Significance of saguaro cactus alkaloids in ecology ofDrosophila mettleri,a soil-breeding,cactophilic drosophilid

Drosophila mettleri is a soil-breeding, cactophilic drosophilid which lives in the Sonoran Desert. Several chemical constituents of cacti in this region have been identified as having major roles in insect-host plant relationships involvingDrosophila. For example, isoquinoline alkaloids, which are present in senita cactus, have been shown to be toxic to seven of the nine species tested. The two tolerant species areD. pachea, the normal resident, andD. mettleri. Necroses of senita cacti are often used as feeding substrates byD. mettleri adults, but this species has never been reared from senita rots. Soil, which have been soaked by juice from saguaro and cardón rots, are the typical breeding substrates of this species. The tissues of both of these cacti also contain alkaloids, chemically related to those in senita, but at much lower concentrations. Alkaloid concentration in saguaro-soaked soil was found to be 1.4–27 times the average concentration in fresh tissue. Alkaloids were extracted from saguaro tissue and used in tests of larva-to-adult viability, developmental rate, and adult longevity. Elevated concentrations of saguaro alkaloids had no significant effect on the longevity ofD. mettleri, but significantly reduced the longevity ofD. nigrospiracula andD. mojavensis, two nonsoil breeding cactophilic species. Viability and developmental rates of all three species were affected, but the effect onD. nigrospiracula was comparatively greater. It is argued that the adaptations that allowD. mettleri to utilize the saguaro soil niche also convey tolerance to alkaloids present in senita tissue. The ability to utilize senita necroses as feeding substrates represents an ecological advantage to D. mettleri, in that the density of potential feeding sites is increased as compared to species which are more specific in their host-plant relationships.     

Coadaptation ofDrosophila and yeasts in their natural habitat

The mutualistic interactions of cactophilicDrosophila and their associated yeasts in the Sonoran Desert are studied as a system which has evolved within the framework of their host cactus stem chemistry. Because theDrosophila-yeast system is saphrophytic, their responses are not thought to directly influence the evolution of the host. Host cactus stem chemistry appears to play an important role in determining where cactophilicDrosophila breed and feed. Several chemicals have been identified as being important. These include sterols and alkaloids of senita as well as fatty acids and sterol diols of agria and organpipe cactus. Cactus chemistry appears to have a limited role in directly determining the distribution of cactus-specific yeasts. Those effects which are known are due to unusual lipids of organpipe cactus and triterpene glycosides of agria and organpipe cactus.Drosophilayeast interactions are viewed as mutualistic and can take the form of (1) benefits to theDrosophila by either direct nutritional gains or by detoxification of harmful chemicals produced during decay of the host stem tissue and (2) benefits to the yeast in the form of increased likelihood of transmission to new habitats. Experiments on yeast-yeast interactions in decaying agria cactus provide evidence that the yeast community is coadapted. This coadaptation among yeasts occurs in two manners: (1) mutualistic increases in growth rates (which are independent of the presence ofDrosophila larvae) and (2) stabilizing competitive interactions when growth reaches carrying capacity. This latter form is dependent on larval activity and results in benefits to the larvae present. In this sense, the coadapted yeast community is probably also coadapted with respect to itsDrosophila vector.     

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. Arizona Agricultural Experiment Station journal article no. 3815.     

Metabolism of lathosterol byDrosophila pachea

Drosophila pachea is a Sonoran Desert cactiphilic species unable to utilize cholesterol or cholestanol for larval growth and maturation. Lathosterol (7-cholesten-3β-ol) was added to a sterol deficient medium on which an axenic culture ofD. pachea was maintained. 7-Dehydrocholesterol was identified as the sterol metabolite in adult flies by gas liquid and thin layer chromatography and by its UV spectrum. One of 12 papers to be published from the Sterol Symposium, presented at the AOCS Meeting, April 1970. Taken from a thesis submitted by K.C. Goodnight for the Ph.D. degree, University of Arizona. Contribution No. 1715, University of Arizona Agricultural Experiment Station.     

Comparison of larval and adult P-450 activity levels for alkaloid metabolism in desertDrosophila

The cytochrome P-450 monooxygenase system has been implicated in plant utilization by at least three species ofDrosophila (D. nigrospiracula, D. mettleri, andD. mojavensis) that are endemic to the Sonoran Desert of the southwestern United States and northwestern Mexico. Basal and induced levels of total cytochrome P-450 were determined for third-instar and decapitated 2- to 5-day post eclosion adults of the three desert species. Total P-450 levels, both basal and induced for all species assayed, were significantly higher for adults than for larvae by up to 20-fold. On a per organism basis, the levels of in vitro metabolism of the cactus alkaloid, carnegine, and patterns of response to induction by cactus tissue for adult desertDrosophila approximated those of larvae. Induction by phenobarbital, however, resulted in levels of in vitro carnegine metabolism that were up to 5.6-fold higher in adults than in larvae.     

Ecological aspects of cactus triterpene glycosides I. Their effect on fitness components ofDrosophila mojavensis

The effects of pentacyclic triterpene glycosides extracted from agria and organ pipe cacti on three fitness parameters of the cactophilic fruit fly,Drosophila mojavensis were tested. Triterpene glycosides from organ pipe increased development time and reduced larval viability while those from agria produced smaller adults (reduced fecundity). In addition, the microbial communities in the organ pipe saponin media were less dense than those in the media to which agria saponins had been added. The role of cactus triterpene glycosides in the ecology of thisDrosophila species is discussed.     

The distribution and phylogenetic significance of desmethylsterols inChenopodium andAtriplex: Coexistence of Δ7- and Δ5 -sterols

Twenty-one species in the Chenopodiaceae were analyzed for sterol composition. In ten of eleven species ofChenopodium, the major desmethylsterols were Δ⁷-sterols accompanied by lower proportions of Δ⁵-sterols. InC. fremontii this pattern was reversed. The sterol profiles of five species ofAtriplex were characterized by the coexistence of Δ⁷- and Δ⁵-sterols in ratios of 0.3∶1 to 0.4∶1. MaleAtriplex plants contained higher proportions of Δ⁵-sterols than femaleAtriplex plants. OneCeratoides and twoSalicornia species contained Δ⁵-sterols as their predominant sterols.     

Effect of host sterols on the sterol composition and virulence of a nuclear polyhedrosis virus ofHeliothis zea

The type of sterol in the diet ofHeliothis zea affected not only the sterol composition of the insect larva but also the virulence and/or sterol composition of a single-nucleocapsid nuclear polyhedrosis virus (HzSNPV). This baculovirus, which was purified by differential and sucrose density gradient centrifugation, had a sterol content of 40 ng per 10⁶ polyhedra. When the sterol composition of HzSNPV was characterized by gas liquid chromatography, reversed phase-high performance liquid chromatography, mass spectrometry, proton nuclear magnetic resonance spectrometry and/or ultraviolet spectroscopy, the sterols in the virus were similar to those of the host. The HzSNPV isolated from larvae fed Δ_{5_}, Δ_{0_} or Δ_5,7-sterols contained primarily cholesterol, cholestanol or 7-dehydrocholesterol, respectively. Changes in the sterol composition of HzSNPV affected its LD₅₀, but not LT₅₀, in larvae containing Δ₅-sterols. The LD₅₀ of virus isolated from larvae containing Δ_{0_}, Δ_{5_} and Δ₇-sterols decreased from 275,423 to 32,359 to 5,012 polyhedra/larva, respectively. The latter virus was also more virulent than the one that was isolated from larvae containing Δ_5,7-sterol and had an LD₅₀ of 58,884 polyhedra/larva. In contrast, the LD₅₀ of an HzSNPV (Sandoz, Inc.) containing Δ₅-sterol was not affected by the presence of Δ_{5_}, Δ_{0_} or Δ_5,7-sterols in the tissues of the host (1,413; 1,288 and 355 polyhedra/larva, respectively). The results of this study indicate that the sterol composition ofH. zea can affect the sterol composition of HzSNPV and therefore may affect the ability of this biological control agent to control its economically important insect host.     

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-Δ^7,22,Δ^7,25(27) and Δ^7,22,25(27)-sterols constituted the predominant sterols for the seed materials, whereas the 24-ethyl-Δ⁷ and Δ^7,22-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-Δ^7,22,25(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.     

Sterol composition of the phytolaccaceae and closely related families

Total sterols were analyzed from 28 species of Phytolaccaceae and from 29 species of closely related families—Basellaceae, Portulaccaceae, Molluginaceae, and Stegnospermataceae. Eighteen of twenty-eight species of Phytolaccaceae contained dominant Δ⁷-sterols while six species had dominant Δ⁵-sterols. Three species had dominant Δ⁰-sterols. Sterol composition strongly reflected taxonomic position. Nineteen of twenty-nine species from Basellaceae, Portulaccaceae, Molluginaceae, and Stegnospermataceae contained dominant Δ⁷-sterols while ten species contained dominant Δ⁵-sterols. Until recently Δ⁷-sterols were considered rare in higher plants. It appears that a large number of species in the order Caryophyllales contain primarily Δ⁷-sterols.     

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%).     

Inhibition of C28 and C29 phytosterol metabolism by N,N-dimethyldodecanamine in the nematodecaenorhabditis elegans

Effects on the metabolism of campesterol and stigmasterol inCaenorhabditis elegans were investigated using N,N-dimethyldodecanamine, a known inhibitor of growth, reproduction and the Δ²⁴-sterol reductase of this nematode. 7-Dehydrocholesterol was the predominant sterol (51%) ofC. elegans grown in stigmasterol-supplemented media, whereas addition of 25 ppm amine resulted in a large decrease in the relative percentage of 7-dehydrocholesterol (23%) and the accumulation of a substantial proportion (33%) of Δ²⁴-sterols (e.g., cholesta-5,7,24-trienol) and Δ^22,24-sterols (e.g., cholesta-5,7,22, 24-tetraenol) but yielded no Δ²²-sterols. Dealkylation of stigmasterol byC. elegans proceeded in the presence of the Δ²²-bond; reduction of the Δ²²-bond occurred prior to Δ²⁴-reduction. Addition of 25 ppm amine to campesterol-supplemented media altered the sterol composition ofC. elegans by increasing the percentage of unmetabolized dietary campesterol from 39 to 60%, decreasing the percentage of 7-dehydrocholesterol from 26 to 12%, and causing the accumulation of several Δ²⁴-sterols (6%).C. elegans also was shown to be capable of dealkylating a Δ²⁴⁽²⁸⁾-sterol as it converted 24-methyl-enecholesterol to mostly 7-dehydrocholesterol. The proposed role of 24-methylenecholesterol as an intermediate between campesterol and 7-dehydrocholesterol was supported by the results.     

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.     

Changes in Δ5- and Δ7-sterols during germination and seedling development ofCucurbita maximaduring germination and seedling development ofCucurbita maxima

While seeds ofCucurbita maxima contain both Δ⁵- and Δ⁷-sterols, the former, which have been described earlier, now have been found to disappear during germination. This suggests that a function exists for the Δ⁵-compounds only in the early part of the life cycle ofC. maxima, unlike most of the other higher plants studied. In contrast to the Δ⁵-sterols, the level of Δ⁷-sterols increased during germination as well as during seedling development and maturation. The period of transition between germination and seedling development appeared to be of special importance in terms of sterol changes. This period represented a surge of sterol biosynthesis with an ontogenetic shift in sterol composition from approximately equal amounts of 24α- and 24β-ethyl stereochemistry to a predominance of the former. The sterol composition of the mature plants included only about 5% of the 24β-ethylsterols. The configurational relationships were demonstrated by high resolution¹H-NMR. The sterols of the mature plants were: 25(27)-dehydrochondrillasterol, 24β-ethyl-25(27)-dehydrolathosterol, avenasterol, spinasterol, 22-dihydrospinasterol and 24ξ-methyllathosterol. Based on the changes which occurred in the relative amounts of the Δ⁷-sterols, it did not appear that the Δ⁵-components were being converted to their Δ⁷-analogs. A portion of this work was presented at the meeting of the American Oil Chemists' Society in May, 1985 in Philadelphia.     

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.     

Diversity of sterol biosynthetic capacity in the caryophyllidae

The order Caryophyllales, along with its two associated orders, the Polygonales and Plumbaginales, comprise the angiosperm subclass Caryophyllidae. We have now characterized the sterol compositon of 231 members of this subclass. This includes 210 species and 21 cultivars in 108 genera within the 14 families of these three orders. From these data, clear differences in biosynthetic capability and putative relationships between taxa have been established. Members of the two monofamilial orders (Polygonales and Plumbaginales) contain Δ⁵-sterols in ratios typical of “main line” angiosperms. Members of families in the Caryophyllales contain Δ⁵-sterols, or Δ⁷-sterols or mixtures of Δ⁵- and Δ⁷-sterols. In the majority of species where Δ⁷-sterols are the dominant sterols produced, trace amounts to almost equal amounts of Δ⁵-sterols are also present. Replicate samples of many of these species have shown that the ratio of Δ⁵-sterols to Δ⁷-sterols in these species is stable over time and/or location. From these data, it appears that the conversion of Δ⁷-sterols to Δ⁵-sterols is highly regulated in the majority of species within this order. In these families, similarities in sterol composition correlate well with taxonomic relatedness. Relationships between these taxa with respect to biosynthetic capability can now be postulated. Based on a paper presented at the Symposium on Plant and Fungal Sterols: Biosynthesis, Metabolism and Function, held at the AOCS Annual Meeting, Baltimore, Maryland, April 1990.     

Sterols of the spongeTethya amamensis: Occurrence of (24E)-24-ethylidenecholesta-5,7-dienol, (24E)-24-propylidenecholesta-5,7-dienol,and (24Z)-24-propylidenecholesta-5,7-dienol

The spongeTethya amamensis, collected from Kagoshima Bay, Japan, contained at least 24 sterols, including Δ⁵-sterols (82.2% of total sterols) and Δ^{5, 7}-sterols (17.8%). The predominant sterols were cholesterol (29.0%), cholesta-5,22-dienol (13.8%), 24-methylcholesta-5,22-dienol (10.9%), 24-methylenecholesterol (8.3%), 24-methylcholesta-5,7,22-trienol (6.8%), 24-ethylcholest-5-enol (6.1%), and isofucosterol *4.1%). Combined gas liquid chromatography-mass spectrometry suggested the presence of 3 uncommon sterols, (24E)-24-ethylidenecholesta-5,7-dienol, (24E)-24-propylidenecholesta-5,7-dienol, and (24Z)-24-propylidenecholesta-5,7-dienol as minor components. The sterols ofT. amamensis also contained small amounts of 24-norcholesta-5,7,22-trienol and (24Z)-24-ethylidenecholesta-5,7-dienol.     

Premating Isolation Is Determined by Larval Rearing Substrates in CactophilicDrosophila mojavensis. III. Epicuticular Hydrocarbon Variation Is Determined by Use of Different Host Plants inDrosophila mojavensis andDrosophila arizonae

Adult epicuticular hydrocarbon profiles of male and femaleDrosophila mojavensis have been implicated as determinants of mate choice leading to premating isolation between geographically isolated populations. Hydrocarbon profiles of a Baja California and a mainland Sonora population ofDrosophila mojavensis, ayellow body mutant strain ofD. mojavensis, and a population ofD. arizonae were compared among flies that had been reared on two cactus substrates and a synthetic laboratory growth medium in order to assess the degree to which natural rearing substrates influence adult hydrocarbon composition. Twenty epicuticular hydrocarbon components, ranging from C₂₉ to C₄₁, were recovered by gas chromatography that represented major classes of alkanes, alkenes, and alkadienes. We found differences in relative amounts of epicuticular hydrocarbons among Baja and mainlandD. mojavensis, and theyellow body mutants. There were few differences betweenD. mojavensis andD. arizonae. The effects of rearing substrates were remarkable: most of the differences were due to the effects of lab food vs. cactus, but there were significant rearing substrate effects due to differences in the two cacti used. Eleven hydrocarbon components differed in abundance between males and females or showed significant sex × rearing substrate interactions from ANOVA. The effects of rearing substrates on epicuticular hydrocarbon composition inD. mojavensis are concordant with changes in the intensity of premating isolation between populations, implicating host ecology as a major determinant in patterns of mate choice in this species.     

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.     

Sterol compositions of seeds and mature plants of family cucurbitaceae

The sterol fractions of the unsaponifiable lipids obtained from 32 seed and mature plant (leaves and stems, pericarp of the fruit, and roots) materials from the 12 generaApodanthera, Benincasa, Citrullus, Coccinea, Cucumis, Cucurbita, Gynostemma, Lagenaria, Luffa, Momordica, Sechium andTrichosanthes, of the family Cucurbitaceae were investigated by gas liquid chromatography (GLC) on an OV-17 glass capillary column. Among the 23 sterols with Δ⁵-, Δ⁷- and Δ⁸-skeletons identified by GLC, the Δ⁷-sterols were found to be the major sterols of most of the Cucurbitaceae investigated. The seed materials contained 24-ethyl-Δ⁷-sterols possessing Δ²⁵-bonds, i.e. 24-ethylcholesta-7,25-dienol and 24-ethylcholesta-7,22,25-trienol, whereas the mature plant materials contained 24-ethyl-Δ⁷sterols without a Δ²⁵-bond, i.e. 24-ethylcholest-7-enol and 24-ethylcholesta-7,22-dienol, as the most predominant sterols, with a few exceptions. The isolation and identification of 24α-ethylcholesta-8(14),22-dienol from the aerial parts ofCucumis sativus also is described.