Dominance of Δ7-sterols in the family caryophyllaceaein the family caryophyllaceae

The predominant 4-desmethylsterols from the leaves of 12 species in 11 genera of the family Caryophyllaceae are 24-ethyl-Δ⁷-sterols. In eight species,Scleranthus annus L.,Paronychia virginica Spreng.,Lychnis alba Mill.,Silene cucubalus Wibel,Dianthus armeria L.,Gypsophilia paniculata L.,Saponaria officinales L. andMyosoton aquaticum (L.) Moench, the major sterols are spinasterol (24α-ethylcholesta-7,22E-dien-3β-ol) and 22-dihydrospinasterol (24α-ethylcholest-7-en-3β-ol), with spinasterol at more than 60% of the desmethylsterol in the latter six species. Both 24α-and 24β-ethyl-Δ⁷-sterols are present in two species,Minuartia caroliniana Walt. andSpergula arvensis L., which possess 24β-ethylcholesta-7,25(27)-dien-3β-ol and 24β-ethylcholesta-7,22E,25(27)-trien-3β-ol as well as spinasterol and 22-dihydrospinasterol.Cerastium arvense L.,C. vulgatum L. andArenaria serpyllifolia L. possess 24-alkyl-Δ⁵ and Δ⁷-sterols. These three species synthesize sitosterol (24α-ethylcholest-5-en-3β-ol), 24ζ-methylcholest-5-en-3β-ol, spinasterol, 22-dihydrospinasterol and the stanols, sitostanol (24α-ethyl-5α-cholestan-3β-ol) and 24ζ-methyl-5α-cholestan-3β-ol. Avenasterol (24-ethylcholesta-7,24(28)Z-dien-3β-ol) was also isolated from five species. Sterol biosynthetic capability may be a useful characteristic in examining the taxonomic relatedness of plants in the Caryophyllaceae.     

Cooccurrence of C-24 alkylated Δ7- and Δ5-Sterols in the leaves ofBeta vulgarisin the leaves ofBeta vulgaris

The 4-desmethylsterols from the leaves ofBeta vulgaris are a mixture of Δ⁷-sterols (71%) and Δ⁵-sterols (29%). The Δ⁷-sterols isolated are spinasterol (24α-ethylcholesta-7,22-dien-3β-ol; 45%), 22-dihydrospinasterol (24α-ethylcholest-7-en-3β-ol; 24%), and avenasterol (24-ethylcholesta-7,24(28)-dien-3β-ol; 1.5%). The Δ⁵-sterols isolated are sitosterol (24α-ethylcholest-5-en-3β-ol; 15%), 24ζ-ethylcholesta-5,22-dien-3β-ol (7.5%), and 24ζ-methylcholest-5-en-3β-ol (7%).     

The sterols ofCucurbita moschata (“calabacita”) seed oil

From the sterol fraction of seed oil from commercialCucurbita moschata Dutch (“calabacita”) Δ⁵ and Δ⁷ sterols having saturated and unsaturated side chain were isolated by chromatographic procedures and characterized by spectroscopic (¹H and¹³C-nuclear magnetic resonance, mass spectrometry) methods. The main components were identified as 24S-ethyl 5α-cholesta-7,22E-dien-3β-ol (α-spinasterol); 24S-ethyl 5α-cholesta-7,22E, 25-trien-3β-ol (25-dehydrochondrillasterol); 24S-ethyl 5α-cholesta-7, 25-dien-3β-ol; 24R-ethylcholesta-7-en-3β-ol (Δ⁷-stigmastenol) and 24-ethyl-cholesta-7, 24(28)-dien-3β-ol (Δ^7,24(28)-stigmastadienol).Lipids 31, 1205–1208 (1996).     

Diversity of sterol composition in the family chenopodiaceae

The predominant 4-desmethylsterols from the leaves of 13 species in eight genera of the family Chenopodiaceae are 24α-ethylsterols. In four species,Chenopodium ambrosioides L.,C. rubrum L.,Salicornia europaea L. andS. bigelovii Torr., the C-22(23) double bond is introduced into more than 70% of the 24α-ethylsterols producing spinasterol (24α-ethylcholesta-7,22E-dien-3β-ol) in the first two species and mixtures of spinasterol and stigmasterol (24α-ethylcholesta-5,22E-dien-3β-ol) in the latter species. The saturated side chain analogues predominate with more than 70% of the 24α-ethylsterols in eight species.Salsola kali L.,Suaeda linearis (Ell.) Moq.,Kochia scoparia (L.) Roth., andBassia hirsute (L.) Aschers. synthesize sitosterol (24α-ethylcholest-5-en-3β-ol), andAtriplex arenaria Nutt.,C. album L.,C. urbicum L. andC. leptophyllum Nutt. possess mixtures of sitosterol and 22-dihydrospinasterol (24α-ethylcholest-7-en-3β-ol). Sitostanol (24α-ethyl-5α-cholestan-3β-ol) was isolated fromSuaeda linearis as an 18% component of the total 4-desmethylsterol and in lesser amounts from four other species. In all species synthesizing 24-ethyl-Δ⁵-sterols, a 24ξ-methylcholest-5-en-3β-ol was also present at 1.0–20% of the total 4-desmethylsterol. Avenasterol [24-ethylcholesta-7,24(28)Z-dien-3β-ol], isofucosterol [24-ethylcholesta-5,24(28)Z-dien-3β-ol), cholesterol (cholest-5-en-3β-ol) and 24ξ-methyl-5α-cholestan-3β-ol also were isolated from several species. Species in the family Chenopodiaceae and the type genusChenopodium may be categorized into one of three groups based on sterol biosynthesis: the Δ⁷-sterol producers; the Δ⁵-sterol producers, and those producing mixtures of both Δ⁷- and Δ⁵-sterols in relatively fixed percentage compositions.     

Unusual tetraene sterols in some phytoplankton

Sterols were analyzed from four phytoplankton strains which are under investigation as possible sources of food for oysters in culture. One strain ofPyramimonas contained only 24-methylenecholesterol as a major sterol component.Pyramimonas grossii, Chlorella autotrophica andDunaliella tertiolecta each contained a complex mixture of C₂₈ and C₂₉ sterols with Δ⁷, Δ^5,7 and Δ^5,7,9(11) nuclear double bond systems. Sterols were found both with and without the C-22 side chain double bond. Ergosterol and 7-dehydroporiferasterol were the principal sterols in each of the latter three species, which also contained the rare tetraene sterols, 24-methylcholesta-5,7,9(11),22-tetraen-3β-ol and 24-ethylcholesta-5,7,9(11),22-tetraen-3β-ol.     

Conversion of cyclolaudenol to 24α- and 24β-ethylsterols in the cucurbitaceae

[2-³H]Cyclolaudenol was converted into α-spinasterol, 24β-ethylcholesta-7,25-dien-3β-ol and 24β-ethylcholesta-7,22,25-trien-3β-ol by seedlings ofCucurbita maxima. As 24-methylenecycloartanol is the obligatory precursor of 24-ethylsterols, it can be assumed that the transformation of cyclolaudenol to 24-methylenecycloartanol must have occurred. These results lead us to postulate the existence, in the Cucurbitaceae family, of an enzymatic system capable of isomerizing Δ²⁵ alkylsterols into Δ²⁵⁽²⁸⁾ sterols.     

Sterol composition of two freshwater molluscs of genusDiplodom

The sterol composition of two taxonomically related freshwater species,Diplodom patagonicus andDiplodom variabilis, respectively, from Lake Nahuel Huapi and the Río de la Plata river were studied by gas liquid chromatography and mass spectrometry. Cholesterol was the main sterol in both species and it was followed by 24-methylcholesta-5, 22-dien-3β-ol, 24-methylcholest-5-en-3β-ol, 24-ethylcholesta-5,22-dien-3β-ol and 24-ethylcholest-5-en-3β-ol. The river species collected within the proximity of marine influence showed less cholesterol and more 24-methylcholesta-5,22-dienol, 24-methylcholest-5-enol and 24-ethylcholesta-5,22-dienol than the lake species.     

Sterols of the oyster,Crassostrea virginica

A commericial sample of the oyster,Crassostrea virginica, obtained from Maryland waters of the Chesapeake Bay, contained 31 desmethylesterols and at least eight 4-monomethylsterols. The combined gas liquid chromatography-mass spectra of the minor components showed the presence of 6 unusual sterols, 24-ethylcholest-22-en-3β ol, 4α-methyl-24-ethylcholestan-3β-ol, occelasterol, (24E)-24-propylidene-cholest-5-en-3β-ol, (24ZO-24-propylidene-cholest-5-en-3β-ol, and 24-methylene-cholestanol. The C-24 configuration of 24-ethylcholest-5-enol, 24-methyl-cholesta-5,22-dienol, and 24-ethylcholesta-5,22 dienol were elucidated by 220 MHz nuclear magnetic resonance spectrometry.     

Composition and biosynthesis of sterols in selected marine phytoplankton

Six species of phytoplankton,Pseudoisochrysis paradoxa, Isochrysis galbana, Monochrysis lutheri, Platymonas suecica, Thalassiosira fluviatilis and aChaetoceros species, were cultured in the laboratory and their sterol contents analyzed utilizing digitonin precipitation, thin layer and gas chromatography and gas chromatography-mass spectrometry. A total of 7 sterols were found in phytoplankton. The occurrence of these sterols, cholest-5-en-3β-ol, cholest-5,22-dien-3β-ol, 24-methylcholesta-5,24(28)-dien-3β-ol, 24-methylcholest-5-en-3β-ol, 24-methylcholesta-5,22-dien-3β-ol, 24-ethylcholest-5-en-3β-ol and 24-ethylcholest-5,22-dien-3β-ol, differed significantly among the various phytoplankton species. Cultures ofP. paradoxa biosynthesized both of the sterols found in this species when incubated in the presence of¹⁴C- or³H-mevalonic acid for 0.5–9 days. These sterols were cholesterol and 24-methylcholesta-5,22-dien-3β-ol. Since 5 of the sterols found in the phytoplankton commonly occur in mollusks which feed on phytoplankton, it is likely that at least some of the tissue sterols in mollusks are of dietary origin. Research trainee, HL 07295-02, National Heart, Lung and Blood Insitute.     

Inhibition of sterol biosynthesis in chlorella ellipsoidea by AY-99441

WhenChlorella ellipsoidea was grown in the presence of 4 ppm AY-9944, complete inhibition of Δ⁵-sterol biosynthesis was achieved. However total sterol production remained unaltered. As a result a number of sterols accumulated that appear to be intermediates in sterol biosynthesis. These sterols were described and identified as (24S)-5α-ergost-8(9)-en3β-ol, (24S)-5α-stigmast-8(9)-en-3β-ol, 4α-methyl-(24S)-5α-ergosta-8, 14-dien-3β-ol, 4α-methyl-(24S)-5α-stigmasta-8, 14-dien-3β-ol, 4α-methyl-(24S)-5α-ergost-8(9)-en-3β-ol and (24S)-4α-methyl-5α-stigmast-8(9)-en-3β-ol. The occurrence of these sterols inChlorella ellipsoidea is the first time they have been noted in biological material. The accumulation of these sterols in treated cultures indicates that AY-9944 is an extremely effective inhibitor of the Δ⁸→Δ⁷ isomerase and the Δ¹⁴ reductase of these plants. The occurrence of small amounts of other sterols in treated cultures has led to a proposed pathway for thebiosynthesis of sterols inChlorella ellipsoidea. Scientific Article No. A1775, Contribution No. 4565 of the Maryland Agricultural Experiment Station.     

Sterols ofKalanchoe pinnata: First report of the isolation of both C-24 epimers of 24-alkyl-Δ25-sterols from a higher plant

Eighteen sterols were isolated from the aerial parts ofKalanchoe pinnata (Crassulaceae) including four novel sterols,viz. (24R)-stigmasta-5,25-dien-3β-ol (24-epiclerosterol), (24R)-5α-stigmasta-7,25-dien-3β-ol, 5α-stigmast-24-en-3β-ol, and 25-methyl-5α-ergost-24(28)-en-3β-ol. 24-Epiclerosterol and its Δ⁷-analog occur together with their 24S/β-epimers in the same plant making this the first report of the isolation of both C-24 epimers of Δ²⁵-unsaturated 24-alkylsterols from a non-marine organism. Iodine-catalyzed isomerization of stigmasta-5,24-dien-3β-ol (24-ethyldesmosterol), the main sterol ofK. pinnata, yielded 24-epiclerosterol among other products.     

Novel brominated phospholipid fatty acids from the Caribbean spongeAgelas sp.

The very long-chain fatty acids, (5E,9Z)-6-bromo-5,9-tetracosadienoic, (5E,9Z)-6-bromo-23-methyl-5,9-tetracosadienoic, (5E,9Z)-6-bromo-5,9-pentacosadienoic and (5E,9Z)-6-bromo-24-methyl-5,9-pentacosadienoic acids, were identified in the phospholipids (mainly phosphatidylethanolamine) of the spongeAgelas sp. Structure elucidation was accomplished by means of mass spectrometry and chemical transformations, including deuteration with Wilkinson's catalyst. All of the sterols from the sponge had the Δ5,7 nucleus, with 24-methylcholesta-5,7,22-trien-3β-ol (ergosterol) and 24-ethylcholesta-5,7,22-trien-3β-ol being the most abundant.     

The lipids of the common house cricket,Acheta domesticus L. III. Sterols

Sterols constitute 1.95% of the total extractable lipids ofAcheta domesticus L., of which 18% are esterified. The free sterols consist of cholestane-3β-ol (0.5%), Δ⁵-cholestene-3β-ol (83.5%), Δ⁷-cholestene-3β-ol (2.3%) Δ^5,7-cholestadiene-3β-ol (3%), Δ^5,22-cholestadiene-3β-ol (4%), Δ^5,7,22-cholestatriene-3β-ol (0.2%), campestane-3β-ol (0.03%), Δ⁵-campestene-3β-ol (1.0%), Δ⁷-campestene-3β-ol (trace), Δ^5,7-campestadiene-3β-ol (0.2%), stigmastane-3β-ol (0.09%), Δ⁵-stigmastene-3β-ol (2.1%), Δ⁷-stigmastene-3β-ol (0.04%), Δ^5,7-stigmastadiene-3β-ol (0.4%), Δ^5,22-stigmastadiene-3βol (0.1%). The same sterols are present in the esterified sterol fraction. Δ⁷-Sterols and Δ^5,7-sterols are present in significantly larger amounts in the esterified fraction than in the free sterol fraction. By a comparison with the sterols of the cricket food, it is clear thatA. domesticus is capable of removing methyl and ethyl groups from C-24 of sterols of the campestane and stigmastane type. The ability to introduce a Δ⁷ double bond into saturated and Δ⁵-sterols is indicated, and it is suggested that Δ⁷-sterols of the C₂₇, C₂₈, and C₂₉ sterol series may be intermediates in the conversion of Δ⁵-sterols to Δ^5,7-sterols. Associate Professor, Department of Chemistry, University of Michigan, Ann Arbor, Mich.; Alfred P. Sloan Foundation Fellow, 1968–68. Public Health Service Predoctoral Fellow, 1968–67.     

Metabolism of sitosteryl β-D-glucoside and its nutritional effects in rats

[4-¹⁴C]Sitosteryl β-D-glucoside, intragastrically administered to rats, was not absorbed by the intestinal mucosa. At three hr after the application, radioactivity was concentrated almost exclusively in the digesta of stomach, small intestine as well as cecum and colon, whereas only low proportions of radioactively labeled compounds were found in the various tissues of the gastrointestinal tract. Minor proportions of labeled metabolites of [4-¹⁴C]sitosteryl β-D-glucoside, such as sitosterol and sitosteryl esters, were formed in the small intestine in vivo and in slices of small intestine in vitro. In the tissues of cecum and colon as well as the digesta derived from them, high proportions of labeled coprositostanol, i.e. 24α-ethyl-5β-cholestan-3β-ol, that obviously had been formed by bacterial degradation of the substrate were detected. The feeding of sitosteryl β-D-glucoside (0.5 g/kg body weight×day) over a period of four weeks did not alter significantly body weights or organ weights of rats. Analyses of steryl lipids of the various organs and tissues confirmed the findings obtained with the radioactive substrate: neither sitosteryl β-D-glucoside nor sitosterol or sitosteryl esters derived therefrom had been transported in appreciable amounts to organs and tissues outside the alimentary canal during the feeding period. Minor proportions of unmetabolized sitosteryl β-D-glucoside were detected in the tissues of stomach and intestine, whereas large proportions of the substrate were found in feces of rats that had received the sitosteryl β-D-glucoside-containing diet; coprositostanol was found in feces of these animals in high proportions as well. Thus, the use of sitosteryl β-D-glucoside as emulsifier or preservative in food and feed does not appear to involve any risk. The systematic nomenclature of the sterols referred to by trivial names is, cholest-5-en-3β-ol (cholesterol); 5α-cholestan-3β-ol (5α-cholestanol); 5β-cholestan-3β-ol (5β-cholestanol, coprostanol); 24α-methylcholest-5-en-3β-ol (campesterol); 24α-methyl-5α-cholestan-3β-ol (5α-campestanol); 24α-methyl-5β-cholestan-3β-ol (5β-campestanol, coprocampestanol); 24α-methyl-cholesta-5,22-dien-3β-ol (brassicasterol); 24α-ethylcholest-5-en-3β-ol (sitosterol, β-sitosterol); 24α-ethyl-5α-cholestan-3β-ol (5α-sitostanol); 24α-ethyl-5β-cholestan-3β-cholestan-3β-ol (5β-sitostanol, coprositostanol); 24α-ethylcholesta-5,22-dien-3β-ol (stigmasterol).     

Dealkylation of 24-ethylsterols byTetrahymena pyriformis

WhenTetrahymena pyriformis was incubated with sitosterol ([24R]-24-ethylcholest-5-en-3β-ol]) or itstrans-Δ²²-derivative (stigmasterol), the C-24-dealkylated product, cholesta-5,7,trans-22-trien-3β-ol, was obtained in both cases. 24(S)-24-Ethylcholesta-5,7,trans-22-trien-3β-ol also was found to be a metabolite. When sitosterol was the substrate, 24(R)-24-ethylcholesta-5,7-dien-3β-ol was obtained as a third product. Identifications were made by mass spectroscopy, quantitative chromatography, labeling with¹⁴C, and by other means. The dealkylated product (cholestratrienol) represented 30% of the sterols isolable after incubation. The administration of sterols to this organism did not induce sterol biosynthesis, since 2-¹⁴C-mevalonate failed to yield radioactive sterol in the presence of added stigmasterol.     

Nature of fecal sterols and intestinal bacterial flora

Sterol excretion in the spontaneously atherosclerosis-susceptible White Carneau (WC) pigeon, the Silver King (SK) pigeon and the Show Racer (SR) pigeon was studied by thin layer chromatography (TLC), argentation TLC and gas liquid chromatography. Unlike man and the chicken, these pigeons excreted no coprostanol or coprostanone derivatives of sterols. Moreover incubation of¹⁴C-labeled cholesterol with pigeon feces indicated that, also unlike man and the chicken, these pigeons are unable to convert it to coprostanol. Bacteriologic examination revealed the absence of gram-negative anaerobic flora and of members of the genusBifidobacterium in both the WC and SR pigeons. On the other hand, one of the two SK pigeons examined showed evidence of the presence of bothBacteroids fragilis andB. bifidum in the upper intestinal tract. Although no qualitative experiments were performed, no unusual characteristics of the aerobic flora were noted in these pigeons. In addition, analysis of human stool specimens indicated a “normal” bowel flora. The flora of the intestinal tract of the chicken is similar to that of the human. Because of this similarity, it appears that differences in environment (living conditions, diets) between the human and the chicken are of little consequence. The results obtained in this study suggest the possibility that the anaerobic gram-negative flora and sponsible, at least in part, for the chemical conversion of cholesterol to coprostanol. Presented in part at the Fourth International Symposium on Drugs Affecting Lipid Metabolism, Philadelphia, September 1971, and at the AOCS Meeting, Los Angeles, April 1972. The following nomenclature has been used for the steroids referred to in this paper: cholesterol, cholest-Δ⁵-en-3β-ol; coprostanol, 5β-cholestan-3β-ol; campesterol, 24-methylcholest-Δ⁵-en-3βol; stigmasterol, 24-ethylcholest-Δ^5,22-dien-3β-ol; β-sitosterol, 24-ethylcholest-Δ⁵-en-3β-ol; coprocampestanol, 24-methyl-5β-cholestan-3β-ol; coprostigmastenol, 24-ethyl-5β-cholest-Δ²²-en-3β-ol; coprostigmastanol, 24-ethyl-5β-cholestan-3β-ol; coprostanone, 5β-cholestan-3-one; campestanone, 24-methyl-5β-cholestan-3-one; stigmastenone, 24-ethyl-5β-cholest-Δ²²-en-3-one; and β-sitostanone, 24-ethyl-5β-cholestan-3-one.     

Free and esterified sterols of the marine dinoflagellateGonyaulax polygramma

Free and esterified sterols of the common marine dinoflagellateGonyaulax polygramma were identified using capillary gas chromatography—mass spectrometry (GC-MS). Fractions containing free 4α-methyl and 4-desmethyl sterols were isolated by column chromatography and shown to consist of at least 20 components. Major sterols included 4α,23,24-trimethyl-5α-cholestan-3β-ol (dinostanol), 4α,23,24-trimethyl-5α-cholest-22E-en-3β-ol (dinosterol), cholest-5-en-3β-ol (cholesterol), 23,24-dimethyl-5α-cholest-22E-en-3β-ol and 23,24-dimethylcholesta-5,22E-dien-3β-ol. Although the same group of sterols was found in the free and esterified sterol fractions, the proportions of individual sterols were quite different. The complexity of the sterol distributions, together with the predominance of dinostanol, distinguishes the sterol composition of this alga from those of other members of theGonyaulacaceae.     

Sterol metabolism in the nematodeCaenorhabditis elegans

The metabolism of various dietary sterols and the effects of an azasteroid on sitosterol metabolism in the free-living nematodeCaenorhabditis elegans was investigated. The major unesterified sterols ofC. elegans in media supplemented with sitosterol, cholesterol or desmosterol included 7-dehydrocholesterol (66.5%, 40.5%, 31.2%, respectively), cholesterol (6.7%, 52.3%, 26.9%), lathosterol (4.4%, 3.6%, 1.7%) and 4α-methylcholest-8(14)-en-3β-ol (4.2%, 2.1%, 3.8%). Esterified sterols, representing less than 20% of the total sterols, were somewhat similar except for a significantly higher relative content of 4α-methylcholest-8(14)-en-3β-ol (23.3%, 23.4%, 10.6%). ThusC. elegans not only removes the substituent at C24 of dietary sitosterol but possesses the unusual ability to produce significant quantities of 4α-methylsterols. WhenC. elegans was propagated in medium supplemented with sitosterol plus 5 μg/ml of 25-azacoprostane hydrochloride, the azasteroid strongly interfered with reproduction and motility ofC. elegans and strongly inhibited the Δ24-sterol reductase enzyme system; excluding sitosterol, the major free sterols of azacoprostane-treatedC. elegans were cholesta-5, 7, 24-trien-3β-ol (47.9%), desmosterol (9.4%), fucosterol (2.1%) and cholesta-7,24-dien-3β-ol (2.0%). These 4 sterols are likely intermediates in the metabolism of sitosterol inC. elegans.     

Developmental regulation of sterol biosynthesis inCucurbita maxima L.

Twenty-two sterols were identified by capillary gas chromatography and capillary gas chromatography/mass spectroscopy inCucurbita maxima grown under green-house conditions. Both whole plants and individual tissues (leaves, stems, roots, cotyledons, flowers) were analyzed at weekly intervals during the 12-week development of the plant. In whole plants, sterol accumulation parallels plant growth except for a period in the mid-life cycle where there is a reduction in the amount of sterol accumulated on a total sterol/plant and mg sterol/g dry wt basis. This reduction in the amount of sterol is coincident with the visual onset of flowering. During development, the percent contribution of each class of sterol (Δ^5_, Δ^7_, Δ^0_-sterols) remains relatively constant. However, the percent contribution of an individual sterol species varies depending on the tissue examined and the developmental period selected for analysis. While the young plant (<2 weeks) possesses elevated levels of sterols with the Δ²⁵⁽²⁷⁾-double bond, the trend was toward a reduction in the amounts of these sterols with development. Leaves and stems accumulate large quantities of 24ζ-ethyl-5α-cholesta-7,22-dien-3β-ol (7,22-stigmastadienol) and 24ζ-ethyl-5α-cholest-7-en-3β-ol (7-stigmastenol), while roots accumulate only 7,22-stigmastadienol as their principal sterol. Male flowers and roots were found to contain elevated levels of Δ^5_-sterols.     

Detailed sterol compositions of two pathogenic rust fungi

Teliospores of cedar-apple rust Gymnosporangium juniperi-virginianae were collected from the eastern red cedar Juniperus virginiana, and aeciospores of quince rust G. clavipes were collected from the fruit of English hawthorn Crataegus laevigata. The sterol fractions were separated by HPLC, and their identities were determined by 600 MHz ¹H NMR. Twenty-six sterols were isolated from G. juniperi-virginianae and 18 sterols were isolated from G. clavipes. The principal sterol of both fungi was (Z)-stigmasta-7,24(28)-dien-3β-ol. Other major sterols were (24S)-ergost-7-en-3β-ol, (24S)-stigmast-7-en-3β-ol, and (24S)-stigmasta-5,7-dien-3β-ol. The sterols of the hosts were found to be very different from those of the fungi. The 24-alkyl sterols of the fungi had the 24α-configuration, whereas those of the hosts had the 24β-configuration. Similarities to the sterol composition of the AIDS pneumonia fungus Pneumocystis carinii are discussed.