Philippine red Allium cepa Lin. (native red onions), obtained from Pangasinan, Nueva Vizcaya, and Nueva Ecija, were evaluated for its LDL-cholesterol lowering effect in Sprague Dawley rats by measuring the total cholesterol, triglyceride and HDL-cholesterol levels, and by computing LDL-cholesterol using the Friedewald equation. Forty eight (48) rats were used, divided into six groups, a normal control (NC) group and five treatment groups (two control treatment groups: ACC-commercially available atorvastatin calcium tablet and QC-standard quercetin dihydrate; and three experimental treatment groups: RIPangasinan, RII-Nueva Vizcaya, and RIII-Nueva Ecija). The LDL-cholesterol lowering effect of the red onions was compared to commercially available lipid lowering drug (atorvastatin calcium). And to prove that the LDL cholesterol lowering effect of the onions is due to flavonoids, standard quercetin dihydrate was used. Results showed that onion extracts exhibited LDL-cholesterol lowering effect like that of the atorvastatin calcium. Likewise, standard quercetin dihydrate showed a significant LDL-cholesterol lowering effect, which proved that flavonoids are effective in lowering LDL-cholesterol. It can be concluded that red onions, obtained from three different sources, are equally effective in lowering LDL-cholesterol, due to the presence of flavonoid in the extracts.

Keywords:  Allium cepa, LDL, flavonoid, Friedewald equation, quercetin.