Methylsterols

Dreier et al. [44] determined sterols in lacustrine sediments. Samples of wet lacustrine sediments were heated under anoxic conditions at 150, 175, 200 and 250°C for five days at 175°C for five days with influx of potassium hydroxide and methanol to remove sterols and at 175°C for 12, 18, 24 and 48h, after which extraction was performed. Heating the sediment increased the amounts of extractable sterols provided that the temperature did not exceed 200°C, because degradation became rapid above that temperature. The behaviour of sterol ketones was similar, but the temperature limit was slightly higher. The various levels of the sterols extracted are tabulated 4-methylsterols had a high stability towards thermal degradation under the conditions used. 

Methylation at C-4 of sterol nucleus was one of the other factors affecting activity enhancement. Thus, in general, 4-methylsterols (14,15) and 4,4-dimethylsterols (8,13) exhibited higher activity than 4-desmethylsterols. A similar structure-activity relationship was observed also in the HHPA-induced inflammation on mouse ear [35]. Whereas cholesterol (7) did not show inhibitory activity, several 4,4-dimethylcholestane derivatives, 0-12, exhibited activity. 4,4-Dimethylcholestane-3a,5a-diol (12) was the most potent inhibitor its activity was comparable to that of ursolic acid (210) [35]. Compound 12 reduced also the inflammation induced by teleocidin B (3), one of the indole alkaloid-type of tumor promoters [53]. 

Sitosterol and stigmasterol were the major components of celery seed oil. The other components were cholesterol, brassicasterol, campesterol, 97-campesterol, 95-avenasterol, 97-stigmasterol and 9 7-avenasterol (Zlatanov and Ivanov, 1995). Oil bodies isolated from celery cell suspension cultures contained at least 60% of the total steryl ester present in the cells. Free sterols comprised < 0.5% of the total lipid in the oil body. Sterylesters constituted 4.5% of the total lipid of celery oil bodies. The proportion of precursor 4-methylsterols in the free sterol fraction of celery was greater in the oil body (Dyas... 

Lipases liberated from the testa and the cross cells promote rapid hydrolysis of the oil, and therefore, it should be extracted within hours of milling. Attempts have been made to upgrade oil with 30% free acid by reaction with glycerol and the enzyme Lipozyme Mucor miehei lipase) followed by neutralization. The major acids in rice bran oil are palmitic (12-18%, typically 16%) oleic (40-50%, typically 42%), and linoleic acid (29 2%, typically 37%). The oil contains phospholipids ( 5%), a wax that may be removed and finds industrial use, and unsaponifiable matter including sterols, 4-methylsterols, triterpene alcohols, tocopherols, and squalene among others. 

Improved methodology for the rapid assay of hepatic HMG-CoA reductase has been described and new and simplified assays are available for cholesterol 7a-hydroxylase, 4-methylsterol oxidase, 3/3-hydroxy-steroid dehydrogen-ase, the biosynthesis of bile acids, and microsomal cholesterol levels.The rate of biosynthesis of gibberellins has been monitored by a bioassay based on /3-amyrin production of Amaranthus seeds. 

Ever since, dinosterol and many other 4-methylsterols (XII),... 

Table 5.1 Characteristic major sterols in phytoplankton classes (after Volkman et al. 1998). Positions of unsaturation are given by A nomenclature (see Box 2.8), 4Me = 4-methylsterols, dinos = dinosterol.The Prochlorophyceae and Cyanophyceae do not appear to synthesize sterols...

Fig. 5.16 Summary of postulated diagenetic pathways for 4-methylsterols (large arrows indicate biogenic input aromatic steroid formation as for regular steroids in Fig. 5.14 after de Leeuw et al. 1989 Peakman et al. 1992 Rechka et al. 1992).

Sterols are also present in free and esterified forms. We will take the review of Folstar (1985) as the reference. Free sterols constitute on average 2.2% of the total lipids and the esters with fatty acids 3.2 Mi. In the sterolic fraction, 92.7 % are 4-desmethylsterols, 2 % are 4-methylsterols and 5.1% are 4,4-dimethyl-sterols. The three major components belong to the first category sitosterol (53-54% of the sterolic fraction), stigmasterol (20—22 %) and campesterol (18-19%), The qualitative composition has been reported to be independent of the geographical origin. 

Saturated plant sterols, referred to as stands, occur in nature only in trace amounts. 4-Methylsterols are intermediates in sterol biosynthesis and are always present in fats and oils accompanying 4-desmethylsterols. The predominant 4-meth-ylsterols are citrostadienol, obtusifoliol, gramisterol, and cycloeucalenol. 4,4 -Dim-... 

The composition of the triterpene alcohols, 4-methylsterols and sterols are given in Tables 3.145-3.147. 

The triglyceride compositions of coconut and palmkernel oils are compared in Table 3.86 (Bezard etaL, 1971a,b). The sterols, 4-methylsterols and triterpene alcohols are given in Tables 3.145-3.147 (Fideli et al, 1966 Gracian and Martel, 1969 Itoh etal, 1973). 

Other minor components characterized include tocopherols (90 mg/kg), triterpenol alcohols and cinnamic acid esters, sterols and 4-methylsterols. These are characteristic of the oil (Derbesy and Richert, 1979 Peers, 1977 Itoh et al, 1974). The major triterpene alcohols are a- and jS-amyrin, butyrospermol and lupeol. The major sterols are a-spinasterol, previously confused with )8-sito-sterol and A7-stigmasterol (Derbesy and Richert, 1979 Itoh era/., 1974). (Tables 3.145-3.147). 

Table 3.146 4-Methylsterols (mg/kg) of some commonly occurring vegetable oils (adapted from Itoh etal., 1973a, b, 1974)... 

Fig. 7.11 Outline of the pathway from squalene epoxide, the common Unk between all triterpenoids sensu latiore, to cholesterol and P-sitosterol. Carpesterol might be synthesized via cycloartenol —> 24-methylenecycloartenol —> subsequent methylation at C-28 —> 4-methylsterol congener —> oxidation at C-6 —> 30-acylation...

Special laboratory cartilage Sterol analysis (P, tissue, lymphoblasts) 4-methylsterols 4,4 -dimethylsterols> 4-carboxysterols T T... 

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