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Nonconjugated Unsymmetrical Dienes
Published in George B. Butler, Cyclopolymerization and Cyclocopolymerization, 2020
The cyclization of squalene to steroids was investigated with homogenates of rat and hog liver.58 Both converted squalene to lanosterol; however, rat liver homogenate also produced cholesterol. The process is aerobic and requires reduced pyridine nucleotide. This process appears to be a biological analog of cyclization of 5-hexenyl radicals, a process studied extensively in connection with mechanistic investigations of cyclopolymerization. The cationic or oxygen initiated cyclization of squalene to lanosterol was proposed to occur by an intramolecular series of four successive cyclization reactions with the neighboring double bond reacting with the active species generated.59 This process is analogous to cyclopolymerization with the exception that no intermolecular interactions are proposed.
Norethisterone exposure alters the transcriptome of Marine Medaka (Oryzias melastigma) larvae
Published in Chemistry and Ecology, 2021
Xueyou Li, Xiaona Lin, Yuebi Chen, Zhongduo Wang, Yusong Guo, Gyamfua Afriyie, Ning Zhang, Zhongdian Dong
Many progestins have strong biological activity, even at ng/L, which poses a potential threat to aquatic organisms [35–37]. In addition, coexistence with other pollutants may cause more complex effects [35]. The role of synthetic progestins, such as NET, in fish, may be multifaceted, and the potential mechanisms are still uncertain. This may depend on the progestin type, exposure time, species, and developmental stage [6]. By changing gene expression and disrupting the normal signal transduction cascade, even low concentrations of NET continuously discharged into the aquatic environment may have numerous consequences for the health of aquatic vertebrates [27,37–39]. Studies have shown that progestins can regulate the expression of genes involved in steroid production [10,31,40,41]. In this study, even low-level NET exposure inhibited the synthesis of cholesterol-related genes, including 24-dehydrocholesterol reductase (dhcr24), 7-dehydrocholesterol reductase (dhcr7), 3-hydroxy-3-methyl Glutaryl-coenzyme a reductase (hmgcra), squalene epoxidase (sqle), and lanosterol 14-alpha demethylase (cyp51a1) (Figure S2). Of these, sqle can catalyze the oxidation of squalene to (S)-2,3-epoxyquinene, which is the rate-limiting enzyme in steroid synthesis [42]. Hmgcr is the rate-limiting enzyme gene in cholesterol synthesis and non-sterol isoprene synthesis [43]. These results suggest that a low concentration of NET may affect steroid synthesis by affecting the expression of steroid related genes in marine medaka.
New non-conventional lithocholic acid derivatives: synthesis and characterisations for mesogenic properties
Published in Liquid Crystals, 2020
A large amount of work has been carried out for the formation of liquid crystals (LC) using cholesterol, but not using lithocholic acid. These are naturally occurring bile acid complex molecules and it is hard to change their structure and morphology. Cholesterol derivatives are basically the class of cholestanes and cholic acid derivatives are the class of cholanes. These are made of cells either from sterols, i.e. lanosterol (animals and fungi), or from cycloartenol (plants). These molecules possess chirality and are thus optically active. Bile acids and their derivatives display self-association in aqueous solutions [1–4] and the chemical structure of each bile acid is responsible for the extent to which it aggregates [5]. Due to their unique assembling properties, bile acids and bile salts have gained importance in supramolecular chemistry [6,7]. The lithocholic acid and cholesterol molecule contain a steroid backbone like all bile acids and ends in a four-carbon chain containing carboxyl group (i.e. lithocholic acid). It also has a hydroxyl group on the far end of the molecule as can be seen in the chemical structures given below.
Itraconazole-loaded micelles based on linear-dendritic poly (ethylene glycol)-b-poly (ε-caprolactone)
Published in Journal of Biomaterials Science, Polymer Edition, 2018
Shida Li, Wenxiu Wei, Weiping Jia, Lechen Zhao, Hongmei Xu, Feilong Zhou, Li Zhu, Zhimei Song, Sijia Feng, Runliang Feng
ITR, as a tirazole antifungal drug, mainly inhibits 14α-demethylation of lanosterol in the biosynthesis of ergosterol which is a main component of fungi cell membrane. Once ergosterol level decreases or ergosterol is replaced with unusual sterols, fungal membrane permeability will obviously be changed, resulting in cytoplasm outflow and fungi death. Its target molecule is cytochrome P450-Erg11p or Cyp51p, a catalyst for the oxidative removal of 14α-methyl of lanosterol in the fungi cells. Ergosterol synthesis proceeds in mitochondria and endoplasmic reticulum. Hence, to display its antifungal effect, sufficient ITR must penetrate into the fungal cell membrane [25,31,32]. As a surface-active copolymer like MPEG-PCL, APEG-PCL would interact with Candida albicans whose cell membrane contains hydrophilic protein/saccharides and hydrophobic phospholipid. The interaction promoted the cellular uptake of ITR-M via endocytosis pathway, leading to better activity although drug’s release from micelles was much slow in the culture medium. The slow and sustained release of ITR from the internalized micelles should make ITR keep working for a long time. Small particle size (section 3.1) of the ITR-M should be of benefit of enhancing drug’s penetration into fungal cell. In contrast, crude itraonazole’s uptake mode might be a concentration-dependent diffusion [33]. The poor dispersion of ITR in the culture medium caused a slow diffusion of ITR into the fungal cells. Combination of crude ITR’s slow diffusion with its fast release resulted in its comparable antifungal activity to that of ITR-M.