In vitro lipase inhibition and in silico modelling analysis of the resin glycosides from the seeds of Ipomoea muricata and pharbitin from Pharbitidis Semen

Resin glycosides (RGs) are the unique constituents of Convolvulaceae plants. This study aims to investigate the inhibitory effects of the RG fraction from Ipomoea muricata seeds (IMRG) and that of pharbitin from Pharbitidis Semen (seeds of I. nil) on three representative digestive enzymes, lipase, α-amylase and α-glucosidase, in vitro. The results indicated that both RG fraction had lipase-selective inhibitory activity. Three genuine RGs, as three muricatins, and a glycosidic acid methyl ester, previously isolated from I. muricata seeds, showed clear lipase inhibition. In silico analysis of these four compounds was performed using both porcine (PDB ID: 1ETH) and human (PDB ID: 1LPB) lipases. Docking simulations using all four active molecules confirmed highly stable binding scores to the active sites of both pancreatic lipases. In conclusion, we demonstrated here for the first time that the IMRG fraction, pharbitin and four compounds from I. muricata are responsible for lipase inhibition in vitro.