Swapnadip Thakur

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.

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.

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.

Sterols of some Clerodendrum species (verbenaceae): Occurrence of the 24α- and 24β-epimers of 24-ethylsterols lacking a Δ25-bond

Abstract The configurations at C-24 of 24-alkylsterols of six samples of Clerodendrum species (Verbenaceae) — the aerial parts of C. fragrans , C. inerme , C. infortunatum , C. scandens , and C. sipho - nanthus , and the seeds of C. infortunatum — were examined by NMR. All samples contained 24β-ethylsterols possessing a Δ25 -bond, clerosterol and 22-dehydroclerosterol, as the dominant sterol components. The other 24-ethylsterols lacking a Δ25 -bond, 24-ethyl-22-dehydrocholestanol, 24-ethylcholesterol, and 24-ethyl-22-dehydrocholesterol, which were present as minor components, were shown to be mixtures of the 24α- and 24β-epimers, with the 24α-epimers predominating in all cases. Four minor 24-methyl-sterols, 24-methylcholestanol, 24-methylcholesterol, 24-methyl-22-dehydrocholesterol, and 24-methyllathosterol, were shown to be C-24 epimeric mixtures, whereas two others, 24-methyl-22, 25-bis-dehydrocholesterol and 24-methyl-22-dehydrolathosterol, were found to be present only as the 24β-epimers. This is the first report of the occurrence of 24β-ethyl-22-dehydrocholestanol in higher plants.

The 24α- and 24β-epimers of 24-ethylcholesta-5,22-dien-3β-ol in two Clerodendrum species

Abstract 13 C NMR spectroscopy of the 24-ethylcholesta-5,22 E -dien-3β-ol isolated from the aerial parts of Clerodendrum fragrans and C. infortunatum demonstrated the occurrence of a minor amount of the 24β-epimer, poriferasterol, in addition to,the dominant 24α-epimer, stigmasterol. This was confirmed by 400 MHz 1 H NMR spectroscopy after enrichment of the 24p-epimer by repetitive reverse-phase HPLC. The ratios (24α:24β) of the C-24 epimeric mixtures were estimated to be 23:2 for the C. fragrans sterol and 19:1 for the C. infortunatum sterol.

Sterols of Cajanus cajan and three other leguminosae seeds

Abstract The occurrence of 24-epiclerosterol, three Δ 8(14) -sterols [24α- and 24β-methyl-5α-cholest-8(14)-en-3β-ols and 24α-ethyl-5α-cholest-8(14)-en-3β-ol] and four 14α-methyl-Δ 9(11) -sterols [14α,24α- and 14α,24β-dimethyl-5α-cholest-9(11)-en-3β-ols, 14α-methyl-24α-ethyl-5α-cholest-9(11)-en-3β-ol and 14α-methyl-24β-ethyl-5a-cholesta-9(11),25-dien-3β-ol] has been demonstrated in the seeds of four Leguminosae species, Cajanus cajan , Cicer arietinum , Pisum sativum and Vigna mungo . These compounds were minor sterol constituents. In addition, 24α-ethyl-5α-cholest-9(11)-en-3β-ol and 24-methylenepollinastanol were isolated and identified from V. mungo seeds. Sitosterol was the principal sterol in all of the four Leguminosae seeds investigated.

Structural features of the acidic polysaccharide of Spondias pinnata gum exudate

Abstract The purified, homogeneous, acidic polysaccharide isolated from the gum exudate of Spondias pinnata, and its degraded product prepared by controlled autohydrolysis, were found to contain d -galactose, l -arabinose, and d -galacturonic acid. Complete methylation followed by hydrolysis, both before and after reduction with lithium aluminum hydride, revealed the probability of a (1 →3)-linked, galactan backbone. The linkages of the interior parts were confirmed by methylation studies, and by the results of periodate oxidation and Smith degradation.

Latex extractables of Calotropis gigantea

Abstract The hexane and methanol soluble extract of the latex coagulum of Calotropis gigantea afforded two new triterpene esters, viz . 3′-methylbutanoates of α-amyrin and ψ-taraxasterol, besides the known 3′-methylbutanoates of three triterpene alcohols. The compositions of the alkane fraction, total triterpene alcohol fraction, and free, acetyl and 3′-methylbutanoyl triterpene alcohol fractions of the extract were determined.

24β-methylcholesta-5,22E,25-trien-3β-ol and 24α-ethyl-5α-cholest-22E-en-3β-ol from Clerodendrum fragrans

Abstract Two minor sterols isolated from Clerodendrum fragrans were identified as 24β-methylcholesta-5,22E,25-trien-3β-ol and 24α-ethyl-5α-cholest-22E-en-3β-ol of which the former has so far been detected only in a marine sponge. The other sterols identified in the plant were clerosterol, 22E-dehydroclerosterol and several other common sterols.

7-oxodihydrokarounidol-3-benzoate and other triterpenes from the seeds of cucurbitaceae

The highly-polar fractions of the nonsaponifiable lipids obtained from the methanol extracts of 10 Cucurbitaceae seed materials were investigated for their components. Fourteen dihydroxy triterpenes and their derivatives, and one oxo-sterol were characterized. They are 7-oxodihydrokarounidiol-3-benzoate (7-oxomultiflor-8-ene-3α,29-diol-3-benzoate), isokarounidiol-3-p-methoxybenzoate (multiflora-6,8-diene-3α,29-diol-3-p-methoxybenzoate), karounidiol-3-benzoate, karounidiol, isokarounidiol, 5-dehydrokarounidiol, 7-oxodihydrokaroudnidiol, bryonolol, 3-epibryonolol, loranthol, betulin, 29-hydroxylupeol, erythrodiol, (23Z)-cycloart-23-ene-3β,25-diol and 7-oxositosterol among which the first two were the new naturally occurring compounds. Karounidiol and 7-oxodihydrokarounidiol were detected in all of the investigated seed materials.