Siamese neem flower extract suppresses cholesterol absorption by interfering NPC1L1 and micellar property in vitro and in intestinal Caco2 cells

lt;p gt; lt;em gt;Siamese neem lt;/em gt;( lt;em gt;Azadirachta indica A. Juss lt;/em gt;var. lt;em gt; siamensis Valeton lt;/em gt;) ( lt;em gt;A. lt;/em gt; lt;em gt;indica) lt;/em gt; leaf extract, a traditional ayurvedic medicine, has been reported to exhibit antipyretic, antibacterial, antidyslipidemic, and antihyperglycemia effects. This study investigated the mechanism of hypocholesterolemic effect of methanolic extract of Siamese neem flowers in lt;em gt;in vitro lt;/em gt; studies and in Caco2 cells. Pancreatic cholesterol esterase and 3hydroxy 3methylglutarylCoA (HMGCoA) reductase activities were assessed. Cholesterol micelle formation was prepared for lt;em gt;in vitro lt;/em gt; cholesterol physicochemical property analyses, micelle size  and solubility, and transport of cholesterol into the Caco2 cells. The expression of niemannpick C1 like 1 (NPC1L1), and its major regulator, peroxisome proliferatoractivated receptor lt;em gt; lt;/em gt;d (PPARd), were determined by western blot and real time polymerase chain reaction, respectively. lt;em gt;A. indica lt;/em gt; flower extract inhibited pancreatic cholesterol esterase activity and increased cholesterol micelles size. Uptake of cholesterol  into Caco2 cells was inhibited by lt;em gt;A. indica lt;/em gt; flower extract in a dosedependent manner. In addition,   lt;em gt;A. indica lt;/em gt; extract inhibited HMGCoA reductase activity, resulting in low level of intracellular cholesterol accumulation, together with increased cytosolic NPC1L1 protein expression and decreased PPARd gene expression. In conclusion, lt;em gt;A. indica lt;/em gt; flower extract has cholesterollowering effects by inhibiting intestinal cholesterol absorption, interfering micellar cholesterol formation, and attenuating cholesterol synthesis. As such, lt;em gt;A. indica lt;/em gt; flower extract has potential for developing into nutraceutical product for prevention of hypocholesterolemia. lt;/p gt;