Platycodi radix affects lipid metabolism in mice with high fat diet-induced obesity

An aqueous extract of Platycodi radix inhibited the hydrolysis of triolein emulsified with phosphatidylcholine by pancreatic lipase in vitro and it reduced the elevation of rat plasma triacylglycerol level 2-4 h after oral administration of a lipid emulsion containing corn oil. These preliminary results suggested that the aqueous extract of Platycodi radix may inhibit the intestinal absorption of dietary fat by inhibiting its hydrolysis. Therefore, we examined the antiobesity activity of the aqueous extract of Platycodi radix by testing whether the extract prevented the obesity induced by feeding a high fat diet to mice for 8 wk. Body weights at 3-8 wk and the final parametrial adipose tissue weights were significantly lower in mice fed the high fat diet containing 5% aqueous extract of Platycodi radix than in the controls fed the high fat diet. The aqueous extract of Platycodi radix also significantly reduced hepatic triacylglycerol concentrations that were elevated in mice fed the high fat diet alone. Inulin, which is a major component of Platycodi radix, had no effect on the hydrolysis of triolein emulsified with phosphatidylcholine by pancreatic lipase in vitro, and did not prevent obesity or the fatty liver induced by the high fat diet. On the other hand, the total saponin fraction of the aqueous extract inhibited pancreatic lipase activity in vitro. Therefore, the antiobesity effect of the aqueous extract of Platycodi radix in mice fed a high fat diet may be due in part to the inhibition of intestinal absorption of dietary fat by the saponins of Platycodi radix.