Identification of bioactive compounds by GC-MS and α-amylase and α-glucosidase inhibitory activity of Rauvolfia tetraphylla L. and Oroxylum indicum (L.) Kurz: an in vitro and in silico approach

Background The practice of ethnomedicine remains to be the primary source of healthcare in many parts of the world, especially among the tribal communities. However, there is a lack of scientific outlook and investigation to authenticate and validate their medicinal values. Objective The present study investigated the trace and heavy metal content, bioactive compounds, α-amylase, and α-glucosidase inhibitory activity of Rauvolfia tetraphylla and Oroxylum indicum using in vitro and in silico methods. Methods Trace and heavy metal content of Rauvolfia tetraphylla and Oroxylum indicum were detected using Atomic Absorption Spectroscopy. Bioactive compounds were analyzed and identified by the GC-MS technique. α-Amylase and α-glucosidase inhibitory activity of the plants were studied using the spectrophotometric method using UV/VIS-Spectrophotometer. In silico molecular docking was carried out in AutoDock vina and the structures visualized using PyMol and Biovia Discovery Studio software. Statistical and graphical representations were performed using Excel and OriginPro. Results The trace and heavy metallic content such as Zn, Ni, Pb, Cr, Cu, and Mn were reported from both the plant. No Cd was detected in both the plants. GC-MS analysis revealed four major compounds in R. tetraphylla and seven in O. indicum. Biochemical studies showed that the leaf extract of O. indicum posses the strongest α-amylase and α-glucosidase inhibitory activity. R. tetraphylla showed weaker enzyme inhibition. Molecular docking study revealed that three compounds from O. indicum (O2, O3, and O6) and two from R. tetraphylla (R1 and R2) showed strong binding affinity to α-amylase and α-glucosidase. However, leaf extract of O. indicum showed better binding affinity with the enzymes compared to R. tetraphylla. Conclusion Inhibition of α-amylase and α-glucosidase in an important strategy of diabetes control. The present study revealed the in vitro α-amylase and α-glucosidase inhibitory activity of Rauvolfia tetraphylla and Oroxylum indicum. In conclusion, the study identified that the leaf extract of O. indicum as a potential inhibitor of glucose metabolizing enzymes and could be a source of antidiabetic agents.