Amaranth squalene reduces serum and liver lipid levels in rats fed a cholesterol diet.

In this study, the hypocholesterolaemic effect of amaranth grain, oil and squalene are examined. In experiment 1, rats are given a semi-purified diet containing 1% (w/w) cholesterol for four weeks and either amaranth grain (AG; 300 g/kg) or amaranth oil (AO; 90 g/kg) substituted in experimental groups. Both AG and AO lowered serum and hepatic cholesterol and triglyceride levels. Faecal excretion of cholesterol and bile acid in the AO group increased, while AG affected only bile acid excretion. In experiment 2, rats were fed the cholesterol diet for four weeks and injected (i.p.) with saline (control), amaranth squalene (AS) or shark liver squalene (SS, 200 mg/kg) for seven days. The hypolipidaemic effects of AS were evident in both serum and liver. In addition, AS markedly increased faecal excretions of cholesterol and bile acid, and slightly inhibited 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity. In contrast, none of these effects were observed in the SS group. This preliminary study suggests that the cholesterol-lowering effect of AS may be mediated by increased faecal elimination of steroids through interference with cholesterol absorption, and that different sources of squalene (plant versus animal) may affect cholesterol metabolism differently.

Protective effect of 4',5-dihydroxy-3',6,7-trimethoxyflavone from Artemisia asiatica against Abeta-induced oxidative stress in PC12 cells.

Amyloid beta protein (Abeta)-induced free radical-mediated neurotoxicity is a leading hypothesis as a cause of Alzheimer's disease (AD). Abeta increased free radical production and lipid peroxidation in PC12 nerve cells, leading to apoptosis and cell death. The effect of 4',5-dihydroxy-3',6,7-trimethoxyflavone from Artemisia asiatica on Abeta induced neurotoxicity was investigated using PC12 cells. Pretreatment with isolated 4',5-dihydroxy-3',6,7-trimethoxyflavone and vitamin E prevented the Abeta-induced reactive oxygen species (ROS). The 4',5-dihydroxy-3',6,7-trimethoxyflavone resulted in concentration-dependant decreased Abeta toxicity assessed by 3-(4, 5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. However, treatment with these antioxidants inhibited the Abeta-induced neurotoxic effect. Therefore, these results indicate that micromolecular Abeta-induced oxidative cell stress is reduced by 4,5-dihydroxy-3',6,7-trimethoxyflavone from Artemisia asiatica.

Inhibitory effect of ursolic acid purified from Origanum majorana L on the acetylcholinesterase.

We screened 139 herbal spices in search of the acetylcholinesterase (AChE) inhibitor from natural resources. AChE inhibitors, which enhance cholinergic transmission by reducing the enzymatic degradation of acetylcholine, are the only source of compound currently approved for the treatment of Alzheimer's Disease (AD). Among these herbs, edible plants and spices, the ethanol extract from Origanum majorana L. showed the highest inhibitory effect on AChE in vitro. By sequential fractionation of Origanum majorana L. the active component was finally identified as ursolic acid (3 beta-Hydroxyurs-12-en-28-oic acid). The ursolic acid of Origanum majorana L. inhibited AChE activity in a dose-dependent and competitive/non-competitive type. The Ki value (representing the affinity of the enzyme and inhibitor) of Origanum majorana L. ursolic acid was 6 pM, and that of tacrine was 0.4 nM. The concentration required for 50% enzyme inhibition of the active component (IC50 value) was 7.5 nM, and that of tacrine was 1 nM. This study demonstrated that the ursolic acid of Origanum majorana L. appeared to be a potent AChE inhibitor in Alzheimer's Disease.

Inhibitory effect of Artemisia asiatica alkaloids on acetylcholinesterase activity from rat PC12 cells.

We screened 42 Korean traditional tea plants to determine the inhibitory effect of acetylcholinesterase and attenuation of toxicity induced by amyloid-beta peptide, which were related to the treatment of Alzheimer's disease (AD). The methanolic extract from Artemisia asiatica among tested 42 tea plants, showed the highest inhibitory effect (48%) on acetylcholinesterase in vitro. The methanolic extract was further separated with n-hexane, chloroform, and ethyl acetate of water, in order. The chloroform solubles, which were high in inhibitory effect of acetylcholinesterase, were repeatedly subjected to open column chromatography on silica gel. From the highest inhibitory fraction (78%) on acetylcholinesterase, the single compound was obtained by the Sep-Pak Cartridge (C18: reverse phase column). This compound was found to react positively on Dragendorff's reagent (potassium bismuth iodide), which typically reacted with the alkaloid. This compound was purified by HPLC (mu-bondapack C18 reverse phase column: 3.9 x 150 mm). The IC50 (the concentration of 50% enzyme inhibition) value of this compound was 23 micrograms/ml and the inhibitory pattern on acetylcholinesterase was mixed with competitive/non-competitive type. We examined the effects of this compound on toxicity induced by A beta (25-35) in rat pheochromocytoma PC12 cells. Pretreatment of the PC12 cells for 2 h with an alkaloid of Artemisia asiatica (1200 microg/ml) reduced the toxicity induced by A beta. This study demonstrated that an alkaloid of Artemisia asiatica, which was metabolized to small molecule in digestive tract and then could pass through the blood-brain barrier, appeared to be an acetylcholinesterase inhibitor with a blocker of neurotoxicity induced by A beta in human brain causing Alzheimer's disease.