Modulatory effect of plant-derived indole alkaloid fraction on β-galactosidase (Lactase): An integrated in silico and in vitro study

Lactose intolerance is a widespread digestive disorder which has been the subject of extensive research since its discovery in the 1960s. It is caused due to insufficient lactase activity in the small intestine leading to ineffective lactose hydrolysis and is often associated with gastrointestinal symptoms. The present study aims to evaluate the potential of plant-derived indole-alkaloids to modulate lactase activity. Natural compounds extracted from medicinal plants, including Catharanthus roseus, Alstonia scholaris, Tabernaemontana divaricata and Peganum harmala were investigated for their interaction with lactase enzyme. The research encompassed a structural analysis of lactose and lactase, followed by blind docking studies using the CB-Dock server to assess the interaction between the enzyme and alkaloid-containing natural products. Pocket P3 showed strongest binding with indole-3-acetic acid (-7.0 kcal/mol), then came alkaloid extracts from Catharanthus roseus and Peganum harmala (-6.8 kcal/mol). Computational predictions were validated through in vitro assays such as ONPG and enzyme activity assays, for measuring β-galactosidase activity. ONPG-based qualitative assay resulted in increased chromogenic response in the presence of alkaloidal fraction compared to enzyme control. This multimodal approach offers insight into the potential role of natural compounds as complementary or alternative approaches for controlling lactose intolerance and their possible involvement in boosting lactase function.