Preliminary investigations on the serine and aspartic protease inhibitors from Nothopegia beddomei

Aqueous stem bark extract of Nothopegia beddomei was assayed for serine and aspartic protease inhibitors by using trypsin and pepsin as the target enzymes, respectively. Crude bark extract was dialyzed and subjected to inhibition assays. The thermal stabilities of serine and aspartic protease inhibitors were studied by incubating the extract at 4 ºC, room temperature and 37 ºC for a period of one month and subjecting to higher temperatures (55 ºC, 75 ºC and 95 ºC) for 15 minutes. The crude bark extract of N. beddomei exhibited serine and aspartic protease inhibitory activities. However, the serine protease inhibitory activity was significantly higher. The approximate molecular mass of both serine and aspartic protease inhibitors were more than 8 kDa. Both types of inhibitors were identified as mixtures of thermally stable and labile compounds due to their variations in inhibitory activities with time at different temperatures. Attempts made to purify the protease inhibitors using ion exchange chromatography and ammonium sulphate precipitation were unsuccessful. In conclusion, the results indicate both serine and aspartic protease inhibition activities in N. beddomei bark extract are governed by mixtures of protenaceous and non-protenaceous molecules.