Ten New Dammarane-Type Saponins with Hypolipidemia Activity from a Functional Herbal Tea- Gynostemma pentaphyllum

Abstract

Gynostemma pentaphyllum (thumb.) Makino is a functional herbal tea commonly used in Asian countries and regions to reduce blood lipid levels. G. pentaphyllum saponin is the main component, but there are still a large number of components with lipid-lowering activity that have not been found. In this study, 10 novel dammarane-type saponins, (1-10) and a known one (11) were isolated from G. pentaphyllum. Ten new compounds were identified and named as yunnangypenosides A-J (1-10), and another known one (11) was also obtained. Their chemical structures were determined by MS, NMR spectroscopic analyses. Moreover, the cytotoxicities on human HepG-2 hepatocellular carcinoma cells of these isolates were evaluated, and the results showed that compounds 1-11 had no obvious cytotoxicity. Finally, all these compounds were evaluated for their lipid-lowering effect by means of the oil red O staining method. Ten compounds could significantly reduce lipid levels except of 2, especially 8 exhibite the strongest hypolipidemia activity.

Keywords: Gynostemma pentaphyllum; chemical constituents; dammarane-type saponins; isolation and identification; lipid lowering effect.

Figure 1

Chemical structures of compounds 1–11.

Figure 2

Key HMBC correlations of compounds 1–10.

Figure 3

The effect of the isolated compounds on the survival rate of HepG-2 human hepatocellular carcinoma cells. The cells were pretreated with concentrations (6.25, 12.5, 25, 50, and 100 µg/mL) of compounds 1–11 for 1 h. The data show the mean ± SD of three independent experiments performed in triplicates.

Figure 4

Lipid lowering effects of the isolated compounds in HepG-2 human hepatocellular carcinoma cells. The cells were pretreated with concentration (50 µg/mL) of compounds 1–11 for 24 h and then stained with oil red O for 1 h in the dark environment.

Figure 5

Scheme illustrating the entire isolation process.