Identification and Partial Characterization of Trypsin Inhibitory Activity in Seed of Some Fruit Plants

Plant proteinase inhibitors are natural plant defense agents against pest and predators. Many plant serine proteinase inhibitors have been purified and characterized particularly from the seeds of Leguminosae family. In this study, some common fruit plant seeds were evaluated for proteinase inhibitory activity. The seed extract of six fruit plants (Prunus domestica, Prunus persica, Prunus amygdalus, Prunus armeniaca, Citrus aurentium and Aegle marmilos) showed significant inhibitory activity against trypsin. The seed extract of P. domestica showed highest trypsin inhibitory activity (133.81 TIU mg⁻¹ protein). The highest protein content was found in P. persica and P. armeniaca (106.90 and 105.52 mg g⁻¹ flour respectively). Zymogram analysis showed variable number of trypsin inhibitor isoforms ranging from single band for A. marmilos to four isoforms for P. domestica and P. armeniaca. The seed extract of all plants, except C. aurentium, exhibited trypsin inhibitory activity over a broad range of pH and temperature. The inhibitory activity in seed extract of A. marmilos was found to be the most stable at higher temperature retaining almost 60% of inhibitory activity at 90°C.