Sterol metabolism. XXVI. Pyrolysis of some sterol allylic alcohols and hydroperoxides

The thermal decomposition of the allylic alcohols 5α-cholest-6-ene-3β,5-diol, cholest-5-ene-3β,7α-diol, and cholest-5-ene-3β,7β-diol and of the allylic hydroperoxides 3β-hydroxy-5α-cholest-6-ene-5-hydroperoxide, 3β-hydroxycho lest-5-ene-7α-hydroperoxide, and 3β-hydroxycholest-5ene-7β-hydroperoxide to six common major pyrolysis products cholest-5-ene-3β,7α-diol, cholest-5-ene-3β,7β-diol, 3β-hydroxycholest-5-en-7-one, cholesta-3,5-dien-7-one, cholesta-4,6-dien-3-one, and cholesta2,4,6-triene was established.     

Sterol metabolism. XLI. Cholesterol A-ring autoxidations

Chromatographic and spectral evidence is adduced for the presence of cholest-5-en-3-one, cholest-4-en-3-one, and cholest-4-ene-3,6-dione in samples of cholesterol aged naturally in air or subjected to irradiation in air by ⁶⁰Co gamma radiation. These findings establish an additional mode of air oxidation of cholesterol to A-ring 3-ketones. Moreover, the oxidation by air of cholest-5-en-3-one induced by ⁶⁰Co gamma radiation yielded cholest-4-en-3-one, cholest-4-ene-3,6-dione, and the epimeric 3-oxocholest-4-ene-6-hydroperoxides. Cholest-4-en-3-one was not altered by irradiation in air, nor was cholesterol isomerized to cholest-4-en-3β-ol upon irradiation. From these observations it is deduced that the radiation-induced A-ring dehydrogenation of cholesterol yields initially cholest-5-en-3-one which upon isomerization yields cholest-4-en-3-one not further oxidized and which by a second oxidation yields the epimeric 3-oxocholest-4-ene-6-hydroperoxides which decompose to cholest-4-ene-3,6-dione.     

24-hydroxycholesterol levels in human brain

24-Hydroxycholesterol (cerebrosterol, cholest-5-ene-3β;, 24ξ-diol) occurs at low levels in human (Di Frisco , De Ruggieri and Ercoli , 1953; Ercoli and De Ruggieri , 1953a, 19536; Schubert , Rose and Burger , 1961; Van Lier and Smith , 1969 , 1970), equine (Ercoli , Di Frisco and De Ruggieri , 1953a; Ercoli and De Ruggieri , 1953a, 1953b; Fieser , Huang and Bhattacharyya , 1957) and bovine (Richter and Dannenberg , 1969) brain tissue. Only one of two possible C-24 epimeric alcohols appears to occur in human brain (Van Lier and Smith , 1970) and the sterol may be regarded as a true endogenous trace-level sterol and not as an artifact of autoxidation derived during isolation and analysis. As a phase of our continuing interests in the presence of trace-level polar sterols in human tissues (Van Lier and Smith , 1967 , 1969, 1970 , 1971a; Smith and Van Lier , 1970), we sought to measure levels of 24-hydroxycholesterol in different parts of human brain by gas chromatographic means. The present report deals with our measurements of 24-hydroxycholesterol in human cortex, subcortical white matter, midbrain, pons, and cerebellum.     

The conversion of 5α-lanost-24-ene-3β,9α-diol and parkeol into poriferasterol by the alga Ochromon as malhamensis

The 4,4-dimethylsterols 4α-lanost-24-ene-3β,9α-diol-[2-³H₂] and parkeol-[2-³H₂] were synthesized from lanosterol and subsequently incubated with cultures of Ochromonas malhamensis. 5α-Lanost-24-ene-3β,9α-diol was converted into poriferasterol with three times the efficiency of parkeol. Clionasterol was also found to be labelled from both parkeol and 5α-lanost-24-ene-3β,9α-diol. No significant incorporation of radioactivity into sterols was obtained after feeding 5α-lanost-24-ene-3β,9α-diol to higher plants, the chlorophyte alga Trebouxia, yeast or a cell free homogenate of rat liver.     

南海疏枝刺柳珊瑚中甾醇类化合物的研究

本文对采自海南三亚海域的疏枝刺柳珊瑚(Echinogorgia pseudossapo)化学成分进行研究,分离到11个甾醇类化合物。经波谱数据分析,分别鉴定为cholest-5-en-3β-ol(1),24-methylene-cholest-4-ene-3β,6β-diol(2),24-norcholesta-22-en-3β-ol(3),acanthovagasteroid A(4),calicoferol E(5),calicoferol F(6),6-hydroxy-cholest-4-ene-3-one(7),echinoflorasterol(8),echissaposterol(9),24-methylcholest-5-en-3β,7α-diol(10)和24-methylcholest-5,22(E)-dien-3β,7α-diol(11)。除化合物8外,其余化合物均首次从该种海洋动物中分离得到。     

The isolation of cholest-5-ene-3β,26-diol from human brain (Short Communication)

Cholest-5-ene-3beta,26-diol, isolated from human brain, was further characterized by oxidation to 3-oxocholest-4-en-26-ol and to 3-oxocholest-4-en-26-oic acid. Identification was achieved by comparison (by t.l.c., g.l.c. and g.l.c.-mass spectrometry) with corresponding reference compounds derived from kryptogenin.     

A rapid,sensitive method for simultaneous measurements of tissue levels of oxygenated derivatives of cholesterol

A mass spectrometric procedure which utilizes multiple selected ion monitoring (SIM) for measuring the tissue levels of cholest-5-en-3β,7α-diol, cholest-5-en-3β,7β-diol, cholest-5-en-3β,25-diol, and cholest-5-en-3β-ol-7-one is described. Trimethylsilyl ethers (TMS) of sterols in a lipid extract are analyzed directly by focusing the ions at $\text{m}\text{e}$ 546, 472, and 443. Endogenous cholesterol serves as an internal standard and its concentration is determined by gas chromatography. The sensitivity of this method has allowed measurement of 2 ng of oxygenated sterol which corresponded to the amount present in 1 mg of rat liver.     

Sterols of Agarum cribosum: desmosterol in a brown alga

The sterol composition of the cold water brown alga Agarum cribosum was determined by GC—MS. Six of the seven sterols found were identified as stigmata-5,(E)-24(28)-dien-3β-ol (fucosterol), 24-methylenecholest-5-en-3β-ol (24-methylenecholesterol), cholest-5-en-3β-ol (cholesterol), 3β-hydroxycholest-5-en-24-one (24-ketocholesterol), 24ξ-stigmasta-5,28-diene-3β,24-diol (saringosterol) and cholesta-5, 24-dien-3β-ol (desmosterol).     

Selective oxidation of steroidal allylic alcohols

Pyridinium chlorochromate in CH₂Cl₂ containing pyridine (2%) at 2—3°C has been found to effect the high yield selective oxidation of the hydroxyl function of a number of steroidal allylic alcohols. Under these conditions the oxidation of cholest-4-cn-3β-ol to the corresponding ketone was effected in 92% yield. Only the allylic hydroxyl function of 5α-cholest-8(14)-ene-3β,15α-diol, 5α-cholest-8(14)ene-3β,15β-diol and 5α-cholest-8(14)-ene-3β,7β-diol was oxidized under these conditions to give the corresponding α,β-unsaturated ketones in high yields. 5α-Cholest-8(14)-ene-3β,7α,15α-triol gave 5α-cholest-8(14)-ene-3β,7α-diol-15-one in 82% yield. Attempted oxidations of the 5α-cholestan-3β,15α-diol and 5α-cholest-7-ene-3β,15α-diol, both lacking an allylic hydroxyl function, under these conditions, were unsuccessful. Selective oxidation of the allylic alcohol function of 5α-cholest-8(14)-ene-3β,15β-diol using activated manganese dioxide gave 5α-cholest-8(14)-en-3β-ol-15-one in high yield while oxidation of the corresponding 15α-hydroxy epimer using manganese dioxide was unsuccessful.     

Sterol hydroperoxide metabolism by Salmonella typhimurium

In order to rationalize multiphasic dose-response data evincing mutagenicity towards Salmonella typhimurium TA1537 for sterol hydroperoxides 3 beta-hydroxy-5 alpha-cholest-6-ene-5-hydroperoxide and 3 beta-hydroxycholest-5-ene-7 alpha-hydroperoxide their metabolism by the bacterial test strain was investigated. The 5 alpha-hydroperoxide was isomerized to the 7 alpha-hydroperoxide and reduced to 5 alpha-cholest-6-ene-3 beta,5-diol; the 7 alpha-hydroperoxide was reduced to cholest-5-ene-3 beta,7 alpha-diol and transformed to 3 beta-hydroxycholest-5-en-7-one. The 3 beta,5 alpha-diol and 3 beta,7 alpha-diol were not interconverted nor was either transformed to the 7-ketone.     

Comparative placental steroid synthesis. II. C19 steroid metabolism by guinea-pig placentas and fetal adrenals in vitro

Placental homogenates from guinea-pigs at 16, 20, 35 and 55 days gestation were incubated with 7α-³H-dehydroepiandrosterone and 4-¹⁴C-androstenedione and analyzed for conversion products by reverse isotope dilution methods. ¹⁴C-3α-Hydroxy-5α-androstan-17-one, ¹⁴C-androstane-3α, 17β-diol and ³Handrost-5-ene-3β, 17β-diol were isolated from homogenates incubated with substrates for 2 hours. ³H, ¹⁴C-Testosterone was isolated from preparations incubated for 15 minutes or with high substrate: tissue ratios. Androst-4-ene-3, 17-dione, 5α-androstane-3, 17-dione, 5β-androstanedione derivative and C₁₈ steroid formation could not be demonstrated. These results demonstrate the capacity of guinea-pig placentas to convert dehydroepiandrosterone and androstenedione to testosterone and to derivatives reduced in ring A (5α) and at carbon 17. The activity of the Δ⁵-3β-hydroxysteroid dehydrogenase enzyme system appears to have been rate limiting.Homogenates of adrenals from 44–55 day old fetuses converted 4-¹⁴C-pregnenolone to androst-4-ene-3, 17-dione and 6β- and 11β-hydroxyandrostenedione. A guineapig fetal-placental unit is postulated, with steroid metabolic characteristics different from the human unit. Both permit reduction of fetal adrenal cortisol production and placental removal of C₁₉ steroids.     

Inhibitors of sterol synthesis. Chromatography of acetate derivatives of oxygenated sterols

The separation of the acetate derivatives of a number of oxygenated sterols was achieved by medium pressure liquid chromatography on silica gel columns and by normal and reversed phase high performance liquid chromatography. We have explored the application of these chromatographic systems for the analysis of oxygenated sterols of plasma samples from two normal human subjects. The addition of highly purified [14C]cholesterol to plasma permitted the detection and quantitation of oxygenated sterols formed by autoxidation of cholesterol during processing of the samples. Special attempts to suppress autoxidation of cholesterol included the use of an all-glass closed system for saponification and extraction under argon followed by rapid removal of cholesterol from the polar sterols by reversed phase medium pressure liquid chromatography. Chromatographic analyses of the [3H]acetate derivatives of the polar sterols provided a sensitive approach for the detection and quantitation of the individual oxygenated sterols. Oxygenated sterols detected in plasma included cholest-5-ene-3 beta,26-diol, (24S)-cholest-5-ene-3 beta,24-diol, and cholest-5-ene-3 beta,7 alpha-diol. After correction for their formation by autoxidation of cholesterol during processing of the samples, very little or none of the following sterols were observed: cholest-5-ene-3 beta,7 beta-diol, 5 alpha,6 alpha-epoxy-cholestan-3 beta-ol, 5 beta,6 beta-epoxy-cholestan-3 beta-ol, and cholestane- 3 beta, 5 alpha,6 beta-triol, and the 25-hydroxy, 22R-hydroxy, 21-hydroxy, 20 alpha-hydroxy, and 19-hydroxy derivatives of cholesterol.     

Simultaneous quantification of several cholesterol autoxidation and monohydroxylation products by isotope-dilution mass spectrometry

An assay based on isotope-dilution mass spectrometry with deuterium-labeled internal standards was developed for simultaneous quantification of cholest-5-ene-3 beta,7 alpha-diol (7 alpha-hydroxycholesterol), cholest-5 beta,6 beta-epoxy-3 beta-ol (cholesterol-5 beta,6 beta-epoxide), cholest-5 alpha,6 alpha-epoxy-3 beta-ol (cholesterol-5 alpha,6 alpha-epoxide), cholest-5-en-7-one-3 beta-ol (7-oxocholesterol), cholestane-3 beta,5 alpha,6 beta-triol, cholest-5-ene-3 beta,25-diol (25-hydroxycholesterol), and cholest-5-ene-3 beta,26-diol (26-hydroxycholesterol) in one single serum sample. Recovery experiments and replicate analyses showed that the assay was sufficiently sensitive, accurate, and precise. The concentrations of the listed compounds in sera from 19 healthy subjects were determined and are presented.     

The structural determination of a new steroidal metabolite from the brown alga Sargassum asperifolium

An investigation of the natural products chemistry of the brown alga Sargassum asperifolium from the red sea yielded a new steroidal metabolite, 24-vinyl cholest-4-ene-24-ol-3-one, saringosterone (3), a known steroidal metabolite, 24-vinyl cholest-5-ene-3b,24-diol, saringosterol (4), and known diterpene with a hydroazulene skeleton, dictyone (1). The identification of the isolated metabolites was established mainly by spectral methods and chemical transformation of the dictyone (1) to its acetate (2).     

Furostanol glycosides from Trigonella foenum-graecum seeds

Two new furostanol glycosides trigofoenosides A and D have been isolated from the Trigonella foenum-graecum seeds as their methyl ethers, A-1 and D-1. Their structures have been determined as (25S)-22-O-methyl-furost-5-ene-3β,26-diol, 3-O-α-L-rhamnopyranosyl (1 → 2)-β-D-glucopyranoside; 26-O-β-D-glucopyranoside (A-1) and (25S)-22-O-methyl-furost-5-ene-3β,26-diol, 3-O-α-L-rhamnopyranosyl (1 → 2)-[β-D-glucopyranosyl (1 → 3)]-β-D-glucopyranoside; 26-O-β-D-glucopyranoside (D-1).     

Triterpenoids from Mangifera indica

From the neutral fraction of the n-hexane extract of stem bark of Mangifera indica, (var./cv Banganpalli) six new tetracyclic triterpenoids, cycloart-24-ene-3β,26-diol, the C-24 epimers of cycloart-25-ene-3β,24,27-triol, the C-24 epimers of cycloartane-3β,24,25-triol and 3-ketodammar-24E-ene-20S,26-diol together with the known compounds cycloartenol, α-amyrin, β-amyrin, sitosterol 3β-hydroxycycloart-25-en-26-al, dammarenediol II, the C-24 epimers of cycloart-25-ene-3β,24-diol, 24-methylenecycloartane-3β,26-diol, ψ-taraxastane-3β,20-diol and ocotillol II have been isolated. The acidic fraction of the same extract, on esterification with diazomethane followed by chromatography, yielded methyl mangiferonate, methyl isomangiferolate, methyl mangiferolate and the diazomethane adduct of methyl mangiferolate. The structures were elucidated by spectroscopic and chemical methods.     

Zur biogenese des aza-oxa-spiran-systems der steroidalkaloide vom spirosolan-typ in Solanaceen

5α,6-³H₂-Solacongestidine and 5α,6-³ H₂-(22S)-dihydrosolacongestidine administered to Solanum dulcamara as well as 16-³H₂-(22S: 25R)-22,26-epimino- cholest-5-en-3β-ol (25-isodihydroverazine) and 7α-³H-(22S: 25R)-22,26-epimino-cholest-5-en-3β,16β-diol administered to Solanum laciniatum were converted to coladulcidine and solasodine, respectively. These results are discussed in relation to spirosolane alkaloid biosynthesis.     

Microbiological transformation of diosgenin by resting cells of filamentous fungus,Cunninghamella echinulata CGMCC 3.2716

Microbial transformation of the steroidal sapogenin diosgenin (1) by resting cells of the filamentous fungus, Cunninghamella echinulata CGMCC 3.2716 was studied. Four metabolites were isolated and unambiguously characterized as (25R)-spirost-5-ene-3β,7β-diol-11-one (2), (25R)-spirost-5-ene-3β,7β-diol (3), (25R)-spirost-5-ene-3β,7β,11α-triol (4), and (25R)-spirost-5-ene-3β,7β,12β-triol (5), by various spectroscopic methods (¹H, ¹³C NMR, DEPT, ¹H–¹H COSY, HMBC, HSQC and NOESY). Compound 2 is a new metabolite. The NMR data and full assignment for the known metabolites (25R)-spirost-5-ene-3β,7β-diol (3) and (25R)-spirost-5-ene-3β,7β,11α-triol (4) are described here for the first time. The biotransformation characteristics observed included were C-7β, C-11α and C-12β hydroxylations. Compounds 1–5 exhibited no significant cytotoxic activity to human glioma cell line U87.     

Occurrence of 24-epimers of cycloart-25-ene-3β,24-diols in the stems of Euphorbia trigona

¹³C NMR spectroscopy has demonstrated that the cycloart-25-ene-3β,24-diol isolated from the stems of Euphorbia trigona is a 1:1 mixture of the 24-epimers. This seems to be the first instance of the detection of the natural occurrence of 24-epimeric cycloart-25-ene-3β,24-diols.     

The synthesis of 25-hydroxycholecalciferol-23,23,24,24-t4 of high specific activity

Catalytic tritium reduction of cholest-5-en-23-yne-3beta,25-diol diacetate (VIII) gave cholest-5-ene-3 beta,25-diol diacetate-23,23,24,24-t4 (IX) having a specific activity of 92 Ci/mmol. Bromination, dehydrobromination and hydrolysis of the labelled material gave cholesta-5,7-diene-3beta,25-diol-23,23,24,24-t4 (XI) which was photolyzed to the previtamin and then thermally equilibrated to 25-hydroxycholecalciferol-23,23,24,24-t4 (I).