| Bamboo shoot, the underground sprouts of bamboo (Gramineae), is one of the ancient and widely consumed vegetables in Asia. In the current study, The hypothesis is that the presence of phytochemicals rather than dietary fiber in bamboo shoot can modify cholesterol absorption, excretion and synthesis in the rat or a human liver cell line. The objectives consisted of the following: (1) to conduct animal research to evaluate the in vivo bioactivity of bamboo shoot on serum and hepatic lipids; (2) to study the effect of bamboo shoot on fecal neutral and acid steroid excretion in the rat; (3) to extract and separate fractions from the bamboo raw material using column chromatography; (4) to perform cell culture studies to screen for active fractions; (5) to apply advanced techniques such as GC-MS and LC-MS to identify the likely chemical structures of the active compounds; and (6) to use the PCR technique to study the effect of bioactive components in bamboo shoot on HMG-CoA reductase mRNA expression (the rate limiting enzyme in cholesterol biosynthesis).;In section one, the effect of two dosage levels of bamboo shoots ( Phyllostachys edulis) on serum lipids were investigated. After four weeks on the experimental diet, a significant decrease in both serum total cholesterol and LDL cholesterol were observed in following treatments: bamboo shoot I (30% and 50%, respectively) and bamboo shoot II (37% and 60%, respectively) as compared to the wheat fiber and oat bran control groups. This hypocholesterolemic effects were found not to be attributable to dietary fiber but to other phytochemicals. Serum HDL was slightly, but significantly increased and triglycerides remained unchanged. High dosage bamboo shoot II significantly decreased final liver weight, liver cholesterol and liver triglyceride contents. In section II, a continuing study of section I evaluated the effect of bamboo shoot excretion on fecal neutral sterols and bile acid excretion in the rat. The excreted neutral sterols were significantly elevated in cholesterol, coprostanol and phytosterols. Compared to control fiber groups, rats fed dietary bamboo shoot had a significantly higher dose dependent output of cholic acid. Lithocholic acid, the product of cholic acid, was significantly depressed in both bamboo shoot treatments. Since sodium cholate (1%) was present in the diet, this further indicated that bamboo shoot can decrease cholesterol absorption by increasing exogenous cholesterol excretion. In section III, bamboo shoot was extracted and fractionated to water-soluble and ethanol-soluble fractions. The latter was further fractionated into eight sub-fractions by column chromatography. The Hep G2 cell line (immortalized human hepatocytes) was used to screen the active fractions. The active compounds identified are various phytosterols. More than seventeen phytosterols were discovered, but only six were identified. The remainders are isomers and unknown sterols. Although several of the bamboo shoot fractions can decrease cell cholesterol level, only the crude extract of bamboo shoot is able significantly down regulate HMG-CoA mRNA expression. This indicates that several of the sterols in bamboo shoot co-regulate cell cholesterol metabolism and co-operate in the resultant hypocholesterolemic properties. |
