A preliminary study revealed that 3,4-di(OH)-hydrocinnamate (HC), a polyphenolic compound, lowered the plasma lipids in high-cholesterol fed rats. Accordingly, this study was designed to test the lipid-lowering efficacy of a synthetic derivative, 3,4-di(OH)-phenylpropionic (L-leucine) amide (PPLA), in rats fed a high-cholesterol (1%, wt/wt) diet. As such, HC or PPLA was given as supplement to a high-cholesterol diet for 6 weeks at a dose of 0.137 mmol/100 g diet. The supplementation of HC and PPLA significantly lowered the plasma and hepatic cholesterol and triglyceride levels compared to the control group. The activities of hepatic HMG-CoA reductase (164 +/- 9.12 and 124.74 +/- 17.09 pmol/min/mg protein vs. 245.41 +/- 13.01 pmol/min/mg protein, p < 0.05) and ACAT (411.49 +/- 11.48 and 334.35 +/- 17.68 pmol/min/mg protein vs. 490.41 +/- 16.69 pmol/min/mg protein, p < 0.05) were significantly lower in the HC- and PPLA-supplemented groups than in the control group. However, PPLA was more effective in inhibiting the enzyme activities than HC. The excretion of neutral sterol was significantly higher in HC- and PPLA-supplemented groups than in the control group. Therefore, these results indicate that PPLA, a leucine-attached version of HC, exhibited a similar significant hypocholesterolemic effect to HC in rats fed a high-cholesterol diet.
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