skyrin biosynthetic pathway which lies before skyrinanthrone.