Heat Stable Protease Inhibitors from Sesbania grandiflora and Terminalia catappa

Aims: Protease inhibitors play a vital role in the regulation of protease activity and display promising therapeutic effects against diseases in humans. The aim of this study was to investigate protease inhibitory activities and their heat stabilities from parts of five medicinal plants.

Study Design: Experimental.

Place and Duration of Study: Department of Biochemistry, Faculty of Medicine, University of Peradeniya, Sri Lanka between March 2012 and February 2013.

Methodology: Water extracts were prepared using fresh plant parts of Mangifera zeylanica (MZ) bark, Sesbania grandiflora (SG) bark, flower, leaves and seeds, Terminalia bellerica bark and seed, Terminalia catappa (TC) bark, fruit and leaves and Terminalia chebula bark and seed. Percentage inhibitory activities of the extracts against pepsin and trypsin were measured. Final concentrations of the extracts used for pepsin and trypsin inhibitory assays were 0.2 and 0.13% respectively. Remaining inhibitory activities were measured after heating the extract at 60, 80 and 100°C up to 1 h. All the experiments were conducted in triplicate for three times.

Results: Maximum pepsin inhibitory activity was detected in TC bark (98%) followed by SG bark (67%) and MZ bark (31%). Rest of the extracts showed 10 to 16% pepsin inhibition or no inhibition. Maximum trypsin inhibitory activity was detected in SG bark (95%) followed by TC bark (86%) and MZ bark (39%). Rest of the extracts showed 6 to 18% trypsin inhibition or no inhibition. Inhibitory activities of SG and TC barks remained when heated for 1 h at 60, 80 and 100°C. The maximum loss recorded was with the trypsin inhibitory activity (27% loss) when SG bark was heated at 100°C for 1 h.

Conclusion: S. grandiflora and T. catappa barks demonstrated strong protease inhibitory activities which were heat stable. Further studies are necessary to isolate, characterize and elucidate the structures of these protease inhibitors.