Sterol

About: Sterol is a research topic. Over the lifetime, 8117 publications have been published within this topic receiving 309926 citations. The topic is also known as: sterols & sterol lipids.

Toxins from sea cucumbers (holothuroids): chemical structures, properties, taxonomic distribution, biosynthesis and evolution.

Abstract: Studies on structures, biological activities, chemical properties, taxonomic distribution, biosynthesis, and evolution of toxins from sea cucumbers (the phylum Echinodermata, the class Holothurioidea) were reviewed with special emphasis on recent results from our laboratory. These toxins are triterpene oligoglycosides having very often one or several sulfate groups in carbohydrate moieties. Their aglycones belong to lanostane derivatives and sometimes contain shortened side chains. Many aglycones are labile in the acid medium. There is a relationship between structures of the glycosides and taxonomic positions of corresponding animals, producers of these toxins. Toxins from sea cucumbers act on delta 5-sterol-containing biological membranes with the formation of glycoside-sterol complexes followed by the disturbance of membrane permeability and inhibition of activities of some membrane enzymes. The presence of the toxins causes the alterations in membrane sterol compositions of toxic sea cucumbers in comparison with non-toxic species. These alterations include the change of delta 5-sterols for those having 7(8)- and 9(11)-double bonds as well as biotransformation of a part of free sterol fractions into sterol sulfates and sterol xylosides.

Antimicrobial activity of resin acid derivatives.

Abstract: The wide potential of resin acids as bioactive agents gave rise to a growing effort in the search for new applications of the natural forms and their derivatives. In some of these compounds, the antimicrobial activity is associated to the presence in the molecules of functional groups such as the hydroxyl, aldehyde, and ketone or to their cis or trans configurations. The resin acid family covers a spectrum of antimicrobial activities against several microorganisms, from bacteria to fungi, in which the mode of action was studied by electron microscopy. The morphological alterations are consistent with an unspecific mode of action causing inhibition of the fungal growth or damaging the fungal cells in parallel with a mechanism of resistance based on the retention of the compound by the lipid accumulation. The sterol composition of phytopathogenic fungi Botrytis cinerea and Lophodermium seditiosum treated with methyl cis-7-oxo-deisopropyldehydroabietate revealed the presence of ergosterol (M+ 396) and dihydroergosterol (M+ 398) in both cultures showing that this compound did not interfere with the ergosterol metabolic pathway of both fungi.

Some effects of chitosan on liver function in the rat.

Abstract: Chitosan, a natural product derived from chitin, possesses hypocholesterolemic properties similar to those of cholestyramine, but there has been no report concerning its effects on the equilibrium between dietary cholesterol and de novo cholesterol synthesis in the liver. In this work, we studied the effects of chitosan on plasma and liver cholesterol levels, liver weight, and the key regulatory enzyme of cholesterogenesis 3-hydroxy-3-methylglutaryl coenzyme-A (HMG-CoA) reductase in rats fed a sterol diet containing 1% cholesterol and 0.2% cholic acid. The animals given the sterol diet showed increases in plasma and liver cholesterol, which were lowered by 54% in plasma and 64% in liver by 5% chitosan, while cholestyramine completely blocked such increases. HMG-CoA reductase activity was considerably increased in the sterol-cholestyramine group, but was greatly decreased in both sterol and sterol-chitosan groups. There was no change in liver weight or appearance after treatment with chitosan, but cholestyramine-treated animals manifested secondary effects from the treatment, including smaller yellowish livers. High mol wt chitosans [> 750 kilodaltons (kDa)] were found to be less effective as hypocholesterolemia than a 70-kDa preparation. Also, when the 70-kDa chitosan was used at 2.5%, 5%, and 7.5% of the total diet, its effectiveness was greatest at the higher concentrations; indeed, incorporation of 7.5% chitosan in the sterol diet for 3 weeks completely prevented any decrease in plasma high density lipoprotein cholesterol or increase in the plasma cholesterol level and liver weight. This formula greatly reduced the increase in liver cholesterol content due to the sterol diet, with values of 8.8 +/- 1.3 for the sterol-chitosan diet vs. 18.2 +/- 0.8 mg/g tissue for the sterol diet. The increased intake of sterols considerably lowered both HMG-CoA reductase activity (33-fold) and HMG-CoA reductase mRNA levels (3-fold) in rat liver, but in the sterol-chitosan group, HMG-CoA reductase activity was 7.7 times more elevated than in the sterol group, although it was still lower than the control value, whereas HMG-CoA reductase mRNA levels were normal. The results obtained did not differ significantly when rats were studied for 1, 3, or 6 weeks. These results taken collectively indicate that the 7.5% chitosan formula maintained adequate cholesterol homeostasis in rats, despite a greatly increased intake of cholesterol.