Fumiko U. Rosenstein

Sterols of cucurbitaceae: The configurations at C-24 of 24-Alkyl-Δ5-,Δ7- and Δ8-sterols

The major sterols of the seeds ofBenincasa cerifera, Cucumis sativus, Cucurbita maxima, C. pepo andTrichosanthes japonica and of the mature plant tissues (leaves and stems) ofCitrullus battich, Cucumis sativus andGynostemma pentaphyllum of the family Cucurbitaceae were 24-ethyl-Δ7-sterols which were accompanied by small amounts of saturated and Δ5-and Δ8-sterols. The 24-ethyl-Δ7,22,Δ7,25(27) and Δ7,22,25(27)-sterols constituted the predominant sterols for the seed materials, whereas the 24-ethyl-Δ7 and Δ7,22-sterols were the major ones for the mature plant tissues. The configurations of C-24 of the alkylsterols were examined by high resolution1H NMR and13C NMR spectroscopy. Most of the 24-methyl- and 24-ethylsterols examined which lack a Δ25(27)-bond (i.e., 24-methyl-, 24-methyl-Δ22-, 24-ethyl- and 24-ethyl-Δ22 sterols) were shown to occur as the C-24 epimeric mixtures in which the 24α-epimers predominated in most cases. The 24-ethylsterols which possess a Δ25(27) (i.e., 24-ethyl-Δ25(27)-and 24-ethyl-Δ7,22,25(27)-sterols) were, on the other hand, composed of only 24β-epimers. The Δ8-sterols identified and characterized were four 24-ethyl-sterols: 24α-and 24β-ethyl-5α-cholesta-8,22-dien-3β-ol, 24β-ethyl-5α-cholesta-8,25(27)-dien-3β-ol and 24β-ethyl-5α-cholesta-8,22,25(27)-trien-3β-ol. This seems to be the first case of the detection of Δ8-sterols lacking a 4-methyl group in higher plants, and among the four Δ8-sterols the latter two are considered to be new sterols. The probable biogenetic role of the Δ8-sterols and the possible biosynthetic pathways leading to the 24α- and 24β-alkylsterols in Cucurbitaceae are discussed.

Sterols of the Cucurbitaceae

Abstract The sterol constituents of 32 seed and mature plant (leaves and stems, pericarp of the fruit and roots) materials from the 12 genera of the family Cucurbitaceae were investigated, and 44 sterols were identified or newly characterized. The sterols found were those possessing the following 7 types of skeletons: saturated, and Δ 5 -, Δ 7 -, Δ 8 -, Δ 8(14) - and 14α-methyl-Δ 9(11) -unsaturated, and 14α-methyl-9β,19-cyclo skeletons, with the side chains of 24-unsubstituted, Δ 24 -, 24-methyl-, 24-methyl-Δ 22 -, 24-methylene-, 24-ethyl-, 24-ethyl-Δ 22 -, 24-ethyl-Δ 24(250 -, 24-ethylidene-, 24-ethyl-Δ 25 - and 24-ethyl-δ 22,25 -substituted, 24-methylene-25-methylated and 24,24-dimethylated (24,24-dimethyl-, 24,24-dimethyl-Δ 22 - and 24,24-dimethyl-Δ 25 -substituted) structures. The configurations at C-24 of the 24-alkylsterols were examined by high resolution 1 H NMR and 13 C NMR spectroscopy. The 24-methyl- and 24-ethylsterols lacking a Δ 25 -bond examined (i.e. 24-methyl-, 24-methyl-Δ 22 -, 24-ethyl- and 24-ethyl-Δ 22 -sterols) were shown to occur as the C-24 epimeric mixtures, or as a single diastereoisomer, either 24α- and 24β-epimer. The 24-ethylsterols bearing a Δ 25 -bond (i.e. 24-ethyl-δ 25 - and 24-ethyl-Δ 22,25 -sterols) were, on the other hand, composed of only 24β-epimers. The possible biosynthetic sequences to the cucurbitaceous sterols are discussed.

Compositions of triterpene alcohols of seeds and mature plants of family cucurbitaceae

Compositions of the triterpene alcohol fractions of the unsaponifiable lipids obtained from 28 seed and mature plant [aerial parts (leaves and stems), pericarp of the fruits, and roots] of 13 genera of the family Cucurbitaceae were determined by gas liquid chromatography (GLC) on an OV-17 glass capillary column. Among the 14 tetracyclic and pentacyclic triterpene alcohols identified, isomultiflorenol was found to be the major component for most of the seed materials. The abundance of this triterpene suggests that it may be a taxonomical marker of the seeds of Cucurbitaceae since only a few higher plants are known to contain isomultiflorenol. The mature plant materials of the Cucurbitaceae, on the other hand, were shown to contain either one or some of the common triterpene alcohols such asα- andβ-amyrins, cycloartenol and 24-methylenecycloartanol as the major triterpene constituents.

Copper Deficiency Increases In Vivo Hepatic Synthesis of Fatty Acids, Triacylglycerols, and Phospholipids in Rats

Abstract This study examined the influence of dietary copper status on the in vivo hepatic fatty acid synthesis and the incorporation of nascent fatty acids into various hepatic lipid classes. Fifty weanling male Sprague-Dawley rats were assigned to two dietary treatments, copper deficient (5.4 nmol/g of diet) and copper adequate (102 nmol/g of diet). After 7 weeks of treatment, rats were injected with 0.111 MBq of [1-14C] acetate (1.85 GBq/mM)/100 g body wt through the femoral vein. Five rats from each treatment were sacrificed at 3, 6, 9, 12, and 24 min after injection. Radioactivities of nascent fatty acid samples were used to determine relative rates of fatty acid synthesis and their assembly into triacylglycerols and phospholipids. Linear increases were observed up to 12 min after injection for total hepatic fatty acid synthesis and their assembly into triacylglycerols and phospholipids for both treatments. In addition, 46% and 30% of total fatty acid synthesized were assembled into triacylglycerols and phospholipids, respectively, for both groups. Furthermore, hepatic fatty acid synthesis and assembly into triacylglycerols and phospholipids were enhanced more than 2-fold by copper deficiency when the data were expressed as per liver per 100 g body weight.

Hydrogenation of stigmasterol

Hydrogenations of stigmasterol over 5% Pd/C, 5% Ru/C, Pt, Raney Ni, Raney Co, Ni/kieselguhr, and tris(triphenylphosphine)chlororhodium catalysts and with diimide generated from hydrazine andp-toluenesulfonylhydrazide were studied to determine the best conditons for the selective reduction of the Δ22 double bond. The best results (maximum stigmasterol reduction, minimum stigmastanol formation) were obtained with Raney nickel at room temperature and atmospheric pressure.

Isolation of brassicasterol from steam deodorizer distillate of rapeseed oil: Some properties of its acetate tetrabromide and its reduction to 22,23-dihydrobrassicasterol

Brassicasterol (5,22-ergostadien-3β-ol) was isolated from the steam deodorizer distillate of rapeseed oil and purified by acetylation, bromination, chromatography on 20% AgNO3/SiO2 columns and hydrolysis. Brassicasteryl and stigmasteryl (5,22-stigmastadien-3β-ol) acetates were brominated, and the yields of products and solubilities of the tetrabromides from the two steryl acetates were compared. Stigmasteryl acetate tetrabromide is less soluble than the corresponding brassicasteryl derivative; yet the latter precipitates selectively during bromination of a mixture of the two steryl acetates. This is explained on the basis of the stereochemistry of the bromine atoms in the side chains of the two steryl acetate tetrabromides. Hydrogenation of brassicasteryl acetate over Raney nickel gave the 22,23-dihydro derivative in excellent yield. The latter was separated from small amounts of ergostanyl acetate on a 20% AgNO3/SiO2 column.

Alterations in Lipid Composition and Fluidity of Liver Plasma Membranes in Copper-Deficient Rats

Abstract In view of the importance of membrane fluidity on cell functions, the influence of phospholipid acyl groups on membrane fluidity, and the changes in lipid metabolism induced by copper (Cu) deficiency, this study was designed to examine the influence of dietary Cu on the lipid composition and fluidity of liver plasma membranes. Male Sprague–Dawley rats were divided into two dietary treatments, namely Cu deficient and Cu adequate. After 8 weeks of treatment, liver plasma membranes were isolated by sucrose density gradient centrifugation. The lipid fluidity of plasma membranes, as assessed by the intramolecular eximer fluorescence of 1,3-di(1-pyrenyl) propane, was significantly depressed by Cu deficiency. In addition, Cu deficiency significantly reduced the content of arachidonic and palmitoleic acids but increased the docosatetraenoic and docosahexaenoic acids of membrane phospholipids. This alteration in unsaturated phospholipid fatty acid composition, especially the large reduction in arachidonic acid, may have contributed to the depressed membrane fluidity. Furthermore, Cu deficiency also markedly altered the fatty acid composition of the triacylglycerols associated with the plasma membranes. Thus, the lipid composition and fluidity of liver plasma membranes are responsive to the animals Cu status.

Purification of sitosterol

Sitosterol and stigmastanol are obtained from the Raney nickel catalyzed hydrogenation of stigmasterol. The sitosterol was separated from stigmastanol by silica gel column chromatography of its dibromide. Sitosterol was also obtained from the steam deodorizer distillate of crude cottonseed oil and purified by manifold recrystallizations of the free sterol from isopropanol and its acetate from alcohol-acetic acid mixtures at a low temperature.

Selective uptake and lack of dealkylation of phytosterols by cactophilic species ofDrosophila

The selective absorption of cholesterol and campesterol and discrimination against sitosterol was demonstrated withDrosophila mojavensis andDrosophila nigrospiracula, using a synthetic medium and 2 natural host cacti. Preferential absorption of trace amounts of phytosterols from a large quantity of other lipids occurred whenD. arizonensis andD. mojavensis were reared from agria cactus. The absence of dealkylation of sitosterol to cholesterol was demonstrated withD. mojavensis andD. mettleri, reared on a sterol-deficient medium supplemented with sitosterol.

Purification of campesterol and preparation of 7-dehydrocampesterol, 7-campestenol and campestanol

Campesterol ([24R]-24-methyl-5-cholesten-3β-ol) was isolated from a soybean sterol mixture and purified on a small scale by column chromatography and on a large scale by crystallization from acetone to 97% purity. From this, 7-dehydrocampesterol ([24R]-24-methyl-5,7-cholestadien-3β-ol) and campestanol ([24R]-24-methyl-cholestan-3β-ol) were prepared. The acetates and benzoates of all four compounds also were obtained and compared to the corresponding members of the ergostane series.