Soybeans are known to produce a phytoalexin, which can also determine plant resistance to pathogen infection. Day (1974) states that phytoalexin produced in response to invading pathogens host plant. Keen (1981) reported that a compound phytoalexin gleceolin on cotyledons. Ingham et al. (1980 In Keen, 1981) reported gleceolin isomer III on soybean leaves. Moreover, Keen (1981) reported that the cause gleceolin accumulated in the plant tissue are biotic factors, and directly or indirectly in the biosynthesis induced by certain enzymes.