Conventional Sterols

The systematic analyses of Bergmann dealt with more than fifty species of sponges and his elucidation of sterol structure was limited to the major components. 

Doree s clionasterol was found to be a mixture of poriferasterol (171) and a monounsaturated sterol (166) for which the original name was retained 178). These two sterols were subsequently reported as the most common ones in sponges (76,17). 

A C29-sterol, chondrillasterol (172), which seems to be confined solely to Porifera in the animal kingdom, was reported as the major sterol component of Chondrilla nucula (23). 

Among the Cis-sterols, 24-methylenecholesterol (164) which is widely distributed in marine organisms was found in Chalina arbuscula and Tetilla laminaris (25). Henze s spongosterol from Suheritesv/2is separated into neospongosterol (159) and cholestanol (147), (27). Cholestanol (147) was found in eleven other sponges (77), often as a major sterol constituent, and cholesterol (149) was found in Microciona prolifer a and Halichondria panicea (24). 

Bergmann also recognized the importance of sterol analysis for the taxonomy and phylogeny of sponges, and attempted to correlate sterol distribution with sponge taxonomy (77). 

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It has been suggested [6] that these unusual sterols, especially in those cases where these unusual sterols comprise the entire sterol content of the organisms, likely replace conventional sterols as cell-membrane components. Evidence for this comes from subcellular fractionation and subsequent analysis of two marine sponges [10]. The sterol composition of the membrane isolates was found to be identical to that of the intact sponge. Most common variation of the marine sterol is in the side-chain, situated deep in the lipophylic environment of the phospholipid bilayer. This suggests that unusual fatty acids might accompany the sterols, and indeed this is often the case [8]. 

In addition to cholesterol and 5a-cholest-7-en-3y8-ol, many C2g and C29 conventional sterols are present in Echinodermata. These sterols are probably derived from the diet. However, echinoderms are able to synthesize sterols. Thus, [ C]mevalonic acid was incorporated into squalene, lanosterol and desmosterol by the sea urchin. Echinus esculentus [87]. The ability of ophiurpids to synthesize sterol from [ C]acetate has also been demonstrated [88]. Sterol biosynthesis by a holothuroid was first investigated by Numura [89], and sterol biosynthesis from [ C]acetate in sea cucumbers has also been reported [90]. 

Figure 19.14 Main conventional sterols encountered in demosponges.

Many examples of conventional sterols, but with short side chains, were isolated from Damiriana hawaiiana... 

Sodano, G. (1979) Non-conventional sterols from marine sponges occurrence and biosynthesis, in Biologic des Spongiaires (eds C. Lwi and N. Boury-Esnault), Colloques Internationaux du CNRS, No. 291, Editions du CNRS, Paris, pp. 393-399. 

Regarding sterols, only three species, Myriapora trun-cata (Mediterranean Sea), Bugula neritina (California, Florida, and China), and Biflustra grandicella (China), appear to have been studied comprehensively. The first species contains only A7-3,5,6-trihydroxysterols, the second species contains exclusively conventional sterols... 

The sterol composition of most arthropods concerns mainly cholesterol, whose average levels are often more than 90%. Regarding other conventional sterols in cmstaceans, mention should be made of the hermit crab, Pagurus bemhardus, whose eggs contain approximately 40% desmosterol (Teshima, 1991). Similar results (cholesterol 70%, desmosterol 20%) have been obtained recently in the snow crab, Chionoecetes opilio (Souchet and Laplante, 2007). 

Table 1 lists the conventional sterols reported in sponges. The term conventional is used to cover sterols with the conventional Cig tetracyclic nucleus having the usual Cs side-chain or else modified by the addition of one or two carbon atoms at C-24. The 24-norsterols are also included. 

Amphotericin B Cholesteryl (Amphotec) [Antifungal/Polyene Mocrollde] Uses AspCTgillosis if intolCTant/refractory to conventional amphotericin B, systemic candidiasis Action Binds ceU membrane sterols, alters permeability Dose Adults Peds. Test dose 1.6—8.3 mg, over 15-20 min, then 3-4 mg/kg/d 1 mg/kg/h inf w/ renal insuff Caution [B, ] Disp Inj SE Anaphylaxis fever, chills, HA, nephrotox, -1- BP, anemia Notes Do not use in-line filter Interactions See Amphotericin B EMS See AmphotCTicin B OD May cause cardiac arrest s ptomatic and supportive... 

The influence of native vegetation on the composition of SOM was studied in well-dated volcanic soils at the Mount Etna region, Sicily, Italy. Whole soil samples were taken under chestnut and oak stands, and their humic acids (Baglieri et al., 2007) and nonfractionated whole soil samples were analyzed by Py-FIMS. The proportions of compound classes in Table 14.4 show that the roughly 2000-year-old soil under an oak stand was significantly richer in lipids, sterols, and free fatty acids than was the soil under chestnut. In another pair of soil samples with a longer period of soil formation (about 7000-9000 years), the difference between oak and chestnut was +4.2% for lipids, +2.6% for sterols and +2.5% for free fatty acids (not shown). This predominance of aliphatics in the soils under oak confirms Nierop et al. (2003), who also found the release of aliphatics from oak stands into soil by conventional lipid extractions and GC/MS. 

The fatty/waxy products contained the lipophilic substances, including fatty oils, waxes, resins and colorants. Valuable pharmacological effects were proved for some minor constituents of these products (e.g. triterpenes, diterpenes, sterols and carotenoids). Thin layer chromatography and on-line UV-VIS spectroscopy were used for the quick identification and quantity determination of these compounds using authentic samples as standards. The SFE method proved favorable in terras of both extraction yield and speed of carotenoids. The CO2 extracts of the lavandin, clary sage and thyme have been enriched in triterpenic compounds (a-es P-amyrin, oleanic acid, ursolic acid, etc.) and phytosterols. Both free and esterified triterpenoids were present in the extracts of the different samples. Furthermore camosol and other diterpenes were detected in the SFE extract of Lamiaceae plants. The fatty acid composition was only slightly different for extracts obtained by SFE and conventional hexane extraction. 

The similarity in the fatty acid composition of HOSO and olive oil may lead to cases of adulteration or fraud, in view of the price difference between the two oils. These adulterations may be difficult to detect through conventional analytical methods. The nature of an oil can be traced through a study of its sterol composition. 

The concentration of LDL-cholesteroi in the blood is a function of its rate of production and rate of removal from the bloixistream. Diet influences LDL-cho-lesterol by changing its rate of removal or clearance, according to the following scenario. Let us briefly return to the topics of proteins and DMA, A transcription factor called sterol response element binding protein (SREbP) binds to a stretch of DNA called the sterol response element. The sterol response element has the structure CACCCCAC. In discussing any sequence of DNA, it is conventional to... 

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