Saponin from purple eggplant (Solanum melongena L.) and their activity as pancreatic lipase inhibitor

Abstract

Recently, obesity is one of the global problem, and orlistat is one of the known anti-obesity drugs, which works by inhibiting pancreatic lipase activity. Previous study has revealed that purple eggplant mesocarp, which contain alkaloids, flavonoids and saponins, has activity as pancreatic lipase inhibitor. On other hand, many class of saponin are inhibitor for the enzyme. Therefore, the aims of this study are to isolate and identify the saponins of purple eggplant (Solanum melongena) methanol extract and to test the activity as pancreatic lipase inhibitor. This study was conducted on four stages: 1) sample preparation, extraction and concentration of compounds from eggplant purple mesocarp; 2) saponin isolation by thin layer chromatography; 3) UV-Vis and FT-IR analysis to predict the class of the saponin isolates; and 4) pancreatic lipase inhibition assay. Extraction has been done by maceration using methanol as solvent, while the isolation was conducted by preparative thin layer chromatography using methanol: acetone (1:1) as eluent. Inhibition assay using titrimetric method with porcine pancreatic lipase (Sigma product) as enzyme, olive oil as substrate and orlistat as standard inhibitor. The result has showed that: the methanol extract of purple eggplant mesocarp contains two type of saponins that active as pancreatic lipase inhibitor, with the activity hundreds times higher than orlistat, at the same mass; and based on their UV-Vis and IR spectra, the isolates were predicted as steroid saponins.