Cassiae Semen (seeds of Cassia tora) showed a remarkably different HPLC chromatogram after being treated with a crude enzyme extract from Aspergillus usamii. Increased and decreased compounds were identified as aurantio-obtusin and glucoaurantio-obtusin, respectively. The aurantio-obtusin content reached its maximum level ($133.58{pm}0.39;{mu}g/mg$ extract) after being incubated for 50 min at $37^{circ}C$, whereas the inactivated crude enzyme-treated control remained unchanged ($54.13{pm}1.33;{mu}g/mg$). On the other hand, the glucoaurantio-obtusin content decreased by less than one-third ($51.09{pm}1.63;{mu}g/mg$) ofthe untreated control ($143.19{pm}2.12;{mu}g/mg$), suggesting that an increase in aurantio-obtusin content originated from the enzymatic cleavage of its glucoside glucoaurantio-obtusin.