Saponin isolates from cucumber (Cucumis sativus L.) fruit mesocarp and their activity as pancreatic lipase inhibitor

Abstract

Obesity can be tackled by anti-obesity drugs, like Orlistat, that inhibit digestive enzymes such as pancreatic lipase. The drug has limited availability and is quite expensive. Earlier studies have shown that mesocarp cucumber (Cucumis sativus L.) juice is capable of inhibiting pancreatic lipase and some types of saponins from other plants are also inhibitors for pancreatic lipase. This study seeks to isolate the saponin class from cucumber mesocarp, as well as determine its activity as a pancreatic lipase inhibitor relative to Orlistat. Extraction of saponin from cucumber mesocarp was done by methanol maceration of dry mesocarp powder. Saponin isolation was conducted using TLC and identified by phytochemical tests and then by UV-Vis and FTIR spectroscopy. Inhibition test of pancreatic lipase activity was done using the titrimetric method, with porcine pancreatic lipase (Sigma) as the enzyme, olive oil as a substrate and Orlistat as a standard inhibitor. The results showed that the methanol extract of cucumber mesocarp contains saponins that are active pancreatic lipase inhibitors. There are two types of saponins in cucumber mesocarp that have pancreatic lipase inhibition power that is more than twice as strong as Orlistat at the same weight. Based on the spectrum of UV-Vis and FT-IR the two saponin isolates were probably varieties of triterpenoid saponin.